Dear Sir,
The thickness of pipe material depends upon pipe diameter, Design pressure, design temperature, corrosion allowance joint efficiency (seamless or welded)and no. of cycles. Your mail was silent about the pipe diameter, design temperature and pressure, joint efficiency (no. of cycles are generally same for a particular plant). So may be by comparing the other parameters you will find the reason for the excess thickness required for the pipe with non sour service. Moreover the thickness can be verified by using thickness calculation equation given in ASME B31.3.
Reagrds
Parmod Garg
-----Original Message-----
From: Mandal Pankaj SPEL-T1
Sent: 28 June 2004 12:28
To: 'PipingDesign@yahoogroups.com'
Subject: [PipingDesign] SOUR Service material - Pipe wall thickness
Dear Sajit,
I am not sure if variation in wall thickness of pipes is really due to sour service.
SOUR services (for example crude pipes in well-head platforms) contain sulphur which is highly corrosive and induces cracking regardless of pipe wall thickness. Please refer to NACE MR0175 / ISO 15156 - 2003 for details regarding material selection for sour piping.
Wall thickness calculation for sour piping still remains the same, based on hoop stress (internal pressure).
-----Original Message-----
From: A.R.Mani [mailto:firreza@yahoo.com]
Sent: 26 June 2004 18:58
To: <a href="/group/PipingDesign/post?postID=uRbo4z40Rd7isk8ubhIjDoi4VriiF3iZWPHLKKb93jUW9tr_ghzC05doof6nD25bPLqd8b0C45vbh3q7QF4YI-z8YOO8RiY">PipingDesign@yahoogroups.com</a>
Subject: Re: [PipingDesign] SOUR Service material - Pipe wall thickness
Dear Sajit
One factor which is very important is the seamless or welded type pipe.It is possible that the pipe used in the sour service is welded but the one in non-sour service is seamless.Also some contractors select the thickness in accordance with market availability of the material irrespective of the required calculated thickness and offer their Piping Material Specification based on market not design!!!
Cheers
Mani
Sajit Viswan <sviswan@tebodin.co.om> wrote: I have 2 - 900# CS Shell piping classes, one for SOUR the other non-SOUR is identical in pipe material and the corrosion allowance. Material is ASTM A 333 Gr 6. CA = 3 mm. The pressure temperture ratings are also the same. However the thickness differs for the same size, 12". For the non-SOUR class it is sch 120 and for the SOUR is sch 100. Which is about 4 mm less thick. What is that which makes the thickness lesser for the SOUR service material. Any guesses?
Sajit
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