SAIMC Johannesburg elects new chairperson

February 12th, 2016, Published in Articles: EngineerIT

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Mike Banda, chairman SAIMC Johannesburg.

The Society for Automation, Instrumentation, Measurement and Control (SAIMC), Johannesburg branch elected a new chairperson at its AGM held in Bryanston on 10 February 2016. Outgoing chairperson Eric Carter handed over to former secretary Mike Banda.

Other committee changes included; Alvin Seitz stepping down as treasurer and Cheryl Hird taking over as treasurer, with Elri Klee taking over as secretary and Gary Friend now vice chairperson. Committee members are Andrew Bharath, Eric Carter, Ann de Beer, Steve Elliott, Kudzai Mberi, Tebogo Mulauzi, Jabulani Radebe and Alvin Seitz.

Friend gave an update to members regarding the SABS TC165 standards that have been adopted to date; IEC/SANS 61508 functional safety of electrical/electronic programmable electronic safety-related systems; IEC/SANS 61511 series on functional safety – safety instrumented systems for the process industry sector; IEC/SANS 62443 series on industrial communication networks – network and system security; and IEC/SANS 62682 series on management of alarm systems for the process industries.

Speaker 

Friend was also the speaker of the evening, wearing his Extech cap, and gave an in-depth presentation on surge protection in IS loops. The talk covered what the standards say (control room and field devices), running cables through IS trunking, cable lengths for IS loops (IIA, IIB and IIC gas groups, and Exia, Exib and Exic), using IS isolators in SIL loops, and mobile devices.

SABS60079-25 dictates that sensors in Zone 0 “shall” be fitted with surge protection. The use of the word “shall” is binding and a rule. A risk assessment must be done in susceptible areas for instruments in zones 1 and 2. For example, if the field wiring is 100 m or the instrument is 10 m up, then surge protection is recommended. IS surge protection is available for the field instrument and the field wiring can land on surge protected terminals to protect IS interface and PLC/DCS card. These devices must be documented in the IS loop.

“For Exd field instruments requiring the field wiring run to be in IS trunking or multicore, an isolator can be fitted in Exd enclosure in the field and then run back to an isolator in the control room. Care must be taken on which is active and passive for all connections and that the IS calculations are safe,” he explained.

Limitations on IS cables lengths  have always been an issue generally limited by the Co capacitance value. Zone 0 or 1, IIC has Co=83 nF (for Uo of 28 V), but changing to Zone 2 (Exic), it becomes 272 nF. Also, if the area gas group can be defined as IIA or IIB, the Co value is high and it is likely that the limiting factor will be the working voltage at the end of the cable.

Friend also spoke of Safety Integrity Levels (SILs): SIL3 is generally specified and is an over specification which carries a high cost. “In a nuclear plant, perhaps 5% of the loops could be SIL3, although individual components can be SIL3 capable, the hardware fault tolerance values dictates that 1oo2 or 2oo3 redundancy must be used to achieve SIL3. It is the safety function that is SIL rated, not the components and it must include full closed loop”.

In terms of mobile devices, Friend explained that there is still clarification needed but it is important that the mobile device is Icasa approved. “Ex rugged mobile devices will change the way we work by improving communications, providing auditable maintenance, safety for lone workers, and video collaboration. Ensure that the special conditions of the Independent Communications Authority of South Africa approval (the X behind the certificate number) do not limit what you can do with the mobile device.

Contact Ina Maartens, SAIMC, Tel 086 107-2462, admin@saimc.co.za

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