Flow, level & control

advanced Coriolis meters Chemical plant

safety system features B

ASF’s Freeport, Texas plant manufactures superabsorbent polymer (SAP), which absorbs and retains large

amounts of liquids. The water-absorbing polymer has thousands of uses, ranging from diapers, masking tape, and artificial snow, to hot and cold therapy packs, motionless water beds and even grow-in-water toys. According to Daniel Siddiqui, BASF’s

Instrumentation and Electrical Lead Engineer, plant operators needed to replace flow meter instrumentation for the SIS, an engineered set of hardware and software controls used on critical process systems. The previous mass meter equipment was under review for replacement and BASF was researching options to upgrade to newer technology. Siddiqui says: “BASF wanted to explore options that would maintain our high safety standards but were economical.” The plant’s SIS was required to meet

safety integrity level (SIL) 3, a measure of system performance and probability of failure for a safety instrumented function, as defined in the IEC 61508 functional safety standards. Among other items, SIL 3 requires a SIS safety instrument with an override for any unusual conditions. Redundant flow meter instruments are required to alert operators to any flow deviations and trigger a safety alarm. Every time the deviation is greater than five per cent, the SIS system shuts down the production line. Operators knew that selecting the right instrumentation was critical to minimising any


intermittent or false alarm trips that would result in production line shutdown. Apart from the economic burden from loss of production and wasted material, premature stopping under full load – rather than normal ramp down for shut off – can introduce significant equipment wear and tear. “We reached out to KROHNE and the quote

we received represented significant cost efficiencies compared to the other vendors,” comments Siddiqui. BASF tested the KROHNE meter at its central laboratory located in Germany and approved it for SIS service. After reviewing a variety of options, BASF chose

a design featuring two KROHNE OPTIMASS 6400 Coriolis twin bent tube mass flow meters in a series to create the required redundancy. The flow meters are available in sizes

ranging from DN 08 to 250 and can be made in stainless steel 316L, Hastelloy C22, and Duplex steel UNS S31803. The BASF installation includes 2-inch meters – the external meter is made of 316 stainless steel, while the internal is composed of Hastelloy. Compliant with the User Association of

Automation Technology in Process Industries (NAMUR) standard installation lengths, the OPTIMASS 6400 operates in high temperatures up to 400°C, as well as cryogenic applications down to -200°C. It also handles pressures up to 200 bar (2,900 psi). It features the new MFC 400 signal converter, which offers fast, completely digital signal processing as well as enhanced diagnostic and status indications.

Price versus Performance and entrained gas management

Plant operators reviewing options determined that the price along with performance reliability on the OPTIMASS 6400 was superior to all other options. If operators obtained a reading showing a deviation or another issue with a process monitoring parameter, the meter helped identify the issue in advance, while still performing reliably under the abnormal conditions. In addition, the OPTIMASS 6400 offered a

key advantage – entrained gas management. Entrained gas can disturb the sensitivity of mass flow measurement of liquids, decreasing accuracy or even stopping measurement completely. The new Coriolis mass flow meter technology ensures both stable and uninterrupted measurements with high gas content. The OPTIMASS 6400 provides a reliable indication of gas bubbles in the process by using a combination of various measurements to detect a two-phase flow. With values between zero- and 100 per cent gas or air content in the line, it maintains the mass density measurement continuously and provides measured values at all times. At the same time, it can report the two-phase status and output a preconfigured alarm, in accordance with NAMUR NE 107 requirements. The smaller physical footprint of the meters

selected was another benefit making installation easier. For example, the KROHNE

April 2021 Instrumentation Monthly

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