Short spool pieces? 1

[Chinook82]

We're about to replace qty 16 old magmeters with new ones. However the new ones have a shorter lay length leaving a 6.25" gap from old to new in our 20" lines. 55 PSIG water service, ambient temperature,
150# flanges.

Having custom spool pieces manufactured is looking expensive and standard rubber expansion joints typically have a free length of 8 inches.

Any easy solution?

Thanks, Dave

 

[zdas04]

That is a truly awful length difference. Weld neck flanges are 5.6 inches from face to bevel so two don't fit. It appears that they make a 20-inch slip on flange which is 2.88 inches from flange face to hub. So you could put two of them on a 6.25 inch stub, but you couldn't fit studs into the half inch gap.

I thought you could put in a wafer check (without the flapper) to fill the gap, but the ones I've found are 8.625 inches thick.

What you could do is make a spacer piece that fits between the flange gaskets like a wafer check would, but is 6.25 inches thick. It won't be cheep, but no solultion in 20-inch is going to be cheep.

David

 

[ColonelSanders83]

Use two slip on flanges on a pup piece and select bolts long enough to clamp it together like a wafer check valve.

an extension of zdas04's thinking. Sure as hell beats having a custom piece machined and this is perfectly suitable for the service.

A question properly stated is a problem half solved.

Always remember, free advice is worth exactly what you pay for it!

http://www.ap-dynamics.ab.ca/

 

[StevenHPerry]

Could you split the difference and get 3" thick polypropelene spacers on both sides? That sounds better to me for some reason than a single 6" long one.

Paddle spacers have standard lengths, but custom lengths are not unheard of. Maybe not 6x the standard lay length... but it's possible I suppose.

- Steve Perry

http://www.linkedin.com/in/stevenhperry

This post is designed to provide accurate and authoritative information in regard to the subject matter covered. It is offered with the understanding that the author is not engaged in rendering engineering or other professional service. If you need help, get help, and PAY FOR IT.

 

[moltenmetal]

Spacers are the way to deal with this, but they won't be cheap. At this distance, you could just weld two lap joint stub ends together to form a spacer of the correct length, and then through bolt the thing to hold it in place "wafer style". Flangeless spacers of this type are routinely used in plastic-lined pipe systems. When you think of it, they're not a whole lot different than a device like a wafer style magmeter. Ugly, but it would work.

 

[SEP87]

We regularly use coupling rings, just a fancy spacer really, for natural gas applications. We buy ours off the shelf so the price is not an issue. For a specific length requirement the price would be significantly more.
As previously mentioned, making it yourself could be much easier, the only possible issue with this is getting the required approvals for it (if necessary). Bodging bits together, although functional, may lead to a lot of hassle in the long run regarding conformance etc.

 

[donf]

I second Moltenmetal's suggestion (two stub ends, no flanges). I've used them before for the same reason and service.

donf

 

[racookpe1978]

Assuming a 150 lb flange bolt pattern?

6.25 inch gap - 2x 0.125 gaskets = 6.00 gap.

5.60 weld neck flange length + slip-on flange (over the weld neck) with a 3/8 weld margin under the slip-on flange for the internal slip-on weld = 5.975

Since you need 16x "spacers," make a bench jig clamping both end flanges so they are perpendicular to the center line and have a proper (2-bolt) hole alignment for the bolts.

The slip-on flange, at just over 2 inches long itself, might be the only thing giving you a problem: The slip-on flange may jam against the increasing OD of the weld neck flange, requiring you to trim the weld neck slightly. Going to depend on manufcturing tolerances there. However, at 55 psig water service, stresses will be very, very low for a 3/8 thick (minimum) fitting wall.

 

[Chinook82]

Thanks guys for your help with this one. I ended up with a couple of quotes that fit the bill. One from the major flange supplier in Texas, and the other from a local fabricator using water jet cut flanges out of 1/2" and then welding the length of pipe in between. Came in at $1600 a piece.