Pressure safety valves and testing

DNV has developed and implemented a risk-based inspection (RBI) methodology that allows operators to reduce cost by focusing maintenance effort on poor performers, while simultaneously maintaining or improving safety.

With an ever-increasing focus on reducing maintenance expenditure, there is a need for safety critical equipment to function reliably. With preventative maintenance on pressure safety valves (PSVs) being one of the more significant integrity costs, increasing efficiencies in this area is important, with potential for time savings and performance improvement.

DNV’s RBI methodology involves a dual approach: with a quantitative assessment to account for random failures and a qualitative one for the system fluid-driven mechanisms.

The DNV two-pronged approach has several advantages:

It considers the behaviour of the specific PSV
It can include data from a wider set of PSVs as required
The change in risk from a change in interval is known and the risk from potential failure of any PSV is limited.

Example: For a PSV maintained every two years, an increase from two to three years cannot be considered without knowing how the PSV performed at the two-year interval. In the worst case, with the PSV subject to a time-dependent failure mechanism, there may be a relatively high probability of failure at two years meaning that on a three-year interval, the PSV would be inoperable for a year and the equipment unprotected from a pressure excursion. With proof of successful pre-overhaul pop (pre-pop) tests at 2 year intervals, an increase in maintenance interval may be justified.

Pressure safety valve manager

The Pressure Safety Valve Manager digital tool is client-accessible and contains all the information used in the RBI, including the (pre-pop) results. Detailed tabs contain the PSV performance history for the asset(s). The tool may also communicate with the operator’s computerized maintenance management system (CMMS) to accurately relay, not only the performance history of each PSV, but also information useful for maintenance planning, such as shutdown requirements, online testing capabilities etc.