Heat Transfer

Re-Design & Manufacture Of 2 Hairpin Exchanges

Customer: PD&MS

Location: UK

Challenge

The client’s original heat exchangers were constructed in 1991 & they required replacements designed to code and legislation (ASME VIII Div. 1: 2019). 

The changes in code meant calculation methods & resulting thicknesses changes. Based upon bringing the heat exchanger shells in line with the current code, the shell thickness had to increase by 3.86mm per side. This meant that the required number of tubes would not fit into the shell.

Scope

When cutting the door openings in the side of the steel plates, they were prone to buckling. Engineers had to devise a simple solution whereby if ‘𝑥’ is removed then an equal volume should be replaced in the area surrounding the opening. This methodology is applied to all openings cut when designed in accordance with ASME VIII Div. I.

The area cut out resulted in a shortfall of 356,809.7mm3. This would be a fail and we had to explore other options such as increasing pipe thickness to overcome this challenge.

Benefits

As a full turnkey provider, of heat transfer solutions we devised a solution by machining short lengths of pipe from code compliant forgings where we could increase the outside diameter. The obvious solution was to increase either the nozzle wall thickness or increase the pipe wall thickness (not possible due to the required surface area). We did neither and locally increased the wall thickness by using an alternative to pipe - off the shelf forged bar- which helped solve the problem as well we being lower in cost. Overall, this alternative method resulted in an overall project cost saving of 10%.

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