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It has been debated over uphill l
2

It has been debated over uphill l

It has been debated over uphill l

(OP)
It has been debated over uphill low hydrogen welding is preferable over downhill cellulose welding for plant applications. The fact is that it has been proven that over the last several decades through extensive mechanical testing and field application that the metallurgical differences between the two are negligible.
The concerns in the past have been Hydrogen embrittlement ,poor weld quality ,or cracking issues .The fact is that with the advancements in welding electrodes and Welding Procedures (WPS) show that heat input in the HAZ is reduced and causes less stress on the weldment and parent material .
To sum it up this has become a preferred method of welding in the midstream and processing side of the oil and gas industry due to its high quality welds, production, and flexibility in application in adverse wind conditions where low hydrogen electrodes fail due to porosity issues.
The main factors for weld failures are contributed to pour craftsmanship in assembly, inferior materials and unqualified welding operators. If the welding procedures are followed , proper materials selected and all NDE requirements fulfilled all welds should be equally reliable .

RE: It has been debated over uphill l

Yes, I have heard the same arguments. Basically, an experienced or skilled welder can do either progression with adjustments and it comes down to welder comfort and their preference.

RE: It has been debated over uphill l

Refinery and Chemical Process Industry Owners have traditionally required uphill low hydrogen precesses for fill passes while permitting cellulosic electrodes for the root pass (mostly in the uphill direction). Hydrogen embrittlemnet and the need for preheat to mitigate it is still paramount. Low hydrogen electrodes do provide greater resistance to hydrogen embrittlement. Refineries often incorporate heavy wall piping and equipment while gathering lines and pipelines normally do not. The susceptibility to hydrogen embrittlement increases with wall thickness as well as carbon equivalent. There are legitimate reasons for requiring low hydrogen electrodes; however, in many instances cellulosic electrodes would provide sound welds. One of the problems we have is finding welders who are capable of producing radiographically sound welds per ASME B31.1 and B31.3 when using cellulosic electrodes; hence, root passes are made with GTAW with fill passes made with low hydrogen electrodes.

There are also legitimate reasons to use cellulosic electrodes to provide sound, serviceable welds in carbon and low alloy steels used in the pipeline industries.

RE: It has been debated over uphill l

I do agree with Stanwled. One of the main reasons that downhill process and cellolosic electrodes are not preferred for industry owners is that we have to come across a lot of fittings and there is alwasy a mismatch of internal diameter, making it difficult for fabricator to maintain a uniform joint as required by downhill cellolosic root pass.

RE: It has been debated over uphill l

(OP)
Our contractors have been using the downhill welding procedures for years in processing facilities and have never had issues finding qualified welders maintaining B 31.3 quality welds. The fact is the contractors we have used welding with the 6010/8010 downhill procedure maintained a lower reject rate than the companies that have used the uphill procedure. Hydrogen embrittlement comes from not properly followed welding procedures . That is why we test our welders and have QA/QC to make sure that they are adhered to!
As to the internal high low issues if you stay within B31.3 standards on mismatch no experienced welder will have any trouble making X-ray quality welds regardless of the welding process used.

RE: It has been debated over uphill l

jnjsengineer,
Apparently, your Contractors and their welders are exemplary. Many are not, and the lowest bidder generally wins the job.

RE: It has been debated over uphill l

(OP)
Stanweld, That is a fact we do hire contractors with quality welders but have found that these companies still maintain competitive rates due to higher production percentages and less rework.

RE: It has been debated over uphill l

In my experience the better quality welders tend to also be the more productive ones.

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"

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