gas detection case studies

Fonterra Facility, Mosgiel

En-equip recently supplied a large quantity of Vulcain gas detection equipment to monitor gas in the new Fonterra bulk milk powder storage facility in Mosgiel. The equipment needed to comply with NZ standard AS1668.2 where Carbon Monoxide gas (CO), in this case generated by forklifts in enclosed spaces, must be limited by mechanical ventilation systems to protect workers against health risks.

At the Mosgiel store, seven separate zones are monitored via multiple sensor networks (24 sensors in total) each with their own and individual groups of extract fans. The extract fans are enabled when any of the sensors in that zone detect a CO gas level of 25ppm or greater, and are then modulated via Siemens variable speed drives from 30% to 100% of full rated speed proportional to gas levels of 25ppm to 100ppm.

Vulcain VA301C zone controllers feature an integral buzzer and visual alarm indicator, as well as an alarm relay which closes when a gas level of 200ppm or greater is detected by any zone sensor.

Calibration of the sensors and an annual system test are also carried out as part of the ongoing product support offered by en-equip.

Carpark Extract System - Torrens Terrace Apartments (Wellington)

En-equip supplied a control system for the car park extract in the new Torrens Terrace apartment building in Wellington. The system needed to comply with AS/NZ standard 1668.2 which requires that the time waited average for the exposure limits to Carbon Monoxide gas is taken into account and that there is an audible visual alarm if this is exceeded or if there is a sensor fault.

As the building is made up of apartments, a Siemens SED2 IP54 variable speed drive (VSD) was provided with a slow ramp-up rate and reduced speed during the night times meaning minimal noise is produced during operation. The control system works via a feedback signal from 3 CO detectors back to a Siemens LOGO controller which triggers the VSD to run at a fixed speed dependant on the time of day.

En-equip engineers pre-commissioned and tested the equipment prior to dispatch, and the client was also supplied with detailed wiring diagrams. The operation of the system was tested onsite using pre-mixed gases after which full Asbuilt commissioning reports for the LOGO, VSD, and gas detectors were provided. A re-calibration service will also be carried out when the sensors require new certification.