ARE YOU PERFORMING YOUR PSSR'S CORRECTLY?

A closure of an UV (shutoff valve) was provided in the design of the plant, to avoid two phase flow when carryover occurred.  During an abnormality, the shutdown system activated the UV but the UV did not close. The RCA revealed that the UV did not close due to excessive friction caused by the presence of construction debris left behind that prevented the UV from closing

WASTE WATER TANK INCIDENT

On September 9, 2003, Employees #1 and #2 were extending the guardrail system to the hatch and platform area on top of a tank located on the Brewery property. The tank was used for the storage of solid waste at the waste water treatment facility. The tank was 40 ft in height and 48 ft in diameter. The employees were arc welding the guardrail system, 40 ft above the ground, when an explosion occurred. Employee #1 fell to the ground receiving fatal injuries. Employee #2 fell to the inside of the tank, an opening of approximately 10 ft left due to the explosion. The tank had to be drained in order to recover the body. Employee #2 apparently died from injuries due to the explosion

Credit:Osha.gov

ARE YOU INSPECTING YOUR PILOT OPERATED VALVES CORRECTLY?

A Pilot operated relief valve failed to lift during planned recertification in the workshop. The cause of failure to lift identified as a plug fitted in the pilot exhaust port. Plug was removed from pilot exhaust port and RV functioned as intended.  On inspection of three remaining RV’s on compressor discharge, it was
found that another RV also had a plug fitted in the pilot exhaust port.

ARE YOU CONSIDERING HUMAN FACTORS DURING YOUR HAZARD IDENTIFICATION?

 An ammonia leak occurred in the machinery room of an unoccupied arena. An employee was attempting to add oil to an ammonia compressor when he observed a leak (fill hose was not attached). Approximately 200 lbs ammonia was released.
Qualified person was trained, but with minimal experience in this procedure. No written procedure was available, and an error occurred while executing the procedure. The shut-off valve type (wrench-operated,
mufti-turn, no position indicator) added complexities to the process.

Source: British Columbia Safety Authority 

WHY HAZOP STUDY IS IMPORTANT

 Approximately 200 lbs ammonia was released to atmosphere. The condenser safety valve activated due to ‘no cooling’ in the condenser while the ammonia compressor was operating. While restarting the plant after a power failure, the operator forgot to start the condenser circulating pump (which should be started before starting the compressor). The compressor was started without condenser cooling, and as a result, ammonia gas temperature began to rise, thus raising the gas pressure in the system. Eventually the gas pressure rose more than the safety valve setting, activating the safety valve which released the
ammonia to atmosphere.
The compressor’s high pressure safety cut off did not activate. The high pressure cut off is supposed to activate and shut off the compressor unit when the system senses a high pressure condition.

Source: British Columbia Safety Authority 

ARE YOU SPECIFYING PRESSURE GAUGES CORRECTLY?

 Approximately 100lbs ammonia was released into an unoccupied processing room of an industrial facility when a pressure gauge failed on the liquid line to an ammonia evaporator. Inspection revealed that a second pressure gauge (on the hot gas line for the same installation) was pinned at maximum pressure. Both pressure gauges had a range of 0 to 150psi and were installed in a system with an operating pressure of 150 to 160psi. The pressure gauge failed from over-pressure operation.

Source: British Columbia Safety Authority

ARE YOU INPECTING SMALL BORE TUBING?

 An ammonia leak occurred at a commercial-industrial facility. Approximately 10 lbs ammonia entrained in approximately 200 litres of compressor oil was released when a suction side 3/8-inch pressure sensing line failed. The suction side oil pressure pushed approximately 200 litres of oil from the reservoir onto the floor where the entrained ammonia then escaped to atmosphere. The 3/8-inch stainless steel tubing within the compression fitting failed when a circumferential crack completely fractured. The crack within the
3/8-inch stainless steel compression fitting did not show up on external inspection. Metal fatigue appeared to be a factor, along with unit vibration and initial metal stress within this type of compression joint.
 

The refrigeration contractor identified the main cause and factors leading to the failure as a severe vibration condition of the compressor. This severe vibration condition only occurs when only happens when the control slide valve is at, or at near its minimum position. The vibration was so intense that the contractor immediately shut the compressor down. Also, the contractor’s investigation discovered the ‘PHD’ vibration monitoring system was inactive. When the monitoring system was activated, the compressor in fact shut down on ‘high vibration.’ 

Source: British Columbia Safety Authority