Route piping over or under cable trays?

[DGrayPPD]

Which is the better practice in the event that piping must cross cable trays?

Is it dependent upon the pipe joining method or insulation? If there's a chance of leakage I would think that routing the pipe under the cable trays would be better. But...

Does the radiant heat from piping impact routing underneath cable trays?

This is just a general question because I came across another piece of literature that I wanted to investigate further.

Thanks
DGrayPPD

 

[SwinnyGG]

In my world, always under.

Couple reasons:

1) In the world I operate in, wet utilities require a lot more maintenance and attention than electrical utilities do. Assuming you're talking about hung cable tray (not cable tray on the floor..) putting wet utilities underneath makes them a lot easier to access and maintain.

2) If there's a leak, I'd rather not spray my electrical service with solvent or paint or both

3) Replacing cables inside tray can be done in many cases without accessing the tray along it's full length. I.e. cables can usually (not always) be pulled from one end, or at least pulled through straight sections between tray elbows/tees without uncapping the whole tray. Wet utilities are usually harder to replace in this manner, so it benefits everyone to maximize access to them.


If radiant heat or possible high pressure spray from a leaking fitting is a problem, it is relatively easy to shield the cable tray from either of those hazards.

 

[SandCounter]

I would think under. You still have the possibility of spray from under, but you are protected from drips. If radiant heat is a concern, it doesn't matter if it is under or over as it will go out in all directions (radially). Convective heat would be a concern if you have natural air circulation or forced in an upward direction. Don't rule out using a sheet-metal heat shield or splash guard around either the pipe or the cableway in the vicinity of the crossing.

I used to count sand. Now I don't count at all.

 

[BigInch]

Where did you ever see pipe over cable?

Reaction to change doesn't stop it

 

[DGrayPPD]

Piping handbook referred to high temperature piping being routed over cable trays because the radiant heat could have an adverse effect on the cables.

 

[BigInch]

I'd ventilate, insulate and move them farther apart.

Reaction to change doesn't stop it

 

[SwinnyGG]

What 'piping handbook' are you referring to?

Radiant heat does not just go up.

 

[DGrayPPD]

Piping Handbook 7th Edition - Nayyar

 

[DGrayPPD]

I agree with routing pipe under cable trays not over. Just when I read something like that in a published book, I like to get second opinions to back me up.

 

[Gator]

Would this piping not be insulated anyway? That seems like a lot of wasted heat.

 

[DGrayPPD]

That would be my thoughts too Gator.

 

[Krausen]

In the pipeline facility world, this is company/operator preference. Typically the cables inside the tray are a higher priority to be able to access. Ergo, tray under

Tolerance is the virtue of the man without convictions -GK Chesterton