dhananjay aar webinar series ii[1] (read-only) · 2020-06-04 · dhananjay s. deshpande technex...

6/3/20

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Advantage Ammonia

Dhananjay S. Deshpande

Technex HVAC&R Engg Works304, Om Shivshakti CHS, Sector-6, Khanda colony

West, New Panvel – 410206Mobile no: 09833889734 / 09769288737

Email: [email protected]@gmail.com

1AAR Webinar II - 04 June 2020

} There are mainly two types of compressor’s are used in Ammonia i.e. Screw and Reciprocating

2AAR Webinar II - 04 June 2020

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AAR Webinar II - 04 June 2020

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} Compressor failure is a big, expensive problem in the refrigeration & Air conditioning industry. Compressor manufacturers, repairer are concerned about failure of their product & services, since it can reflect negatively on them.

} Most of the Compressors were still being “killed” by system problems. System problems, if corrected, would have saved the compressor.

} Replacement of compressors failed at a rate of four times greater than that of original compressors if we are not taking proper care.


} The Compressor } Each compressor manufacturer specifies application limits in

which the compressor may be operated safely. The most important limits are protected by safety controls and the operator must make himself familiar with the operation, set point and function of the following:

} A. Low (suction gas) pressure cut-out } B. High (discharge gas) pressure cut-out } C. Low differential oil pressure cut-out } D. High oil temperature cut-out } E. High discharge temperature cut-out } F. Any additional safety controls which may be fitted


} Temperature or Pressure Changes } Many factors such as mechanical malfunction, ambient temperature,

or product load can have an effect on the normal operating temperatures/pressures of the refrigeration system. Every plant operator should understand:

} 1. The normal operating pressures & temperatures in system } 2. The causes and effects of a change in temperature or pressure in

system: } The low pressure (low side) part of the system } The intermediate pressure part of a two-stage system } The high pressure (high side) part of the system } 3. what action to take upon a change in temperature or pressure in

order to restore the system to normal





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• Incorrect application• Incorrect design, installation and operation.• System component failures or application• Malfunctioning, improperly applied or wrong settings in

controls.• Improper maintenance• Incorrect diagnosis



• Most Failures are preventable!

• Compressor failures can normally be traced back to:

o 1. Refrigerant Slugging / Flooded start o 2. Flood backo 2. Lack of Lubricationo 3. System Contaminationo 4. Overheating

} Many compressors run thousands of hours with out oil changes, new parts, a tune up or any other form of maintenance.

} Preventative maintenance is the key to compressorLongevity.


} Slugging always occurs on startup, but a very rapid change in system operating conditions can also cause slugging.

} A loud knocking noise heard at the compressor start up is evidence of slugging. The noise is produced by hydraulic compression – the compressor is trying to do something it wasn’t designed to do – compress a liquid.



} Refrigerant will condense in any cold part of a system during the off cycle. The coldest parts of the system are the evaporator and suction line. On the next start-up, this liquid mixture will return to the compressor as a slug.

} Extremely high pressure will be reached in a cylinder. A hole may be punched in the top of a piston. More often, the suction, discharge, or both valve reeds will be bent or broken.

} If a compressor continues to run with this damage, the cylinder head will found very hot compared to any other cylinders. Slugs can break connecting rods, even crankshafts.


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} Improper setting / installation of level controllers or hand expansion valve.

} Also liquid slugging can prevent by installing correct size of accumulator or surge drum in suction line.


} Flooding is the continuous return of liquid refrigerant as droplets in the suction vapor instead of all super-heated vapor.

} This flood back washes oil off of piston and cylinder liner surfaces.

} All bearing surfaces will prematurely wear. Resulting in Overheating of compressor component.

} On a compressor with a crankcase sight glass, flooding can be observed as constant foaming of the oil during run.



Liquid floodingCauses radial forces on therotors and lendthem to seize in the housing on the flange and slider

} Avoid low load on the evaporator. } Oversized Metering device} Head pressure too high and or low pressure too low} Low flow through Evaporator } Oversized system


} Major cause of compressor failure could be Loss or lack of lubrication, especially if we include flood back and flooded starts. Other causes of lack of lubrication could be as simple as not enough oil in the crankcase.

} During operation, always oil leave should be visible in the crankcase, separate oil from ammonia in oil separator and returning to the compressor at the same rate that it left the compressor.


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Due to loss of the oil film from cylinder liner, rubbing happens between piston rings and cylinder liner and cylinder liner dimeter increases.


} Maintain adequate oil level in the compressor sump or in oil separator in case of screw compressor.

} Reasons for oil carryover in the system is that the oil separator mal functions, worn out piston rings. Check and correct the above mentioned causes.

} Oil pump failure or dirty oil filters in the compressor, repair/replace the pump and oil filters.


} Contamination was found to be the major cause of compressor failure.

} Refrigeration system should contains only two things should be inside is refrigerant and oil. Anything else is a contaminant!


} The presence of water in a system can lead to other contaminations due to the formation of oxidation, corrosion, the refrigerant decomposition.

} Chemical breakdown results from excessive heat , results in oil and refrigerant breakdown, Ferric oxide (Fe2O3) - (Red iron oxide) or Ferrous oxide (Fe2O4) -(iron oxide black), acid formation creates higher wear of the bearing surfaces.



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• If the heat Is high enough, the oil breaks down chemically.

• Compressors should operate within the safe limits of the discharge temperature.

• Oil and refrigerant break down In severe overheating and create CARBON and ACIDS, Which can cause harm throughout the entire system.






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Increased friction, resulting in excessive wear, excessive energy consumption, and the possibility of premature breakdown of equipment

Excessive wear on bearings and seals, leading to premature failure

Premature shaft and coupling failure

Excessive lubricant leakage from shaft seal

Failure of coupling and foundation bolts

Increased vibration and noise



Points to be checked on compressor are:

Drive end Male rotor bearing section, fe-male rotor bearing sectionNon-drive end Male rotor bearing section, fe-male rotor bearing sectionOil injection pointCenter of the compressorNear shaft seal on rotor shaft

Effects of vibrations:

Premature failure of the compressor, bearings failure, screw rotors failure, gas & oil leakage from mechanical joints on the compressor and breakages on the pipes connected to the compressor

} The most important factor contributing to a safe operation may be the operator's knowledge of preventive maintenance. Each component of a system requires routine checking, cleaning and possible replacement.

} Periodic checking / changing of oil} Check pressure drops across condensers and chillers} Draining of oil from various components} Purging of non-condensable gases} Checking of safeties} Removal of scales from condensers} Checking of Vibration levels in the compressor} Annual checking of the compressors as per manufacturers

guidelines.


} Daily:

} HP, LP & OP pressure

} Refrigerant level and oil level

} Water level in cooling tower / evaporative condenser

} Flow of media to be cooled

} Specific gravity of brine.


} Weekly:

} Cleaning of filters, strainers of pumps, sump of the cooling tower or evaporative condenser if required.

} Checking tension of compressor drive belts.

} Checking the proper oil return to the compressor from oil separator.


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} Monthly:

} Air purging

} Draining of oil

} Sump cleaning of Cooling tower / evaporative condensers

} Checking of oil filters, liquid line strainers.


} Quarterly:

} De-scaling of condenser.

} De-scaling of water jacket of compressor head.

} Cleaning of pump impeller.

} Greasing of motors, pumps.

} Adjust belt tension of compressor and motor if required.


} Half Yearly:

} Checking of earth leakages.

} Cleaning of switch gear contacts and electrical panels.

} Checking of compressor and motor alignment.


} Yearly:

} Replacement/checking of internal parts of compressor

} Pressure testing of receiver, oil separator & condenser – factory act.

} Painting of equipments and pipelines as per standard colour code with arrow mark.

} Pipe line insulation repair / replacement.


To avoid repeated compressor failure, repair work on site may only be carried out if the fault is exactly known other wise serious damage to the compressor.

Possible Repair Works:q Exchanging the check valve

q Exchanging the pressure relief valve

q Exchanging oil flow switch / oil level switch

q Repairing / replacement of shaft seal.

q Checking the thrust bearing clearance


m Oil Filter – & Replacement

m change after first 50...100 h (operating hours) recommended

m check all 5.000 h (or yearly respectively)

l replace in case of pressure drop > 0.5 bar

m Oil Changem With NH3 (unsoluble lubricants)

l first change after 100 running hours (oil and oil filter)

l topping when required -- change after approx. 3000 running hours (or yearly respectively)


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m Shaft Sealm Leakage tolerable up to 0,2 cm3/hm Inspection intervals -- depending on application

l MT & LT all 10.000 h

m Replacement after 20.000 .. 40.000 hrs. recommended

m Pressure Relief Valvem Maintenance free

l Opening pressure differential Dp = 28 barl Tightness check recommended after actuation

(è High pressure cut-out) m Replacement after 100.000 h recommended



Thank You

Technex HVAC&R Engg Works

Dhananjay S Deshpande

Email [email protected]@gmail.com

mailto:[email protected]

dhananjay aar webinar series ii[1] (read-only) · 2020-06-04 · dhananjay s. deshpande technex...

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