Threaded Flange on 6" Pipe

[sider]

Hi all,

we have a project requirement for screwed flange on 6" piping. How usual is this solution and what problems can be expected?

The pipe will be located 3 m above the ground.

The current issue I foresee is that during the screwing of the flange, it would be hard to match the hole's position and the required length of the spool.
Also, not sure how that can be screwed, I suppose you need immense force...not sure a person can screw that on the ladders?

BR

 

[bimr]

Like Socket Weld fittings, threaded fittings are mainly used for small pipe diameters (Small Bore Piping); generally for piping whose nominal diameter is NPS 2 or smaller. The dimensional standards for taper pipe threads are given in ASME B1.20.1. That document gives all required dimensions including number of threads per inch, pitch diameter, and normal engagement lengths for all pipe diameters.

• Threaded piping is commonly used in low-cost, noncritical applications such as domestic water, fire protection, and industrial cooling water systems.
• Threaded fittings are normally made of cast gray or malleable iron, cast brass or bronze, or forged alloy and carbon steel.
• They are available in three pressure rating: Class 2000, 3000 and 6000.

https://www.wermac.org/fittings/threaded_general.html

 

[sider]

Okay, more of a story to it.

The system is chilled water, 10/20°C, we don't expect much thermal cycling since the system will work continuously on pretty much same load.

Victaulic client doesn't want it...welding little issue because of site.

However, in your comments, I realized that pipe specification for threading calls for a different thickness than our installed pipe (installed 168,3 x 4...required 165,1 x 5)...not sure can that be welded...I believe the outer dimensions must be the same, or?

 

[LittleInch]

Looks like you have two different pipe specs / standards there.

168.5 is 6.625", ASME B36.10 pipe.
165.1 is exactly 6.5", so looks like an older or different pipe spec - Only one /I can see is BS 1387 / EN10255

but 4mm isn't a lot for threaded pipe.

A slip on flange would be ok to weld to that, but make sure you order the right sized flange....

 

[sider]

How can these 2 different specs pipes be connected?

They system is flanged, so if I install 168,3 mm flange with raised face and fasten it to 165,1 mm flange, wouldn't the cross section for flow be obstructed slightly, because of internal diameter difference? Would that be an issue?

 

[LittleInch]

Yes, but only marginally. No different to jointing two pipes same OD, but different wall thickness.

It's more about having the same flange and whether that fits.

This sounds like an impending mismatch of pipe codes, sizes and flanges here....

 

[TBP]

6" diameter steel pipe in North America is 6-5/8" OD, and has been since the 1800's.

In my experience, intermingling Imperial & metric dimensions on the same job is a recipe for disaster.

If you have one of these simple measuring tools, it instantly settles all discussions over "what size pipe this is". It has saved me countless hours over the years.

Pipe Caliper – Black Anodized – Oregon Rule Co.

oregonrule.com

Remember that there are 2 separate scales - one is the actual OD, the other is pipe OD.

 

[Compositepro]

"Pipe" always has the same OD regardless of wall thickness, and the size is only nominal. "Tubing" is defined by its exact outside diameter.

 

[racookpe1978]

I regularly use 6 and even 8 inch NPT threaded fittings on temporary lube oil pipe assemblies for flush fittigns and lineups. But those are temporary use, low temperature (60 to 150 deg F) and low pressure assemblies.
Every threaded fitting MUST BE allowed to be screwed tight, then not further loosened! Screwing additional fittings on the end of an incomplete assembly spool is certainly appropriate and needed at times, but those "added fittings" MUST BE screwed on so the original fittings are not loosened. Screwing elbow nbr 4 or flange 4 or pipe 5 onto spool 1+2+3 can further tighten joints 1-2, 2-3, 3-4 etc. That very often occurs.
Putting the final spool into place with a bolted connected very often - but not always! - requires a union type joint than can allow rotation to align bolted flanges or a series of fixed (welded) joints.

Permanent assembly of a threaded joint over 4" nominal diameter? Not common, but allowed if it meets that's project's specific code. Not a generic national paragraph, but that owner's (and his insurance/operating) pipe specification.