When toxic gas or oxygen levels get out of control, it’s vital to have the right systems in place. RC Systems can help you determine the best way to protect your people and equipment with a range of detection systems.
Refineries often employ a combination of detection systems. From portable devices used for site walks and confined space releases to fixed systems that use computer modeling to identify high-risk leak locations.
Portable
Using portable gas detectors on the job ensures workers remain protected from toxic or flammable gases that could leak into their breathing zone. A wide variety of detectors are available, each with its own sensitivity and detection range to suit the specific application. Digital innovations are rapidly improving the accuracy and speed of these systems, with improved diagnostics and intelligence minimizing the frequency of false alarms caused by everything from birds flying through an open path gas detector beam to trucks passing through a chemical sensor’s field.
Portable gas detection monitors are critical safety equipment for all personnel working in confined spaces. They are also vital for monitoring the presence of hazardous chemicals like benzene. These chemicals can cause skin irritation or even respiratory failure if the vapor concentrations reach dangerously high levels. In fact, a single exposure to benzene is enough to meet the Occupational Exposure Limit (OEL) of 25ppm for an eight-hour period, making it an extremely dangerous and potentially deadly contaminant.
While many combustible and toxic gases have identifiable odors, other chemicals such as hydrogen sulfide, carbon monoxide, nitrogen accumulation (causing oxygen deficiency), or a cloud of oleophilic hydrocarbons can be invisible and odorless. Therefore, a reliable gas detection system must be in place to ensure the health and safety of all refinery workers.
Depending on the location and potential hazards, fixed gas detectors can be either sampling or in-situ monitors. A sampling device will collect a sample of the gas and send it away for analysis, while an in-situ open path detector will pass a beam of infrared light over the gas effluent to detect it based on its odor or composition.
Regardless of the type of system selected, it is important that all monitors are regularly tested and calibrated. This can either be done on-site by a technician or may need to be sent away for calibration at an external service laboratory. Depending on regulation, local requirements, or the type of sensors used, the test and calibration intervals can vary from daily to once every year.
Fixed
Depending on the type of refinery and activities being performed, a range of different gases will be monitored. For example, as a primary function of a hydrocarbon processing plant, it is common to monitor for toxic, flammable, and asphyxiant gases such as methane, benzene, carbon dioxide, hydrogen sulfide, sulfur dioxide, nitrogen oxide, and nitric oxide.
For safety and process management purposes, it is vital to have a robust monitoring system in place at any site. This should include both portable devices and fixed systems. Using a combination of both types is ideal as they provide a complementary set of technologies that work together to cover the most comprehensive range of possible gas hazards and threats.
Portable gas detectors are designed to be carried by workers and offer an on-the-go, point-of-detection solution. They can be used to detect one or more gases and typically include alarms to help employees take action. These types of systems are great for assisting with site walks, issuing permits for entry into confined spaces, working around high-risk equipment, and integrating into the overall plant alarm system.
Fixed gas detection monitors are usually mounted at a strategic location in the refinery to continuously monitor a given area and can be integrated into the overall plant alarm system. Depending on the application, this may include identifying leaks or triggering a shutdown of an entire section of the plant.
The two main types of fixed gas detectors are sampling instruments and in-situ open-path systems. Samplers collect gas through tubes or receptacles and then analyze it in an internal cell, while open-path detectors send a beam of light through a sampled stream to assess the chemical composition of the gas. Open-path detectors can be used to monitor large areas, as opposed to a single point, and are less likely to be impacted by obstructing objects in the line of sight.
Both systems are vital for ensuring that people and assets remain safe in hazardous workplaces. With the advancement of digital technology, it is now easier than ever to improve performance and reliability, as well as simplify use and maintenance, for these types of monitoring solutions. If you are looking to improve or enhance your current gas detection system, be sure to speak with a specialist for advice on the best options for your site.
Open Path
The release of toxic or combustible gases dispersed over a wide area can be a disaster waiting to happen. Such a leak only needs an ignition source to start an explosion or fire that could quickly spread, damaging equipment and possibly putting workers at risk of injury or death. Gas detection systems are one of the best ways to prevent such incidents by alerting personnel to unsafe levels of toxic or combustible gas vapors in the air.
Open-path gas detectors use a light source and detector to measure the presence of a hazardous concentration of toxic or combustible gases. The detectors send a beam of modulated light into the space being monitored and measure the amount of light absorbed by the presence of the gas. Open path monitors are known for accurately sensing the presence of gases over a wide area, which is why they are very popular on pipelines and offshore drilling platforms. They are also very effective at detecting gas in outdoor areas, where the risks of fires and explosions are much greater due to undetected combustible leaks.
Unlike point detectors, open path monitors can operate in harsh environments with heavy vibration and operating temperatures up to +65C. Depending on the model, they may be resistant to the penetration of liquids and dust. They are also more reliable than sampling monitors and require less maintenance. Most models can detect multiple types of toxic and combustible gases, including a combination of both.
Many portable and fixed gas detectors are designed to work in the harshest environments and can stand up to extreme weather conditions, corrosive work environments, and temperature swings. In addition, they are often able to send real-time data to a central monitoring system so that operations can be monitored remotely. These models can also often connect via 4-20mA, RS485, or relays and are typically housed in stainless steel explosion-proof enclosures. Typical uses for this technology include monitoring safety, process, and environmental parameters in refineries, chemical plants, pipelines, and industrial facilities, as well as oil exploration, drilling, and production fields.
Combination
A refinery handles a diverse range of toxic and flammable gases. In addition to the perimeter/fence-line monitoring, it’s critical for a refinery to have gas detectors in place throughout the process areas for both combustible and toxic hazards such as hydrogen sulfide, carbon monoxide, oxygen, and hydrocarbon gas. These are the most common types of gases found in a refinery, but every plant is different, and it is important to understand what the specific hazards are at each facility to determine the best solution.
A combination system can provide the most effective coverage for a refinery by combining portable devices with either open-path or fixed-point detectors. A reputable provider of safety systems will help you assess your needs and recommend the appropriate detectors.
Personnel can wear portable devices and typically use a thermal difference principle to detect dangerous gases. They work by placing two beads in close proximity – one inert and one coated with a chemical catalyst – and as the catalyst is heated, it causes the other to heat up, resulting in a change in electrical resistance. This is then measured and converted to a reading that can be used to indicate the presence of a toxic or combustible gas.
On the other hand, fixed devices are generally installed at a strategic location and connected to a supervisory control and data acquisition system for constant monitoring. They often operate over a large area, which can require multiple detectors to cover the entire facility.
For expansive areas such as a refinery fence line or a pipeline route over flat terrain, an open path detector can be ideal as it sends a beam of light through the gas effluent stream to measure its composition by absorption. However, this method is not as effective in a complex refinery process field where distillation columns, scrubbers, and reaction vessels may be obstructing the line of sight.
New digital innovations have the potential to minimize the shortcomings of this type of detector, such as the frequency of false alarms caused by rogue readings on chemical sensors or physical obstructions in the line of sight of the open path detector beam. These innovations can also improve accuracy and diagnostics for existing systems and can make them easier to maintain, calibrate, and troubleshoot.
