Pigging for slug removal 3

[mithuntech]

Wet gas field development project requires the transfer pipelines 12" to 16" sizes to be designed for slug removal by pigging.
The frequency of pigging is not available at this stage of the project. These pipelines also needs to be designed for intelligent pigging.

Please share your views on the following:
1. Whether sphere pigs & sphere pigging arrangement are to be used for this application or the conventional pig traps suitable for foam pigs/ bi-di pigs/intelligent pigs would be good enough to remove the slugs?
2. Whether an automated sphere loading mechanism with actuated valves would be required as these launchers are in unmanned facility?
3. Whether it is advisable to use sphere tee as the gas is of dirty service?

 

[brimmer]

Go with conventional pig traps suitable for foam pigs/ bi-di pigs/intelligent pigs. Can launch any pig type from these. Launchers suitable for sphere pig may not be long enough or right design to accommodate the other pig types, especially the smart tools. Also, not sure sphere pigs are best choice, very limited, not very good for cleaning the pipeline.

 

[zdas04]

In addition to brimmer's points, spheres do not work when there is a significant density difference across them (i.e., gas behind them and liquid in front), because they will deform and roll over the liquid, every time. I tried running spheres in a gas pipeline that was regularly pigged with conventional pigs. The spheres picked up something less than 20% of the liquid that the conventional pigs normally recovered. Spheres are great for product separation when there is a small density difference (e.g., separating propane from pentane in a products line), but not for big differences.

For conventional pig traps, you will never be able to pre-engineer the traps for ideas that future smart-pig engineers think up. I address this by putting a flange between the closure and the first tie-in point. Then if you ever want to run a smart pig that is 5% (or 200%) longer than the trap was designed for you can drop in a spool piece to accommodate the longer pig. Cheap insurance.

[bold]David Simpson, PE[/bold]
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[LittleInch]

By "Sphere pigs" do you mean Spheres? or are these some strange rotund version of a pig?

Agree with the others - go with conventional pig trap

If you're looking at an unmanned facility to remote launch more than one pig, then you need a special design - basically a long pipe in which you pre-install pigs to a certain location and then add branches with actuated valves behind each pig. Then fit the pig in on a visit and sit back. Pipe should be same ID as your pipelines and you use a reducer to load the pigs in ( they do need some force to do this so think about how and where you load the pigs. I've seen inserts or cartridges used where they load the pigs in the main site then install them into a fixed piping structure with a fast close door like a pig trap, but really a slightly oversized pipe.

Many ways of remote launching multiple pigs.

Sphere tees are great for spheres, but if you've got liquid and dirt are a bit of a liability really and just gradually fill up with rubbish you can't clear out.

Agree with zdas04 - leave a lot of room and add a flange to swap out the trap if you need to for inspection purposes.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[pennpiper]

mithuntech, You wrote:
"Wet gas field development project requires the transfer pipelines 12" to 16" sizes to be designed for slug removal by pigging."

Does this mean you want the same pig to fit and perform in the 12" part of the line then transition to the 16" and continue working just the same (and visa versa)?

Sometimes its possible to do all the right things and still get bad results

 

[zdas04]

Penpiper,
I wondered that as well. It is such a very horrible idea. I inherited a line that goes in the ground 18-inch and comes out 20-inch and there are no records of where it changes. Every "dual diameter" pig we ever ran either got stuck in the 18-inch or just ran over the liquid in the 20-inch. It was a nightmare from day one. I asked the guy that "designed" it and he said "the model said that that was the best hydraulics. I looked at the model and it was 0.5 psid better than just running the 20-inch (and the 18-inch fittings were all special order so he didn't get discounts on them like he did on the 20-inch fittings, he ended up "saving" negative 2% on that line over just running 20-inch).

[bold]David Simpson, PE[/bold]
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[LittleInch]

I just read it as a bunch of pipes which could be between 12" to 16".

Zdas04 - I like the "negative saving".... Changing from 18 to 20" sounds like a bad flow assurance call on the design. About as silly as the constant or bespoke ID thing the FA guys love to put forward to make their analysis easier and theoretically make it more efficient. They can get rather upset when I ask them how accurate their flow modelling software is compared to reality and hence why they think that is a good idea.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[mithuntech]

Thank you all for the responses.

@LittleInch
By "sphere pigs", i meant spheres.

@pennpiper
No. I meant different pipelines of sizes 12" and 16". Not dual diameter pigging as you mentioned.