Whether we shall consider MAWP for tubes in the heat exchangers design? 1

[mechengineer]

Hi,

Whether we shall consider MAWP for tubes in the heat exchangers design?
I don't think this is necessary, even if it is given by some softare. The reason is that the tube material is not required CA as per TEMA RCB-1.517. The tube machanical design is just based on the design pressure.

Regards

 

[SnTMan]

MAWP of tubes both internal and external is usually considered in evaluating the exchanger MAWP. In my experience the tubes only rarely govern.

Regards

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[mechengineer]

@SnTMan,

However, I think that you didn't consider the CA for the tubes, how to get the MAWP of tubes?

Regards,

 

[SnTMan]

CA is not often applied to tubes. If one is specified it is usually much less than the CA for main components. It must be stated whether it is to be applied to OD or ID or to both.

If tube CA is specified then tube MAWP calculations are carried out considering CA as with any other components.

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[mechengineer]

HTRI design margin 10% will allow to block 10% of tubes if the tubes leak till the heat transfer area is lower than design required. in that case, it may replace the bundle due to the tubes failed. That may be the reason why it does not consider the CA in the heat exchanger design.
The design loads for the tubes are not only the internal/externla pressure. There are the axis loads due to the thermal expansion and the tube sheet bending, and the loads/stresses at the weld joint of tube to tube sheet is more complex. Currently, there is not possible to get the true MAWP for the tubes as an individual component by calculation and it is not necessary.

MAWP may be only applicalbe for simple loads and shape of the components. The heat exchanger structure complex leads to complex tresses analysis. Thus, whole heat exchngers will not be evaluated by MAWP except by the design pressure. Or MAWP may only be applicable for shell and channel with flanges without the bundle.

Another way to get the MAWP for whole heat exchager is taking the assumed MWAP as the input of the design pressure and rerun the calulation by software.

I hate MAWP and feel it is just a game of consuming engineer time and energy without values whatever in technical and commercial. Link

Regards