Weld slag removal question 2

[jari001]

Hi everyone,

I'm in the middle of sourcing a 450 gallon 304L IBC (intermediate bulk container) on short notice to meet a fast pace project. In order to get the IBC made quicker, the vendor has presented the option of not removing weld slag to decrease the lead time. I understand slag to be residual flux that was fused together during the welding process around the weld area, and if that is true, then I would want the flux to be removed so that the passivating liquid is not prevented from having thorough contact with all surfaces. The IBC will hold ambient water and steam condensate.

So my question is can weld slag interfere with the passivation process? I have concerns that in the instances the hot condensate is directly discharged into the IBC without mixing into ambient temp water, that the hot condensate become an issue for those areas that weren't properly passivated due to the slag not being removed.

I would appreciate your comments on this matter.

 

[gtaw]

How does the welder or inspector visually inspect the weld if it is covered with slag?

Best regards - Al

 

[TugboatEng]

My experience with SMAW stainless is that is a proper weld will randomly fire the hot slag off and on to your lips. No visual inspection required.

 

[Dhurjati Sen]

So, no quality checks for the weld joints?
Does the IBC come under any fabrication code?

If that is the case, keep the slag.



DHURJATI SEN
Kolkata, India

 

[jari001]

So that's a good point, visual inspection of the welds can't be done without removing the slag. The manufacturer says they test the IBC with a pressure decay test using compressed air after fabrication.

The IBC comes with a UN number, I don't know if that implies a fabrication code. The IBC is not an ASME pressure vessel, and is sold with no official pressure rating; it's basically a rectangular atmospheric tank.
Example item:

https://www.uline.com/Product/Detai...Vc-W1Ch39jQSsEAQYASABEgJqT_D_BwE&gclsrc=aw.ds

 

[gtaw]

This may be helpful to you: 49 CFR § 178.274 - Specifications for UN portable tanks.

In essence, the vessel/container must be designed and constructed in accordance with ASME Section VIII. That would pull in the requirements of ASME Section IX for the qualification of the welding procedures and the welders. Per Section VIII, the completed welds would have to be visually inspected. In order to do that, the welds have to be free of slag.

Al

Best regards - Al

 

[EdStainless]

And slag left on welds will often result in corrosion because of the crevices formed under it.

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P.E. Metallurgy, consulting work welcomed

 

not removing weld slag to decrease the lead time

Let me understand this correctly: shoddy workmanship is the best way somebody could think of to decrease production time?

I have a better suggestion: put running shoes on the welders. Steel toed, of course.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[mfgenggear]

Yeppers people taking short cuts.
Who ever said to leave the weld slag
Needs re training.

I not familiar with these specs.
Maybe someone can advise if NDT
Is required on the welds.

Welds minimum must pass visual inspection
And has to be certified visually.
If a manufacturer is suggesting to leave weld slag on the tanks, a be red flag has
Be noted. Now some one needs to audit
All their manufacturing procedures.

 

[gtaw]

I doubt this is a custom unit. Its more than likely an off-the-shelf item, but to carry the IBC UN31A/Y rating, it must meet the standards. The regulation I came up with is the CFR I cited. It specifies ASME section VIII for design and construction. The purchaser is buying a commodity, no different than buying a loaf of bread or a gallon of milk. Each has requirements to be met. As for an audit, who would perform it? I don't know if a third party such the UL issues a certificate that the manufacturing facility is "certified" to produce the vessel or if the manufacturer simply "certifies" it as meeting the requirements by attaching the label to the vessel.

A lot of commodities do not involve third party oversight, audits, or certification. The manufacturer "certifies" the product as meeting the required standard, end of story. If there is a problem, you take it up with the seller or the manufacturer. Lawyers make a good living doing what they do and the insurance companies collect good premiums to cover any claims. When the cost of the claim is more than the insurance coverage, the manufacturer goes out of business. The auctioneer sells the equipment and property, often to someone that takes the bones and goes back into business under new ownership.


Best regards - Al

 

[mfgenggear]

I see however they had to certify their product. And falsifying certifications is a felony. This is a safety issue.
Even if it is an off the shelf product.
I must of misunderstood the op.
It appeared to me the way he explained it it was custom product.
Because it has to be welded and to save time bypass removing weld slag.
Then passivated.
Very cheasy.
Commercial products I guess.
Even a customer can audit the manufacturer.
Make sure it is to the specification requirements
I have done this my self many times.
But it is part of the contract and they have to comply.
This may be diffrent.
It is not unusual for a customer quality dept.
To audit a supplier for conformance .

 

[mfgenggear]

@jari001
I use to try to rework parts the had contamination and caused excessive corrosion from SS parts.
the corrosion was very difficult to remove and a lot of parts were scrap.
Have the mfg take great care in processing product correctly if there contamination
And causes corrosion there will be issues.
Make sure they follow proper procedures.
Even if it delays the product.
A little extra care will prevent bigger issues later. No short cuts.

 

[kingnero]

What amount of time do you (or they) win by not removing the slag???
Also, am I the only one who thinks air pressure testing a 450 gallon container is at least a bit sketchy (even if it is only a pressure decay or low pressure test)?

 

[jari001]

I told the vendor yesterday that the slag removal will be required based on earlier input about the inspection process being hindered by the slag presence and my concerns about the passivation not occuring uniformly.

This is a commodity item like gtaw says, but I think is made at the time of the PO clearing, so they don't have any premade waiting to be bought. In my case, asking for 304L (vs 304) made it slightly custom - it was explained to me that changing and verifying the sheet stock to meet 304L was going to add time (necessary and understandable). In the end, whatever time they could have saved was more than eaten up by the fact that the shop had a COVID positive worker and now they're on a skeleton crew.

A follow up question -
gtaw mentioned 49 CFR § 178.274 as a relevant guideline for building these types of tanks - and if it is following ASME principles, does that mean this IBC would be considered a code vessel?

 

[kingnero]

I don't know the situatie where you are located, but there is no practical difference between 304 and 304L. All we have in europe is dual cert. material.
Another load of bovine faeces. I wouldn't want to do business with that shop.8

 

[jari001]

@kingnero

I'm in the US and thought the same about the 304 that's used here, but when I asked if the steel was dual certified 304 and 304L I didn't get an immediate "yes" so I asked that the verification and accompanying paperwork be planned for in time and price.

 

[gtaw]

The vessel can be designed and fabricated in accordance with ASME without being "code stamped".

I worked in an ASME shop that fabricated both stamped and unstamped vessels. The only difference was the stamped vessel was visually inspected and the hydro was witnessed by the Authorized Inspector. The AI also cosigned the code paperwork and witnessed the attachment of the nameplate. It essential doubled the price of the vessel.

Best regards - Al

 

[jari001]

@gtaw

Thanks for the clarification.

 

[mfgenggear]

@GTAW
Please advised what was the requirement for the code stamp?
vs not code stamp, was different type of vessels

 

[EdStainless]

If they order the sheet as 304 then the MTR will come saying 304, even if the material (and if it was melted in the US or EU it is nearly assured) is 304L. So they go back and ask for a revised MTR. If they bought this out of distribution then the ask the distributor who may or may not have another MTR for this heat on hand that lists 304L or 304/304L. If they don't then they they go back to the mill for one. And since they already made the sale they aren't in a rush.
There is no reason to not order everything dual certified. The mills dropped the price premium for "L" about 50 years ago.

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P.E. Metallurgy, consulting work welcomed