Whatever Type of Screw Chiller,
TopChiller Can Fulfill the Chiller Solution for You.

  • Over 20 years of screw chiller manufacturing experience: TopChiller specialized in screw chiller design and manufacturing over 20 years
  • Up to 24 months warranty time: TopChiller promise standard 12 months warranty can extend to 24 months covered all screw chillers
  • Famous brand spare parts: Each screw chiller from TopChiller using world first class  refrigeration spare parts
  • Technical support& Training service: TopChiller can provide screw chiller installation and on-site commission service
  • 8 Hours troubleshooting: We promise 8 Hours quick response to solve screw water chiller if the case of any screw chiller error or alarm
  • Free screw chiller solution: TopChiller give all clients screw chiller and central chiller solutions free of charge
  • Screw Chiller
  • Screw Chiller
  • Screw Chiller
  • Screw Chiller

Why TopChiller Can Be a Reliable Chiller Factory

Over 20 Years Manufacturing Experience
TopChiller specialized in screw chiller design and manufacturing
24 Months Warranty Time
TopChiller promise 24 months warranty time covered all screw chillers
Famous Brand Spare Parts
Each screw chiller from TopChiller using world first class spare parts
Technical Support & Training Service
TopChiller provide screw chiller installation and on site commission
8 Hours Troubleshooting
We promise 8 Hours quick response to solve screw water chiller error
Free Screw Chiller Solution
TopChiller give all client screw chiller and central chiller solutions free of charge

Your Premier Screw Chiller Manufacturer

As a professional screw chiller manufacturer, all screw chillers from TopChiller including air cooled screw chiller or water cooled screw chiller is equipped with original Bitzer brand or Handbell brand screw type compressor.

This kind of semi-hermetic screw compressor with 4 steps (100%-75%-50%-25%) of cooling capacity for energy efficiency, alongside a touchscreen PCL control system. A different refrigerant such as R407c, R134a, R410a, and R404a are available depending on the working condition and ambient temperature.

Each screw chiller manufactured by TopChiller with fully protection devices including :

Compressor inner protection, over current protection, high/low-pressure protection, over temperature protection, water flow protection, phase sequence/missing protection, low coolant protection,anti-freezing protection, exhaust overheat protection.

These full protection devices can make sure all screw chiller working without any alarm or error.

All screw chillers are with SIEMENS PLC program control system, a smart computer interface with big LED touching screen, self-diagnosis for easy operation and supervision.

Compared with air cooled screw chiller, water cooled screw chiller need external cooling tower and cooling pump running together.

As a professional screw chiller manufacturer, TopChiller has exported many screw chillers to the Philippines, Australia, New Zealand, Malaysia, Singapore, Indonesia, Chile, Mexico, Costa Rica, Brazil, Argentina, Colombia, South Africa, Nigeria, Saudi Arabia, Dubai, Spain, Italy, etc.

If you are waiting for a professional screw chiller supplier, TopChiller is your best choice in refrigeration filed. If you have any screw chiller inquiry, please do not hesitate to contact TopChiller sales to get a good price.

 

 

Screw Air Chiller Technical Specifications

    o

screw chiller main parts

TopChiller: Your Premier Screw Chiller Manufacturer

Screw chillers having air cooled screw chiller and water cooled screw chiller. Compared with scroll compressor chillers, screw chillers with large cooling capacity for some certain industrial or commercial usage.

Air Cooled Screw Chiller

Air Cooled Screw Chiller

Both types of these two screw chillers are widely used for various industries applications such as HAVC, big building&hotel air conditioning, central chilled water supply, chemical processing, die casting,food&beverage processing, pet food, Pharmaceutical, plastic processing, automotive, energy&power project, packing, and printing…

Water Cooled Screw Chiller

Water Cooled Screw Chiller

Screw chiller expertise is common in all major industries, it uses the screw compressor to get this name. The utility of screw chiller has the advantages of large power, compact structure, stable operation, simple operation and wide application range, and is suitable for large air conditioners such as hotels, hotels, factories, hospitals, etc., especially in high-rise buildings with less load, and can display its uniqueness superiority.

Screw Chiller: The Completely Buying Guide for Importer

1. What is a Screw Chiller?

A screw chiller is an industrial chiller with screw type of compressor.

Like all chilling systems, screw chillers are composed of an evaporator, compressor, condenser, expansion valve. What sets it different from other types of chillers is its screw type compressor, which uses two helical rotors that propel and compress the refrigerant vapor.

Because of less number of moving parts and the rotary motion, screw chillers are more durable and quiet. They are smaller and lighter and are a popular choice by the users.

Screw chillers can be applied in a variety of cooling applications and are reliable for heavy-duty performance under harsh conditions and environment.

Screw Chiller

Screw Chiller

2. What is the difference between Screw Chillers and Reciprocating Chillers?

Regardless of which type of compressor, all of them have one common function-converting a source of power into stored energy in the form of compressed air.

Simply speaking, a compressor sucks in enough air and decreases its volume. As a result both the temperature and pressure rises. Most air compressors either are reciprocating piston type or rotary screw type.

2.1 Reciprocating Chiller

A reciprocating compressor has a piston move downwards, reducing pressure in its cylinder by creating a vacuum.

This difference in pressure forces the cylinder door to open and bring gas in. When the cylinder goes back up, it increases pressure, thus forcing the gas back out. The up-and-down motion is called reciprocating motion.

There are a lot of moving parts like piston, piston ring, crankshaft, connecting rod, valves, etc. that causes lesser reliability and more chance of breakdown.

The internal temperature at which the pistons operate is around 150 to 200 Deg C. This is because of the friction generated by the contact of piston rings against the cylinder walls.

The space required by the piston compressor is more. Separated compressor compartment is needed for its noise and vibration.

Small compressors are air cooled but large machines from 30HP and above are only water cooled.

2.2 Screw Chillers

For a study of screw chillers, we must know something about the screw compressors.

The screw refrigeration compressor is a kind of rotary refrigeration compressor, and has both piston type and power type (speed type).

screw compressor working

screw compressor working

Features of screw compressors:

  •  1) Compared with reciprocating piston refrigeration compressors, screw refrigeration compressors have a series of advantages such as high speed, lightweight, small size, small footprint and low exhaust pulsation.
  • 2) The screw refrigeration compressor has no reciprocating mass inertia force, good dynamic balance performance, stable operation, small vibration of the machine base, and the foundation can be made smaller.
  • 3) The screw refrigeration compressor has a simple structure, a small number of parts, and no wearing parts such as a gas valve and a piston ring. Its main friction parts such as a rotor and a bearing have high strength and wear resistance, and are lubricated. The condition is good, so the machining amount is small, the material consumption is low, the operation cycle is long, the use is relatively reliable, the maintenance is simple, and the operation automation is facilitated.
  • 4) Compared with the speed compressor, the screw compressor has the characteristics of forced air transmission, that is, the displacement is almost independent of the exhaust pressure, and the surge does not occur at a small displacement, and is broad. High efficiency can still be maintained within the working conditions.
  • 5) using the slide valve adjustment, can achieve energy stepless adjustment.
  • 6) The screw compressor is not sensitive to the liquid inlet and can be cooled by injection. Therefore, at the same pressure ratio, the discharge temperature is much lower than that of the piston type, so the single-stage pressure ratio is high.
  • 7) there is no clearance volume in the screw compressor, so the volumetric efficiency is high.
screw compressor working

screw compressor working

Working principle of screw compressor:

Working principle of screw compressor

Working principle of screw compressor:

1. Inhalation process:
The screw-type intake side suction port must be designed so that the compression chamber can fully inhale, and the screw type air compressor has no intake and exhaust valve groups, and the intake air is only adjusted by opening and closing of a regulating valve.

When the rotor rotates, the space of the groove of the main and auxiliary rotors is the largest when it is turned to the opening of the intake end wall.

At this time, the space of the groove of the rotor communicates with the free air of the intake port, because the groove of the air is exhausted.

The air is exhausted in its entirety. At the end of the exhaust, the groove is in a vacuum state. When it is turned to the intake port, the outside air is sucked and flows into the groove of the main and auxiliary rotors in the axial direction.

Screw air compressor maintenance reminds that when the air fills the entire tooth groove, the air intake side ends face of the rotor turns away from the air inlet of the casing, and the air between the tooth grooves is closed.

2. Closure and transportation process:
At the end of the inhalation, the main and auxiliary rotors will be closed with the casing and the casing will be closed.

At this time, the air is not closed in the groove, that is, [closed process].

The two rotors continue to rotate, and the tooth peaks coincide with the groove at the suction end, and the mating surface gradually moves toward the exhaust end.

3. Compression and injection process:
During the conveying process, the engaging surface gradually moves toward the exhaust end, that is, the gap between the engaging surface and the exhaust port gradually decreases, and the gas in the groove is gradually compressed, and the pressure is increased, which is [compression process].

At the same time, the lubricating oil is also injected into the compression chamber and mixed with the chamber gas due to the pressure difference.

4. Exhaust process:
When the meshing end face of the rotor in the maintenance of the screw air compressor is turned into communication with the exhaust of the casing, (the pressure of the compressed gas is the highest), the compressed gas starts to be discharged until the meshing surface of the tooth peak and the groove moves to the exhaust.

End face, at this time, the space between the two rotor meshing surfaces and the casing exhaust port is zero, that is, the completion (exhaust process), at the same time, the length of the groove between the rotor meshing surface and the casing air inlet reaches a long time, the inhalation process is going on.

Working principle of screw compressor

5.Lubricating oil and capacity adjustment system for screw chiller

The main functions of lubricating oil in screw chiller compressors are lubrication, cooling and capacity adjustment.

The oil pressure in the piston cylinder pushes the piston and spool to move forward/backward in the compression chamber.

In particular, the differential pressure oil supply system in the Hanbell RC-2 series can eliminate the use of external oil pumps in piston compressors.

However, in some special applications, an external oil pump is still required to ensure the safe operation of the screw chiller.

The bearings in the RC-2 series Hanbell screw compressors only need to provide a small amount of oil for lubrication.

The oil injected into the compression chamber can form an oil film in the compression chamber to increase the efficiency of the compressor and absorb some of the heat generated in the above process.

In order to separate the lubricating oil mixed from the refrigerant gas, an oil separator is required to ensure that as little oil as possible is carried into the screw chiller refrigeration system.

Pay special attention to the temperature of the lubricant, which is an important factor affecting the life of the compressor bearing.

High lubricating oil temperature will reduce the viscosity of the oil, resulting in a decrease in the lubricating ability and heat absorption capacity of the lubricating oil. It is recommended to keep the viscosity of the lubricating oil above 10 mm2/s.

The oil temperature should be kept above the system condensation temperature to avoid migration of refrigerant into the system during the summer. When the ambient temperature is too low, the viscosity of the lubricating oil is high.

In this case, the pressure drop of the oil passage in the oil passage is too large to be properly loaded, resulting in a heavy load starting of the compressor. It is recommended to equip the oil heater to heat the oil to increase the oil temperature in a short time.

If the compressor is operating under extreme conditions, an external oil cooler is also required. Have Hanbell determine the amount of cooling required for the oil cooler and the oil flow.

It is recommended to use some lubricating oil with high viscosity under the conditions of severe working conditions.

At this time, the exhaust temperature is higher, which can lower the viscosity of the lubricating oil and ensure the proper viscosity of the lubricating oil.

In addition, there may be a phenomenon in which the amount of oil returned from the evaporator is insufficient, such as a flooded refrigeration system, etc., and oil return is difficult in these systems, resulting in loss of oil in the compressor.

If there is a problem of insufficient oil return in the system, it is recommended to install a secondary oil separator between the compressor venting condenser of the screw chiller to further reduce the oil entering the system.

Precautions:

1. It is recommended to install the optional oil level switch to avoid malfunction of the compressor oil level.

2. The screw compressor can withstand a certain short liquid attack with respect to the piston compressor, but the long-term liquid compression affects the viscosity of the lubricating oil, and the bearing lubrication is insufficient, which easily causes the compressor to be stuck.

Screw chiller four-stage capacity adjustment system load status sharing:

25% (33%) load

When the compressor of the screw chiller is started, the solenoid valve is activated and the piston is at the 25% (33%) load position.

In this state, the high-pressure oil coming from the fuel tank is continuously injected into the piston cylinder through the capillary tube, and the high-pressure oil in the piston cylinder is directly bypassed to the suction port. At this time, all the pistons remain in their initial positions.

Note: The 25% load condition is designed to shorten the start-up time only, avoiding the motor starting current being maintained for a long time and tripping protection.

Do not operate for a long time under the 25% load state after the start-up process. It should be directly loaded and operated (especially under large differential pressure/pressure ratio) to prevent damage to the rotor, bearings and other components due to excessive compressor discharge temperature will effect the screw chiller operation.

50% (66%) load

When the 50%/66% solenoid valve is activated by the temperature control, the power failure is turned off by 25%, and the high pressure oil coming from the fuel tank flows into the piston cylinder, pushing the piston to the right, when moving to 50%/66%.

Since the high-pressure oil is returned from the oil discharge hole through the 50%/66% to the suction port, the piston stops operating at this position, and the compressor of the screw chiller is kept at the load state of 50%/66%.

75% load

AdvantaWhen the screw chiller 75% solenoid valve is activated, the 50% solenoid valve is turned off when the power is turned off, and the high oil pressure pushes the piston to continue to move to the right.

When moving to 75%, the high pressure oil is returned from the oil discharge hole through 75% to The suction port, so the piston stops running at this position, and the compressor of the screw chiller is kept at 75% load.ge of semi-hermetic screw compressor.

100% load

When we turn off all the solenoid valves of the screw chiller, the high oil pressure continues to flow into the piston cylinder, gradually pushing the piston to the suction side.

When the slide valve contacts the dead center of the compression chamber, the piston also reaches. Its dead center position, at this time there is no phenomenon of bypassing the compressed gas. At this time, the compressor of the screw chiller reached full load operation.

Spray cooling motor, motor working temperature is low, long life; open compressor uses an air-cooling motor, motor working temperature is high, affecting motor life, machine room working environment is poor; using exhaust cooling motor, the motor working temperature is very high, The motor has a short life.

Generally, the external type of oil is large in volume, but the efficiency is high; the built-in oil is combined with the compressor, and the volume is small, so the effect is relatively poor.

The secondary oil splitting effect can reach 99.999%, and the compressor can be well lubricated under various working conditions.

semi-hermetic screw compressor working principle

semi-hermetic screw compressor working principle

They sit slightly off-center in a shaft, with one side always touching the wall.

As they move at high speeds, they accomplish the same goal as the reciprocating compressor-one part of the shaft is always at a different pressure than the other, so gas can come in at the low pressure point and exit at the high pressure point.

The screw compressor has a male and a female rotor. The male rotor drives the female rotor if it is an oil-injected screw compressor technology, and a timing gear drives both rotors in the oil-free compressor technology as both rotors will run harmonically with minimum calculated clearance between both elements.

The basic principle of a screw compressor is as the male and female rotors are rotating in the opposite direction, they draw air in between them.

As the air progresses along with the rotors the air is compressed as the volume space between the rotors decreases, hence creating compressed air that is displaced to the outlet.

2.3Advantages and Disadvantages of Screw Chillers compared to Piston Chillers

Advantages:

1)Less possibility to break down: As screw compressor has only two moving parts which are not in contact with each other, so there is no wear or tear, and hence it is less possible to break down.

2)Less noise: In a screw compressor, the screws rotate in one direction and thereby causing less noise, heat and vibration. Furthermore, screw compressor is skid mounted and therefore foundation is not required.

3)Suitable for continuous operation: For the above reasons, screw compressors are suitable for 24 hours of continuous operation.

4)Energy saving: More air flow at less power consumed. The difference is more beneficial viable at 20HP and above machines.

5)Compact in size: Screw compressors are smaller in size and lighter in weight, and can be installed in a sealed compartment.

6)Resistant to harsh conditions and environment: Taken care of in the right way, this compressor can last around 2 to 5 times longer than the piston compressor.

Disadvantages:

1)Higher Price: Compared to a piston compressor, screw compressors are pricey.

2)Higher lubricant consumption: It has a complicated lubricating system and thus consumes more lubricant.

3)High precision installation requirements: Installation required higher precision and techniques.

3. Screw chiller working principle and flow diagram

Generally there are 2 types of screw chillers: air cooled screw chiller and water cooled screw chiller

Let’s have a look at how these two types of screw chiller working and its flow diagram as below:

For air cooled screw chiller:

The air-cooled screw chiller having a key component as the semi-hermetic screw type compressor, and the air cooled screw chiller unit is out of the evaporator as a gas refrigerant;

After the screw compressor is adiabatically compressed, it becomes a high temperature and high pressure state.

The compressed gas refrigerant is condensed by isostatic cooling in a condenser, and after condensation, it is changed into a liquid refrigerant, and then expanded to a low pressure through a throttle valve to become a gas-liquid mixture.

The liquid refrigerant under low temperature and low pressure absorbs the heat of the cold matter in the evaporator and becomes a gaseous refrigerant again.

The gaseous refrigerant re-enters the compressor through the pipeline and begins a new cycle. This is the four processes of the refrigeration cycle.

This is also the main working principle of the air-cooled screw chiller.

air cooled screw chiller working principle

air cooled screw chiller working principle

The evaporator is one of the most important part in both air cooled screw chiller and water cooled screw chiller.

There are 3 types of evaporators or coolers for screw chillers.

1. Dry Shell and Tube Evaporator

The dry evaporator refrigerant passes through the heat exchanger tube, and the cold water runs outside the high efficiency heat exchange tube.

The heat exchange efficiency of such a heat exchanger is relatively low, and the heat transfer coefficient is only about twice the heat transfer coefficient of the light pipe.

But the advantage is that it is easy to return oil, and the control is relatively simple, and the charging amount of the refrigerant is about 1/2 to 1/3 of the filling amount of the full liquid type unit.

dry shell and tube evaporator

dry shell and tube evaporator

2. Flooded evaporator

The operation of the flooded evaporator and dry evaporator is exactly the opposite.

The cold water passes through the heat exchange tube, the refrigerant completely immerses the heat exchange tube, and absorbs heat and evaporates outside the heat exchange tube.

There are many needle-shaped holes on the surface of the heat transfer tube of the Flooded evaporator, and there are spiral protrusions on the inner surface of the tube to enhance the heat exchange on the cold waterside.

The high-efficiency heat transfer tube that simultaneously enhances the boiling outside the tube and the heat transfer inside the tube increases the heat transfer coefficient by about 5 times compared with the light tube.

Flooded Chiller Evaporator

Flooded Chiller Evaporator

3. Falling film evaporator

Falling film evaporators, also known as spray evaporators, are similar to full liquid evaporators, but they differ from full liquid evaporators.

The refrigerant of the evaporator is sprayed from the upper part of the heat exchanger to the heat exchange tube, and the refrigerant only forms a thin film of cold liquid on the heat exchange tube, so that the refrigerant is reduced in boiling evaporation.

The static liquid level pressure increases the heat exchange efficiency, and the heat exchange efficiency is increased by about 5 times compared with the full flooded screw chiller.

Falling film evaporator

Falling film evaporator

Falling film evaporation is flow boiling. Since the thickness of the liquid film on the outer surface of the tube is small, the boiling point without static pressure increases, and the heat transfer coefficient is high.

The bubbles generated by flooded evaporation (that is, immersed evaporation) tend to accumulate on the surface of the heat exchange tube, resulting in a decrease in heat exchange efficiency, and the heat transfer effect is not as good as that of falling film evaporation.

In general, falling film evaporation is a small temperature difference, but it is necessary to prevent fouling and affect heat transfer efficiency.

In summary: The Flooded type means that the refrigerant is between the copper tube and the shell tube, and the chilled water flows inside the copper tube.

The dry type evaporator is the opposite of the two. The refrigerant evaporates in the copper tube, and the water flows between the copper tube and the shell tube.

They are mainly used for the heat pump air conditioner. In industrial low temperature chillers, ordinary dry evaporators are generally used.

“Flooded” means that the “shell-and-tube evaporator” used in the unit adopts the “flooded evaporator”, which is a shell-and-tube evaporator that is different from “dry” and “falling-film”.

Its “shell process” takes the refrigerant cycle, and the “tube process” takes the chilled water cycle. From the cross-section, it is as if there is a large cylinder of refrigerant in the cylinder, and the water pipe bundle is immersed in the refrigerant.

It is just the opposite of the “dry evaporator”. The dry type is the “tube” refrigerant, and the “shell” water is like the refrigerant tube bundle soaked in the water.

The Flooded evaporator and the flooded screw chiller have higher heat transfer efficiency than the dry evaporator/dry screw chiller unit, and the temperature difference between the outlet water temperature and the evaporation temperature is small, and the resistance along the path is small.

which is suitable for units with large circulation ( For example, the centrifuge), the cooling effect is good. However, refrigerant charge requirements are large and a dedicated oil return system is required to help the compressor return oil.

Advantages and disadvantages of dry and flooded evaporators

The Flooded shell and tube evaporator runs water in the tube, and the refrigerant evaporates outside the tube cluster, so the heat transfer surface is basically in contact with the liquid refrigerant.

Generally, the amount of refrigerant charged in the casing is about 55% to 65% of the effective volume of the cylinder, and the refrigerant liquid is heated and vaporized and then returned to the compressor through the liquid separator at the top of the cylinder. Easy operation and management, high heat transfer coefficient.

The disadvantages are:
1 When the evaporation temperature of the refrigeration system is lower than 0 °C, the water in the pipe is easy to freeze and destroy the evaporation pipe.

2 The refrigerant is filled in a large amount

3 Influenced by the height of the refrigerant liquid column, the evaporation temperature at the bottom of the cylinder is high, which will reduce the heat transfer temperature difference

4 The lower part of the evaporator cylinder will accumulate oil, and there must be reliable oil return measures, otherwise it will affect the safe operation of the system.

The dry shell tube type, that is, the refrigerant of the non-full liquid evaporator flows in the tube, and the water flows outside the tube cluster.

There are usually several processes for refrigerant flow. Due to the gradual gasification of the refrigerant liquid, the higher the flow rate, the more the number of process tubes.

In order to increase the water side heat exchanger, a plurality of baffles are arranged on the outer side of the tube heat transfer tube, so that the water flows across the tube cluster multiple times.

The advantages are:
1 Lubricating oil enters the compressor with the refrigerant, there is generally no problem of oil accumulation

2 less refrigerant is filled, generally only about 1/3 of the full liquid type;
When 3t0 is around 0 °C, the water will not freeze.

However, the use of this evaporator must be noted:
1 There are multiple processes for the refrigerant. If the end cover is not well treated, it will produce effluent, which will make the liquid entering the next process unevenly distributed and affect the heat transfer effect

2 There is a leakage problem on the water side. Because there is a gap of 1~3mm between the outer edge of the baffle and the casing, and there is a gap of about 2mm between the heat transfer tube, water leakage will occur.

The practice has proved that water leakage will cause the water side heat transfer coefficient to decrease by 20% to 30%, and the total heat transfer coefficient by 5% to 15%.

4.Features of air cooled screw chiller:

1. Semi-hermeitc screw type high-efficiency compressor, with single-machine system and dual-machine series selection, the unit is compact in structure and convenient in maintenance; adopts the new 5:6 screw rotor design, stable operation, high efficiency and energy saving.

2. Advanced intelligent frosting method. Microcomputer control analyzes the temperature of each point at any time, optimizes the defrost cycle time, and ensures that the defrost does not affect the normal operation of the equipment in time.

3. Professional motor cooling unit. Meet the operating conditions of severe working conditions.

4. With a new generation of high-efficiency heat exchange tubes, the heat transfer coefficient can be increased by 5%.

The double-slot tube-plate design and advanced tube expansion technology make the structure more sealed and reliable, completely avoiding the possibility of mutual penetration.

150Ton air cooled screw chiller

150Ton air cooled screw chiller

For water cooled screw chiller:

When the water cooled screw chiller is working, the screw compressor draws the low-temperature and low-pressure refrigerant in the evaporator into the cylinder, and the compressor steam is compressed into high-temperature and high-pressure refrigerant, then enters the condenser through the exhaust pipe.

The high temperature and high pressure refrigerant gas exchanges heat with the cooling water in the condenser, transfers heat to the cooling water, and the refrigerant gas condenses into a high pressure liquid.

The high pressure liquid from the condenser is throttled and depressurized by the thermal expansion valve and then enters the evaporator.

In the evaporator, the low-pressure liquid refrigerant absorbs the heat of the chilled water and vaporizes, so that the chilled water is cooled and cooled to become the required low-temperature water.

The vaporized refrigerant gas is again sucked into the compressor for compression, and is discharged into the condenser.

So that it is continuously circulated and continuously circulated, thereby achieving cooling of the chilled water.

Water cooled screw chiller must go along with a cooling tower, water pump, insulation water tank, to make a complete water cooling system.

water cooled screw chiller working principle

water cooled screw chiller working principle

Features of water cooled screw chiller:

Efficient semi-hermetic screw compressor, the screw chiller unit runs smoothly and the noise is low.
Inspiratory cooling results in low motor operating temperatures and long motor life.

With high-quality bearings, the bearing life is at least 40,000 hours. Built-in oil separator for smaller size and better results.

It can be safely implemented in the range of 0% to 100% or stepless energy regulation to maximize power conservation.

The condenser adopts high-efficiency shell-and-tube heat exchanger (optional stainless steel plate heat exchanger), built-in high-efficiency heat exchange tooth tube, reasonable design and good heat exchange effect;

The evaporator adopts high-efficiency shell-and-tube heat exchanger (optional stainless steel plate heat exchanger), built-in high-efficiency heat exchange tooth tube, reasonable design and good heat exchange effect;

Suitable for R22, R407c, R134a, R404A and other working fluids.
Less moving parts and low failure rate. An economizer can be selected to further increase compressor refrigeration capacity and efficiency.

A spray chiller can be selected to extend the range of applications for the compressor.
Oil cooling can be selected to increase compressor efficiency and compressor application.

120ton water cooled screw chiller

120ton water cooled screw chiller

Advantages of screw chillers

1. Simple structure, less moving parts, less wearing parts, only 1/10 of the piston type, low failure rate and long service life.

2. The circular motion is stable, there is no surge phenomenon during the low load operation, low noise and low vibration.

3. The compression ratio can be as high as 20 and the EER value is high.

4. Convenient adjustment, the stepless adjustment in the range of 10%~100%, high efficiency in partial load, and significant power saving.

5. Small size, lightweight, can be built as a fully enclosed large capacity screw chiller unit.

6. Not sensitive to wet strokes.

7. It is a positive pressure operation, and there is no problem of intrusion of outside air.

150Ton screw chiller in Kuwait

150Ton screw chiller in Kuwait

Screw chiller applications:

1. Industrial screw chiller
It can provide 5~15°C chilled water, or use ethylene glycol solution as the coolant. It can provide -5~+5°C process frozen aqueous solution, which can be used as ice storage, low temperature air supply, central air conditioning and other production processes.

At the same time, according to the requirements of the user, I can specially design the unit to provide a large temperature difference chiller (the temperature difference between the inlet and outlet water is 8~15°C).

Or higher than the water temperature unit (outlet water temperature 15 ° C ~ 25 ° C). The cooling capacity is 94KW-3360KW.

75Ton air cooled chiller

75Ton air cooled chiller with screw compressor

2, medium temperature screw chiller
The outlet water temperature is -5 ° C ~ -45 ° C, using imported semi-closed screw compressor unit (with economizer); can provide -5 ° C ~ -45 ° C low temperature.

Ethylene glycol solution or brine solution can be used as a cold source for chemical, pharmaceutical, cold storage, an ice rink and other processes. The cooling capacity is 55KW-2000KW.

3, low temperature screw chiller
The effluent temperature is -45 ° C ~ -110 ° C, can provide -45 ° C ~ -110 ° C alcohol or calcium chloride aqueous solution chilled water; using a binary stack or ternary cascade screw refrigeration system. High energy efficiency ratio and stable operation.

At the same time, it can be designed according to the requirements of use, ultra-low temperature type, anti-corrosion type, explosion-proof type special industrial screw type chiller, which can meet the requirements of various industries for process cold source.

Nowadays, the use of screw chillers is seen in many industries. For this screw chiller, which different industries can be used in the application process, in order to allow users in different industries to choose more For more understanding.

let’s take a brief look at some of its scope of applications.

First, the construction industry

Screw chillers can be used in some construction industries.

There are many places used in the construction industry.

For example, it can supply chilled water to concrete, and it can change the molecular structure of concrete.

Screw-Chiller-for-Concrete-Cooling

Screw-Chiller-for-Concrete-Cooling

In the process of construction, it is more suitable for the purpose of use, and its application can also invisibly play a role in the hardness and toughness of concrete, so it is now seen in many construction industries.

The development in this industry will also become larger and larger, and users who have processed in this industry can choose to use this equipment.

Second, the food industry

This type of chiller equipment can also be used in some food industries.

We all know that after many foods are processed, they need to be packaged, but the food heated by high temperature needs to be cooled when it is put into the package.

The screw chiller can play such a role, allowing the hot food to cool quickly and fit into the bag, so it is still used in this food industry.

SCREW-CHILLERS-FOR-FOOD-PROCESSING

SCREW-CHILLERS-FOR-FOOD-PROCESSING

Third, Big factory or central air conditioning of HVAC 

The cooling capacity of screw chiller is higher than that of the scroll chiller.

So this screw chiller can be mainly used in chemical plants, ink printing plants, automobile manufacturers or central air conditioning systems or other large industrial refrigeration.

screw chiller for air conditoning and HVAC

screw chiller for air conditioning and HVAC

The above is the application of screw chillers in the construction, food industries, air conditioning for big buildings.

Now with the development of various industries, the application of such screw chillers will gradually increase, and it will become a must in many industries in constant innovation.

Some tips for selecting a correct screw chiller

In industrial production, mechanical equipment generates heat during operation. If this heat cannot be dissipated in time, it will affect the normal operation of the equipment as well as the quality and production efficiency of the product.

Another situation is that the processed product needs to reach a certain temperature during processing in order to be processed normally or to achieve higher yield and production efficiency.

Then the temperature of the processed product must reach the desired temperature before or during processing. At this time, it’s showing the time of screw chiller

But how to size a suitable screw chiller for your business?

  • Cooling capacity
    The cooling capacity of the screw chiller is directly related to the normal use of production equipment and operating efficiency. If the cooling capacity is too small, the ideal cooling effect cannot be achieved, and the production efficiency is reduced, the operating energy consumption is increased, and the production equipment cannot normal operation so that the production line is shut down.                                                                                                However, if the selection is too large, the energy is wasted and the operating cost is also increased. The higher the cooling capacity of the chiller, the higher the price of the chiller. Therefore, the matching of the cooling capacity is very important.
  • Chilled water flow rate
    The amount of chilled water is the ice water cooled by the chiller, which acts directly on the cooled part, but because of the water flow, it will directly affect the heat transfer effect.            This flow rate is based on the material, density and heat transfer ratio of the part to be cooled. Calculated, and some equipment is required to cool the flow, because the amount of water is not enough to cool down.                                                                                                             Therefore, the water flow is directly related to the operation of the screw chiller and the cooling effect of the production equipment.
  • Inlet and outlet water temperature
    When the production equipment or the production raw materials are in production and processing, when cooling is required, there is a temperature difference between the inlet and outlet of the chiller connected to the production equipment.                                                           This temperature difference is the actual heat generated by the production equipment so that it can be quite accurate. Calculate and select the right screw chiller.
  • Understand the volume, weight, specific heat, and density of the equipment parts being cooled or the raw materials for production and processing.
    This can quickly and efficiently calculate the cooling capacity of the required chiller. Also note the time required for the initial temperature of the cooled material to drop to the target temperature, which is also the way to calculate the cooling capacity.                                              There is also a clear understanding of the highest and lowest temperatures required or affordable for the production equipment or materials to avoid impact on equipment or materials.
  • What is the cooling medium?
    The cooling medium generally includes: tap water, ethylene glycol solution, oils and fats, sea water, food and beverage, and so on.
  • Air-cooled chiller or water-cooled chiller?
    Although the air-cooled chiller and the water-cooled chiller are both chillers, the cooling method of the unit itself is different, so the installation method is different.                                   The air-cooled type is convenient, and the water pipe and the power supply can be operated, but the cooling effect is slightly worse than that of the water-cooled chiller, because the air-cooled chiller is cooled by air, and the air is greatly affected by the ambient temperature. The group installation location also requires space around the chiller. The water-cooled chiller is cooled by its own use of water, so the name is water-cooled. The water-cooled chiller needs to be installed with a cooling tower to cool the unit. In the pipeline project, there are two more water pipes than the air-cooled chiller, but the water-cooled cold water The effect of the machine is much better than that of air-cooling. Even in the selection, it can be one model smaller than the air-cooled type. Therefore, under the installation conditions, most users will choose the water-cooled chiller.

You can refer the above points to size a correct screw chiller for your business.

To select a suitable screw chiller for your industry is very important, besides the above information, there are also some other useful tips for your reference:

1. The main control parameters of the screw chiller are the refrigeration performance coefficient, rated cooling capacity, input power, and refrigerant type.

2. The selection of the screw chiller should be considered according to the cooling load and use. For refrigeration systems with long periods of the low load operation, a multi-head piston compressor unit or a screw compressor unit should be used for easy adjustment and energy saving.

3. When selecting a screw chiller, priority is given to units with a higher coefficient of performance values. According to statistics, the average of screw chiller operating time under 100% load is about 1/4 of the total running time.

The operating time ratios of 100%, 75%, 50%, and 25% of the total operating time were approximately 2.3%, 41.5%, 46.1%, and 10.1%.

Therefore, when selecting a screw chiller, priority should be given to models with a flatter efficiency curve.

At the same time, the adjustment range of the screw chiller load should be considered when designing and selecting. The multi-head screw chiller has excellent partial load performance and can be selected according to actual conditions.

4. When selecting a screw chiller, pay attention to the conditions of the nominal working condition. The actual cooling capacity of a chiller is related to the following factors:
a) cold water effluent temperature and flow rate;
b) Inlet water temperature, flow rate and fouling coefficient of cooling water.

5. When selecting a screw chiller, pay attention to the normal working range of the unit, mainly because the current limit of the main motor is the current value of the shaft power under nominal conditions.

6. In the design selection, it should be noted that under nominal operating conditions, the outlet temperature of cold water should not exceed 15 °C, and the outdoor dry bulb temperature of air-cooled screw units should not exceed 43 °C.

If it is necessary to exceed the above range, it should be understood whether the range of use of the compressor is allowed, and whether the power of the main motor is sufficient.

There is another important tip for using a screw chiller- the refrigeration oil or lubrication oil for screw compressors.

Why the screw compressor need the refrigeration oil or lubrication oil?

Refrigerated oil plays a very important role in the operation of the screw chiller refrigeration system.

Purpose of using refrigeration oil or lubrication oil:

1, Reduce Friction
The injection of lubricating oil forms an oil film on each friction surface of the screw compressor, which reduces friction and reduces energy consumption.

2, Take Away Frictional Heat
Injecting lubricating oil can take away frictional heat, keep the temperature of the moving pair within a reasonable range, and also take away various mechanical impurities to prevent rust and cleaning.

3, Reduce Leakage
Filling the friction surface gap with lubricating oil can seal the friction surface of the refrigeration compressor

Screw Compressor Lubrication Oil

Screw Compressor Lubrication Oil

Classifications of refrigeration oil or lubrication oil:

1. Natural mineral oil (referred to as mineral oil)
Mineral oil is a lubricating oil extracted from petroleum. It can only be dissolved with weakly polar or non-polar refrigerants;
Mineral oil is divided into four varieties: L-DRA/A, L-DRA/B, L-DRB/A and L-DRB/B;

2, synthetic oil (referred to as synthetic oil)
Synthetic oil makes up for the shortage of mineral oil, usually has a strong polarity and can be dissolved in a more polar refrigerant (such as R134a);

3. There are two main types of synthetic oils.
Polyester oil: Multi-polyester (POE) oil has better comprehensive performance
Polyether oil: Epoxy acetylene-propylene oxide polyether (PAG) has better comprehensive performance

Why TopChiller can your reliable screw chiller supplier?

TopChiller is a professional screw chiller manufacturer with decade years of experience. We have installed thousands of various screw chiller units in Singapore, Australia, Indonesia, Nigeria, Saudi Arabia, Kuwait for different industrial and commercial applications.

We also have after sales team can do installation and commission at screw chiller project site. After installation, our engineer will give your stuff a full detailed training of how to use the screw chiller and maintenance guide.

Common fault analysis of screw chillers

For the use of screw chillers, some common fault problems include high voltage fault, low voltage fault, low valve temperature fault, compressor overheat fault, communication fault, etc.,

But in order to effectively solve these fault problems, you must first link The main working principle of the screw chiller, and among them, the four processes of the refrigeration cycle, after the adiabatic compression of the compressor, becomes a high temperature and high pressure state.

The compressed gas refrigerant is condensed by isostatic cooling in a condenser, and after condensation, it is changed into a liquid refrigerant, and then expanded to a low pressure through a throttle valve to become a gas-liquid mixture.

The liquid refrigerant under low temperature and low pressure absorbs the heat of the cold matter in the evaporator and becomes a gaseous refrigerant again. The gaseous refrigerant re-enters the compressor through the pipeline and begins a new cycle.

After understanding the main working principle of the screw chiller, the common faults of the screw chiller are analyzed below.

1. High-Pressure Alarm

The compressor discharge pressure is too high, causing the high voltage protection relay to operate. The screw compressor from chiller discharge pressure reflects the condensing pressure.

The normal value should be 1.40~1.60MPa, and the protection value should be set to 2.00MPa.

If the long-term pressure is too high, it will lead to an excessive operating current of the compressor, easy to burn the motor, and easily cause damage to the valve port of the compressor exhaust port.

What should be done is to control the discharge pressure of the compressor in a safe range.

2. Low pressure alarm

The screw compressor suction pressure is too low, causing the low voltage protection relay to operate. The suction pressure of the compressor reflects the evaporation pressure.

The normal value should be 0.40~0.60MPa, and the protection value should be set to 0.20MPa. If the suction pressure is low, the amount of return air is small, the cooling capacity is insufficient, and the electric energy is wasted.

The heat of the compressor motor for return air cooling is poor, and the motor is easily damaged! The solution is the same as the high pressure fault, try to keep the compressor within the normal pressure range.

3. Low valve temperature error

The outlet temperature of the expansion valve reflects the evaporation temperature, which is a factor affecting the heat exchange.

Generally, it has a temperature difference of 5.0 to 6.0 °C from the outlet water of the refrigerant water. When a low valve temperature fault occurs, the compressor will stop.

When the valve temperature rises, it will automatically resume operation with a protection value of -2.0 °C.

4. Compressor overheat fault

A thermistor is embedded in the winding of the compressor motor, and the resistance is generally 1kΩ. When the winding is overheated, the resistance value will increase rapidly.

When the winding exceeds 141kΩ, the thermal protection module SSM will act to cut off the unit operation and display the overheat fault. The TH fault indicator lights.

5. Communication failure

The control of each module by the computer controller is realized through the communication line and the total interface board.

The main cause of the communication failure is the poor contact or open circuit of the communication line, especially the interface is affected by moisture oxidation, and the unit electronic board or the total interface If the board is faulty, the address dial switch is improperly selected, and the power failure can cause a communication failure.

The above five kinds of fault phenomena are the most common, and understanding these fault phenomena and judgment ability and solution has an irreplaceable effect on extending the service life of the screw chiller.

Besides the above, we must point the screw compressor out. Because the screw compressor is the key refrigeration part for a screw chiller.

The screw compressor has the characteristics of small size, lightweight and easy maintenance, and is a type of development that is faster in refrigeration compressors.

On the one hand, the screw line and structural design have made great progress. On the other hand, the introduction of special milling machines for screw rotors, especially grinding machines, has improved the machining accuracy and machining efficiency of these key components, and the performance of screw compressors has been effectively improved.

Due to the continuous improvement of the working reliability of the screw compressor, it has gradually replaced the reciprocating compressor in the medium cooling capacity range and occupied part of the market of centrifugal compressors.

In operation, there are a lot of operational details to be aware of in order to ensure smooth and efficient operation of the equipment and improve production efficiency.

screw compressor

screw compressor

 

Screw compressor can’t running

Electrical fault:

First check if the power supply wiring of the compressor is correct, whether the power switch is properly closed, whether the power fuse is blown, and whether the power supply voltage reaches 90% or more of the rated voltage.

Check the compressor’s pressure relay components for damage and pressure regulator settings. Poor contact of the start button, this situation is less common, because the current screw compressor, unless it is cheap to buy a very low-cost machine, it is generally not a problem, even if it is solved, it is very simple.

Operation failure:

At the time of starting, the pressure of the outlet switch and the outlet is not set too high, the switch of the electrical circuit is not restored, and the setting of voltage and current is unreasonable.

The general screw compressors have automatic protection devices, so when some parts of them fail, they cannot be started normally. Start and stop the control loop.

Because there are many electrical components, there are more control points and the failure rate is relatively high. Start button, stop button or switch, etc., may cause the host to fail to start or stop due to improper operation.

Such as the start button, stop button, emergency stop button, control panel, etc., excessive force during operation may cause the button to be stuck on the edge of the button housing and cannot be reset.

Screw chiller failure:

Mainly including compressor motor failure, rotor lock and so on. When the compressor is overloaded for a long time, it will form a rotor tooth surface and the bearing fatigue damage will be stuck; the compressor lubricating oil pipeline will be blocked to form a lack of oil, causing the anode and the anode and the bearing temperature to be too high and damaged and locked.

If the bearing and the male and female rotors are disassembled when repairing the compressor, the installation is not cautious and the installation accuracy is not up to the requirement. The anode and the anode are not parallel and the male and female rotors cannot be rolled.

In addition, when the compressor is repaired improperly, an external solution is applied to the rotor, and the axial and radial gaps between the female and male rotors are changed so that they cannot rotate.

Under normal circumstances, the manufacturer has set parameters such as lubricant level, oil pressure and filter pressure difference on the compressor control system.

If the above conditions occur, it will stop actively to protect the compressor.

However, some users tend to increase the set parameters or short-circuit certain alarm lines and pipelines for convenience and save money, causing the equipment to leave the monitoring and causing the failure.

Generally, the probability of motor failure in the compressor is relatively low, but if it occurs, it will be more troublesome, and it needs to be excluded and repaired by professionals.

Compressor Exhaust pressure is too low

Under normal circumstances, the in-service compressor can eliminate the exhaust pressure caused by the high altitude, but can not ignore the increase in gas consumption.

If there is no large leak point in the compressed air line, it is a problem with the compressor unit itself. We can check if there are any problems with the following aspects:

1. Is screw chiller maintenance timely?

The displacement of the compressor drops. First, see if the compressor has been serviced? Many times, the displacement of the compressor drops, there is no big problem, that is, the customer is neglected to maintain.

If the working environment is not ideal, the compressor air filter is easy to block. Lighter can use dust to remove dust; blockage is serious, need to replace the new air filter.

2. Are the intake valves all open?

The compressor discharge is reduced, check the unit, if just maintenance, remove the three filter and oil problems, then first check the compressor intake valve.

Remove the air intake hose, turn on the compressor, and see if the opening of the intake valve is normal. The theoretical design life of the intake valve is 100,000 times.

Because each manufacturer uses different brand batches, the quality is also different. Therefore, the failure of the intake valve may cause the unit to reduce the exhaust volume.

If the intake valve cannot be fully opened when the compressor is loaded, it can be concluded that the exhaust gas volume is a failure of the intake valve and should be removed for repair or replacement.

3. Motor failure

After the intake valve failure is removed, if the unit exhaust volume has not changed, consider whether the motor is faulty.

Due to local short circuit in the motor coil, or bearing wear, the motor shaft wears, causing the motor speed to be lower than the rated speed, causing the compressor to discharge.

The motor coil, bearing, etc. should be repaired, and the compressor displacement should be tested after repair…

Closer to this principle is the belt-driven compressor, which should take into account the belt load and the intact state.

Sometimes the belt speed is insufficient due to the slip or slack of the belt, resulting in low exhaust pressure.

4. Pressure switch setting working pressure is too low

This kind of situation is often caused by changes in working conditions, or after the system has been adjusted, overhauled, etc., the system parameters are moved.

Otherwise, under normal circumstances, the working pressure will not be easily mishandled after being set.

Screw Compressor parameter setting is not recommended by the user at will but should be combined with the equipment supplier and the user to comprehensively consider the working conditions and equipment operating characteristics, and set a reasonable value.

Compressor Exhaust oil content is too high

For companies that are very concerned about air quality, it is critical that the air contains too much oil. There are many reasons for this problem, mainly due to the following reasons:

first, the oil level is too high;

second, the return pipe filter or orifice is blocked;

the third is that the oil and gas separation core is damaged.

The fourth is that the gas pressure of the compressor is too low; then the minimum pressure valve fails; the last is the problem of the lubricant itself.

If too much foam is used, it will also increase the oil content of the gas.

1. Too much cooling oil added to the compressor

An excessive amount of lubricating oil is added, which exceeds the allowable range.

Although the separation system separates the oil and gas during the operation of the compressor, in the discharge of the gas, the gas also entrains the cooling oil into the gas, causing the discharge. The oil content in the gas is too high.

2. The return line is faulty

In the working process of the screw compressor, the oil return pipeline shoulders an important responsibility. The oil separation inside and the compressor inlet will form a pressure difference. Under this pressure difference, the oil return pipeline is responsible for the oil separator.

The oil collected at the bottom is sent back to the compressor and continues to be used during the next compression cycle.

If there is a fault such as blockage, breakage and incorrect installation on the return line, the oil collected at the bottom of the oil separator cannot be sent back to the compressor, causing too much oil to accumulate at the bottom, and this part of the oil that is not sent back to the compressor is As the gas is discharged, there is a phenomenon of oil in the exhaust process.

3. Oil separation core is damaged

During the operation of the screw compressor, if the oil separation core is damaged, such as damage or perforation, it loses the role of oil and gas separation.

That is to say, the exhaust gas of the mixed gas and the compressor is directly penetrated, and a large amount of cooling oil is not separated, and as the gas is discharged together with the body, an oil failure occurs during the exhausting process.

4. System pressure control is too low

If the system pressure control is too low, the centrifugal force in the separator will be less than the centrifugal force required for the work, then the function of the separator will not be fully reflected, resulting in the oil content in the separator entering the next step is too high, beyond its separation range.

As a result, the oil and gas separation is not complete, and oil failure occurs during the compressor exhaust process.

5. Minimum pressure valve failure

During the operation of the screw compressor, the function of the minimum pressure valve is to ensure that the system pressure is controlled above the minimum pressure during operation.

If the minimum pressure valve fails, the minimum pressure of the system will not be guaranteed. Since the gas consumption of the luck equipment is very large, the system pressure is too low, and the oil return pipeline cannot return oil.

The oil that collects at the bottom of the oil separator will not be returned to the compressor and will expel the compressor with the compressed gas, causing oil failure during the exhaust process.

6. The quality of the cooling oil is unqualified

If the compressor is added with a relatively poor defoaming lubricant, or the ambient air humidity is high, the water leakage at the bottom of the lubricating oil station will cause the lubricating oil to foam, causing the oil content in the exhaust gas to increase.

Compressor Exhaust temperature is too high

Mechanical failures include:

a. oil stop valve failure;

b. compressor oil filter failure;

c. thermal control valve (temperature control valve) malfunction;

d. compressor oil regulator abnormal;

e. compressor oil cooler Abnormal (this fault is common in water-cooled compressors);

f. Compressor head failure, including poor lubrication and unreasonable design of the machine itself, installation is not necessary;

g. air filter failure; h. oil and gas separator failure; i. Temperature sensor and computer failure, abnormal reading.

The effects of compressor oil include:

a. insufficient compressor oil;

b. deterioration of compressor oil, poor fluidity of oil, reduced heat exchange capacity;

c. improper selection of compressor oil viscosity;

d. The quality is not good: the thermal oxidation performance is poor, the viscosity temperature performance is poor, and the air separation ability is poor.

The screw compressor cannot be unloaded

Loading and unloading are the basic functions of the compressor. They cannot be loaded and unloaded, and the compressor is useless.

Because if it can’t be loaded, the compressor has no compressed air output; if it can’t be unloaded, after there is no compressed air demand downstream, it can be imagined as: “The consequence of constantly inflating a balloon.”

When the compressor exceeds the rated pressure during operation, it will continue to load and run, and the maximum pressure value will be set to cause the screw compressor to trip or the safety valve will act.

If the actual air consumption of the production is not greater than the gas volume of the compressor unit and a large amount of leakage of the pipeline, the compressor may not be unloaded mainly for the following reasons:

a. If the pressure switch is set improperly or after setting, there will be elegant and false, and the false number will be reported.

b. The intake valve is not working properly, the card is stuck, etc.;

c. When the system stops using the gas, the venting solenoid valve is invalid, and the performance state is the pressure slowly. Rise, not like loading up;

d. control loop failure;

e. loading solenoid valve failure, such as loading at the same time of unloading, and the loaded gas volume is greater than the unloading, so the pressure continues to increase.

In the current screw compressor design and production level, many of the problems with screw compressors are mostly caused by untimely maintenance or improper operation.

If we strictly abide by the screw chiller operation process and pay attention to screw chiller maintenance, then I believe that many unnecessary failures will not happen.

Selection points and troubleshooting of screw chillers

Screw chiller selection points

1. The main control parameters of the screw chiller are the refrigeration performance coefficient, rated cooling capacity, input power and refrigerant type.

2. The selection of screw chillers should be considered according to the cooling load and use. For refrigeration systems with long periods of low load operation, a multi-head piston compressor unit or a screw compressor unit should be used for easy adjustment and energy saving.

3. When selecting a screw chiller, priority is given to units with higher performance coefficient values. According to statistics, the average chiller operating time under 100% load is about 1/4 of the total running time. 100%, 75%, 50%, 25% of the total running time

The operating time ratio of the load is approximately 2.3%, 41.5%, 46.1%, and 10.1%. Therefore, when selecting a correct screw chiller, priority should be given to models with a flatter efficiency curve.

At the same time, the adjustment range of the chiller load should be considered when designing and selecting.

The multi-head screw chiller has excellent partial load performance and can be selected according to actual conditions.

4. When selecting a suitable screw chiller, pay attention to the conditions of the nominal working condition. The actual cooling capacity of a chiller is related to the following factors:

a) cold water effluent temperature and flow rate;

b) Inlet water temperature, flow rate and fouling coefficient of cooling water.

5. When selecting a proper screw chiller, pay attention to the normal working range of the model unit, mainly because the current limit of the main motor is the current value of the shaft power under nominal conditions.

6. In the design selection, it should be noted that under the nominal working condition flow, the outlet temperature of cold water should not exceed 15 °C, and the outdoor dry bulb temperature of the air-cooled unit should not exceed 43 °C.

If it is necessary to exceed the above range, the compressor should be known. Whether the range of use is allowed, and whether the power of the main motor is sufficient.

The control of each module by the computer controller is realized through the communication line and the total interface board.

The main cause of the communication failure is the poor contact or open circuit of the communication line, especially the interface is affected by moisture oxidation, and the unit electronic board or the total interface If the board is faulty, the address dial switch is improperly selected, and the power failure can cause a communication failure.

Causes and treatment of abnormal vibration of the screw chiller unit?

  1. The screw chiller unit anchor bolts are not tightened or loose; tighten the anchor bolts.
  2. The screw compressor shaft and the motor shaft are misaligned or dissimilar; re-align.
  3. The vibration of the pipeline causes the vibration of the unit to increase; add support points or change the support points.
  4. The screw compressor draws in too much oil or refrigerant liquid; when it stops, the disk drives the liquid out of the compressor.
  5. The spool valve should not stop at the required position, but vibrate there; check the oil piston, the four-way valve or the increase/decrease solenoid valve for leaks and repairs.
  6. The vacuum in the suction chamber is too high; open the suction shut-off valve and check if the suction filter is blocked.

The reasons for the insufficient cooling capacity of the screw chiller unit and the treatment methods?

  1. The position of the spool valve is not suitable or other faults (the spool valve cannot be attached to the fixed end); check the position of the indicator or angular displacement sensor and check the spool valve.
  2. The suction filter is clogged, the suction pressure loss is too large, the suction pressure is decreased, and the volumetric efficiency is lowered; the suction filter is removed and cleaned.
  3. The screw chiller is not properly worn, causing excessive clearance; checking, adjusting or replacing parts.
  4. The resistance loss of the suction line is too large, and the suction pressure is much lower than the evaporation pressure; check the suction shutoff valve and the suction check valve to find the problem for repair.
  5. Refrigerant Leakage between high and low pressure systems; check the driving, parking bypass valve and return valve, and find problems for repair.
  6. The injection quantity of refrigerant is insufficient, and the sealing effect cannot be achieved; check the oil circuit, oil pump and oil filter to increase the fuel injection amount.
  7. The exhaust pressure is much higher than the condensing pressure, and the volumetric efficiency is lowered; check the exhaust system piping and valves to remove the resistance of the exhaust system. If the system seeps into the air, it should be discharged.

Reasons for the abnormal sound of the screw chiller during operation and treatment

  1. There is debris in the rotor tooth groove; the rotor and the suction filter are inspected.
  2. Damage to the thrust bearing; replace the thrust bearing.
  3. The main bearing is worn, the rotor is rubbed against the body; the main bearing is repaired and replaced.
  4. The spool is deflected; the slide guide block and the guidepost are inspected.
  5. Loose joints of moving parts; disassemble the machine for maintenance and strengthen the relaxation measures.

Causes and treatment of screw chiller exhaust temperature or oil temperature drop?

  1. Inhalation of wet steam or liquid refrigerant; reducing the amount of liquid supplied to the evaporation system.
  2. Continuous no-load operation; check the spool valve.
  3. The exhaust pressure is abnormally low; the water supply is reduced or the number of condenser inputs is reduced.

The reason and treatment of the screw chiller slide valve movement are not flexible or not working?

  1. The four-way reversing valve or solenoid valve is not flexible; check the four-way reversing valve or solenoid valve coil and wiring.
  2. The oil pipeline system is blocked; overhaul.
  3. The oil piston is stuck or leaking; repair the oil piston or replace the seal.
  4. The oil pressure is too low; overhaul and adjust the oil pressure.
  5. The slide valve or guide key is stuck; overhaul.

The reason and treatment of the screw compressor body temperature is too high?

  1. The moving parts are abnormally worn; the compressor is repaired and the damaged parts are replaced.
  2. Inspiratory severe overheating; reduce inhalation superheat.
  3. Leakage in the bypass line; check whether the driving or parking bypass valve leaks.
  4. The compression ratio is too large; detecting the suction and exhaust pressures and reducing the pressure ratio

Why is the compressor reversing when the screw compressor is stopped?

  1. The suction and exhaust check valves are not closed tightly; overhaul and eliminate the jamming of the valve plate.
  2. Prevent the reversed bypass line valve from opening in time; check and repair.

How to arrange large, medium and small repairs or maintenance of screw chillers?

  1. The motor of screw compressor: disassembly, overhaul and replacement, bearing refueling, a period of 2 years, refer to the motor use manual.
  2. Coupling: Check the coaxial between the compressor and the motor (check whether the elastic transmission piece is damaged or the rubber pin is worn) for 3-6 months.
  3. Oil separator: clean the interior for a period of 2 years.
  4. Oil cooler: remove scale (water-cooled) and grease stains for a period of six months; depending on the water quality and dirt.
  5. Oil pump: trial and error repair, the period is 1 year.
  6. The oil filter (including crude oil filter), suction filter: cleaning, the period of six months. It should be cleaned for the first time driving for 100-150 hours.
  7. Oil pressure regulating valve: Checking capacity check, the period is 1 year.
  8. Sliding valve: action check, the period is 3-6 months.
  9. Safety valve, pressure gauge, thermometer: calibration, the term is 1 year.
  10. Safety valve, pressure gauge, thermometer: calibration, the term is 1 year.
  11. Pressure relay, temperature relay: Verification, the term is about half a year. See the instructions.
  12. Electrical equipment: Action check, the period is about 3 months. See the instructions.
  13. Automatic protection and automatic control system: the period is about 3 months.

Installation and commissioning of screw chiller

Preparation before the start of the screw chiller:

The correct commissioning of the screw chiller is an important part of ensuring the normal operation of the refrigeration unit, saving energy and prolonging the service life.

For on-site installation of large and medium-sized refrigeration systems, the requirements should be familiar with the layout and connection of the entire system, the outline structure and component performance of each equipment, as well as the electronic control system and water supply system.

To this end, engineers such as refrigeration and hydropower should participate in the commissioning.

Users should carefully read the product operation manual provided by the factory before commissioning, and proceed step by step according to the operation requirements.

The operator must undergo special training from the factory to obtain the operation certificate of the unit before the operation can be carried out, so as to avoid fatal damage to the unit caused by the wrong operation.

A Preparation before screw chiller commissioning

(1) Since the screw chiller is a medium and large chiller, it is necessary to closely cooperate with the design, installation and use during commissioning.

In order to ensure that the commissioning work is carried out in an orderly manner, it is necessary for the relevant personnel to form a temporary commissioning team to fully conduct the commissioning work.

(2) The personnel responsible for commissioning should be fully familiar with the structure and performance of the screw chiller, familiar with the safety technology of the chiller, clarify the methods, steps and technical requirements to be debugged, formulate detailed and specific commissioning plans, and make each post the commissioning staff clarifies their tasks and requirements.

(3) Check whether the installation of the screw chiller meets the technical requirements, whether the foundation of the screw chiller meets the requirements, and whether the size, specification and material of the connecting pipeline meet the design requirements.

(4) The power supply system of the unit should be fully installed and commissioned.

(5) Pass the water test on the cold water and cooling water system separately, flush the dirt of the waterway system, the water pump should work normally, and the circulating water volume meets the requirements of working conditions.

(6) Clean and debug the environmental site to achieve clean, bright and smooth.

(7) Prepare the various common and specialized tools required for commissioning.

(8) Prepare various measuring instruments and meters for pressure, temperature, flow, quality, time, etc. required for commissioning.

(9) Prepare the safety protection equipment necessary for commissioning operation.

B screw chiller commissioning

(1) Charge of refrigerant.

At present, the refrigeration unit is generally filled with refrigerant before leaving the factory. After the installation on site, if no accidental damage is found in the visual inspection, the relevant valve can be opened directly (you should read the manufacturer’s instruction manual first, in transit, on the unit).

The valve is normally in the off state for commissioning. If the refrigerant has been leaked or insufficient, first find the leak point and eliminate the leak, then add the required grade of refrigerant according to the product instruction manual. Note that the refrigerant charge should meet the technical requirements.

(2) Some users are charged with refrigerant on site, and the refrigerant charge and refrigerant grade must be in accordance with regulations.

The refrigerant charge is insufficient. Will result in insufficient cooling. An excessive refrigerant charge will not only increase the cost but also adversely affect the operating energy consumption.

(3) Before charging the refrigerant, sufficient refrigerant should be prepared in advance. When filling, it can be directly charged from the special filling valve.

Since the system is in a vacuum state, the pressure difference between the refrigerant and the system in the cylinder is large.

When the valve is opened (the air in the connecting pipe should be blown out with the refrigerant first, so that the air does not enter the screw chiller unit and affect the performance of the unit), the refrigerant is quickly replaced by the cylinder.

In the flow system, after filling, the liquid filling valve should be closed first, and then the connecting pipe should be removed.

Screw chiller starting up and operation

  • Check the oil level and oil temperature of each screw compressor: the oil level is 1/3~2/3; the oil temperature is 50°C~60°C, and the hand heater should be hot.
  • Check the main power supply voltage and current: the power supply voltage is in the range of 340V ~ 480V; the three-phase voltage unbalance value <2% (> 2% absolutely can not be turned on); the three-phase current unbalance value <10%.
  • Dynamic chilled water pump and cooling water pump: After the circulation of the two water systems is established, adjust the opening of the evaporator and condenser inlet and outlet valves.
  • Check the chilled water supply temperature: Whether the set value is suitable or not, it can be changed.
  • Check before screw chiller starting: Check the tightness of the electrical joint (main circuit, control circuit), at least the oil tank should be heated for 24 hours so that the oil tank temperature can not be lower than 38 degrees.
  • Check before screw chiller starting: Check the status of each valve of the screw chiller unit, water pump, pressure gauge, thermometer, filter, etc.
  • Check before screw chiller starting: Check the end of the whole screw chiller unit. Check the condition of the cooling tower if you are operating the water cooled screw chiller.
  • Check before screw chiller starting: firstly open the chilled water pump and cooling water pump of the water system to check whether the water system is running normally, ensure that the gas is not entrained, and ensure that the water pressure drop of the water system is within the required range.

Monitoring and adjustment of screw chiller operation

For screw chillers, the following should be mainly concerned during operation:

1. The temperature and pressure of the chilled water inlet and outlet of the evaporator.

2. The temperature and pressure of the condenser cooling water inlet and outlet.

3. The pressure and temperature of the refrigerant in the evaporator.

4. The pressure and temperature of the refrigerant in the condenser.

5.Electrical current and voltage of the main motor.

6. The pressure and temperature of the lubricant.

7. Is the screw chiller unit running smoothly, is there any abnormal noise?

8. Whether the valves of the screw chiller unit have leaks.

9. Is the joint with each water pipe tight?

From the above, the most important is Danfoss expansion valve adjustment. Here are some tips for you on how to adjust the thermal expansion valve of your screw chillers:

1. The evaporator outlet should use the thermometer to measure the temperature or look at the suction pressure to check the superheat.

2. Danfoss expansion valve adjustment superheat is too small (supply volume is too large), the adjustment rod should be rotated clockwise half a circle or a circle (ie increase the spring force, reduce the valve opening), increase the degree of superheat, so that Reduced refrigerant flow;

The number of turns of the adjusting rod thread at one time should not be too much (the adjusting rod thread rotates one turn, and the superheat degree changes about 1-2°). For the same reason, reduce the superheat degree counterclockwise and increase the cooling capacity.

3.Danfoss expansion valve adjustment experience:

Turn the adjusting rod thread to change the opening of the valve so that the evaporator can just be frosted or dew on the outside of the return pipe.

For a screw chiller with an evaporation temperature lower than 0 degrees, if it is touched by hand after frosting, there is a feeling of coldness that sticks the hand, and the opening degree is appropriate; for the evaporation temperature above 0 degrees, the condensation is visible. The judgment of the situation.

4. The correct commissioning of Danfoss expansion valve directly affects the cooling effect and energy saving of the cold storage. The cooling of the cold storage is slow, mostly the improper adjustment of the Danfoss expansion valve.

According to the thermal properties of the refrigerant, the lower the pressure, the lower the corresponding temperature; the higher the pressure, the higher the corresponding temperature. Among them, the adjustment of the Danfoss expansion valve is the most critical.

The opening degree of the Danfoss expansion valve is small, the flow rate of the refrigerant is low, and the pressure is low; the opening degree of the Danfoss expansion valve is large, the flow rate of the refrigerant is high, and the pressure is high.

If the expansion valve outlet pressure is too low, the corresponding evaporation pressure and temperature are too low. However, due to the decrease in the flow rate into the evaporator, the pressure is reduced, the evaporation rate is slowed down, the cooling capacity per unit volume (time) is decreased, and the cooling efficiency is lowered.
Conversely, if the expansion valve outlet pressure is too high, the corresponding evaporation pressure and temperature are too high. The flow rate and pressure entering the evaporator are increased. Because the liquid evaporates excessively, the excessive moisture (or even liquid) is sucked by the compressor, causing the wet stroke (liquid blow) of the compressor, causing the compressor to fail to work normally, resulting in a series of work. Bad conditions, even damage the compressor.

Therefore, the opening degree of the expansion valve should be adjusted according to the current water temperature, that is, adjusted under the pressure corresponding to the water temperature.

The expansion valve must be carefully and patiently adjusted. The pressure must be transferred to the pressure gauge after passing through the evaporator to the water temperature for boiling exchange (evaporation) and then entering the compressor suction chamber through the pipeline. It takes time.

Each time the expansion valve is mobilized, it usually takes 10~15 minutes to stabilize the adjustment pressure of the expansion valve on the suction pressure gauge, and the adjustment cannot be rushed. The suction pressure of the compressor is the main parameter for adjusting the pressure of the expansion valve.

It is usually prone to failures such as clogging of the filter, leakage of the temperature sensitive agent, and the like. The adjustment reaction is not sensitive, the adjustment is out of control or cannot be adjusted.

When frost is formed at the inlet of the expansion valve (or the valve cover is also frosted), the temperature of the inlet pipe is lower than normal temperature, or even condensation;

The suction pressure of the compressor is lower than the corresponding pressure at the storage temperature, the screw chiller operating temperature and the exhaust temperature is high, and the cooling temperature drops slowly or can not be lowered, mostly due to the filter plugging of the expansion valve or the dirty plugging failure.

Conclusion

As a leader in screw chiller manufacturing, TopChiller having 20 years experience in design and making screw chillers.

We have a complete of screw chiller models and cooling capacity from 50Ton to 100Ton-150Ton-200Ton can even up to 300Ton and 500Ton Max.

Both air cooled screw chiller and water cooled screw chiller from manufactured by TopChiller are featuring precision workmanship, compact design and high cooling efficiency.

All the refrigeration major components from screw chiller designed by TopChiller are world-first refrigeration brands.

We are willing to provide technical support to all clients, we have both standard and custom designs in air screw chiller and water screw chiller.

Contact our refrigeration engineering to help you get suitable screw chiller design and solution.

Get TopChiller Quotation