Rugged instrumentation for reliable measurement and control

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E-Help Tip: Monitoring and Alarm Options for Gas Supply Valves

Q: We have an existing Rosemount 1151DP tied to a Provox DCS. We also have a Moore Industries DDA 4-Wire Current and Voltage Alarm in the system to provide a Flow Switch Low and Flow Switch High interlock to our gas supply valves. Will newer products from Moore Industries provide more – or better – protection than the DDA?

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A: The STA Safety Trip Alarm and SPA2 Site Programmable Alarm have alarm functions and can be used instead of the DDA. Both products have FMEDA reports which define the Probability of Failure on Demand and can provide a better degree of protection than the DDA. Additionally, the HIM HART Interface Module has alarming functionality that could also be used with the 1151DP transmitter.

The STA monitors the analog signal and is specifically designed for IEC 61508 applications. It is approved by exida for use in Safety Instrumented Systems (SIS) up to SIL 2 and in redundant architectures (1oo2, 2oo3, etc.) up to SIL 3.

Like the STA, the SPA2 can also monitor the analog signal and provides up to four alarms, a display, and an optional 4-20mA retransmission. The SPA2 is our most popular alarm choice for loops that are not specifically designed in accordance with IEC 61508/61511The HIM monitors the digital component of a HART signal and can be specified with up to two optional relay outputs, which can be configured for signal level alarms or for a number of HART status bits. It can be used to provide diagnostic coverage for a HART transmitter since it monitors the transmitter’s status bits.

Do you want more information? Look up a data sheet to download. Or visit the catalog.

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