Refrigeration and Air Conditioning Pressure Vessels: The Importance of In-Service Inspection

September 13, 2018

Primarily used on closed-loop refrigeration and air conditioning systems, the pressure vessels described here are constantly under attack from a number of processing factors. If those changes should affect the vessels adversely, the subsequent pressure changes will likely weaken a weld seam or cylindrical plate. Monitoring such events, on-site inspections prevent such dynamic processes from impacting these crucially important system fittings.

The High-Pressure Refrigeration Cycle

Fans and expansion valves function inside large-scale refrigeration units. The vapour compression cycle is underway, and there's a lot going on inside the pipes and evaporator coils. Above or adjacent to the expansion tank, a compressor is activating everytime the pressure drops below a predetermined threshold. Ignoring the physics of the matter for the moment, gases are condensing then expanding. Hot liquids are flowing, and the condenser/evaporator assemblies are being pressed hard by this state changing cycle.

Ammonia Hazards

In the air conditioning frame, a furnace is drawing fuel from a large tank. Another vessel is storing heated water, so there's a heat exchanger inside the equipment. Somewhere nearby, another pressure vessel is discharging a chill. This is the refrigeration receiver. Every one of these cylinders is experiencing transitory pressure changes, not like a plain storage tank, which maintains a nice, predictable pressure spread. On top of these varying on-site fluid forces, there's the refrigerant medium to worry the in-service inspector. Ammonia, a respiratory, skin, and eye hazard, one that possesses corrosive properties, is flowing in the pipes and fittings. If the fluid stresses do cause a system breach, an ammonia leak could result in a deadly accident.

The Importance of In-Service Inspections

Let's not underestimate the design process, as it took place back at the factory. The commissioning stage tests every single pressure vessel to its limits and beyond. However, the forces in play inside a hard-working refrigeration and air conditioning system are uncompromising, and they work at durable cylinder profiles 24/7, every day, every week, and every year. As a pressure vessel expands and contracts, weld seams deteriorate. Then, faced with corrosive ammonia, the material base experiences additional fatigue. An in-service inspection, one that's conducted regularly, is required to track those fluctuating process dangers.

In-service inspections carry out non-destructive tests and some that are potentially destructive, should the results call for the extra assessment work. Then, if the site already has a planned maintenance program in service, the logbooks and documents used to record all notable system issues can also be utilized. They act as a trend indicator, one that indicates a future failure incident, as caused by the state changes in this industrially scaled refrigeration and air conditioning system.

Contact Details

Fusion - Weld Engineering Pty Ltd
ABN 98 068 987619

1865 Frankston Flinders Road,
Hastings, VIC 3915

Ph: (03) 5909 8218

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