Vent-hole on the reinfrocement pad, wedding band (discussion)

[JackCH]

Vent hole or Tell Tale hole is sweep hole, and often seen in the reinforcement pad or similar structure, such as wedding band, full Encirclement/Reinforcing Saddles and Pipe Repair Sleeves.

The Use of Vent Hole
For pipe line welding. the vent hole serves as a vent during welding for entrapped gas (air) and prevents the reinforcing pad from becoming a "jacketed" vessel. The trapped gas could pressurized to over 50 psig if the trapped gas is heated from 66F to 1200F. The high pressure could blow off the melt steel during the welding (it is a safety issue).
The vent hole could be simply sealed by welding after the welding is done, leave alone (such as reinforcement pad) or plugged (for thread hole).

Misuse
Some engineer does not understand the purpose of vent hole and use it whenever see a pad (band). It is very common to say the vent hole for the tie in wedding band (sleeve), even though the vent hole is not necessary since the gap between the two side pipes and the gap between the band and pipe is connected and no air could be trapped.

Do I miss something?

 

[LittleInch]

Tie-in wedding band??

Can you describe / draw to understand what you mean. If I understand you correctly this is then surely exposed to the process fluid so if it has a hole in it will leak out??

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

 

[JackCH]

When someone uses vent hole for wedding band, they use a half coupling and a plug (see the attached picture). Someone says it is for venting, even says it is for X-ray inspection. Lot of copycat in the reality!

 

[racookpe1978]

Your drawing cannot be connected as-drawn, nor as-specified.

You have drawn and specified a screwed coupling 3/4 x 2 inch, but the pipe sizes are 3/8 (0.375) and 2 inch.

The drawn images (which usually reflect what is to be installed!) are shown as if 1-1/2 or 1-3/4 and 2 inch.

If a threaded coupling, there is no reason to add yet another leak point by requiring another threaded plug to the coupling. And, a vent point is not really even needed for a even a socket-welded coupling.

 

[LittleInch]

There are so many odd things here I don't know where to start.

So you're trying to connect a new .375 X65 pipe to a 60 year old .25 X 52 pipe - why? The design pressure will be limited by the connecting pipe so this doesn't make much sense unless you're doing this for a revision to the area classification. Either way I don't understand why you're not welding this using a transition piece - the .375 pipe internally machined down to mate with the existing??

Item 6 is unfortunately missing off our picture and is the key item

As there is a path for any air trapped inside the tie- in sleeve via the end connection of the pipes there is no need for any plug or hole in this strange sleeve arrangement. both of the extra plugs appear superfluous to me and look too small to work as a bag hole insertion.

Can you provide a better picture / sketch of item 6

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

 

[Gator]

OT There seems to have been many odd things here recently.

Piping Design Central

 

[11echo]

Your connecting two 24" pipe sections together, one with sch.10 wall(older one) and the newer one with sch.20 or STD. WT. wall. AND you want to use a "wedding band"!?? ...Never heard this term, but appears to be a coupling!?? ...My answer is WHY! You have lengths of pipe connected together all the time without "wedding bands", the pipes are just butt welded together. Now they do have different wall thicknesses, but it's standard practice to just "back taper" the thicker walled pipe(4 to 1 min.) to match the thinner one and butt weld the pipes together. And why you want to put couplings with threaded plugs? This is a buried condition correct, what good will that do? Why make it more complicated

 

[racookpe1978]

No, no.

We have all got to be reading this stupid sketch-extraction-from-a-real dwg wrong, in about as many different ways as is ever possible.

0.250 wall thickness, 0.375 wall thickness (WT), right?
x-65 and X-52 are "grades" perhaps?
24" L-1015 is perhaps 24" diameter? Pipe assembly nbr 1015?
So what is the diameter of Pipe 1?
21'-10 is the approximate length of pipe 1?
But what are the values in the BOM for parts 2,3,4, and 5? welded-on fittings for 2 inch diameter?

 

[valleytank]

There is already a much better way to achieve this connection of yours that was already hinted at with the appropriate internal bevel that is easy to achieve and butt weld-out/xray/mag do what you need to do. Ditch the threaded plugs altogether like 11echo mentioned. They are always weak points for LOPC, are often prepared wrong/wrong sealant, often overlooked, and should be used where needed unlike in the drawing.

Remember to perform the adequate UT/Visual on this daylighted pipe prior to making your cut-line decisions.