TUBE/SHELL HEAT EXCHANGER 4

[padovano]

I have a tube/shell exchanger with steam been the hot liquid and Fuel oil the cold liquid.The steam is in the tubeside.It has been designed to work with a maximum pressure of 13bars. I would like to know if any small modification can be done to the heat exchanger such that it can support steam pressure of up to 17bars.

 

[hanon]

If the steam condensates inside the exchanger you could laminate in a the pressure control valve to 13 barg because you will have almost the same heating power indepently of the inlet pressure. The main source of enthalpy is during condensation.

Otherwise if you try to use 17 barg you will have to re-rate your exchanger and make an official test

Hanon

 

[padovano]

Yes the vapour condenses inside the the heat exchanger.
what do you mean by re-rating a heat exchanger. Is it something that somebody in a technical department in a refinery can do or does it need a specialist company to do.Thanks

 

[0707]

Your technical department should be in conditions to make the calculations to re-rate your exchanger. For licensing purposes maybe you have to contract a certified independent third part to witness any required official tests, this procedure has to have with exigencies of your country laws.

 

[EmmanuelTop]

Hello Padovano,

The Maintenance Department inside your refinery should be able to perform a calculation in order to rate your pressure vessel(s) for higher operating pressures. Significant factors include operating temperature, exchanger tube thickness, history (time) of exploatation etc.

I had an opportunity to re-rate naphtha stabilizer column from MAX 7.2barG up to 10barG, because of insufficient condenser capacity.

 

[EmmanuelTop]

Of course, be sure to include all system components (upstream and downstream of the heat exchanger), that will be exposed to higher operating pressure.

Best regards

 

[djack77494]

Do not approach the task of re-rating as if nothing is involved. Whoever certifies that the exchanger is able to be re-rated to a higher pressure must be qualified and the appropriate ASME stamp should be applied. Application of a new stamp involves a well defined process, developed to ensure that the exchanger can indeed safely perform at the higher pressure. It is not at all automatic that your ATTEMPT to rerate the exchanger will be successful. If successful, then the original design was "so overdesigned" that it could have been rated for the higher pressure (but for some reason was not). If the original design was not so robust, than your rerate efforts will not succeed without the need for some mechanical fortification.

 

[frogcurry]

Don't forget to revisit all pressure relief (fire, blowdown, burst tube/ tubesheet rupture) calcs in light of the design pressure change if you proceed with this.