Pig trap design

[vijaydere]

Hello,
I am doing analysis of pipelines connected to pig launcher & receivers for onshore project.
i have considered both ends as a sliding ends.is this a correct way to design it ?
and if it is then is there any limitation or thumb rule for the end displacement coming on the pig trap ?

Vijay.

 

[BigInch]

Sliding is the method used to reduce stress. If you don't let it slide, it is likely to break any and all anchor bolts. That can be accomplished with slots in the baseplates at anchor bolt attachment points. I have gone to the extent of skid mounting at least the smaller diameter launchers and receivers (those that don't actually require a "real" foundation) and letting the whole skid slide on top of an area concrete pavement or slab, using no anchor bolts at all.

As long as you have sufficient flexibility in connecting piping, there is no physical reason to place any artificial limits on the absolute amount of deflection that is acceptable or not. Although many people try to do so, it only increases the resulting stress in the piping.

Independent events are seldomly independent.

 

[vijaydere]

thanks for the reply

 

[LittleInch]

Vijay,

What you will find is that pig traps and it's associated pipework represent the interface between pipeline engineering and design and piping design. These two similar (on the surface at least), design schools, in reality don't work well together on many occasions. Pipeline engineers are quite happy to allow the pipe and trap to move a few mm (15 is the most I can recall) and relieve hundreds of tonnes of force that would otherwise build up if the pig trap or pipeline was "anchored". Piping designers on the other hand like to work with fixed limits and movements and often try and anchor this strange incoming pipe to give them a fixed point to work away from.

The best solution is to allow the trap to slide as BI says and allow such flexibility in the associated piping, normally by having a significant straight length at 90 degrees to the pipeline on simple sliding supports.

However you will find some with two sliding anchors, some with the far end sliding only and some with a huge anchor block buried in front of the trap...

Oh and there's no rule of thumb for this.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[BigInch]

When you start calling yourself a "flexibility engineer", you'll know that you are heading in the right direction.

Independent events are seldomly independent.