PRV Evaluation Due to Manufacturer Recall and Its Impact in an Oil&gas Industry

In 2019 a major PRV supplier published a Product Service Bulletin about the flow capacity reevaluation for some balanced pressure relief valves used in gas or gas/liquid mixture services.

Under certain conditions informed in the Bulletin, the back pressure correction factor (Kb) may be lower than the value used to size the PRV. In these cases, the real overpressure will be greater than the expected. In other words, to a given relief scenario, the required PRV area to keep the overpressure under the limit stablished is greater than the value calculated originally. According to PRV supplier, the cause for this non-conformance is the spring selected to valves.

In November 2019 Petrobras Downstream Engineering Department was informed about the Bulletin. Petrobras has thousands of these pressure relief valves installed in upstream and downstream facilities. So, the question has arisen: how many installed PRV does not offer protection? Due to the potential impact in upstream and downstream installations, it was required a prompt response. Two main action points were identified:

• Contacting Corporative HSE to explain the problem.
• Preparing a technical note to uniform the understanding about this Bulletin, giving practical examples and tips to explore some margins to minimize the need for changing.

In December 2019 Petrobras HSE Department issued a Process Safety Alert to all upstream and downstream units. The Alert was focused on: what and why happened, what should be done and who should be contact both at PRV manufacturer and at Petrobras (focal points).

In April 2020 Downstream Engineering Department issued a technical note to support local engineers during PRV evaluation.

More than 2000 PRV were analyzed in our refineries by August 2020. At least 5% of the valves had the spring replaced. The same work was done in our upstream facilities. Both were assisted by Downstream Engineering Department.

Most PRV did not require spring change. But it is very important to be aware that future modifications (a revamp, for instance) may require a new PRV capacity evaluation. If the installed PRV keeps its original spring, this means that it must be re-evaluated using manufacturer Bulletin guidelines. So, knowledge management is the key to guarantee correct information will be available.

Since Downstream Engineering Department is responsible for Petrobras refineries and gas plants projects, the methodology to evaluate these balanced PRVs was incorporated in our process design manuals. For a more efficient dissemination, it was also made an internal presentation to our process engineers.

Besides the well-done work for the current conditions, the knowledge was consolidated to guarantee successful evaluations in future projects at Petrobras existing refineries and gas plants facilities.