Use of low hydrogen electrodes according to API 650. Avoidable?

[monirri]

Hi.

I am part of a company hired to oversee tank construction by a contractor. API 650 states that low hydrogen electrodes should be used if plates are thicker than 12.5mm. First and second courses of the tanks are thicker (19 and 15mm). Courses are A36 Steel. We remind the contractor that.

But the contractor wants to use manual e6010-e7018 because of a thousand reasons. Besides he presents a WPS based in semiautomatic e71-t11.

I am contemplating the pros or contras

PROS of the reasoning of low hydrogen
higher notch thoughness
lower tendency to crack
higher temperature and hence lower cooling rate

CONTRAS of the reasoning
the standard says "all manual" welding. It wouldn´t apply to the semiautomatic process
machines usually minimise defects

IMPORTANT NOTES: tanks are going to be built in Colombia, operation temp: 166F

What do you think.
1) Should I back-up and accept the use of E6010?
2) Or should I stand stronger only in the verticals?
3) Should I allow them to weld by one side and then remove the root pass by the other side?


THANKS

Carlos F Molina

 

[DekDee]

Carlos,
You mention SMAW (E6010 / E 7018) but also mention FCAW (E 71T-11) ?
Bottom line is E 6010 is not allowed on greater than 12.5 mm thickness, irrespective of whether it is backgouged or not.

It makes no sense to use the E 6010 (unless it is purely for backing) but if you weld both sides with E 7018 backgouged you do not need the backing.
Regards,
DD

 

[IFRs]

Throw them out if they will not (1) do what you ask or (2) don't follow the code or (3) argue with you.

 

[gtaw]

If the working standard requires the use of low hydrogen electrodes, that that is the requirement. The Owner would be the only one permitted to modify the requirements. The contractor nor the organization hired to oversee the project has that authority unless it is specifically delegated to them in the PO or project specification.

Best regards - Al