On a typical oil and gas platform, heat exchangers are critical components for the proper operation of any hydrocarbon separation process plant. It is common practice for seawater to be used untreated apart from dosing with hypochlorite in cooling systems. The operation of the cooler presents a dynamic system, where the structural materials of the component can experience very harsh conditions. Thus, the selection of materials must ensure both economical design and reliable performance.
To test the suitability of materials for these kinds of service conditions, TWI built a set up to simulate the complex in-service environment of a shell-and-tube cooler. TWI then carried out testing of a Ni-based alloy (C276), typically used for this component, in order to assess its resistance to crevice corrosion in the simulated in-service conditions.
A lab-scale experimental set up was developed in order to be able to simulate a dynamic system as that of a shell-and-tube cooler and monitor its complex service environment, typically involving seawater with the heat exchanger design. The test approach was successful in an environment consisting of seawater with high dissolved oxygen concentration and free chlorine at +80°C