Which one is adviceable; to use Design temperature or Operating temperature to calculate Pipeline Expansion?

Question

I need to calculate the pipeline expansion due to thermal loading of a subsea pipeline

Answer 1

The design temperature for a pipeline usually is set by the highest temperature that the pipeline can see with some safety factor. That occurs at the delivery points or on the outlet of any compressor stations that exist along the pipeline.

Typically a gas pipeline's temperature approaches the temperature of its surroundings pretty quickly; therefore, the maximum operating that much of the line sees is well below the design temperature. To design all portions of the pipeline from thermal expansion using the maxmium operating temperature or design temperature is really over kill.

To truly engineer a pipeline, it needs to be broken down into segments for thermal stress analysis. To use the design temperature or the maximum temperature that can occur at only limited points on the line is not engineering.! I realize this takes some extra work and analysis but that is what engineers are suppose to do.

Answer 2

Go with the higher, of the two temps. Always err, on the side of safety. Theoretically, the design temp, should exceed the operating temp, anyway. If not, you're in for a disaster.

Answer 3

you must use max possible expansion given any possible extreme circumstance.

If you dontthen you are negligent and open to being sued.

So you should use a temperature greater than design temperature

i.e. max design +safety factor.

Oh and you should also consider the maximum contractions as well with safety factor.

So you can identify max and min expansions so you know what needs to be taken up.

No cutting corners, the world needs protection.

Answer 4

I would assume the design temerature is greater then the operating temperature, so this would be the worst case and therefore used in designing the expansion requirements.

Answer 5

you should do your calculations based on the design temp. which is the highest temp. that is possible so you will be sure that nothing wrong will happen if the pipe reaches its design temp.