By-pass porting is a pigging technique used for a variety of specific operation issues.
Simply stated, By-pass porting allows a calculated amount of flow to pass through the pig. The most common uses of by-pass porting are to keep solids in suspension in a turbulent flow in front of the pig or to slow a pigs’ speed down for fluid control. The number of ports and also the size and orientation of the ports dictates the total amount of by-pass and is also tuned to the specific issue being addressed.
It should be noted that by-pass porting a pig for liquid management does not allow fluid to slip past the pig. By-pass porting the pig for this purpose slows the pig down so that the fluids will come in at a more manageable rate. As fluids move easily it may be necessary to make adjustments to the amount of by-pass in order to achieve the best results.
There are holes in each sealing component on the pig but adjusting the amount of bypass only needs to be done on a single component. Any and all adjustments must be done on the same component. For example if you block a port on the second disc on the pig and want to reduce the by-pass further you would block a second port on the same disc. If you blocked a second port on a different component you have not changed the by-pass amount.
It would be best to start your program with the pig at full by-pass. Make very detailed notes on run time and the rate at which the plant can deal with the fluids. If you feel the pig could travel at a higher rate of speed you should make adjustments one port at a time.