Pipeline Elastic Bend

[onrush]

Dear members,

In my current project, there is a 3" pygas pipeline with its length 2Km. However, our client requests us to use elastic bend for change of direction wherever possible.

My questions are;

1) What is a elastic bend and how is it installed at site?

2) Why should be a elastic bend used?
(I think that factory-made 5D bend may be sufficient
for pigging.)

3) Where can I get any technical information about elastic
bend? (Website may be better.)

Thanks....

 

[DrillerNic]

A elastic bend is where the pipe is simply bent within it's elastic limit to make the bend. A typical minimum radius is 50D.

An elastic bend is much cheaper than a factory made 5D bend, so if you've got teh space, why not use an elastic bend?

 

[billsumner]

Dear onrush,

You are right in that 5D bends will pass pigs.

I agree with DrillerNic on the 'natural' radius. The self-weight is usually enough to hold it in place.

By far the greater length of pipelines on land and subsea are laid like this. The few exceptions are where field or factory-made bends are used for road/rail/river crossings for land lines and the expansion spool pieces on sealines.

You also need to consider thrust/movement if the line is not buried.

The pipeline wall is used to withstand the forces, and axial friction develops between pipe and soil in the adjacent straight sections.

If you need very much tighter bends than Nic's 50D, you need to examine in some detail how these forces act. Take account of pressure and temperature. The trick is to get the right friction factor with the soil.

Bill