When regulatory requirements are on the line, sometimes the best solution isn’t just accuracy, but also redundancy. PTT Public Company Limited (PTT) in Thailand was faced with local regulation authorities requiring measurement verification regarding volume and level accuracy in spherical LPG tanks at the company’s gas separation plant. Radar level gauges from another supplier were installed to provide the measurements. These level devices were critical to plant operation and safety, but PTT was concerned that the instruments were not reliable. These existing radar level gauges were not able to provide reliable tank content and safety functions for the operational process and governmental verification requirements. The level values often fluctuated incorrectly and then recovered without reason. As a result, feeding-in and -out activities were stopped, causing feeding pumps and valves to shut off. This lead to frequent downtime, preventing operation at full capacity. Another challenge was online verification with the tank in operation. The existing gauge did not perform well due to a big bolt protruding inside the 8-inch pipe. Non-compliance with authority requirements therefore resulted in suspended tank operation. All of these issues contributed to loss in both OPEX and man-hours.
PTT solved the problem by replacing the existing gauge on each tank with a Rosemount™ 5900S Radar Level Gauge with a 4-inch LPG/LNG antenna, specially designed for spherical tanks. This antenna has a unique built-in verification pin feature, which enables authorities to achieve real-time verification of level measurements remotely from the control room.
A new 4-inch schedule 10 stainless steel pipe with a matching flange (8-inch Class 300) was installed in the existing 8-inch pipe. To further improve the safety level, PTT chose to introduce gauge redundancy. Each tank was equipped with an additional Rosemount 5900S Radar Level Gauge, with a SIL 2 rated safety current output connected to a safety PLC. For communication, the existing tank gauge interface unit in the control room was substituted with a Rosemount 2460 System Hub. The existing inventory management software was replaced with Rosemount TankMaster™, but the original host system was kept untouched. Rosemount TankMaster can communicate with other tanks in the system, that are still equipped with gauges of the previous supplier. Tank gauging emulation allows for a step-by-step modernization of a tank gauging system, at a time and budget convenient for the customer. This PTT plant includes 19 tanks, equipped with 38 gauges, 20 of which are already in successful operation with the new tank gauging system from Emerson™. The remaining gauges will be replaced gradually.
PTT estimates that the solution has saved the company $45,000 in downtime, OPEX, and personnel time, increased safety, and most essential of all, enabled compliance with regulatory requirements.
Have you employed emulation to achieve redundancy?