Double Wall Heat Exchanger Safeguards / Code 1

[jserna4]

In using a double wall heat exchanger using potable water and glycol lines, are there additional safeguards that are standard practice? For example a double wall heat exchanger AND a 20 psi differential between the lines. Is this standard practice or unnecessary?

 

[georgeverghese]

What do we mean by double wall - is this is a double tube sheet HX ?

 

[PEDARRIN2]

jeserna4: Plumbing codes typically only dictate the double wall. A larger pressure differential (potable having the higher pressure), while good design practice, is not required.

georgeverghese: Heat exchangers for plumbing are typically shell and tube. Double wall is two walls on the tubes. Occasionally, I have seen plate and frame where the plates have a double wall separating the fluids.

It is a code requirement where the heating fluid could have chemicals that are harmful to people to insure if there is a leak in the tubes, no chemicals enter the potable water side.

 

[jserna4]

georgeverhese: PEDARRIN2 got it. They are special heat exchangers that are designed to protect potable water lines from a potential failure of a wall or tube. Rather than having one wall separate the fluids there is 2 walls and a thin air gap in between.

PEDARRIN2: Thank you for the answer. Are these typically AWWA standards, IPC or something else? EIT here and I appreciate all input!

 

[PEDARRIN2]

IPC 608.16.3 Heat exchangers. Heat exchangers utilizing an essentially toxic transfer fluid shall be separated from the potable water by double-wall construction. An air gap open
to the atmosphere shall be provided between the two walls.

 

[georgeverghese]

Amazing ! Havent seen these in the oil / gas / chemicals business.

Just took a look at this animal on the net - double walls on the tubes and a double tube sheet at both ends for the shell and tube version.

If there is loss of pressure differential, the glycol side would have to be depressured immediately, would imagine.

Must say we've never used potable water as process cooling medium - that is simply forbidden. Would be asked to go back to the drawing board and find some less risky way of doing things, like using a closed loop heat transfer medium or an air cooler etc.

But dont let me get in the way of some established practices in other industries.