Gas Pipeline Valves 1

[Ingemexicano]

Hi!, A control valve in the natural gas pig trap is not working well, it has a leak. So, we are thinking in installing a new valve just right next to the old one (together, no pipeline between). I need to present the justification based on standars (normativity), can somebody tell me if in any standard code talks about this?...or talks about any restriction in valve separation?.

It's a ball control valve, the pipeline pressure is 42 bar, the valve leaks about 0.25 bar in one hour (1 bar in 4 hours)to the reciever barril. Thank you.

Saludos desde México. Gracias

 

[JLSeagull]

Usually ball style control valves are characterized. Examples are Fisher V-Balls. Like other control valves, do not assume that a V-ball is an isolation valve. Positive shutoff often uses double block and bleed valves.

Assure that the valve ball does not extend beyond the flange. If not, I do not know any standard that would prohibit directly coupling a block valve to the control valve. Perhaps piping engineers may be able to site some recommended practices that recommend against.

 

[Ingemexicano]

Thank you for your answer.

I didn't explain myself well. I was actually talking about the isolation valve (it's a ball valve).

We have solved to install a flanged pipeline between both valves. It's best for future manteinance of the new valve.

So, the new valve will actually act as the isolation valve, and the other won't be removed but it won't work as a valve anymore. Our engenierees haven't found any code where it's forbiden to conecct two valves continous together...however we haven't seen such thing like that in industry.

Now we are working in the maintenance plan.

Thank you.

 

[dcasto]

In Mexico, they adopted DOT 192 word for word and there is no rule agaisnt it.

When I say word for word, I meant intent of the rules. I helped our Mexico City Engineering Company get the intent of the DOT rules translated as one of the Engineers in our office was on a committee the help translate the rules in 1997 to 1999.

 

[vzeos]

Ingemexicano:
I have come across this kind of situation in the past. In general, I suggest you remove the operator from the retired valve and weld a steel bracket connecting the valve body and the operating nut, rendering the valve physically inoperable. This way, 5 or 10 years in the future, you won't have someone trying to operating the wrong valve in an emergency.