Function-testing safety valves like emergency shutdown valves (ESDV) or blowdown valves (BDV) is a significant job, and a key element for consideration is the travel time – the time that an ESDV takes to close or a BDV to open. Measuring safety valve travel time requires the operation of these critical devices, normally resulting in a partial plant shutdown with inevitable consequences on the production profile.

BP introduced its Safety Valve Travel Timer (SVTT) software at Sangachal Terminal in Azerbaijan, and after early successes it was further deployed offshore in the Azerbaijan-Georgia-Turkey (AGT) region.

The tool, developed and supported within BP’s Field of the Future program, automates travel time data acquisition and is designed to continuously monitor the operation and movement of ESDVs and BDVs. It calculates the time for a valve to transition from one state to another and compares this against the target time for showing results. The data are automatically collected during both routine and unplanned activities.

Deployment of the SVTT software helps reduce the number of function tests carried out on safety valves, thereby delivering significant cost savings. Moreover, the automated monitoring of safety valves allows proactive intervention on abnormal valve performance before failures occur.

Monitoring 1,841 valves

The onshore implementation of the SVTT covers 438 valves (356 ESDVs, 66 BDVs, and 16 flare valves) located at the Sangachal Terminal. Offshore, the SVTT was configured on 1,403 valves comprising 90 BDVs and 1,313 ESDVs – a combined total of 1,841 valves in the region.

The offshore implementation includes some subsea tree valves, but the monitoring focus and priority are on topside process safety valves. In the SVTT monthly report to the assets, valves are prioritized based on their safety integrity level (SIL) and environmental integrity level (EIL) rating, with particular attention given to valves with SIL/EIL 1 and above.

For wellhead-related valves, continuous monitoring presents a more marginal value opportunity because these valves undergo twice-yearly well integrity tests (WIT), which include pressure buildup test requirements. However, for these valves the SVTT offers continuous logging of valve movement that can track performance, especially when integrated with WIT results.

Travel time was configured using process safety hazard management measures documents, which included the valves’ performance standards. Data were critically reviewed and compared with the information found on the specific safety requirement specification and valves’ manufacturer data sheet. For the majority of valves, the most interesting target is the limit-to-limit time. Depending on the valve body size and application, the target times vary from 1 to 2 seconds up to 30 to 35 seconds.

The deployment of the SVTT software has been accompanied by a rigorous business process. A single point of accountability (SPA) was appointed to own the application in the region and liaise with all the relevant stakeholders within the company, including the Field of the Future development and deployment teams, instrumentation and control technical authorities, asset maintenance staff at multiple assets in the regions, and staff from other BP regions to share learnings and experience. The SPA prepares a monthly report for each asset in the region, providing routine valve movements tracking and data analysis.

Data and results

In the Caspian region safety valve health has been monitored on a continual basis with the SVTT software. The ones that fail to operate on demand or do not move in predefined target times are highlighted as “warning/fail” by the tool and investigated for corrective actions. The software analyzes the raw data to capture successful or unsuccessful valve events. As an example of one of the tool’s benefits, in the Shah Deniz field’s flare staging valves SVTT identified a number of valve openings/closures and recorded time, prompting an investigation. During shutdown a valve was found to be seized. It had operated about 5,000 times in a year, which led to its breakdown. Based on this process, pressure settings were reviewed to prevent recurrence. Other issues that the system has identified include:

  • Switch failure;
  • Corrosion;
  • Low valve air pressure; and

Sticking valve stem. Another important benefit is the reduction of function tests (preventative maintenance [PM]) taking advantage of valve movements during operations. In the Caspian AGT region, more than half of the PM is closed out using the SVTT, which saves at least 1,000 man-hours per year (assuming two to three hours of technician time for process isolation, verification, and de-isolation per PM). Considering that some ESDV PM requires train or full facility shutdowns, the closeout of these safety valves’ PM is estimated to deliver significant value well beyond the man-hour savings.

Around 100 to 120 movements are recorded on average in a month in the region, and of these between 1% and 3% can be “fail” messages. For the valves reported with “pass” messages, credits are taken and function-test PM is rescheduled accordingly. For the valves in “fail” or “unknown” status, a separate list is created, and a detailed analysis is carried out. The valves not complying with the target times are investigated and corrected.

The SVTT has helped BP reduce by half the number of outages needed for routine periodic function testing of critical safety valves. The recorded information has provided auditable proof of the valves’ operational integrity. Continuous valve performance monitoring also has allowed proactive detection of faulty valves, enabling early remedial measures and often avoiding the need for major overhauls, which require valve removal.

The successes in the Caspian have contributed to making this application a BP standard across the company’s operations worldwide.