Welding tests on E Joint produce minimum sparksPosted on Dec 09, 2015
During October, FT Pipeline Systems held a product demonstration day to show the suitability of Eurokote 468 Thixo as a lining product for the E Joint on steel pipe. Pressure testing was carried out to prove that the lining did not crack. Another crucial factor in the success of the E Joint is the welding, therefore welding tests were also performed to demonstrate welding parameters which resulted in minimum spark production and therefore minimum introduction of material into the pipe.
Controlling the amps and volts, speed of pass and temperature significantly reduces the risk of heat transfer burn through to the mainline coating. Careful control of the parameters and the types of welding rod used also keep weld spatter production to an absolute minimum.
The tests were carried out on a straight pipe joint with a 4mm welding gap and the parameters applied resulted in very little spatter and limited access of weld spatter into the pipe.
Pipe joints can be pulled up to 2° in the socket before welding. This does however introduce the possibility of opening the welding gap and allowing a bigger access for weld spatter to enter the annulus. Over the years there has been much conjecture of the use of internal silicone sealants, specifically the DWI approved Sika 11FC. The aim of the sealant is to block the path of weld spatter to the internal lining, allowing more aggressive welding techniques to be applied. The discussions here however result in three common conclusions:
- Silicone bead close to the welding position results in potential contamination of the weld and a fire risk as the 11FC product can catch fire.
- Silicone bead applied to the back of the socket can result in squeezing of the silicone into the pipe annulus. There is also still a fire risk associated with the positioning of the bead. The silicone bead size also has a bearing on (1) and (2).
- Man entry post installation but prior to welding to apply a smooth bead to the internal interface between the spigot and socket pipe. This however defeats the object of a “No Man Access” solution but provides a much lower risk in terms of HSE and quality compared with accessing pipework post welding to repair joints that do not employ the Ejoint system.
With all welding processes, FT Pipeline Systems recommends that the Welding Contractor be asked to draw up a Welding Procedure that is then performed so as to verify the procedure. This way a client can view the parameters of the procedure, the effect of the procedure and the potential risks associated with the procedure. This should always be carried out on a sample joint, lined with the same product as the proposed production pipework and with the same diameter, wall thickness and grade of steel.