PSMS Lessons Learned - Effective Troubleshooting - Loss of Pressure - January 2025

PSMS Lessons Learned – January 2025

Effective Troubleshooting – Loss of Pressure

Safety Management System “thinking” (Plan-Do-Check-Act PDCA mindset) not only helps avoid Abnormal Operating Conditions (AOC’s), it provides a structured approach to troubleshooting / diagnosing problems when they occur. We typically associate pressure related AOCs with over-pressurization, however unexplained loss of pressure can lead to significant safety related issues, particularly with customer owned equipment performance. Applying PSMS principles of PDCA in diagnosing unexplained conditions is yet another practical example of the safety value in always thinking “PSMS”.

Description of Event:

During response to a gas odor complaint at an outside meter set, the responding technician discovered residual gas readings emitted from the boiler exhaust vent. In addition, the customer reported issues with the range burners going out. The technician determined there was a gas flow/pressure issue and initially replaced the meter and service regulator, but the problem persisted. The technician requested a distribution maintenance crew to evaluate potential blockages in the service line. The distribution technician performed an outside leak investigation with no findings and assumed the excess flow valve (EFV) was tripping. Multiple attempts were made to reset the EFV, with the EFV appearing to slowly reset. The technician changed the riser valve, but the low flow issue persisted. Finally, the crew excavated the area over the service tee to investigate the EFV and found that a self-tapping steel service tee cutter was left in an improper position limiting flow into the service line.

Root Cause(s) and Contributing Factor(s):

The steel self-tapping service tee cutter was left in an inappropriate position partially blocking gas flow.

Key Corrective Actions:

• Verified that there was no leak of the service line.
• Reviewed service records and confirmed a 3/4-inch PE service with an EFV served off a 2-inch steel main.
• Determined multiple construction activities / hand-offs over a six month period through review of service records.
• Excavated service tee and EFV and found flow issue was caused by cutter not fully retracted.

Key Lessons Learned:

• Take an “end-to-end” process when investigating pressure related conditions, from the service tee back to the appliance while performing standard leak investigation procedures.
• Bad assumptions lead to bad decisions - Do not always assume an EFV is undersized or is malfunctioning when performing investigations.
• Sketch the problem out (Plan), evaluate/test pressures upstream / downstream of the meter set prior to simply replacing components (Do), Evaluate (Check) identified components along the path of the service starting with the service tee including exposing the tee to examine the position of the cutter, take action(Act) based on step-by-step sequential evaluation of service components that may influence pressure/flow.