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Runcorn, United Kingdom - July 27, 2004
Yokogawa puts safety first with new products and approvals
Yokogawa’s expertise in advanced digital sensing and transmitting technology makes it ideally placed as a supplier of safety-related systems for the process industries.
The recent approval of the EJA Series pressure transmitter by BNFL, plus the development of the EJX pressure transmitter specifically to meet the SIL2 safety standards administered by the TUV, are part of a continuing process which has also seen products such as the YTA temperature transmitter and the Digital YewFlow flowmeter completing evaluation by the independent research organisation Exida.com.
Sensing for safety
Like the earlier EJA Series, the new DPharp EJX Series is based on a sensing technology known as DPharp, developed by Yokogawa, which ensures high accuracy and stability with built-in safety features. The DPharp EJX is the first pressure transmitter series to be delivered as standard with TÜV approval, compliant with IEC61508 and with Safety Integrity Level (SIL) 2 of the new process industry safety standard IEC-61511. It is approved for both single-mode SIL 2 applications and SIL 3 in dual redundant mode. The IEC-61511 standard covers the functional safety of safety-instrumented systems (SIS) for the process industry, and is targeted at end-users implementing SIS for the process industry with the emphasis towards ‘proven in use’ reliability data.
The new transmitters build on Yokogawa’s many years of experience in the development of pressure transmitters. The company released its first digital pressure transmitter, the EJ Series, in 1991, and since then over 1.5 million devices have been sold worldwide. All use the same DPharp sensor and the same measurement software, with only small differences in functionality. However, in terms of reliability and hence safety, the EJX represents a major step forward. Whereas independent tests on the EJA indicated a mean time between failures of 456 years and a safe failure fraction of 88.7%, the corresponding figures for the EJX are approximately 1200 years and 93.2%.
The combination of a digital sensor with integrated processing circuitry also provides simple sensor diagnostics and hence high integrity, and also allows integration with a host monitor or controller in a full digital Fieldbus system.
More importantly, a feature of all DPharp sensors is that thay have always been inherently fail-safe. Because it is an active pressure sensor, the resonators resonant at their natural frequencies - even with no pressure applied. This means that if either one or both of the resonators fail, the transmitter will indicate a capsule error.
Safety systems
These new measurement products complement Yokogawa’s other safety-related systems activities. Yokogawa is the world's most experienced safety system supplier, embracing the IEC 61508 standard to provide customers with total life-cycle support.
The Yokogawa ProSafe family of products covers all industrial safety requirements, including ProSafe SLS for SIL 4 safety-critical applications and Prosafe PLC for emergency shutdown and fire & gas applications up to SIL3. MULCOM (Multiple Protocol Communications Interface) modules fully integrate these applications into the CENTUM CS3000 R3 control system to provide features such as maintenance override, trip status
and SOE recording to 1 ms resolution. All these functions are provided on one common HMI platform while maintaining system segregation.
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