Combustible and poisonous gases are an occupational hazard of the petroleum industry. Hydrogen sulfide, methane and benzene are just a few examples of the potential gases present during extraction, transporting, storing or processing crude oil. As a safety concern companies and technicians work to detect and identify these hazards before they become dangerous. But how do you detect a barely leaking, invisible gas, before it spreads?
The answer: A large, industrial-strength gas detector.
"This is a big five-pound yellow detector bolted to a wall, or maybe put on magnetically," said David Schuler. "It's transportable in the sense that you carry it then bolt it on to something." Schuler manages sales & engineering for GDS Corp, a company that produces gas detectors and gas detection systems, including process monitors that work in tandem with the detectors (sometimes for gas, sometimes flame) to minimize risk for personnel and equipment.
Their latest device, called the GASMAX TX, uses license-free wireless broadcasts to transmit information about toxic or combustible gases present in the area. How does it work? "It depends on the gas," Schuler said. "There are really two methods." For toxic gases such as hydrogen sulfide, the GASMAX TX is outfitted with an electro-chemical sensor, which acts like a battery in reverse. In simple terms, gas molecules go in and electric current comes out. Electronics in the GASMAX convert the current into a calibrated gas value.
For combustible gases such as methane, the GASMAX TX uses an electronic infrared sensor. Hydrocarbon gas passing through the sensor absorbs some of the infrared energy and the drop in sensor output confirms the presence of combustibles. In many situations both hydrogen sulfide and methane can be present in dangerous quantities. Hydrogen sulfide is especially dangerous – at high levels it has no odor and can kill in minutes. "It's extremely dangerous in high concentrations,” said Schuler. The dual channel GASMAX TX supports both combustible and toxic sensors for maximum protection. While extremely important, a gas detector itself doesn't flash or ring; it's part of a system. Most gas detectors are hooked up to a central controller that monitors the health of the detectors and keeps track of the measured gas value. The gas detectors and controller, along with associated strobe lights and warning horns work together to provide the key early warning and allow operators to take proper actions.
"If the level goes above the value set by the customer it triggers the relay," Schuler said. "Typically what happens is warnings go off and the operators of the plant manually do something. Basically when you first start talking to a customer you can tell what industry they’re in by the name of their company. But then you ask 'what kind of gases are you looking for, what do you want to alarm for.' Once you settle on the particular sensor, you have to pick the range. Sometimes it's very low range. Sometimes it's very high range."
Unlike a household smoke alarm, which goes off after the stove is on fire, these gas detection systems create warning situations where catastrophes can be prevented. Because a potential leak can be a few parts per million (compared to air), a warning level situation could mean a mere 10 percent of that gas is in the air.
"It's really not that much," Schuler said. "Then there's the hazard level, that would occur when if you hit 40 or 50 percent of the levels you would consider dangerous. That's when the red strobe goes off and the horn goes off. That's when it's time to take drastic action."