What is gas leak detection in valves, and why is it important?
Safety valves used in industrial gas regulation and control systems are devices designed to ensure a high level of operational safety. These valves incorporate specialized mechanisms that ensure tight shutoff, preventing gas from continuing to flow into the furnace or process equipment in situations where it cannot be safely ignited or burned.
What is Proof of Closure (POC)?
Proof of Closure (POC) is a safety function integrated into certain valves that verifies that the valve is mechanically closed. Its purpose is to confirm that the internal mechanism has effectively reached the closed position, avoiding reliance solely on an electrical or control signal indicating that the valve should be closed.
Possible causes that could prevent effective valve closure include:
- Damage or wear on the valve seat.
- Presence of particles or debris on the valve disc.
- Failure or breakage of the closing spring.
- Mechanical sticking or blockage of internal components.
The implementation of POC systems significantly increases the safety of the combustion system, as it provides physical confirmation that the valve is closed and reduces the risk of fuel gas leaks. This helps prevent dangerous gas accumulation and reduces the likelihood of serious incidents, such as fires or explosions, protecting both personnel and process equipment.
What are the benefits of installing a gas leak detection system on valves?
According to NFPA 86, industrial heating systems must have two automatic safety shutoff valves installed in series within the gas train. Additionally, at least one of these valves must be equipped with a Proof of Closure (POC) device to verify that the valve has physically reached the closed position.
- Independent mechanical confirmation: The POC provides physical verification that gas flow has been interrupted, without relying solely on the control signal.
- Reduced risk of hidden failures: Minimizes the possibility that mechanical failure or internal wear could allow unintended fuel gas flow into the furnace.
- Prevention of serious incidents: Helps prevent explosions caused by the accumulation of fuel gas, which can result in severe injuries, loss of life, and significant damage to equipment and facilities.
- Additional layer of safety and diagnostics: Complements gas shutoff valves by providing an extra level of protection and diagnostic capability for the combustion system.
- Improved operational reliability: When combined with routine inspections, functional testing, and preventive maintenance, helps ensure the safety system operates reliably whenever it is needed.
In industrial safety, the best protection is not only having the proper devices in place, but also ensuring that they remain in optimal operating condition throughout the entire service life of the system.
What are the most common causes of gas leaks in valves?
There are several factors that can affect the proper operation of a gas safety valve and compromise its tight shutoff capability. The most common causes include:
- Damage or wear on the valve seat.
- Fatigue, deformation, or failure of the closing spring.
- Accumulation of dirt, particles, or debris that prevents complete closure.
- Natural wear of internal components due to operating time.
- Corrosion or deterioration of internal mechanical elements.
- Severe operating conditions, vibration, or frequent opening and closing cycles.
Although safety valves are designed to operate reliably for long periods of time, no mechanical device is exempt from wear or failure over time. For this reason, it is essential to implement a preventive maintenance program that includes periodic tightness testing.
As a best practice, it is recommended to perform at least one or two inspections per year to physically confirm that the safety valves maintain a tight shutoff and properly fulfill their protective function. These inspections help detect internal leaks, component wear, or any condition that may increase the system’s operational risk in a timely manner.
Periodic verification of safety valves not only contributes to compliance with industrial safety standards, but also helps prevent fuel leaks, reduce the risk of explosion, and ensure safe and reliable operation of combustion equipment.
How does a gas leak detection system for valves work?
In addition to safety valves equipped with Proof of Closure (POC) devices, NFPA 86 considers another widely used alternative to increase the safety of combustion systems: the Valve Proving System (VPS).
What is the Valve Proving System (VPS)?
A VPS is a system designed to physically verify that gas safety valves maintain a tight shutoff and that there is no fuel flow through them when they should be closed. Unlike POC, which confirms the mechanical position of the valve, the VPS directly verifies the actual sealing capability of the valves.
How does a VPS work?
The system is installed between the two automatic safety shutoff valves in the gas train and performs an automatic test before allowing the equipment to start.
In simplified terms, the operating sequence is as follows:
- Both safety valves remain closed.
- The VPS creates a pressurization or depressurization condition in the space located between both valves
- A sensor monitors the behavior of that pressure for a defined period of time
- If the pressure remains stable within the established limits, the system concludes that both valves are sealing properly and authorizes startup
- If the pressure increases or decreases beyond the permitted values, the VPS interprets that there is an internal leak in one of the valves and blocks system startup until the condition is corrected.
Benefits of VPS
- Physically verifies the tightness of the safety valves.
- Detects internal leaks that cannot be identified through electrical signals or limit switches.
- Significantly reduces the risk of fuel gas accumulation inside the furnace or process equipment.
- Increases the reliability of combustion systems.
- Helps comply with the safety requirements established by NFPA 86 and other applicable standards.
The main advantage of a VPS is that it performs a real test of the valve sealing conditions before each startup, providing a high level of certainty regarding the integrity of the safety system. This makes VPS one of the most effective solutions for preventing fuel leaks and minimizing the risk of fires or explosions in industrial facilities.
While a POC device confirms that a valve has mechanically reached the closed position, a VPS verifies that this closure is truly tight. For this reason, many facilities consider VPS one of the most robust tools for ensuring the safety of their combustion systems.
Which industries use gas leak detection systems on valves?
NFPA 86 establishes specific requirements for safety systems used in industrial heating equipment operating with gaseous fuels. These requirements include the use of devices that reliably verify the closure of safety valves and prevent the accumulation of unburned fuel inside the equipment.
In general, the standard considers the implementation of these safety measures in systems with capacities above 400,000 Btu/hr, a relatively low threshold within the industrial sector. This means that the vast majority of furnaces, dryers, incinerators, process heaters, and other industrial combustion equipment fall within the range where these protections are applicable or highly recommended.
The reason for this requirement is simple: as the thermal capacity of a piece of equipment increases, the amount of fuel that can accumulate in the event of a failure also increases. Even an apparently small leak can create a flammable mixture capable of causing fires, severe damage to facilities, or explosions with serious consequences for personnel.
For this reason, NFPA 86 promotes the use of redundant safety systems, such as automatic shutoff valves, Proof of Closure (POC) devices, and Valve Proving Systems (VPS), with the objective of minimizing the probability of uncontrolled fuel release.
Beyond regulatory compliance, the implementation of these technologies represents an engineering practice focused on protecting people, maintaining plant operational continuity, and preserving productive assets. In industrial combustion systems, safety should not be considered an accessory, but a fundamental component of design and operation.
Do you need to ensure that your safety valves comply with NFPA 86?
At NUTEC Bickley, we help you protect your plant and comply with NFPA 86. We offer industrial gas valves, Dungs valves, and a specialized gas train inspection service to detect leaks promptly, reduce risks, and ensure the safe and reliable operation of your combustion equipment.
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