Trapped Fluid (KV15)


What Happened?

A mechanic was removing a threaded two-inch to one-inch fitting from a two-inch ball valve and nipple.  The fitting threads were tight, so heat was applied to the ball valve with a torch. The fitting was broken loose and turning freely.  As the mechanic put the pipe wrench down on the workbench, the worker assisting him opened the ball valve, causing a sudden gush of hot water and steam, striking the mechanic on the forearm. 

Contributing Factors

Line was not drained and valve was left in the closed position while heat was applied.

What Can We Learn?


Procedures for working on transfer lines should address the possibility of trapped product. 

Using a Questioning Attitude could have been used to identify the unintended consequences of heating a transfer line with or without trapped product.


In the worker’s Physical Environment, fluid was trapped in the system while a heat source was applied. 

Ask the Right Questions

How does this relate to our work?

Where do we have similar traps?

What Tools can we use to avoid a similar incident?

Was a stop work point missed?