Spun Piles Splices Welding

Dear Pang Cs, Please describe what you mean by "spun Piles". I am very familiar with many types of piles, ie driven, drilled, screwed in. But I am not familiar with spun.

Spun piles is made from sprining concrete to the steel reinforcement and wires connected to both end pile head which are made of steel material e.g. BS 4360 43A material and the sprice joint should be welded together to achive the penetration depth as per the design requirements. Picture attached.

Hi pang cs,

The welding procedure depends on pile material. Usually, all site welding is done with SMAW, GMAW or GTAW depending on weld quality requirements. I take this welding is pile to pile. As soon as the weld cools and all quality checks are complete, you can consider driving the pile in.

Hi Nachi,

Thanks for your sharing, what is it mean "weld cools", is it has to be ambient temperature (>25 deg C, pile head is made of BS 4360 43A material, SMAW;either E6013 or E7018 electorde is used) or what about driving the pile immediately after 3-passes welding are completed? I was told we should wait for it to cool down e.g. 5~15-minutes or more, or is this necessary? Any effect when we drive the pile if the weld still hot, that say 150 ~ 250 deg C? if not, the mechanical properties may be affected?

Thank you.

Really interesting question, pang cs!

In theory, the impacts of the pile driver should temper the weld at a high temperature, which must not be so hot that the weld is still plastic and driving it would destroy both the alignment and the joint.

Anybody familiar with ASTM or other body of info on this subject?

Mark

Ok Pamg, your welding (material, electrodes) seems ok to me. Now, as I remember it, when offshore platform jacket piles when welded and welds accepted in NDT are immediately hammer driven in. But then again they do cool down to about 75-100 deg C (or the NDT would not be generally possible). By the time all quality checks are over, the job cools down further, say to about 50 deg C. I do not understand why you would want to hammer in just after 3 weld passes, why not finish all passes so that the required weld size as per designed WPS is attained. Is there any specific reason for this? As it is, you should not remove line up clamps till after 50% of welding is complete (and definitely not stop welding before completion of hot pass). Hammering in when the temp is about 50 deg C is not going to cause any considerable difference in mechanical properties. Hope it helps.

Yes, i have seen cooling using sea water immediately after weld completion to about 120~150 deg C for UT test, i believed to cool it down to the temperature is to enable UT testing cause it is difficult to perform UT above that temperature manually.

FYI, the 3-passes in fact have completed the whole welding for the type of piles. (the joint preparation is; partial penetration joint, throat thickness is 10mm, width of vee-bevel is about 4.5mm+4.5mm=9mm, thickness for the welding section is about 50mm, diameter is 400mm). I come across some engineer requesting us to wait for some time before the pile can be driven after welding completed. I am wondering why shoud this be? The waiting time for weldment cooling down seems to reducing productivity of piling works and is not necessary if it doesn't damage anything.

For plastic reformation to take place, i believed it should be around or higher than 600 / 650 Deg C as AWS D1.1. recommended local heating to correct distortion should be below 600 / 650 deg C and we normally control to maximum about 450 Deg C but not to exceed 550 deg C when correcting some minor distortion due to welding on structures.

Ok, Pang, this is Nachi again. My last contribution came as a guest. In your case it would be best to ask that engineer why he wants and what exactly he wants - "waiting" is vague, but I suppose it is to allow the job to cool down and nothing else. Since it is a partial pen joint you need to ensure whatever weld you have put in is good enough, what NDT do you conduct, MPI would be recommended using HWDC. Plastic deformation is favoured at high temp, but I am not sure about the temperatures you mention 450 -550- 650 deg C , seem very high to me. Perhaps, you could kindly quote me the reference from AWS D1.1. Best luck.

Dear Nachi,

Quoted below from AWS D1.1. Cl. 5.26.2

"5.26.2 Localized Heat Repair Temperature Limitations.

Members distorted by welding shall be straightened by mechanical means or by application of a limited amount of localized heat. The temperature of heated areas as measured by approved methods shall not exceed 1100°F [600°C] for quenched and tempered steel nor 1200°F [650°C] for other steels. The part to be heated for straightening shall be substantially free of stress and from external forces, except those stresses resulting from the mechanical straightening method used in conjunction with the application of heat."

In fact, there are sometime a conflict between a requirements in Civil Engineering that might have some conflict with metal welding and metallurgy but i thought the reason that they have to specify those requirements and recommending as Best Practice to avoid a lot of uncontrol circumstances from happening as there could be lacking of some detail knowledge and experience of personnel on certain subject during filed application. e.g i have come across that when there is welding on rebar by mistake, the rebar should be cut-back 1-meter away from welding point for sound rebar section.

So, the heating is aimed at correcting distortion and in no way it is connected with welds as such. Hence my sugestion to you now is this : go ahead and hammer in your piles as soon as the welded splice temperature drops to a managable level. You have to agree to what it should be in conjunction with the engineer on the job. I would rather have everything at the end properly wrapped up in some technical or practical support and document it for future reference. I shall appreciate if I get a copy of it. Thanks.

Pang cs:

Thank you for the explanations and references you supplied, and the opportunity you gave me to add to my body of information on this subject.

I hope you were served by the information you received as well. You have obviously done your homework; and I think that in discussion with the consulting engineer, you can now lay his/her fears to rest by providing hard information in a number of key areas of concern.

Mark

Dear Mr. Pang PS.

Most of the details given by U are ok. I add some few extra points for your consideration.

1. Since it is piling work and joint being partial penetraiton, E 7018 will be better electrode compared to E 6013. since your mtrl is 50 thick. the weld requires slow cooling , if not it may develop under-bead cracking after welding and also during piling work. so the requirement for slow cooling. for a matter of fact any welding carried out beyond 20 thick required use low hydrogen elctrode ( E 7018) and for thick. beyond 25 or so may require pre heating and post stress relieving ( at 600 to 620⁰ C and soaking for 1 hour per 1 inch thikness) to avoid stress concentration. that is what it was mentioned in AWS D 1.1 or any similar codes.

2.Never use water to cool your welded joints as it may harden the weld and HAZ ( next to either side of weld area - say 20 to 25 mm depending upon job thickness) and may develop cracks / fissures which may propogate during piling.let the joint cools on its own and it hardly will take few extra minutes due to its volume and being in open atmosphere.

3. Use ER 70S-6 1.2 dia. filler wire using GMAW process (inplace of E 7018 used in SMAW ) as it will help to get weld productivity and deeper penetration and strength.

4. No mechnical and metallugical variations can be seen as long as the temp. is below 350 -450 ⁰ C. the and it starts from 550 - 600⁰C onwards and that too in a prolonged cycles in carbon steels.

any other points U would like to have .pl let us know.

SRIDHAR

Mr. SRIDHAR,

Thank you for your answer and it is informative but i think AWS D1.1 did not specified that you must do PWHT, right?

I would like to apology for a mistake in information given about the pile head (shoe) splice plate thickness, it is approx. 15mm only (not 50mm) and single bevelled with a small groove (i.e. 4.5w x 10mm throat thickness, the joint will become single vee 4.5w x 4.5w x 10 mm throat).

I have carried out a measuring of temperature which shows temperature immediate after welding is less than 200 Deg C (150~180) and become around 120 or lower after 5-minutes.

From the the responses and discussion we have, i believed and confident it wouldn't have the risk of cracking and mechanical damages due to hammering immediately after welding.