Environment damage due to Refrigerant R-134a released in mechanical room

Incident Date April 30, 2019

Location: Vancouver

Regulated industry sector: Boilers, PV & refrigeration - Refrigeration

Impact

Injury

Qty injuries: None

Injury description: No injuries

Injury rating: None

Damage

Damage description: Accumulating environment damage due to Refrigerant R-134a released in mechanical room.

(R134a is an inert gas used primarily as a refrigerant for domestic refrigeration and automobile air conditioners. It first appeared in the early 1990s as a replacement for CFC-12 (also known by its trade name Freon), which has ozone depleting properties.

Damage rating: Insignificant

Incident rating: Minor

Incident overview

On April 30, 2019 the service providers replaced two safety valves on this chiller as part of the plants preventative maintenance program.

On May 9th 2019 the service provider returned to this site to perform an unrelated servicing and noticed that the chiller refrigerant circuit had low operating pressure.

A leak detection test was initialed and the leak was traced to the safety valves that were previously replaced. These two safety valves were replaced and the system re- charged with 35 pounds of R134a refrigerant to restore the system charge to a total charge of 120 pounds.

Investigation Conclusions

Site, system and components

This machine room consists of a skid mounted double direct system suppling chilled water to the building cooling system.

Refrigerant used in this chiller unit does not leave the refrigeration machinery room. The chilled water is produced by expanding liquid refrigerant R-134a into a plate heat exchanger called an evaporator, the refrigerant absorbs heat from the chilled water side of the plate heat exchanger which is cooled to approximately 5 Deg. C. Water is pumped into the building chilled water piping system. The chilled water circulates between the building cooling radiators, picks up heat by cooling the occupied space ai then the warmer water flows back to the chiller unit where this cycle is repeated.

Failure scenario(s)

During a preventative maintenance cycle for this chiller unit, the refrigerant side safety valves were replaced by the service providers on April 30th, 2019.

The service providers returned to this site on May 9th, 2019 for unrelated service activities, and noticed that the one of the two refrigeration circuits was low in refrigeration gas pressure. The technician did a leak check and found both of the newly replaced safety valves where leaking.

Facts and evidence

· April 30, 2019 the service providers replaced two safety valves on this chiller as part of the plants preventative maintenance program.

· On May 9th 2019 the service provider returned to this site to perform an unrelated repair and noticed that the chiller refrigerant circuit #2 had low gas operating pressure.

· Gas loss was traced to leaking safety valves recently replaced during a scheduled maintenance cycle.

· The newly installed safety valves were found leaking, and as they were the only pressure side that was touched these are the most likely point of leakage. This was proven by the technician doing a bubble test of the two valves (see photo)

· The leaking valves were removed from service and the chiller left shut-down and out of service, waiting for approval of the new valves.

· The service provider removed these valves and shipped them back to the chiller manufacturer, this was done without the Owners approval, nor was the local BSO given the opportunity to visually inspect these valves, their condition is left to the services providers recollection.

· Report from original value manufacture inclusive in findings

· Testing form submitted by service contractor documents leak test performed at 100 PSI

Causes and contributing factors

It is likely that when the safety valves were replaced during the routine maintenance by service provider if a leak test was performed at 250 PSI this could have eliminate the loss of refrigerant in the machine room. Only tested to 100 PSI the set pressure is 350 PSI

PSI definition: PSI is a unit of pressure expressed in pounds of force per square inch of area. It stands for Pounds per Square Inch

 

Figure 1- Safety valves showing gas bubbles