Gate Vavles on Buried Steel Pipe Watermain 2

[3lockbox]

Rather than using DIP, the City is requiring that I use 12" epoxy coated welded steel pipe in one particular area of a project (variety of reasons) for a watermain relocation (public water supply main). There's a need for a gate valve on this welded steel pipe. My question is this: Are there any steel gate valves rated for "buried service" on a potable water system? Or, would I still need to use standard cast or ductile iron body gate valves with transition pieces on each side to go from iron to steel? If I can't use steel pipe for buried application (due to corossion), then would it be okay to do so if the valve was in a chamber and not buried directly in soil? Never had to deal with steel pipe with gate valves on a potable watermain before, so I aplogize for my ignorance. Would appreciate any help / insight you can provide.

 

[cvg]

ordinary C-500, iron body, bronze mounted double discs should work. May want to use a long body dresser coupling to make the connection. Or flanged also works. Specify a flanged by plain end piece, cut to fit in the field and then weld in. That way you can line up your valve better.

 

[BigInch]

We bury most all steel pipeline valves in direct contact with soil. Specifying that the mfgr coat the valves with a suitable epoxy coating system works quite well.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[JStephen]

I would use valves intended for waterworks service, and I don't think the steel ones generally are.

You could use a flanged valve or use mechanical joint with a transition gasket for plain-end steel pipe.

 

[3lockbox]

Thanks all. From what's said here and other research, it's looks like I will be using a standard flanged DI body gate valve for waterworks applications, along with steel pipe with a flanged end and isolation gasket between the flanges. However, I'm still a bit concerned about field cutting the steel pipe, because the City is requiring the use of cement mortar interior lining and a factory applied fusion bonded exterior coating. Won't that complicate field cuts for fit up?

 

[BigInch]

Sounds like you're trying to tie-in a valve with no spool pieces. That's what will make it complicated.

Alternate suggestion is,

Make two cuts into the existing pipe at a distance apart equal to the valve length + 2 flanges + 2 pipe diameters + gaskets + 2 hairs.

Include two new short lengths of pipe (spool pieces, blue) for fit up, each about a minimum of 1 pipe diameter long plus a bit for final cut.

Bevel the flange ends of the spool and weld the flanges to the spools.

Assemble the spool+ flange, valve and spool + flange and check dimension, marking the field-cut-end of the spool for accurate cutting.

Disassemble, bevel the field-cut-ends of spool pieces and weld-in (red) each spool piece at the field cuts.

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Internal and external coatings will require repair after the tie-in cutting and welding... assuming welded flanges.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[BigInch]

Well it appears alt-chrs don't work very well.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[gerhardl]

In addition to advice from biginch; alternative valve selection:

Alternative valves could be double ecentric,double flanged handwheel and gear operated butterfly valves, ductile cast iron, epoxy coated, approved for drinking water, approved for burial, with stem extension. Plus: probably longer lifetime than centric discs and gatevalves, lower lifetime cost and not as heavy as gatevalves. Minus: not fully open pipeline for pigging.

 

[SteveWag]

JStephen has it correct. Use AWWA valves with Mechanical Joint ends. Replace the gasket with one designed for steel O.D. At most, you will have only ONE field-cut end. Your pipe crew will be using the same tools and equipment as if they were laying DIP. These transition or adapter gaskets are commonly stocked, they are a standard item. I spec epoxy coated valves, seems the industry is moving that way. Even without the coating, you will have no problems with the steel/iron combination.

Steve Wagner

 

[Maury]

Using flanged connections for buried piping is asking for problems. Flanged joints can't accomodate the movement that is going to occur with buried piping. Used mechanical joint valves.

 

[BigInch]

Buried flanges is pretty routine stuff, although I do prefer weld ends EVERYWHERE.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[cvg]

I agree, buried flanges are not uncommon and I have not seen problems either. This is a welded steel pipeline so having a flanged connection is not making things any worse. If you are worried about excessive movement and stress on the pipe, than maybe welded steel is not the material choice for you. However, that is one reason why I recommend possibly a dresser coupling which allows easy connection and some flexibility where you need it most.

 

[BigInch]

... actually there's a lot less movement and higher forces (and/or stresses) in buried pipe than there are in above ground pipe (at equal pressure & temperature) where flexibility is relatively everywhere, except at supports, guides and anchors.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com