hot tap failures

[pipeliner3000]

We are looking to carryout a risk assessment for multiple hot taps with stopple interventions. Does anyone know good sources for industry failure data that may be used to support determination of failure frequency/ probability.

This could potentially be done for one if data was avialble.. any suggestions on how to look at increase in failure likelehood if this needs to be done multiple times - upto 30

 

[Duwe6]

Each Hot Tap will be a separate event. You cannot tap the same point twice. If you follow the API-570 procedure, your RBI probability-of-failure should be a lower probability than the failure of a seam in your pipe.

 

[pipeliner3000]

Thanks. The 'multiple' taps is at a number of different locations but essentially performing the same task.

 

[Kiwi2671]

pipeliner3000,
If you can do it safely once you should be able to do it safely 30 times or even 300 times.
The only time I have been involved with stopple valves was inserting a Tee in a live methanol line. We had a stopple valve and then 2 x balloons as back ups.
To have a failure/accident we had to have failure in all 3 very expensive items.
Risk assessment should be able to factor out any possibilities of failure,
Cheers,
Kiwi

 

[kacarrol]

I've read the book "What Went Wrong" by Trevor Kletx (really good read!) where a bunch of case studies were collected together and summarized into valuable lessons learned. The only reference to hot tapping in there referred to an incident where they hot tapped the wrong line...it seems like there aren't many instances of case studies for hot tapping.

K

 

[Duwe6]

kacarrol, I am willing to bet a 1-week paycheck that why the Trevor Kletx book [have it in my library - highly recommended for anyone on this forum] could find so few instances of catastrophic Hot-Tap failures is that there weren't many.

A Hot-Tap "raises the hair on the back of the neck" of any cognizant engineer or Inspector. Everything gets double-checked, and usually triple- or quadruple-checked. It is a pretty simple process, but the consequences for failure includes maiming and death, and $$millions in liabilities due to the injuries and lost production. Besides, the final Inspectors will be the guy(s) that are operating the Hot-Tap machine. Since any catastrophe will involve them first, they REALLY look things over.