Pipe Pre Heating

Gents,

Please put some light on the pipe pre heating Technology.

We had a DSS (UNS S31803) Pipeline network at 130C buried installation. The problem faced is the expansion of pipe at 130 C. The pipeline installation area is rocky.

Please suggest your views on each alternatives and which will be economical and practically feasible

1. In Buried section we put expansion loop at underground. Till the commissioning of line the loop trench was suggested to remain open and rest of pipeline to be buried. But due to HSE this alternative is rule out.
2. Pipe preheating is suggested at some intermediate temperature of 70C to pre stress the line for every 500 mts of length and then join by tie weld the separate section. But after cooling the pipe there will be compression and the pipe will travel back so the net effect of heating will not be observed. Again in this alternative is hydro testing the line before pre heating or after pre heating
3. To overcome the HSE problem discussed in one above a expansion loop at above ground is suggested. But the concern is the resistance offered by soil to the bend @ underground, which will stress the bend and failure will be at bend
4. If we provide a cushion at the underground expansion loop as discussed in one then HSE Problem can be encountered.

Please provide counsel and any other alternative if possible please suggest.

Regards,

Tebodin & Partner LLC

Md Danish

Pipeline Engineer

tel. +968-2449 6077

fax +968 2449 7290

gsm +968 95525965

e-mail <a href="/group/PipingDesign/post?postID=KGFqbo3DV8XAb9D_XH4X33PqYMjzc3nSv3KojbEJuos237LJx8kd_7VhTY0WqG0nPeyOMGFuJROcH-Pa">mdanish@tebodin.co.om</a>

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[Non-text portions of this message have been removed] Received on Tue Apr 18 23:39:00 2006