Pumps and compressors are vital assets in a chemical processing plant. By count, pumps can easily account for at least a quarter of the rotating equipment in a chemical plant. Many of these pumps and compressors move hazardous media, such as toxic or combustible gases, across the various processing stages. Pump safety is thus of critical importance, and it is often built around preventing gas leakages. Any fugitive emissions at the pump—or even along the complex network of pipes—can lead to catastrophic consequences.
For rotating machinery professionals, there is the constant need to balance equipment operational uptime while safeguarding against hazards such as gas leaks. The need for efficient gas detection around pump and compressor installations cannot be understated. This article introduces the concept of wireless gas detection for pump safety. Gas detection is a power-hungry operation, and the majority of gas detectors in the market are wired devices. With advancements in battery technology and increasing plant adoption of open wireless protocols like WirelessHART, wireless gas detection is transforming the way plant users are detecting gas leaks around assets such as pumps, efficiently enhancing overall plant safety.
Typical Detection Points
There are several segments around a pump where gas detectors are typically deployed. Detectors are also deployed beyond the pump equipment, extending to infrastructure such as the pipe network connected to pumps. Here is a list of
leak-prone areas related to pump operation where there is a need for a gas detection point:
- Pump seal area (mechanical seals, packing glands) – any seal failure can release vapors
- Pump skid enclosure – inside the housing or close to the pump motor
- Ventilation outlets – to detect leaked vapors carried away by exhaust fans
- Nearby process piping joints – any joint or flange in a pipe is a path for leaks
Types of Gas Detection Used
Operators often deploy a diversity of gas detection technologies on pumps, as each technology caters to specific leak scenarios and installation environments. Image 1 summarizes the main types of gas detectors—fixed point, open-path, ultrasonic and portable—along with their key strengths and limitations. This comparison helps illustrate why a diversified detection strategy is often necessary to achieve comprehensive coverage in industrial facilities.
Demand for a Solution
There is an emerging trend of plant users using wireless fixed gas detection to augment the plant’s gas detection capability. Wireless communication in tough industrial applications is not new—in fact, it has been around for more than 30 years through the use of proprietary radios. However, with the modernization of industrial networks and the emergence of the industrial Internet of Things (IIoT), there has been an increasing demand for standardized wireless technologies, otherwise known as open wireless technologies.
Open wireless technologies are increasingly adopted for new applications such as gas detection. Examples of such open wireless technologies include WirelessHART and International Society of Automation (ISA) 100, both of which are based on the Institute of Electrical and Electronics Engineers (IEEE) 802.15.4 technical standard. These 2.4 gigahertz (GHz) signals have low-power features ideal for battery-operated devices and offer mesh network functionality that allows them to cover wide areas.
There are a few main market drivers for open wireless fixed gas detection.
1. Gas detection coverage where and when needed – With open wireless gas detection, the user is able to deploy a scalable network of gas detection points very quickly. Since there are no wires tethered to the gas detectors, placement can be flexible, especially in hard-to-access locations. This eliminates blind spots in the plant where there is no gas detection coverage.
2. Minimization of costs – Wire and conduit costs can be eliminated significantly, even up to 50%. In addition, there is no need for trenching or to obtain permits for new wiring for new gas detection points. Upfront engineering work is reduced.
3. Reliable performance – Open wireless protocols such as WirelessHART are proven-in-use protocols that have been used for more than a decade by multinational facilities across the world. These open standards are backed by multivendor support, and the self-healing mesh networks ensure wireless communication is of optimal reliability. New battery technologies guarantee multiyear operation on gas detectors.
Wireless Fixed Gas Detector Deployment Considerations
For WirelessHART gas detection, there are two sets of deployment considerations, namely the wireless network considerations and the detector position considerations.
• WirelessHART network considerations: Since WirelessHART is a mesh network, it is recommended that each gas detector has at least three neighbors within the effective range. That way, even if one or two of the primary paths become obstructed, there is still a redundant pathway back to the gateway via the third neighbor. These neighboring devices can be instruments from any manufacturer, as long as they are WirelessHART enabled. The effective range mentioned above is dependent on the density of obstacles (e.g., pipes, walls) within the network. The more obstacles, the lower the range. As a rule of thumb, a clear line-of-sight scenario offers 750 feet in effective range, whereas a heavy obstruction scenario reduces effective range to 100 feet.
• Detector position considerations: Determining the ideal gas detector sensor height on a pump system is usually based on the personal knowledge and experience of the system designer or operator. As a rule of thumb, to detect gases that are lighter than air, such as methane or ammonia, detectors should be mounted at a higher level where the gas is likely to migrate. For gases that are heavier than air, such as butane and sulphur dioxide, detectors should typically be mounted closer to the ground, but breathing zones should be taken into account. Hydrogen sulfide (H2S), for example, is a heavy gas with a breathing zone between 4 and 5 feet above ground. In addition, detectors should be positioned away from high pressure leak sources; otherwise, the gas expelled at high speeds may not
be detected.
Case Study: Monitoring an Ammonia Gas Leak
Challenge: The user wanted to monitor ammonia gas leaking from the pipes and pipe flanges connected to a pump system. The challenge in installing a wired gas detector arose because power and signal cables in the facility were prone to being damaged by the high concentration (>90%) of sulphuric acid that was spilled or present in vapor form in this lead metal processing facility. Previous wired detectors had their cables damaged from long-term exposure in a corrosive environment. The user wanted a long-term solution that would eliminate the issue of corroded cables.
Solution: A WirelessHART network already existed in the facility. The gateway (i.e., industrial wireless router) was located about 100 meters from the pipe flange. The high density of piping made it difficult to run wires to a new wired detector, so deploying a WirelessHART gas detector was ideal in solving the challenge of inaccessibility. The nearby network of WirelessHART pressure transmitters provided a strong mesh network for a gas detector to latch on. The user was able to save at least $2,000 in cabling costs per detector just by selecting wireless gas detection over a wired option. More importantly, they were able to create monitoring points instantly without time to lay the cables.
pipe flange
Wireless gas detection adds a valuable layer of flexibility and coverage to traditional gas detection schemes in pump applications. By eliminating the need for costly and complex cabling, wireless detectors can be rapidly deployed in hard-to-reach areas or for remote pump installations. This flexibility allows operators to enhance safety by augmenting open-path and ultrasonic systems with additional monitoring points as and when needed. Wireless gas detection technology is transforming how industrial facilities approach gas detection, even down to its deployment on equipment such as pump systems, ensuring that pump systems remain protected while operating as optimally as possible.
