Case Study: Refiner Solves Persistent Corrosion Problem Using Online Monitoring

Summary

Preem conducts extensive refinement of crude oil and the sale of petroleum products to oil companies active in Sweden and on the international market, mainly in north-western Europe. The feedstock is primarily crude oil in various grades, with renewable feedstocks under evaluation to produce green diesel. Final products include gasoline and different types of lubricants.
 
This case study focuses on a specific instance of severe corrosion identified on the top of a main crude distillation column in Preem’s Lysekil refinery in Sweden. The problem was located near a complex arrangement of pressure relief valves, and attempts were made to alleviate the corrosion through redesign of the piping in that area, and the installation of a new injection quill.
 
However, despite initial success lasting about five weeks, corrosion began to reoccur.
 

Identifying the issue

Severe corrosion was identified on the top of the main crude distillation column near a complex arrangement of pressure relief valves. The corrosion was found to be caused by a broken injection quill that was used to inject a neutralizing amine into the pipes. Without the proper injection of the amine, the pipes were susceptible to corrosion, leading to elevated corrosion rates.
 
The team installed a new quill and the corrosion stopped, but after some months, corrosion began to reoccur at a high rate of about 47 mils/year, indicating that the amine inhibitor was not the long-term answer, with further investigation required.
 

Root cause analysis

The refinery installed a Rosemount Wireless Permasense Corrosion Monitoring System from Emerson to continuously monitor the corrosion rate and identify the root cause of the corrosion (Figure 1).
 

Problem solved

In July 2021, the injection of neutralizing amine was stopped, and the corrosion rate was significantly reduced (Figure 3). In September 2021, another new injection quill was installed, and the corrosion was further reduced to almost zero.

Conclusion

Corrosion mechanisms are often very difficult to detect using manual monitoring methods, increasing the risk of pipe and vessel failure. Online monitoring using wireless clamp-on sensors addresses this issue by continuously providing data to specially designed software, which creates trends and uses algorithms to create alerts in advance of failures. This information is made available to notify plant personnel of impending issues so they can perform mitigation.
 
If your process plant or facility has a known or suspected corrosion issue, consultation with a vendor specializing in this area can help solve the problem before it causes downtime or an incident.
 
_{All figures courtesy of Emerson}