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| Viewing Page 1 of 1 (Total Posts: 5) |
| Author | Comment |
Oz
 May 11, 06 - 12:07 PM |
socket weld fittings
Can anyone tell me why Butt welded fittings are most common in the UK pharmaceutical industry as opposed to Socket weld fittings. Our site standard is for butt welded fittings and i've been asked by a contractor to accept socket welds - and i can't think of a reason to reject his request. I understand the benefits of socket weld, but don't know why they are hardly used. Is it cost? is it quality? or something else? Oz |
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Pyrex
May 11th, 2006 - 12:57 PM |
Re: socket weld fittings
The following is taken from the training section of this site (section c. fittings) It's worth reading all the material that the lads have supplied in the training section, as well as the tips section, there may have been no need to ask the question! Screwed and Socket-Welded Fittings These fittings perform the same function as the Butt-Weld fittings. There function is the same but the method of joining and the dimensioning is different. Normally these fittings are used in sizes 1-1/2" (or 2") and smaller. Welded fittings are specified the same as the pipe, by weight, schedule or wall thickness. Screwed and Socket-Weld fittings are specified per the pressure class. Thread engagements as well as the depths of the sockets for different pipe sizes are different and must be looked-up on an approved dimension table. |
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thehat
May 11th, 2006 - 1:28 PM |
Re: socket weld fittings
A fillet weld is only 45% as good as butt weld, a fillet weld is whats used in a socket weld. Also socket welds are much more prone to failure then Butt welds. |
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Jop
May 11th, 2006 - 1:48 PM |
Re: socket weld fittings
The main reason that socket weld (and screwed) fittings or flanges are not used in the pharmaceutical process industry if the inability to clean (CIP) the socket or threads. As you know the socket weld fitting is only welded on the outside. That leaves an open path on the inside for material to get into the socket between the pipe and the fitting. There it can ferment and contaminate the process. Butt-weld fittings and flanges prevent this problem. Of course socket weld construction could be used on non-pure utility services such as fuel gas, fuel oil, plant water, plant air, etc. I hope this helps. |
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j
May 11th, 2006 - 5:41 PM |
Re: socket weld fittings
I would advise against allowing the contractor to deviate from the site specifications. The specs call up butt weld for a reason whether that reason is apparent to you or not. If at a later date the weld fails or validation pick up on your deviation, it's your neck in the block. There is a reason that many piping designers don't ness. hold formal 3rd level qualifications. We don't need them because we don't make any decisions. The P&IDS tell us what to pipe, The Specs tell us what pipe to use. All we do is decide what direction it goes in. |
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