Tuesday, October 12, 2010

Re: [MW:7506] hot tap and temper bead

Dear Arvinda,

Pradip Sir, explained it very well.Temper bead is the technique normally using during split tee welding to the run pipe before drilling(hot tapping). Temper bead technique is prefered to deposit weld metal so that we can avoid PWHT.However we have to check the hardness of the weld metal and make sure that it is with in the acceptable limit.It is a critical process and separate procedure required for welding of split tee and repair of split tee weld.If it is a pipeline, PQR normally qualified based on API 1104 Appendix B and API 1107. Two longitudinal and two circumferential welds are required to complete split tee welding.one longitudinal weld normally completed by two welders and opposite side completed by another two welders. Welding normally starting from center of the grove and proceed to the end(One welder from center to left end and another center to right end).Normal case ,backing strip used in between the split tee groove and run pipe to avoid the direct contact of the weld metal to the run pipe.Each pass shall be monitored carefully and make sure that all the welding parameters are with in the acceptable range of approved welding procedure specification.  Circumferrential weld also executed by using two welders at the same time.Two buttering layers normally applied to the run pipe surface before starting the circumferential welding .Low hydrogen electrodes are prefered to avoid HIC.Before starting any activity ,we have to measure the thickness of the hot tap location/split tee welding location, inside fluid pressure,fluid flow rate(every operating company have their own norms to asses this values).If these are all with in the safer side ,then only we are authorised to touch the pipe.
 
 
 
 
Regards,
 
Limesh 



On Mon, Oct 4, 2010 at 3:51 PM, Declan Foley <declan1foley@eircom.net> wrote:
Arvinda,

I don't have a copy of spec here, so am not sure. The fact that you are putting a split tee on means that it is a reasonable size hot tap. If you are doing this with no procedure, might I recommend that you not stand too close to this when they retract the drill, particularly if this is a lethal or explosive service............

Declan


On 04/10/2010 04:01, arvinda shan wrote:
Thanks for your response.
 
One more clarification. In our project, for hot tapping activities, split tee welding is going on with out any procedure qualification. As per sec IX QW290.4 , fluid backing, heat input etc... are essential for temper bead welding. For that essential variables no PQR has been qualified.Need separate procedure for doing these activities or no need? Plz clarify.

On Mon, Oct 4, 2010 at 12:54 AM, Declan Foley <declan1foley@eircom.net> wrote:
 Arvinda,

No relationship.....temper bead is a welding process.........hot-tapping is a mechanical process, which involves drilling into a vessel or pipeline!

temper bead is the welding process usually ( but not always ) employed when welding the hot tap fittings (usually weldolets, split tee's etc....) onto the vessel or pipeline as part of the hot tap process.

As regards qualifying welders, you should be very careful here, because depending on service, this can be a hugely critical operation, and doing it wrong can have catastrophic results. Its a while since I have done any but as far as I can remember the best specs are British Gas ( Transco ) PS-P2 & PS-P9

regards

Declan






On 03/10/2010 11:13, arvinda shan wrote:
Dear all,
What is the relation between temper bead and hot tapping? Is there any specific procedure to qualify for hot tapping or only welders to qualify downhill progression?
arvinda
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