Double Shaft Seal

A shaft seal is a small part of the compressor, but it plays an important role in the refrigeration process. To put it simply, it keeps the dangerous refrigerant inside the compressor. When the shaft seal starts leaking refrigerant, production must be stopped.

Take a look at the refrigeration process.

1. COMPRESSOR: Refrigerant (e.g. ammonia gas) vapour in the compressor becomes compressed, causing it to rise in temperature approximately 10°C above outside ambient temperature. The high-pressure, high-temperature vapour then flows into the condenser.

2. CONDENSER: The refrigerant vapour, which is hotter than its surroundings, radiates heat. The vapour condenses and becomes a liquid.

3. RECEIVER: The receiver acts as a reservoir for the liquid refrigerant before the refrigerant becomes metered into the evaporator by a flow expansion device.

4. The liquid refrigerant expands, resulting in a temperature decrease to approximately 10°C below process requirements, and flows into the evaporator.

5. EVAPORATOR: In the evaporator, the low-temperature liquid absorbs heat from the surroundings and evaporates, becoming a liquid-vapour mixture at low temperature, and eventually evaporating completely, before returning to the compressor to begin the cycle again.

The shaft seal is located on the shaft of the compressor, which enters the the driver (E-motor) and protects refrigerant vapour from leaking into the atmosphere. The operating system and location of the shaft seal is the same for both reciprocating and screw compressors.

Do you know that 85% of mechanical seals fail prematurely and unexpectedly?

A shaft seal is the most vulnerable part of the industrial refrigeration system. When the shaft seal fails, the compressor needs to be stopped and immediately isolated from the installation. This creates unexpected work and reduces plant capacity.

RM Support offers a double shaft seal with a pre-warning system. Click here to read about a double shaft seal and to read about the reasons for shaft seal failure.