pipe expansion loop

[been]

Mechanical engineers use expansion loops to take care of thermal expansion on long pipe runs. Are expansion loops required if pipes are free to expand or contract? Is it because the pipe penetrate fire walls and need be fixed at the penetration? Or is it the building design has expansion joints and pipes need to be fixed at wall penetration?

 

[wanebell]

been;

If the piping run is not fixed anywhere along it's length, there does not need to be an expansion loop in the run. I think, however, that you would be hard pressed to find a piping run that is NOT fixed somewhere. This includes not only the ends of the run, but any taps or laterals that are connected to the run.

 

[cjw81]

Been- I worked in a Facility that gives a good example- we ahd a pipe tunnel 3 miles long with saturated steam at 150 psig. Every few hundred feet we had an expansion joint on the line- 12"-10" and 8" joints. The pipe decreased as it came closer to my Facility's end of the tunnel. The joints measured 12" x 4.5'. Basically bothe ends of the joint contained about eight rings of 5/8" packing to make the seal and allow the pipe to expand from either direction. Within a few feet of each, there is a pipe support anchored to floor and ceiling with horizontal members that have sleeves welded on so that pipe can slide over the support. The pipe is never welded to a stationary support, it is allowed to expand and contract smoothly over the length of the run.There were no bends or loops in this run of three miles it was all linear expansion. If you have the room you could make an expansion loop to take up the expansion,but you would be talking about substansial space in this case. Expansion loops are virtually no maintenance, where as joints are a maintenance item. Space is a sustansial predicator of choice.When going through a wall, we use a sleeve and expandable foam or intumessent firestop. Never locate a joint at a wall.

 

[imok2]

Been,
You usually find expansion loops in piping that cover long distances and are on open ground such as the Alaska pipe line .. In buildings you would normally see expansion joints because as jw81 said, you lack the room for large expansion loops.

 

[MJCronin]

bean,

You state: "Mechanical engineers use expansion loops to take care of thermal expansion on long pipe runs".......This statement is not quite complete.

A more accurate statement would be: "Mechanical engineers use expansion loops to take care of thermal expansion STRESS LEVELS and COMPLY WUTH THE PIPING DESIGN CODES on long pipe runs"

Remember, all of the piping design codes currently in effect require the piping engineer to consider thermal expansion stress levels in his design. Hot piping systems that are "thermally bound" have failed, causing loss of property and lives.

Hot piping systems are also designed to utilize mechanical expansion joints to mitigate the effects of thermal expansion.

Suggest that you spend some time with a book such as "Piping Handbook" by Nayaar, where all of this is expained in much more detail....

My opinion only


MJC

"There comes a time in the affairs of man when he must take the bull by the tail and face the situation." W.C. Fields

 

[Hookem]

Engineers (not just mechanicals) use expansion loops as one means (not only) to take care of piping flexibility (not just thermal expansion) on all (not just long) pipe runs.

Expansion loops (or expansion joints or other means) are required because pipes are never "free" to expand or contract. Each loop should be limited to about 12" of movement.

Call a consultant.

 

[been]

Many thanks to all who answered my questions. I would like to point out that my questions started out with hydronic system where volume expansion of the fluid inside pipes are taken up by thermal expansion tank thereby the stress on the piping is pretty much constant. I understand that because of temperature change, say in the range of 150 degrees F there can be substantial pipe elongation. Being a construction document reviewer I see a lot of design documents and quite a bit of variety of them. Some building structural engineers specify aneapansion joints every 20 feet of wall length and mechanical engineers note that the hydronic pipe to have expansion loops at the contruction joints although on the drawings they locate the expansion loops at different locations.

 

[TBP]

Expansion tanks and expansion loops deal with different things. Expansion tanks in hydronic systems deal with the expansion of water, as opposed to the pipe itself. Expansion loops or joints in piping systems deal with the expansion of straight runs of the pipe itself. A large hydronic heating system may require expansion loops or joints, depending upon the layout. Any size of hydronic heating system will require an expansion tank.