In construction of new petrochemical plant, for underground piping work under "D" class fluid services as per ASME B31.3, we propose to carry out shop coating and wrapping of the mill tested ERW pipes manufactured as per ASTM or API standards.For permitting coating and wrapping of such mill tested, there are two opinions amongst the professionals we have talked so far.
One set of professionals feel that in order to meet the requirements of ASME B31.3, it is necessary to retest the mill tested pipes again in the field to hold the hydraulic test pressure for 10 minutes before permitting coating and wrapping, as during milll test, the pipes have been tested for few seconds only though at much higher pressure.
While
Other set of professionals feel that once ASME B31.3 has recommended and accepted the use of mill tested ERW pipes manufactured as per ASTM or API standards which have been tested for few seconds as per the respective code requirement, it automatically comes under the category of tested pipes and can be permitted for coating and wrapping leaving only the girth welds welded in the field which can be coated and wrapped after the 10 minute hydraulic test as per ASME B 31.3.
Our queries therefore are -
1. Whether hydraostatic test of welded pipes as per respective manufacturing standard (e.g. API 5L Gr B, ASTM A 671, etc.) for 3-5 seconds satisfies the requirement of leak test of ASME B 31.3 against clause 345.2.2 (10 minutes)?
2. If yes, then whether the required leak test as per ASME B31.3 against clause nos. 345.1, 345.2.2 and 345.3 can be carried out after coating and wrapping of welded piping components keeping only field joints exposed?
In a past similar situation, I was able to please all parties through the creation of a hydrostatic testing procedure of wrapped piping (exposed joints), pre-approved by all parties, that included the following main points:
1. Complete Mill testing records on all materials used.
2. Charted documentation of hydro pressure.
3. Visual inspection documentation of complete pipe wall surface, immediately prior to coating, with special attention to the removal of all inadvertent arc strikes and grounding marks.
4. Employee training records of all pipe fabrication and equipment operators concerning preservation of the integrity of pressure tested pipe.
It all boils down to the fact that if a wrapped piece of pipe fails under hydrotest pressure, it's still going to have to be repaired and the rework expense falls on the contractor.
I should note that this procedure did not include systems for sour service.
Tim
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