Emerson Exchange 365

Saudi Aramco’s Qurayyah Seawater Plant (QSWP) is the largest facility of its kind in the world. With the capacity to filter and process 14 million barrels a day, QSWP is the source of a vast seawater injection network that includes thousands of kilometers of pipelines and nine downstream plants for injecting high pressure seawater into oil and gas reservoirs.

The efficiency of the entire network depends on QSWP operating smoothly and reliably—around the clock. Any process upset, whether large or small, could have a potentially significant impact on the downstream plants and all the reservoirs they serve.

So when equipment trips started to occur in the Old Treatment Module, one of QSWP’s main process areas, P.B. Sonara, a senior engineer at Saudi Aramco’s Sea Water Injection Department knew immediately that he had to improve the reliability of the equipment

Presenting today at the 2014 Emerson Exchange Americas, Sonara told the story of how he and his team accomplished this.

Each of QSWP’s fourteen Old Treatment Modules can process up to 500,000 barrels of seawater a day and consists of four large media filters, two high-powered seawater pumps, and 24 air-operated valves, all controlled and monitored by Emerson Process Management’s DeltaV distributed control system.

“Several times a month—sometimes two or three times a week—an equipment trip would occur at one of the Old Treatment Modules,” Sonara explained. “It seemed that any time a particular motor started in a module, a high vibration or high temperature alarm would sound and automatically shut down part of the process.” In addition to the lost throughput, which was expensive enough, for each trip event an engineering, operations and maintenance team had to spend approximately three days completing a trip analysis and report.

At first, Sonara’s team wasn’t sure what the root cause of the spurious alarms was. But then they realized that arc welding somewhere in the plant, or certain solenoids in a skid switching on and off, was setting off high vibration trip alarms. A series of tests finally revealed the culprit: improper grounding of wiring in the modules was causing electromagnetic noise to set off alarms and trigger the equipment trips.

“We discussed the issue of frequent equipment trips at specific areas of the plant with Emerson’s experts and identified remedial measures,” Sonara said. “We prepared an in-house engineering package and awarded a contract to a local contractor. This involved installing new instrumentation grounding systems in all Old Treatment Modules, as well as putting in new cabling schemes to ensure that all instrumentation was fully isolated from the rest of the module’s electrical grounding system.”

Crews switched out 30 high-power solenoids in each module with low-power 24V DC replacements and eliminated all interposing relays between air-operated valve solenoids and the DeltaV control system. Cables with low voltage instrumentation signals were rerouted in different cable trays to achieve adequate separation between low and higher voltage cables.

Once these measures were in place, the equipment trips began to fall off dramatically.

“The number of trips decreased from 124 in 2009 to just three in 2013,” Sonara said. “This is the equivalent of saving about 1,800 man-hours or 2.1 million barrels of throughput.  Overall maintenance costs have gone down because personnel are now able to focus on the work that’s most critical.  We came away with valuable knowledge about how to better plan for control system and instrumentation upgrades in the future. And most importantly, QSWP is running at the level of capacity, reliability and efficiency that it should be.”