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Heater Differential Temperature Monitoring and Alarming Using Associated IS

Heater Differential Temperature Monitoring and Alarming Using Associated IS

Challenge: Measure inlet and outlet temperature of a process heater using existing three-wire RTDs and provide a 4-20mA process variable signal, representing the differential temperature across the heater, to a local alarm trip for heater protection and share that differential temperature signal with the Basic Process Control System (BPCS). The measurements are in a hazardous area and plant standards require the use of a certified IS system.

Published: October 23, 2017

Detailed Description of Converting Dry Contacts to Analog Signals

Before converting a dry contact to an analog signal it is important to first determine what signal levels you will need.  Since the TMZ accepts a 4-20mA signal then we can choose any current values within 4mA and 20mA.  For this application we chose 'NOT FULL' to be equal to 20mA, and “NEAR FULL” to be represented at 4mA. 

 

Published: October 11, 2017

Remote Level Monitoring in Tank Farms

Remote Level Monitoring in Tank Farms
A Moore Industries customer wanted to monitor levels in new storage tanks that are remotely located on their tank farm and not connected to their existing MODBUS network. 
Published: October 11, 2017

Sharing Process Variables: Analog Isolation

When sharing one Process Variable (PV) with multiple systems, the connection needs to be thought out carefully.  Creating a series connection for the 4-20mA signal is not a best practice for sharing the PV. The main problem in creating a series connection is when either the DCS or the PLC input is disconnected, intentionally or by accident, both the DCS and the PLC will lose the PV signal.
Published: August 23, 2017

Temperature Q&A with JR Madden: Easy Thermocouple Replacement

Temperature Q&A with JR Madden: Easy Thermocouple Replacement
Q: Is there a less complicated and economical solution to replace a failed thermocouple than a complete shutdown of a boiler?
Published: August 8, 2017
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