REFRIGERATION SYSTEM
UNLOADING MECHANISM OF REFRIGERATION COMPRESSOR
When the compressor is not running then the control piston is not exposed to the lub oil pressure and the spring press the piston and thereby the whole frame to the right. the tension spring turn the lever arm clockwise and the lever inturn presses the unloading ring against the
small spring pressure to force the suction valve to be kept open.
when the compressor starts it get started in unloaded mode and as the pressure of lub oil increases and acts on the piston it forces the control piston to move towards left against the force of the spring to move the frame to left and removing tension from tension spring. this lead to movement of lever to left causing the unloading ring to move down dur to small spring pressure and the suction valve can now operate freely
Q) What are the methods of defrosting?
A)1. using electric heater
2. using water spray
3. switching off the compressor and let the frosting melt off by it own.
Q)What is a back pressure valve and why is it fitted?
A)Back pressure valve is a spring loaded non-return valve fitted on the outlet of the vegetable room to prevent the back flow of refrigerant from the meat room and fish room back to the veg room.
LEAKAGE TEST
It is done by two methods namely:
1. by soap solution method
2. by help of halide torch
RECHARGING OF REFRIGERANTfirst of all we should know that why the requirement of recharging of refrigerant came.The main reason can be leakage of refrigerant. hence before recharging leakage test is a must and once the leakage is found and rectified then only the recharging should be initiated:
PUMPING DOWN:Close the outlet ofthe reciever and keep the compressor running. let it run till the L.P cut out is not initiated. This way gas get collected in reciever.Once the cut out occur wait for a while and let the compressor start again. keep on collecting the gas in reciever untill the suction pressure gauge shows all most zero bar. Now close the suction and discharge valve and check the sigjt glass of reciever to check the amount of refrigerant in the reciever. if the gauge ia one-third full then no need of charging but if it is less the charging is required.
Method Of Charging
1.weight the bottle by hanging it upside down in a spring balance.
2. connect the filling pipe to the gas side valve of the bottle and purge it by refrigerant into a container made specially for collecting thia gas to avoid emiaaion of CFC into the atmosphere.
3.now open the filling valve and now open the gas valve of the bottle and check the weight of the bottle.
4.after filling some amount of gas close the filling valve.open the suction and discharge valve of compressor and start it again to collect all gas again to reciever. repeat process from point 3 again till the level in reciever is not satisfactory.
5.once the level is satisfactory open the discharge valve of reciever and start the plant normaly
TROUBLESHOOTING:-
2 responses to “REFRIGERATION”
Back or valve is not to prevent back flow from fish and meat it is to maintain veg room at positive temp as it’s said that veg freshness is lost if it’s cooled extremely
The refrigerant flow going inside fish room and meat room is more than veg room as they have to maintain less temp inside these 2 rooms. If back pressure valve is not there then from the outlet the refrigerant will flow to veg room leading to decrease in temp inside veg room which is not desirable