Moving Away from Hard-Wired

Wireless gas sensor systems make it safer to explore for oil and gas.

In addition to high concentrations of flammable gases, workers operating in the oil and gas exploration industries are at risk for exposure to "sour gas" -- gas containing H2S (hydrogen sulfide) at potentially toxic levels. Operations located in densely populated areas pose additional threats of exposure to the general public. The danger can develop over time, even if the original source was initially "sweet" (low in H2S).

The NIOSH recommended exposure limit (REL) for H2S gas is 10 ppm, and the OSHA permissible exposure limit (PEL) is 20 ppm. The NIOSH IDLH level, the concentration at which H2S gas is immediately dangerous to life and health, is 100 ppm.

In order to keep its workers safe from flammable and toxic gases, the oil and gas exploration industry installs low-level H2S and flammable gas detection systems on its rigs. Traditionally, these systems have been fixed, hard-wired systems. While these systems have proven to be reliable and effective, the industry continues to look for technology that not only will keep workers safe and meet regulatory requirements, but also improve productivity. An alternative that many companies are finding to be a good solution is wireless systems.

Mobile Rigs, Immobile Detectors
Unlike fixed facilities used for oil and gas production, companies doing oil and gas exploration move their rigs from location to location on a regular basis to maximize operational efficiency and to adapt to market demands. A rig can be in a particular location for as little as two days before it is moved to another location.

Unfortunately, the fixed, hard-wired, H2S/LEL gas detection systems currently being used on the majority of these rigs are not ideal for transportation and repeated deployments. They are difficult and time consuming to install and often require specialized knowledge to install power and signal cables in accordance with both national and local safety regulations.

In addition to being very heavy and difficult to transport, traditional fixed gas detection systems take a long time to install and can pose trip hazards due to use of cables. Cables are run all over the rig, especially in high-risk areas. A big concern is incorrectly installed cables, which can cause trip hazards. This generally involves the use of cable trays and support structure, including the possible penetration of bulkheads or partition structures.

In land drilling applications, ditches are often the solution for safe installation of cables covering long distances. Installers dig ditches approximately 0.5 meters to 1 meter deep and then lay the cables and backfill the ditches. They then tie the end cables or superficially connect them to the rig structure. Junction boxes allow installers to run cables to sensors in high-risk areas where flammable and toxic gases originate or accumulate. When a rig such as this is decommissioned or goes "rig down," workers most often just cut the subsurface cables and leave them in the ground to save time. This is very costly because new cables will have to be run when the detection system is installed in the new location.

Because there have been many developments in wireless technology in recent years, the benefits of deploying wireless solutions are not always widely known. Wireless technologies have matured and can now be reliably used in crucial detection applications. Wireless systems have several advantages over fixed systems for oil and gas exploration companies. For example, wireless systems are now certified for use in applications that require intrinsically safe instrumentation. This allows users to place the sensors as close as possible to gas sources and improves their ability to detect harmful gases.

Unprecedented Flexibility
The cable-free portability of wirelessly connected systems gives safety managers unprecedented flexibility. Wireless gas detectors are compact and light in weight, allowing complete detection systems to be transported in a single case. It allows them to quickly and easily shift from one area requiring monitoring to another area without the hassles, costs, and technical expertise required to relocate hard-wired systems. It also allows them to easily monitor multiple locations at one time and from one location at a lower cost compared to fixed systems, representing one of the ways wireless solutions increase productivity.

Wireless systems also can send alerts to remote safety managers or incident command centers. This is in addition to the traditional on-scene notifications of piercing audible alarms and flashing lights. These alarms provide immediate and unmistakable alerts to workers in the immediate area, but also send a wireless alert so that remote managers can deploy help faster. It also gives safety professionals verifiable assurance that workers, contractors, or responders are reacting to alarms appropriately. Remote connections give safety managers and commanders greater insight into alarm status and greater control when incidents happen.

Lower costs top the list of benefits wireless systems offer. Wired detection systems often cost three to four times more than comparable wireless systems. The reason for this is the high cost of installing cable-based detection systems necessary to meet intrinsic safety requirements. Having to dig trenches and run conduit and cables accounts for the lion's share of the higher cost.

Lower installation costs make wireless systems more portable. Instead of having to move bulky equipment and cables, all you have to do with a wireless system is power down the detectors, move them to the new location, and power them back up. This is a big advantage if you'll be moving them every couple of months.

Power requirements are also a concern. With recent improvements in wireless technology, it is now possible to have low-power, 24/7 radio communications using only a small internal battery. The replaceable batteries will provide up to six months of continuous detection and communication. If battery replacement is an issue, several wireless systems also offer intrinsically safe solar panels that power detectors continuously. Using a fixed-wire system requires a hard-wired power source, which limits system mobility.,/p>

Wireless systems may also provide higher reliability than fixed systems. In a fixed system, a damaged sensor or a damaged cable can shut down a process for hours. With a wireless system, you eliminate the possibility of a damaged cable and sensors can be replaced in minutes, not hours. Battery-powered wireless systems also will continue to operate during catastrophic conditions, including power failures.

Wireless systems are easier to calibrate and maintain. Wireless portable detectors can be calibrated at any location, while fixed devices can only be calibrated at the sensor location. And because wireless systems typically have fewer parts overall, it's easier to fix problems that do arise.

For applications with assets at fixed locations, hard-wired systems do have a couple of advantages over wireless systems. Batteries do have a finite lifetime, while wired systems will run indefinitely, as long as power is available. Wired systems also have an advantage when it comes to how far they can transmit a signal. Fixed systems can transmit signals much further than most wireless systems.

Wireless Systems Improve ROI
The bottom line is that wireless detection systems not only make oil and gas exploration safer, they improve return on investment. Wireless systems pay for themselves over time because of their inherent efficiencies and low installation and maintenance costs. Deploying a wireless gas detection system takes less than hour and requires no specialized training. Just remove the system components from the single portable case and power them on.

All radio connections are done automatically. Power connections are not required because all of the detectors are battery operated. When it’s time to move the system to a new location, simply put the complete system back into the portable case and redeploy in minutes at the new location.

Wireless solutions also can help to reduce such expenses as fuel and travel costs because personnel rely more on remote data sent wirelessly. The solutions potentially can lower insurance premiums as a result of improved worker protection.

There have been many improvements in gas detection in recent years. One of the most significant improvements is with regards to radio and battery technology. While traditional, hard-wired, fixed gas detection systems will always have a place in the industry, portable and wireless gas detection systems can improve worker safety and increase ROI in many oil and gas applications.

This article originally appeared in the July 2012 issue of Occupational Health & Safety.

About the Author

Yan Banducci is global product manager of Fixed and Mesh Networking Systems for RAE Systems (www.raesystems.com).

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