What is the cause of oil foaming in compressor crankcase at the time of starting?

When the compressor is started, the sudden reduction in crankcase pressure causes foaming of the oil-refrigerant mixture. Depending on the amount of refrigerant in the solution, this foam can fill the compressor housing and be pulled into the compressor suction.

What causes oil to foam in a compressor crankcase?

In general, foaming occurs when the oil-refrigerant mixture is exposed to a sudden pressure drop, as is the case in starting up a reciprocating compressor 1. The foaming oil may be sucked into a cylinder, which causes liquid compression and valve failure.

Why is it necessary that the crankcase heater heats the compressor crankcase before starting the compressor?

By using a crankcase heater to bring all of the fluids up to operating temperature before starting, the compressor motor can start easier and pick up where it left off. Without the crankcase heater, these compressors would have to work a lot harder during startup, potentially causing excess wear on the parts.

What are the causes of too much oil in a compressor?

Compressor Oil Level

Too much oil in the compressor can also cause oil trips. Excessive oil can cause enough turbulence in the crankcase to result in a low net oil pressure. In another twist of too much oil in the sight glass, the high level of oil may be caused by liquid refrigerant in the crankcase.

What causes liquid Floodback?

Floodback occurs when liquid refrigerant returns to the compressor during the running cycle. Often a service contractor may see a compressor that failed due to floodback, but because of the severity of the damage, he may misdiagnose the problem.

oil catch can condensation Explained WARNING not a blown head gasket

How do you stop a compressor Floodback?

Refrigerant migration to the crankcase may also result in liquid slugging during start-up. Although refrigerant migration and floodback can be prevented by adding a suction accumulator to the system, accumulators may also flood in a severe flooding condition.

What happens if liquid enters compressor?

In reciprocating compressors, when a large volume of liquid appears inside the cylinder, and the piston cannot expel it through the discharge valve during the short duration when it is open, it leads to excessive pressure buildup inside the cylinder.

What is the effect if the oil return from oil separator to the compressor is blocked?

Oil filters are often installed in the oil return line between the oil separator and the compressor. If this filter is blocked it can lead to excessive oil carry-over, which affects heat transfer in the evaporator.

What causes oil logging?

Too high of a viscosity oil will also be hard to return from an evaporator and will surely cause oil logging. Usually, the heat from the defrost heaters will warm and thin the oil in the evaporator so it can be returned to the compressor once the compressor starts up.

What is a compressor crankcase heater?

The crankcase heater is an electric resistance heater that is usually strapped on, clamped to the crankcase bottom, or inserted into a well within the compressor's crankcase. The crankcase heater is often seen on compressors that operate in ambient temperatures lower than the system's operating evaporator temperature.

When should crankcase heater energized?

The crankcase heater must be turned on a minimum of 12 hours prior to starting the compressor. This will prevent oil dilution and bearing stress on initial start-up. The crankcase heater must remain energized during compressor off cycles.

What causes slugging in a compressor?

Slugging can result in broken valves, broken head gaskets, broken connecting rods, and other major compressor damage. Refrigerant-cooled semi-hermetic compressors will often draw liquid from the suction line through hot motor windings in the motor barrel, which will assist in vaporizing any liquid.

How do I stop my compressor slugging?

The single best device to protect the compressor from slugging and floodback is the suction line accumulator. Accumulators are most often found on low temperature systems, but all refrigeration systems can benefit from this relatively low-cost protective device.

How do you prevent flooding and slugging?

How do you prevent flooding and slugging? Keep superheat at proper levels.

What causes compressor valves to fail?

Some mechanical causes of compressor valve failure are: Spring failure: A wear down of the spring attached to the valve, due to stress could cause the improper functioning of the valve. High-cycle fatigue: The compressor's operation at high cycles over a long time can lead to stress which could affect the valve.

Which of the following symptom S would be indicative of an oil logged condenser?

Which of the following symptoms would be an indication of an oil logged condenser? High discharge line pressure and low liquid line pressure.

How do I know if my evaporator is oil logged?

What is an oil separator on a compressor?

Definition – The air oil separator is a filter like part which separates the oil from the compressed air. Function – During compression oil is injected to lubricate, seal and absorb the heat of compression, then what comes out of the compressor element is a mixture of compressed air and oil.

How do you check the oil pressure on a compressor?

To find out, simply subtract the crankcase pressure from the oil pump discharge pressure to get net oil pressure. In this case, it would be 80 psi – 20 psi = 60 psi net oil pressure.

What causes black oil in AC compressor?

Over time, moisture contamination in an A/C system will form corrosive acids that attack metal surfaces and break down the lubricating qualities of the compressor oil. The result is a dark-colored sludge called “Black Death” that can gum up the orifice tube or expansion valve and ruin the compressor.

How does liquid refrigerant affect the compressor crankcase?

When the compressor does turn on, the sudden pressure drop on the crankcase containing liquid refrigerant and oil will cause the refrigerant in the oil to flash to a vapor. This causes violent foaming in the crankcase.

What is the difference between slugging and flooding?

What is the difference between flooding and slugging? Flooding is a little liquid refrigerant reaching the compressor; slugging is a lot of liquid refrigerant reaching the compressor all at once.

Can liquid damage compressor?

Entering the cylinder liquid refrigerant may damage the reed valve, piston connecting rods, crankshaft, etc. It even leads to total Compressor failure.