Ammonia is one of the most widely produced chemicals and hazardous substances in the industrial sector. The continuous gas level measurement is necessary in order to alert in case of high concentrations in the air to avoid risk of explosions.
Moreover, it is important to use a set of equipment intended to reduce this risk. One of the world’s European market leaders of base chemicals, fertilizers, and mechanical recycling of plastics employs G.M. International devices to detect faults in gas sensors.
CHALLENGE
Gas detectors are common electrochemical sensors for continuous long-term ammonia measurements, and they provide the necessary defense measures in case of a hazard. However, to prevent flammable atmospheres, the entire system for detecting gas must function with absolute reliability in any situation. The Customer needed to update around two hundred gas detector safety loops to align them with the risk control measures, which means to implement suitable equipment capable of detecting gas detectors malfunctioning, or wire breaking. The final goal was to achieve a SIL 2 for all the safety loops involved in the application.
SOLUTION
Two G.M. International devices were used to upgrade the safety loops to a SIL 2: D5254S safety barrier, a power supply and isolating repeater, and D6014D module, an isolator also capable of splitting the signal.
In this application, the D5254S intrinsic safety barrier provides a fully floating DC supply to energize a conventional two wire 4-20mA transmitter located in the hazardous area. In case a fault condition is detected and if the origin of such fault is an open or a short circuit, the output of the barrier is automatically forced to 23mA or 3,5mA. Two independent alarms are also set to trigger further safety actions. The monitoring of both connections and the health of the sensor is then achieved.
The second device used to guarantee further safety was a D6014D isolator. The isolated output of the D5254S is wired to the input of the isolator which, configured as a signal splitter, can provide two analog signals. One is wired to a safety PLC (HIMaTrix I / O Card-ref. X-AI -32 01 analog input board) and the other one to the I/O board of the gas detector cabinet.
BENEFITS
The GMI technical team supported the developing and testing of the solutions provided, starting from the analysis of the existing situation. Fully programmable operating parameters of GMI D5254S module let the configuration have high level of flexibility. Settings and monitoring were also a big plus on this application that now meets the requirements for integrated safety according to SIL 2 level.
