TROUBLE SHOOTING OF REFRIGERATION

1. DISCHARGE PRESSURE TOO HIGH

    a.  Dscharge stop valve not fully open. remedy open fully

    b. Discharge pressue gauge defective. remedy repair or replace

    c. Non condensable in the system. remedy purge with automatic purge

 REFRIGERATION
Basic refrigeration
The job of a refrigeration plant is to cool articles
or substances down to, and maintain them at a
temperature lower than the ambient temperature.
Refrigeration can be defined as a process
that removes heat.
The oldest and most well-known among refrigerants
are ice, water, and air. In the beginning, the
sole purpose was to conserve food. The Chinese
were the first to find out that ice increased the life
and improved the taste of drinks and for centuries
Eskimos have conserved food by freezing it.
1. Introduction
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heat heat
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Danfoss
R64-1869.10
At the beginning of the last century, terms like
bacteria, yeast, mould, enzymes etc. were known.
It had been discovered that the growth of microorganisms
is temperature-dependent, that
growth declines as temperature falls, and that
growth becomes very slow at temperatures below
+10 °C.
As a consequence of this knowledge, it was now
possible to use refrigeration to conserve foodstuffs
and natural ice came into use for this purpose.
The first mechanical refrigerators for the production
of ice appeared around the year 1860. In
1880 the first ammonia compressors and insulated
cold stores were put into use in the USA.
Electricity began to play a part at the beginning
of this century and mechanical refrigeration
plants became common in some fields: e.g. breweries,
slaughter-houses, fishery, ice production,
for example.
After the Second World War the development of
small hermetic refrigeration compressors evolved
and refrigerators and freezers began to take their
place in the home. Today, these appliances are regarded
as normal household necessities.
There are countless applications for refrigeration
plants now. Examples are:
Foodstuff conservation
Process refrigeration
Air conditioning plants
Drying plants
Fresh water installations
Refrigerated containers
Heat pumps
Ice production
Freeze-drying
Transport refrigeration
In fact, it is difficult to imagine life without air
conditioning, refrigeration and freezing - their
impact on our existence is much greater than mos people imagine

Components of Refrigeration Systems

Refrigeration compressor

The refrigeration process is, as implied, a closed
circuit. The refrigerant is not allowed to expand to
free air.
When the refrigerant coming from the evaporator
is fed to a tank the pressure in the tank will
rise until it equals the pressure in the evaporator.
Therefore, refrigerant flow will cease and the temperature
in both tank and evaporator will gradually
rise to ambient.
To maintain a lower pressure, and, with it a lower
temperature it is necessary to remove vapour.
This is done by the compressor, which sucks vapour
away from the evaporator. In simple terms,
the compressor can be compared to a pump that
conveys vapour in the refrigeration circuit.
In a closed circuit a condition of equilibrium will
always prevail. To illustrate this, if the compressor
sucks vapour away faster than it can be formed in
the evaporator the pressure will fall and with it
the temperature in the evaporator. Conversely, if
the load on the evaporator rises and the refrigerant
evaporates quicker, the pressure and with it
the temperature in the evaporator will rise.

evaporator

EVAPORATOR
A refrigerant in liquid form will absorb heat when
it evaporates and it is this conditional change
that produces cooling in a refrigerating process. If
a refrigerant at the same temperature as ambient
is allowed to expand through a hose with an outlet
to atmospheric pressure, heat will be taken up
from the surrounding air and evaporation will occur
at a temperature corresponding to atmospheric
pressure.
If in a certain situation pressure on the outlet side
(atmospheric pressure) is changed, a different
temperature will be obtained since this is analogous
to the original temperature - it is pressuredependent.
The component where this occurs is the evaporator,
whose job it is to remove heat from the surroundings,
i.e. to produce refrigeration.

Components of Refrigeration Systems

Components of Refrigeration Systems
a. Compressor
b. Condenser
c. Evaporator
d. Refrigerant Piping
e. Liquid Circulation
f. Valves and Refrigerant Control

refrigeration compressor,mycom,,sabroe,bitzer,grasso, Insufficient refrigerant charge :

 Insufficient refrigerant charge :
1.Abnormally warm liquid lines :
  When the liquid level in the condeser/
  receiver falls below the liquid line outlet,
  a mixture of liquid and warm high-pressure
  gas will full the liquid line.
2.Bubbles in the sight glaas in the liquid line :                                                                                                     The gas/liquid mixture is visible in the sight
   glass.large bubbles indicate that it is
   necessary to recharge with refrigerant.
   The gaseos mixture in the liquid line
   often leads to noise in the expansion valve.
3.Low suction pressure :
   The tremperature in the refrigeration system
    at the cooling surface and in the suction
     line will be relatively high in relation to the
     suction pressure observed, due to reduced
     supply of refrigerant to the evaporator
4.Reduced plant capacity.
5.Low discharge pressure :
   Reduce the condeser cooling. if the
   discharge pressure does not rise quickly,
   three may be insufficient refrigerant in the
   plant.

INSUFFICIENT OIL PRESSURE

INSUFFICIENT OIL PRESSURE
Oil discharge valve set too low
Remark : The oil pressure does notsufficiently to move the unloading piston
               Set the oil pressure correctly   
Insufficient oil in the compressor
Remark : Insufficient oil in the compressor can mean that the oil pressure does not rise sufficiently to       move the unloading pistons.
Charge the compressor with oil and check the reason for oil consumption                   

Refrigeration compressor runs continuosly

1. Thermostat or low-pressure switch do not cut out when the temperature is too low.
2. Limited supplyof refrigerant to the evaporator.The compressor is running with insufficient suction pressure.
3. Insufficient refrigerant.

Remedy :

1. Operating set points should be adjusted
2. Clean the filters and check to ensure that the expansion device is working correctly
   

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There are almost no limits to the ways in which refrigeration technology can be applied, for example :

1. Food processing industry
2. Multi purpose cold stores,cooling and freezing systems
3. Breweries,maltings and the beverage industry
4. Slaughterhouses
5. Ice plant
6. Ice rinks
7. Ice cream factories
8. Marine application
9. Air conditioning system
10. Concrete cooling
11. Chemical,pharmaceutical and metalurggical proceses
    

condensor,evaporative condenser and water cooled condenser

To determine whether it is necessary to purge the plant,the refrigeration plant must be stopped until all components in the system have reached the same temperature.
The proceed as follows :

1. Stop the compressor,for at least two hours.
2. Close the compressor suction stop valve and any valves between the condenser and receiver.
3. Loosen the pressure gauge in order to check it.
4. Start the cooling pump.After a short time,measure the temperature of the cooling water,which should then be compared with the reading onthe pressure gauge.If the pressure gauge shows a higher pressure than that which corresponds to the cooling water temperature,non condensable gases are present in the condenser.
5. The gases should be purged from the top of the condenser by carefully opening the purging valve or perhaps loosening a screwed connection or something similiar.
6. Repeat the purging process a few more times,at intervals of 3-4 minutes during which the cooling water should run continuously as any water valves which may be installed can otherwise become blocked in open position.
7. If purging is constantly required,please check the plant for leaks.

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.

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.

refrigeration compressor,mycom N62WB,N8WB,N62WA,N4WA,N2WA,N6WA,N42WA,N8WA,N4WB,N6WB,N42WB,N12WB,N124WB,grassoRC2112,RC4212,RC6312,RC8412,sabroe,bitzer

Trouble shooting for refrigeration compressor, mycom,grasso,sabroe,bitzer,carrier,Copeland.

Abnormal pressure in the refrigeration system may damage the refrigeration compressor. At excepcionally high pressure various parts of the plant may explode.
A. Abnormally high pressure
High pressure may be due to :
- parts of the plant being heated externally,e.g.during defrosting or because of higher ambient temperatures (as a consequence of fire,heat radiation from sun or other sourches of heat)
- Expansion of liquid in closed vessel, due to an increase in temperature.
- Or with liquid pumps,the flow of liquid may be restricted e.g by a blockage in the pipe line,clogged filter or overcharging of a vessel
B. Excessive discharge pressure
Excepcionally high discharge pressure may be due to :
- poor condenser cooling e.g.due to failure in the cooling water,blockedfan/cooling water pump,impurities,chalk deposits or deposits on the surfacewhich conduct heat.
- The presence of gases (especially air) in the condenser which cannot be condensed.
- Excessive refrigerant charge.
Remedy :
- Regulate the water/air supply or, if necessary reduce the compressor capacity.
- Purge the air from the condenser.
- The refrigerant fills the condenser,reducing its effective area.
C. Low discharge pressure
Reducing the discharge pressure cause the volumetric efficiency of the refrigeration plant to increase,or increases the compressor capacity and reduces the compressor energy consumption.
However,it is often necessary to avoid low discharge temperatures.Low discharge pressure can increase the cooling water consumption to an unreasonable level, and result in operational problems due to insufficient pressure in the liquid line. A low discharge pressure will reduce the pressur drop through the expansion valves in the plant, or cause vapour to form ,which in turn means that the valves may not be able to supply the evaporators with a sufficient amount of refrigerant to meet the refrigeration requirements.
D. Insufficient discharge pressure
- Compresor short of capacity
- Defective or leaky pressure valves.
- Excessive compressor capacity.
- Bypass between the high pressure and suction side of the compressor.
- Defective piston rings or worn cylinder.
Remedy :
- Check the compressor capacity corresponds to the plant load.
- Check valve plates and piston rings,replace the worn parts.

mycom N8WB,grasso210,310,410,610,610/810,810/412,412/612,612,2x412/912,912,1212

Service and inspections parts refrigeration compressor mycom N8WB for block ice (31 januari 2009)
1. Before service and inspections parts,please follow general recommendations.
2. Remove suction filter and scale trap filter.
3. Remove oil filter and cuno filter
4. Remove oil cooler.
5. Open hand hole cover right side and left side.
6. Open head cover and water jacket.
7. And then remove safety head spring and and discharge valve.
8. Unscrew two nuts from the connecting rod bolt.
9. Insert The T-handle into the Threaded hole at the top of the piston and carefully pull the piston and connecting rod and cylinder sleeve at the same time.

refrigeration compresor,mycom N62WB,N8WB,N62WA,N4WA,N2WA,N6WA,N42WA,N8WA,N4WB,N6WB,N42WB,N12WB,N124WB,grassoRC2112,RC4212,RC6312,RC8412

THE OVERHAUL OF REFRIGERATION COMPRESOR

GENERAL RECOMMENDATIONS :
1. Before servicing compressor,the refrigerant has to be pumped down from the machine.
2. Use clean and well-conditioned tools.
3. Make sure that there is a clean and neatly arranged storage of dismantled components.
Immediately clean every dismantled
4. Dismantled parts of every cylinder (cylinder liner,piston,connecting rod,valves) or of other main components are to be kept together separately and marked if necessary.
5. Always replace damaged or worn compressor parts.
6. Always new gasket and O-ring when reassembling after inspection or repair.
7. Make sure the electric from main panel has cut off.
8. Close suction and discharge valve.
9. Drain oil from oil drain.