Hi. I've seen a hole in a saddle t 3

[treatwater]

Hi.
I've seen a hole in a saddle typs around pipes, what is this? Is there any reasonable explanation?

 

[LittleInch]

These are "weep holes". Anything leaking under the plate would weep out and any gas trapped when welding can escape.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[DSB123]

Just a point - more important than the little hole. Who on earth ordered/specified the length of the studbolts on the flange. These are excessively long and will be prone to corrosion of the threads. Normal practice is to have two to three threads protruding unless the bolts are fastened using hydratight gear.

 

[europipe]

DSB, i think they were cut off from rods, because of the different lenghts. Yes, they are far too long.

 

[LittleInch]

Also that blind flange doesn't look like the same class/pressure rating as the main flange.

I could be wrong as I don't know size and rating of the flanges, but doesn't look right to me.

Also is it missing 50% of the bolts??

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[pennpiper]

treatwater,
I agree with LittleInch on the purpose of the hole.
However I think there is another answer for the Flange and Bolts.
The Flange (re: thickness) and the bolts (re: number, length and quality) are only for shipping. The Yellow color paint on the cover flange is to indicate removal before installation.
-
Possible?


Sometimes its possible to do all the right things and still get bad results

 

[DSB123]

pennpiper,
Have a closer look at the photo. The vessel is sat on its supports - the vessel has "runs" on it which indicates it has been there for a while - in the background you can see the rest of the plant.

europipe,
Do you mean different lengths?? They look to be all the same length to me just some are protruding through a little bit more on the bottom nuts.

 

[Latexman]

If the correct flange or blind flange was in place, I think the bolt length would be much closer to the right length, don't you?

Good luck,
Latexman

To a ChE, the glass is always full - 1/2 air and 1/2 water.

 

[pennpiper]

Treatwater,
Could you give us more pictures of this Vessel, say from a little farther back where the whole vessel shows along with the Saddles and Structural Supports?

Sometimes its possible to do all the right things and still get bad results

 

[rconner]

(Am a little curious, are there any internal threads in the "hole"?)

 

[treatwater]

Yes, there are threads in it

 

[Gator]

"By threading the hole (NPT), the fabricator can thread a test gauge for the 'air/soap' test (usually hold to 15 psig) to check for leakage."

http://www.eng-tips.com/viewthread.cfm?qid=25516

(Also, threading the hole allows a MNPT nipple to be screwed into the repad to extend beyond any insulation thickness)

 

[rconner]

I guess the function of the reportedly tapped hole could simply be to provide very quick and economical means to nondestructively test the leaktightness of the weld(s) i.e. without having to fill or pressurize the entire pipeline or vessel or conduct any more expensive or time consuming NDT by a technician called out to perform same (if the latter is not specifically required by the governing code). If the hole is left open during the final closure weld, I guess it might even provide a more easy outlet for gas behavior according to a modern restatement of Boyles law, as any confined gas heats due to welding (than otherwise might blow back under increased pressure through the molten steel to create a defect), or if oriented downward as it mostly appears who knows could even also drain any condensation if same collects in operational circumstances due to the hole not being effectively plugged? With all these possibilities, might not be a bad idea to ask the fabricator?

 

[DekDee]

Agree totally with LI on the weep hole and why it is there and also Gators post re:Testing

Reinforcing plates and saddles of nozzles attached
to the outside of a vessel shall be provided with at
least one telltale hole (maximum size NPS 1⁄4 tap) that
may be tapped for a preliminary compressed air and
soapsuds test for tightness of welds that seal off the
inside of the vessel. These telltale holes may be left
open or may be plugged when the vessel is in service.
If the holes are plugged, the plugging material used
shall not be capable of sustaining pressure between the
reinforcing plate and the vessel wall.

Just don't agree with the various comments about entrapment of gas whilst welding.
How many millions of reinforcing pads are fully welded onto pipe for supports around the world without a "weep hole or Telltale hole" ?
Just think about it - when you weld around the circumference of a pad there is always somewhere for the air to escape so it will never get heated or pressurised until the very last 2-3 seconds when the start and the finish of the welds are joined and even then it is minimal.
Can't think of why you would need a hole to release any "pressurised gas" ?
Regards,
Shane

 

[DSB123]

DekDee,
"Just don't agree with the various comments about entrapment of gas whilst welding". You are wrong here and ask any welder.The fact that there are loads of repads on pipework nozzles around the world without weep holes is not a valid argument. The larger the Re-pad the more important to remove the welding gases.

 

[DekDee]

DSB123,
I was an ASME qualified pipewelder for 15 years and have been a CWI now for 20 years.
I think I know what I am talking about.

IMHO - and I stress it is my opinion - pressurisation of welding gases is an "old wives tale" and if you can provide evidence of that being the reason for weep holes / tell tale holes I will humbly apologise,
Regards,
Shane

 

[BigInch]

Not that I have any welding experience, however I tend to agree that there is ample evidence of successful welds having been made with and without weep holes. Since saddles and split tee reinforcement pads, etc. are not pressure containing parts, other welds were made beforehand that should guarantee pressure integrity. Weep holes should not be there to guarantee that those welds are not leaking. On the other hand, leaving weep holes open make me worry a lot more about increasing the potential for future corrosion than how much easier it was to make that weld. I also think that the pictured weep hole on an upside down tee wouldn't drain much condensation until it was nearly full up with water anyway. Offshore and in other high humidity locations, would it not make sense to see that they were plugged, or sealed, one way or another.

 

[KevinNZ]

I was told many years ago that we have wep holes on pads because there were cases where water was trapped under the plate (field welding) and when the vessel/pipe heated up the water/steam expanded and bend out the plate. I know there where plate failures around this time, but not sure of the cause. In any case we always have the holes now.

 

[BigInch]

Then maybe it would be a good practice, if your operating temperature was like what, 500F+? How hot would a relatively few mm3 of trapped air or weld gas have to get to generate say, what, 500 plus psi and actually bend pipe inwards, never mind burst it. Shall we run some numbers on that?

 

[rconner]

As to "bending" either the pipe or wrapper plate due to something happening in the interstice served by the tapped hole, I likewise would need to see the calcs that BI talked about before necessarily concluding the theory presented as cause; however, if one tried to pressurize just an interstice area say between the wrapper plate and against the outside of a rather thin and unpressurized at the time vessel or pipe area below that wrapper plate and not with a low pressure/soaped air test but instead with a very high pressure line pipe test pump, I do believe that could well not be good as it would not be the same stress situation as normally pressurizing the pipeline or composite outlet structure from the inside.