The right pig for the job
“A good tradesman never blames his tools” I remember being told by one of the old boys, after scrapping a job while I was an apprentice, but what happens when you need to dig a ditch and you are only provided with a spoon, the answer - it takes a long time, is difficult and the end result may not be very good.
What is the answer?
The same can be said for choosing the correct pigging tool for a pigging operation. Too many times a pig is requested based on very limited information and it is only when a problem occurs that suddenly the information may appear.
The answer I believe to resolving the problem and overcoming pigging’s sometimes unwarranted bad name is communication between the client and the manufacturer.
With good communication, an understanding of the client’s requirements can be obtained allowing the manufacturer to provide the best proposal to suit those needs.
Dual Diameter Pigging Tool
The Basic’s
A rule of thumb for information required when proposing a pigging tool includes:
- Maximum and minimum pipeline internal diameter
- Pipeline length (including lengths of varying ID sections)
- Minimum bend radii
- Pipeline features (such as tee type, barred or unbarred, etc.)
- Pigging operation
- Operational parameters (including temperature, pressure, flow rate, etc.)
Armed with the correct information the manufacturer can tailor a pigging tool to specifically suit the client’s operational and commercial requirements.
Result!
The end result when all the parts are put together is a specific tool manufactured to provide the best operational requirements, in other words the right pigging tool for the job.
July 8th, 2009 at 5:53 pm
We are beginning to work in waxier fields where pigging intervals are too short to use zero-bypass pigs comfortably. However, we don’t see a lot of standard methodology to design bypass pigs and pigging programs, and we don’t have a good library of field experience with bp pigs. So it is difficult to convince operations to routinely use them. Does anyone have good experience and/or a robust approach for bypass pigs?
July 14th, 2009 at 1:05 pm
Waxier crudes can be a problem particularly in smaller diameter lines. You did not state what diameter of line or range of diameters you have a particularly interest in so I have assumed it is in the smaller range say 6” through 12” where you have a particular interest. You can contact me again if I have made the wrong assumption.
Some four or five years ago PE developed a cleaning tool to address the problem you have described along with another common problem which is low flow. We discovered while carrying out our extensive trials, that while removing wax from the pipewall, it was also important to keep anything removed in suspension rather than allowing it to building up ahead of the cleaning tool.
We also discovered that a single jet or for that matter multiple jets from the centre front of the tool body did not give the required action to keep the removed debris in suspension. After a number of modifications to the cleaning head we devised a method of directing the bypass to 360 deg of the pipewall and at the point where the wax was being removed. This ensured that everything being removed was kept in suspension.
We already knew that if the percent bypass through or over a cleaning tool was too great then there was a good chance that the tool would not launch from the trap. Knowing this we incorporated a adjustable bypass and also increased the frictional resistance which then required a high differential pressure to move the cleaning tool forward. This also greatly improved the jetting action on the pipewall because rather than it being at 0.5 bar it was now at 2.0 bar.
We call this tool an “Annular Cleaning Tool” and it has been successfully deployed in not only waxy crude lines, but also low flow waxy crude lines with flow rates down as low as 0.2 metres per second. It has also proved very successful in large diameter, 48” and 56” gas lines for the removal of Black Powder.