Drilling Through Welding Joint

Steel will and can get a lot harder when welded and the weld itself is going to be very hard

Are you sure about that?

From experience I've found welds and adjacent areas to be no harder to drill (cut, tap, file..) than the parent material. It can get tough if the weld wasn't chipped clean is all.

Thinking....unless the weld is quenched wouldn't the heat anneal the steel? ..and any possible hardening depends on the composition of the fill material....MS rods are pretty soft?

Have I been lucky?

OP, have you expressed your concern to the vendor yet?

Wal, I would say you are lucky, most times that I have had to drill through a weld it was considerably harder than the base material but it also depends on the rod used to weld with.Duke

I agree with you that this is not advisable to do this way but just wondering if there any ASME code interpretation doesn't permitting this kind of fabrication.

Yes, this vessel is according to ASME but not stamped. Also this fabrication is done at vendor shop and the reason the drilling through welding joint is because the limited space.

No! No! No!, find another way.

There's an opinion.

Why do you think so ?

Proceed with caution after due diligence. Good general advice for anything I suppose...

Is the vendor willing to take the rap if it goes pear shaped?

I'm trying to picture the placement of this hole. Is it right where the nozzle is welded to the tank? A sketch or other visual would be good.

Would an arrangement of threaded adaptors and Ts on this nozzle not work for your application Zhafir?

Sorry for not attaching clearer picture, it is basically intended to drill a hole through a welding joint between nozzle and shell. as per fig. UG-40(e) in ASME VIII div.1

see below picture with marked red where the hole to be drilled for the insertion of detection system.

I wonder if you could insert a meta tube (of the same material) where you want the hole and weld around the tube.

After the weld is finished you can follow with a drill or reamer to finish the ID of the tube to the exact desired dimension.

If the tube is slightly larger in diameter than the intended hole you will never have to alter the weld.

Bear in mind the tube will still likely become work hardened from the heat of the weld, so it will be hard to finish, but far easier than drilling from scratch.

Post number 2 mentions a threaded coupling being welded into place, which is the route I would pursue.

only after the welding is finish , the drilling can be done i think to avoid incomplete penetration of the welding.

But is it really hard to drill a weld joint? i suppose it is possible since the vendor said it has experience before.

Threaded coupling also is feasible.

There's some good answers here so far.

I did a quick search in Section VIII and couldn't find anything that permitted this, but my suggestion would be to read the UW section (the parts that apply at least).

If you do an FEA analysis on this, I think you can get away with it. However, by drilling into a weld, you could introduce a high corrosion area.

You said the vessel is designed to ASME but not stamped right? If that's the case, then the fabricator is not really held to ASME standards. It's on the owner to take responsibility for the integrity of the vessel. I've run into companies that don't stamp before and it's usually because they don't fully follow the code. I'd be worried about this design and fabrication if this vessel contains harmful products.

Why not just drill into the nozzle about 1" away from the tank wall. That way you are not in the weld and not damaging the tank. You can tap the pipe or weld an extended pipe in the nozzle for your control device.

This way you can come up close to the tank saving the space you need and install a valve in the line so that if you ever need to change or clean your control device it can be done easily with out having to drain the tank.

drill into the nozzle about 1" away from the tank wall

Yes, or install a T and some adaptors to get in there.

I wonder what instrumentation this is for. The position could be critical thus making any alternative positions moot.

I agree Wal initialy I thought the same thing but looking at the op's diagram the nozzle appears to be welded to the tank.

First off, the answer is YES. Welded steel is harder than the surrounding steel.

Titanium tip drill bits, lots of them, Good quality cutting oil. and a drill with a max speed of about 650 rpm turning at about 400. Take your time. If you are not able to mount the part in a drill press and make sure you have adequate stabilizers for your drill and arms as this is going to take awhile.

BTW, 1/2" hole is not small when you have to drill it out by hand. To a CNC machine sure, to a Bosch 1/2 inch VSR drill its huge.

Good luck!

You won't be trying to drill a half inch hole without a pilot hole.

It is not difficult to do with a portable drill and some cutting lube. The hard part is not cutting the hole but holding the drill when the bit jambs. Some care is all that is required.

Hardening of welds? I had to check.

The result of the research shows that the hardness and toughness values of the specimen varies with the carbon contents of the specimen. Generally, there was increase in hardness values with increase in carbon content while toughness decreased. It was also found out that the hardness values were minimal at the weld pool compared to the HAZ. It is the other way round for toughness. Quenching significantly affects the microstructure and thus the mechanical properties of the weld.

Let's say it did get hard. It still wouldn't be harder than a regular HSS drill bit. Properly sharpened with the correct clearance and a cutting lubricant this is well within the realm of possibilities. I wouldn't want to try with a hand brace but a 1/2"Bosch portable drill would have it done in no time with a pilot hole drilled first. A 3/16" pilot would do it and could be drilled with a light weight pistol drill.

Titanium drills? Maybe tungsten carbide tipped if you are doing a real lot and couldn't be bothered to resharpen frequently. A good quality HSS drill bit is the way to go. Have 2 pilot drill bits on hand in case you break one.

Welding a joint with the proper filler rod for the parent metal to be welded should not produce a harder surface then the parent metal. If weld crystallization has formed along the weld lines or surface areas of the welds, there is a flaw in weld technique. The article you refer to is concerning weld quenching effects. This procedure will in fact produce the condition stated.

The article also stated what you said. There were control specimens that were not quenched.

Like I said in post#3. I've never noticed that welds were harder.

I manufacture a portable drill press that could drill the hole with very little effort using the proper drill bit .I have used the same drill bit up to 50 times without sharpening it . I have drilled 1/4" plate in 6 seconds .It will work for most all shapes of material and will go any where you can take a electric drill, 110 V or cordless .it weighs less than 3 LBS ,is very easy to manufacture. I am looking for a tool company to make it and sell it world wide as I can't handle a large volume in my shop .