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refrigeration compressor refrigeration's blog: April 2009

Tuesday, April 14, 2009

condensor,evaporative condenser and water cooled condenser

CONDENSOR

In the condenser,the compressed refrigerant vapours emit the heat collected in the evaporator and during compression.Condensation heat is removed by either cooling water or cooling air.
Poor condenser cooling leads to reduced compressor capacity and increase power consumption.The increased discharge pressure reduce the expected lifetime of the compressors and can even cause some of the components to explode.
However,too much condenser cooling reduces the discharge pressure.
Air cooled condensers
Air cooled condensers can be regulated as follows :
a. Controlling the fan speed,either by start/stop or with pole-changeable motors (the first method is to be preferred).
b. Using dampers to throutle the air flow.
c. Partially filling the condenser with liquid refrigerant. An automatic valve is used to limit the condenser discharge. This method is particularly good when the refrigeration plant is only slightly loaded.
d. The condenser can be split into sections,which can be coupled out and.
Water cooled condensers
Water cooled condensers can be regulated by throttling the flow of water through the condenser.
a. Manual regulation is considered to be adequate in many cases-a more or less constant discharge temperature can be maintained. A two or three way regulating valve can be fitted in the by pass.
b. Automatic water valves :
- Directly pressure controlled
Two way water valves are used in plants with small compressor nits or if cooling water is readily available.
The amount of water is regulated by impulse from the discharge pressure,the valves opens when the pressure rises and shuts when it falls.
- Temperature controlled
In a temperature regulated water valve,The amount of cooling water is regulated by a servo valve which receives impulses from sensor,place in the return line after the condenser. A three a way valve is often fitted in the by pass to ensure that the pump supplies a constance amountof water.

Friday, April 3, 2009

Reciprocating compresor,grasso.sabroe,mycom,bitzer

Refrigeration compressor, troubleshooting for piston compressor grasso,mycom,sabroe,bitzer

A. High suction pressure
Occurs when the gas formation on the evaporator side exceeds the compressor pump capacity in the operating area in question. The reason may be due to the load on the evaporating side being larger than expected,or a mechanical fault in the compressor causing reduced pump capacity.
1. Excessive suction pressure
1.1. The compressor is short of capacity
1.2. Leaky suction valves
1.3. Open by-pass between suction and high pressure sides of the compressor. Leaky safety valve,or the safety valve opens to early.
1.4. Liquid regulator valve set incorrectly.
Remedy :
1.1. Regulate the compressor capacity. Check that all cylinders are working. Check to see if the capacity regulator is working correctly.
1.2. Remove the cylinder covers,then check the valve plates and piston rings.
1.3. Check to see if there is any by-pass in the system.
1.4. Liquid refrigerant in the suction line.Reset,repair or replace the regulating valve.

2. Low suction pressure
An abnormally low suction pressure causes the compression ratio to change,Which in turn many cause damage to the compressor. If there is low pressure in the system (vacuum) air may be drawn into the refrigeration plant.
Low suction pressure results in reduced compressor capacity.
Insufficient suction pressure
2.1. Excessive compressor capacity.
2.2. Insufficient refrigerant charge bubbles appear in the sight glass, an the liquid line may be warm.
2.3. Oil in the evaporator.
2.4. Clogged filter in the liquid line.
Remedy :
2.1. Reduce the compressor capacity.Check the capacityregulation system.
2.2. Check the refrigerant charge.Charge the plant with refrigerant.Locate the leak and repair it.
2.3. Check and clean the filter in the liquid line.