Safety


in the information transmitted in the digital strings, as well as multiple fallback frequencies encoded in the string in case of a failure to receive the next stream of information at the expected frequency, it is possible to maintain seamless communication between the base controller and remotely located detectors, even when there is significant loss of individual strings of information. This fact significantly improves the overall robustness of the wireless link between the base controller and other gas detection system elements. Structures or equipment that may block the signal at one frequency, often have no effect on the signal at the next transmission frequency. This fact allows spread-spectrum RF transmission to work well in many areas where a traditional, single- frequency transmitter or radio would not be able to function.


This type of technology also makes it much easier for many users to share the same frequency range. Because it is extremely unlikely that two different RF system transmitters would hop at exactly the same instant between the same two frequencies, it is nearly impossible for one system’s transmitter to “step on” or block another system’s signal. Because of this fact, it is possible for as large number of digital RF systems to coexist in the same geographic area, without interfering with each other’s signals. This is what makes non-license required, ISM band radio based systems possible.


There are two basic approaches as well to the configuration of the remote server or host used to display and process information. The RF transceiver and software can be installed or plugged into a laptop, tablet or personal computer, in which case the monitoring information is displayed directly on the computer screen or LCD. Use of a laptop or tablet allows the full display of readings, status and alarm state information. The computer or tablet can also function as a communication hub, with digital communication outputs that allow information to be redistributed to additional remote locations.


Another approach is to use a dedicated wireless host to integrate the monitoring results from multiple instruments. Portable, wireless gas detection system servers are certified for use in hazardous locations, and designed to handle environmentally harsh conditions. The wireless host replaces the laptop or tablet used to integrate the system. The wireless host is designed for simplified operation. It includes a display as well as audible and visual alarms, and indicators that show the communication status of the instruments being included in the system.


Sometimes the wireless server is located immediately outside the monitored area, where it can be used to help maintain better communication between workers in the hazardous location and supervisors or emergency responders standing by outside the area. Sometimes the information is transmitted to a more remote location, for instance, the office of the safety manager, or to a third-party rescue provider. Sometimes the information is transmitted redundantly to several remote locations. Wireless technology allows real-time communication on a worldwide basis. Once the monitoring results exist as a digital information stream, the results can easily be sent onward within seconds via RF, cellular telephone, hard-wired landline, or over the Internet, literally anywhere in the world.


Portable wireless systems are scalable and capable of handling anywhere from one or two portable instruments, to 10 or 20 or more gas detectors simultaneously. An important architectural issue is whether multiple systems can be blended “on the fly” into larger systems or information arrays. For instance, a company might own several small, wirelessly integrated multi-instrument systems normally used one-at-a-time. In the event a particular


Author Details


Robert E. Henderson, GFG • Tel: 49 231 564 000 • Email: info@gfg-mbh.com • Web: www.gfg-mbh.com Robert Henderson is President of GfG Instrumentation, Inc. Mr. Henderson has been a member of the American Industrial Hygiene Association since 1992. He is a member of the AIHA Real Time Detection Systems Technical Committee, the AIHA Confined Spaces Committee, and is also a past chair of the Instrument Products Group of the International Safety Equipment Association.


job requires deployment of a single, larger system, or in the event of an emergency, it might be very important for additional monitors to be added very quickly to the smaller systems used during routine operations. The important thing is for the system to be capable of the flexibility required by the nature of the environment being monitored, and the work being performed.


Flexibility in the display of readings and alarm state information is also very important. The primary location for the display of the monitored results might be on the supervisor’s laptop, but the real-time monitoring information might also need to be redundantly displayed in the office of a third party rescue team.


RF wireless systems are able to maintain good communication over relatively large distances, even in structurally congested industrial environments. However, in some monitoring applications, such as underground or below grade vaults, tunnels or sewers, or when the detector is located in close proximity to vessels or structures made of heavy steel, it may not be possible to establish communication even when the wireless host is located within 20 or 30 meters of the remotely located gas detectors. It may be necessary to add an RF repeater unit that can acquire and retransmit the signal to get around corners or intervening obstructions.


Wirelessly integrated systems that are used for real-time health and safety monitoring must be able to identify and sound an alarm if there is a loss of communication between system elements. Generally, wirelessly integrated systems are based on RF transceivers that are able to both send and receive system information. The base controller transceiver constantly monitors to ensure that all remotely located detectors, remote alarms, and other RF enabled system components are in proper communication with the wireless server. Loss of communication between system elements can be detected almost immediately, and used to generate the appropriate local and general alarms. The wireless server does this by regularly polling the instruments in the system. If a remotely located instrument fails to respond when polled, the wireless server is alerted to the existence of a potential communication problem. Similarly, the remotely located instrument expects to be polled by the server. Failure of the remotely located instrument to be polled is


also cause for an alarm to be generated, this time by the remotely located gas detector.


• Real time wireless communication leads to enhanced worker safety


A very important use of real-time wireless communication technology is in confined space entry and rescue procedures. Wireless technology substantially improves the ability of supervisors to maintain communication with entrants, to alert workers if there is a need to evacuate the area, as well as to coordinate rescue activities. Regulations vary, but in many jurisdictions, certain types of confined space entries are permissibly made on a regular basis without the presence of an on-hand safety attendant. In this case, the inclusion of real- time monitoring data transmitted to a central location is a clear enhancement in the safety of entrants.


Wireless communication provides a particular benefit where, in the event of an emergency, rescue services are to be provided by a “third-party” provider. It goes beyond the scope of this article to debate the circumstances under which it is prudent to rely on rescuers who are not physically present at the site until after an emergency has occurred. The fact remains that many programs rely on exactly this approach to conducting a rescue. One thing is very clear, if this is the approach to conducting a rescue, the timeliness in sounding the alarm and / or activating the response team is crucial to the ability of the team to successfully respond to the incident. Having the atmospheric monitoring data and alarm-state information displayed in real-time on a monitor located in the rescue service provider’s office is clearly a large step towards improving the ability of the rescue provider to rapidly respond in an emergency.


When it comes to worker safety, it’s not enough just to monitor the conditions in the atmosphere. It’s what you do with the information that counts. Using wireless technology to distribute information in real time to the people and places where it is needed is transforming workplace safety. The wireless revolution is here to stay.


39


Gas detection controller achieves CSA approval


Oldham, a company within the 3M Personal Safety Division, is pleased to announce that the MX 32 gas detection controller has been certified by Canadian Standards Association (CSA) and now carries the CSA mark of approval. The MX 32 has been certified for use in Ordinary Locations according to CSA standards C22.2 No. 0-10, 61010-12 and UL61010-1.


The MX 32 is a compact, low-profile controller that continuously monitors multiple gas detection sensors. The versatile control system is designed to receive and supervise up to 8 inputs using either Wheatstone bridge mV DC sensors, 4-20mA DC or Serial RS-485 Modbus™. It can be customised and expanded based on individual application needs using Oldham’s stackable din-rail mounted I/O modules. Modules can be installed remotely to simplify field wiring and reduce costs. All modules are also covered by the CSA certification.


The MX 32 comes with several unique features such as its graphic display, voting function, gas measurement, event data logging, RS 485 output, and on-board A/V alarms. It is completely field programmable using COM 32, an advanced and intuitive programming software.


For More Info, email: email:


For More Info, email: email:


46643pr@reply-direct.com


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