Re: Seal Welding of Nipple

From: <Austin>
Date: Wed Jun 13 2001 - 13:13:00 EDT

From time to time we have been called on to seal weld threaded joints. This was normally part of a last ditch effort to save a failing system and to be quite frank was more trouble than it was worth. It seems that no amount of buffing or grinding ever removes enough of the thread sealant to make for good welds. What usually happens is an incredibly hot root pass of 6010 is used to burn out the sealant and then all the slag is ground out of the root. This is bad practice and time consuming, and I would not recommend it. If a threaded joint is suspect replace it, and if they want welded try socket welds.
on 6/13/01 7:41 AM, SARE, RALPH H. at SARERH@YANPET.SABIC.com wrote:

What the Code says.
parag. 328.5.3 Seal welding shall be done by a qualified welder. Seal welds shall cover all exposed threads.

Problem statement.
There are quite a significant numbers of threaded nipple at the plant - pressure gage/vent connection, seal flush on pumps and compressors, gland coolers and other similar misc. applications. Many of these connections are not seal welded - for obvious reason, the need to remove this piping for maintenance purposes.

However, it also a cause of concern if the media is hazardous or if the service is steam. Recently, a work request was initiated by Operation to seal welds all threded nipple carrying steam and flammable commodity during the turnaround. We see two problems - complying with the last sentence of 328.5.3 and maintenance during the repair of compressors/pumps or replacement of gages.

Appreciate to hear the practice in other plants/facilities.Note that we use either sch 80 or sch 160 for all trheaded nipple.

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[Non-text portions of this message have been removed] Received on Wed Jun 13 13:13:00 2001