Hello Robin,

Look into Ric-Wil and Perma-Pipe)(http://www.permapipe.com/) piping systems.  In these proprietary designs, the steam and condensate return piping are encapsulated in an outer conduit which includes intermittant supports.

Regards, John.

robinxie,

Also, check the "Piping Handbook" by Nayaar as well as the "Facility Piping Handbook" by Frankel...... both are by McGraw Hill and both are available from AMAZON

Oh, and get that cheap boss to pay for them, as well as the latest piping code, ASME B31.1...... there is always money for his trips, salary and expenses..... but never any leftover to pay for the things that the staff need to do thier job.

MJC

Lots of site specific things to consider in running buried steam lines. What are the ground conditions? Water table? I worked in the district energy business for a number of years, and the best rule for desiging steam piping like this is "it depends". What makes perfect sense in one system is just wrong somewhere else.

If a high water table isn't a problem, consider using Foamglas insulation rather than one of the pre-engineered systems. I laid a lot of line in an area that was mostly sand, once you broke through the concrete and asphalt. We just laid the line (giving it proper slope), insulated it with Foamglas, wrapped that in heavy roofing paper tied on with wire, and backfilled. It was a fraction of the price of the pre-engineered systems, was impervious to moisture, and VERY IMPORTANT in built up areas - allowed us to field fabricate offsets around the inevitable old sewer that didn't appear on any drawings. I knew of some jobs in other cities that were held up for weeks while waiting for the offset bits to be made-up, insulated and shipped.

We installed manholes at intersections, and in the middle of city blocks for isolation valves, expansion joints, and drip legs. Put 2 openings in the manhole structure so they can be effectively blown out with portable fans. The maintenance crews will thank you for this. Make sure that you install sumps in the manhole floors, and locate the sump under one of the manhole openings. This will allow the crew to pump out any accumulated water. Steam manhole environments are very harsh. Things don't stand up very well in most of them, including sump pumps. We always used portable gasoline driven pumps to remove water. Drop the suction hose (a reinforced high temp hose, or the hot water will collapse it sooner rather than later) into the sump and pump it out.

Consider using properly rated butterfly valves instead of gates. These save a lot of space down manholes. If you have a loop that can be fed from either direction, be aware that not all butterflys are rated to hold in both directions. Most have a better shut off classification in one direction over the other.

I kind of miss digging up streets to lay steam lines in a downtown environment :)

TBP,

How many of the "properly rated butterfly" valves that you have installed give tight shutoff after 10-20 years?  If they actually work, you are lucky.  Gate valves are able to cut through any scale or buildup and are generally a lot more robust valve.  Comments?

They just CAN'T be any worse than gate valves. I've also changed both kinds of valves down manholes. Butterflys are so much smaller and lighter, it makes an ugly job very much easier.

Plus, there's the space factor. There are a number of locations down manholes where it's a butterfly valve, or no valve at all.