Lesson 9 - Heat Exchangers SAQ

** Please answer the following questions.

a)   What are the two purposes of gaskets in a plate heat exchanger?

b)   What is the biggest risk of using gaskets?

c)   List some measures that can be taken when operating and maintaining a plate heat exchanger, in order to minimise this risk.

Response:

a)   The purpose of gaskets is to:

• provide a seal between the plates, which ensures that no fluid leaks out of the heat exchanger; and to

• provide a seal between the flow and distribution channels, thereby determining which fluid flows across each plate and the direction of this flow.

b)   The biggest risk of using gaskets in a plate heat exchanger is leakage. If fluid leaks out of the exchanger, it will result in product loss and also poses a potential safety risk. If one of the fluids leaks into the other fluid, the fluid will become contaminated.

c)   The following operational and maintenance measures can be taken to minimise the risk of leakage on a plate heat exchanger:

• Use gaskets recommended by the supplier that are the correct material and design for the application.

• Replace gaskets at the supplier’s recommended frequency.

• Pressure test the plate pack at regular intervals.

• When replacing gaskets, they must be fitted back into precisely the correct position, otherwise the exchanger will leak when it is closed up.

• Do not over pressurise the plate pack when closing up the exchanger.

• Ensure that the operating pressure and the temperature of the exchanger are within the gasket specifications.

• Ensure that the utility and product flowrates are kept within the design specifications of the exchanger. Furthermore ensure that there is minimal pressure difference between the utility and product streams. 

• Avoid pressure spikes to the exchanger.

• Maintain the product fluid pressure at slightly higher than the utilities fluid pressure.