Reducing pig speed at end of pipe

[david23]

Hi

In our process plant the pipeline is pigged after every product transfer. However this pigging takes a considerable amount of time. During this time any transfer through this pipeline is blocked and so productivity is smaller.
The time could be reduced easily by adding more pressure to the pig. Unfortunately at these higher velocities the pig gets damaged very easily.
Are there commercial solutions available to reduce the speed of the pig at the end of the pipeline?
Either by detecting the pig and then lowering the pressure or by slowing the magnetized pig down with an electro-magnetic force?

Many thanks

 

[ash9144]

You could open a vent at a point near the end of the pipeline. When the pig passed the vent some of the driving pressure would vent off and slow the pig.

 

[HEC]

What industry are you in? Another option may be to close off the compressed air at an earlier point and allow the expansion/pressure decay to slow the pig. Another option would be to put water or other dividing fluid behind the pig rather than compressed air. In that way the pig speed can be controlled. There is more than one way to skin this problem!
Cheers

Mark Hutton

 

[dcasto]

Run a batch program on a plc that adjusts the inlet or outlet valves on the line. You have all the information on the line lenght, diameter ect.

 

[pmover]

lowering the differential pressure across the pig is the solution to lower velocities, but how to achieve can only be done by means of safely operating the "system as a whole". unfortunately, we do not have the knowledge of the "system as a whole". we also do not know if pipeline contains a liquid or a gas.
if the pipeline contains a liquid, i would not be opening vents at end of pipeline.
having encountered similar situation for a gas pipeline, that is the liquid quantity entering the pig catcher/trap was so great, that the only way to handle the liquids and capture the pig safely was to slow it down a little when the liquids started arriving at the pig catcher. so, the valve at pig catcher that allowed gas to flow to processing plant was closed to the point of not causing disruptions to the plant (mainly low inlet pressures), but yet allowed safe handling of the liquids and pig upon receipt. sometimes, this method work aok, and other occasions it did not. eventually, the catcher piping system was modified to allow for safe handling of the liquids and capturing the pig without plant disruption.

perhaps this gives you an idea . . .
good luck!
-pmover