Reduce Gas Spikes to Flare when Pigging

[Leclerc]

We are investigating installing an isolation device in Flareheader to aid gas recovery. Isolation device is likely to be an in-line buckling pin, with a pressure control valve in a by-pass for upstream pressure control. The control valve would be sized for the "normal abnormal" flows of gas, so that the isolation device is only activated by relief events, or those events with an equally low frequency.

Unfortunately, the approximately weekly pigging operation generates "spikes" of gas flow which is fine for the present operation, but which would tend to cause the isolation device to be activated in the new situation.

Are there any ideas out there on how I might modify our pigging operation, attenuate the flow/ pressure spikes, or otherwise deal with this gas generated during pigging?

thank in anticipation.

 

[MortenA]

ABB has a flare gas recovery system. Maybe it considers your problem. Check the web page:

http://www.abb.com/global/abbzh/abb...e=us&m=9F2&c=4DC2A1FB94E2A7BBC1256A3A00318902

Best Regards

Morten

 

[joisy]

We've increased the pigging frequency, that smoothed over the gas flow deviations in each "spike".

but this depends on your system. Please describe it more detailed.

 

[Leclerc]

more details of pigging system for joisy:

Pipeline comes into a pig receiver. Just upstream of the receiver is a barred tee. when the pig has moved past the tee, the oil/gas passes through tee branch to separator. The barring prevents the pig from going to the separator.

The separator level is normally controlled by means of a control valve in this inlet line. At times of pigging, this control system is in manual with the valve shut. On pig arrival, the valve is opened slowly in manual by the operator to avoid flooding the separator and prevent the system being overwhelmed by too much gas being released (on pressure let down), whilst st the same time trying to maintain a decent production rate.