In Part 2, I discussed using Exic for Zone 2 applications ‘Intrinsic safety in normal operation’ i.e. with no safety factor required.
To repeat, firstly and importantly, there is a misconception that the Co values are defined by the design of barrier/isolator. The Co value is actually defined in IEC/SANS60079-11: 2012 Table A.2 page 96.
So, any barrier/isolator with 28 V safety description will have Co = 83 nF (Zone 0/1; IIC). In practice, Co will define the maximum allowable cable length for most cases. However, as explained in Part 2, using Exic where applicable is one method to have longer cable lengths.
Gas Group classification impacts Co parameter as per Figure 1.
Figure 1: Co values.
Figure 2 shows an Exia loop with Co = 83 nF. The max cable capacitance Cc = 63 nF. With a typical cable capacitance of 95 nF/km, this would equate to maximum cable length of 660 m.
Figure 2: IIC IS loop for Zone 0/1 (Co 83 nF).
If the loop was Exic, then Co = 272 nF, so Cc = 252 nF would theoretically allow 2,5 km of cable i.e. no longer a limiting factor. (The limiting factor in this system is likely to be operating voltage at the end of the cable being high enough for the transmitter to work.)
If the Gas Group were IIB then Co = 650 nF, which eliminates capacitance as a limiting factor.
Conclusions
1. For installations requiring long cable runs, classifying the area as Zone 2 offers significant benefit.
2. Alternatively, a IIB (or IIA) classification is another way of allowing longer cables lengths.
Cathodic protection system for hazardous environments Omniflex Remote Monitoring Specialists
IS & Ex
When NSW Ports in Australia embarked on a two-year programme to rehabilitate the structures and combat corrosion levels at its Bulk Liquid Berth 1, it commissioned Melbourne-based consultancy Infracorr to deliver a bespoke cathodic protection) system. To deliver the system safely, Infraccor engaged cathodic protection specialist Omniflex to support the hazardous area and remote monitoring aspects of the CP system design.
Read more...Leading the way in PDS technology
IS & Ex
Booyco Electronics, an original equipment manufacturer specialising in mine safety equipment, has witnessed a surge in demand for its proximity detection systems (PDS) and collision prevention systems (CPS) since the Mine Health and Safety regulation focusing on trackless mobile machinery was promulgated. These systems offer crucial vehicle-to-pedestrian and vehicle-to-vehicle detection capabilities.
Read more...Ensuring lone worker safety
IS & Ex
The Conextivity Group’s startup – Wearin’ – has developed a solution connecting the lone worker with the control centre. This was commissioned by concrete producer, Pro Beton to ensure the safety of its teams of machine operators and cleaners working on production sites during the day, night, and weekends.
Read more...Safety breakthrough in live testing of large equipment
IS & Ex
While essential to effective maintenance, the live testing of mining vehicles and equipment can be hazardous and time consuming; but this has all changed with the SafeGauge range of digital testing systems. Developed in Australia, SafeGauge is now distributed in South Africa by Booyco Electronics, known for its leading role in promoting safety on mines through its proximity detection systems.
Read more...Explosion-protected control units Pepperl+Fuchs
IS & Ex
The new range of control units from Pepperl+Fuchs offers a clever solution for switching and controlling circuits in hazardous areas that are designated ATEX/IECEx Zones 1/21 and 2/22.
Read more...The importance of understanding SIL ratings Omniflex Remote Monitoring Specialists
IS & Ex
Major industrial accidents around the world, like the Bhopal chemical plant disaster, have occurred due to insufficient and poorly designed safety systems. Gary Bradshaw, director of alarm and safety system specialist Omniflex, explains how SIL ratings work and the dangers of the misconceptions that exist around them.
Read more...The importance of understanding SIL ratings Omniflex Remote Monitoring Specialists
IS & Ex
Major industrial accidents around the world, like the Bhopal chemical plant disaster, have occurred due to insufficient and poorly designed safety systems. Gary Bradshaw, director of alarm and safety system specialist Omniflex, explains how SIL ratings work and the dangers of the misconceptions that exist around them.
Read more...Mobile workers 4.0 Pepperl+Fuchs
IS & Ex
Intrinsically safe smart devices enable lone mobile workers to work seamlessly throughout the plant with the help of digital support. The significant increase in production efficiency and reliability is noticeable.
Read more...Functional safety over EtherCAT Eagle Africa Technology
IS & Ex
HMS Networks has released a new version of the Ixxat SafeT100 module, allowing users to implement safe I/Os for FSoE (Functional Safety over EtherCAT), which was previously available only for PROFIsafe and CIP Safety.
Read more...Overcurrent protection for explosion-protected areas Phoenix Contact
IS & Ex
The customisable Caparoc circuit breaker system from Phoenix Contact now also offers modules for explosion-protected areas, thereby extending the range of possible applications.
printer friendly version