Why Your Relief Valve Should Have a Sensing Line

There is a vast variety of valve technologies implemented in residential and commercial applications, with each variation providing certain advantages and drawbacks. One advanced piece of equipment that significantly reduces dangerous system conditions is the relief valve, which effectively monitors and responds to changes in pressure.

These valves require three functional elements to achieve this superior protection: the valve, sensing, and reference force components. This blog will focus on why your relief valve should have a sensing line, especially if your system is highly industrious and potentially hazardous to others. Read on to learn more about relief valve technology, its relevant applications, and how you can ensure better protection for your existing infrastructure.

Basics of Relief Valves

Sensing lines are simply one of three elements that comprise a relief valve. The other functional elements include the valve (such as a spring-loaded poppet valve) and the reference force (usually a mechanical spring). All three work in tandem to provide a fail-safe relief route for backflowing fluids in emergencies. But how exactly does a relief valve function?

Changes in upstream pressure impact relief valves, and increasing pressure levels trigger the valves to open wider, allowing more fluids to escape safely. Conversely, drops in pressure cause the valve to close and seal, preventing escape for the liquids.

The first relief valve to operate as such was invented by French physicist Denis Papin in the late 1670s. Papin’s valve invention featured a weight suspended on a mechanical lever that lowered when steam pressure exceeded the counterweight, opening the relief point. Later, more effective valves with direct-acting deadweights and direct-acting springs were implemented on steam locomotives, providing proper engine pressure and overall performance.

As mentioned before, modern relief valves are quite simple and comprise three elements – valve, sensing, and reference force. The valve element is almost always a spring-loaded poppet valve, which is ideal for either elastomeric or thermoplastic (ultra-high pressure applications) seals. The spring component maintains the airtight seal unless the force of the upstream pressure exceeds this mechanism’s pre-designed tolerance. The spring itself is the reference force that opens and closes the poppet valve. However, relief valve technology is practically useless without the ever-essential sensing element.

The Importance of a Sensing Element

The sensing element detects changes in pressure, triggering the catalytic reference force element. The most common sensing line comes in a diaphragm style—a thin, metallic disc component—and is designed specifically for low-pressure, high-accuracy applications. Alternatively, piston-style sensing elements are sluggish and only suited for the highest pressure relief applications due to their increased friction. But what would happen if your relief valve didn’t feature a suitable sensing line?

Without this essential element, the valve and spring mechanisms can’t sense pressure levels quickly enough to provide the appropriate fail-safe solution in pressure-building situations. Even miscalibrated sensing lines cause functional complications for relief valves, including failing to reach proper pressure levels or maxing that pressure amounts to dangerous levels. And without a properly functioning sensing line, damaging plumbing phenomena like water hammer are more likely to occur, requiring expensive and disruptive infrastructure repair services. Relief valves also prevent pipeline ruptures, explosions, and, subsequently, physical injuries and death to nearby individuals.

Relief valves operate on passive power, which is ultimately activated by the sensing line. These devices are the best-suited defense against catastrophic pipeline conditions, whether controlled pneumatically, hydraulically, or electronically. The simple three-functional element design makes relief valves immensely dependable and reliable, further bolstering the protection of surrounding infrastructure and human life.

Applications for Relief Valves

Due to their efficiency and durability, relief valves are found in a wide variety of applications. Residentially, relief valves are installed onto boiler-based heating systems to reduce the likelihood of ruptures and explosions. While relatively rare, a water explosion is an immensely hazardous situation, as the energy it produces is capable of destroying entire homes. As such, any residential system with boilers should feature last-resort relief routes for gas and hot water.

Commercially, relief valves are used in a cornucopia of applications and industries, including the power generation, petrochemical, semiconductor manufacturing, aerospace and defense, refrigeration, and pneumatic systems sectors. Multi-phase refineries and chemical processing facilities often implement multiple relief valves responsible for monitoring and controlling massive devices, equipment, and pipelines. For convenience and better relay of information, these relief valves are connected by acoustic transmitters or related communications equipment.

Conversely, there are a few non-applications related to relief valves or instances where other valve technologies are better suited for the current situation. For example, any system with consistent, mid-level pressure levels does not require a sensing-capable relief valve. Rather, relief valves are most practical and beneficial when preventing potentially deadly system conditions.

Troubleshooting Faulty Sensing Lines

There are plenty of factors that can negatively impact the effectiveness and performance of your relief valve, from physical objects impeding the mechanics of the valve device to a misaligned cross-connection between the equipment and the pipeline. However, a common culprit for relief valve failure is a faulty sensing line. As such, it’s highly recommended that you diagnose the exact problem before replacing your valve parts. A simple adjustment to the sensing line’s sensitivity is often enough to resume proper functioning conditions. When in doubt, never hesitate to contact professional contractors and industry-familiar individuals for further diagnostic assistance. While these services may cut your business’s profit margins, protecting your equipment and others is well worth the investment long term.

Understanding why your relief valve should have a sensing line ensures you protect your systems and surrounding individuals from potentially harmful situations. Ultimately, this tiny valve component is the catalyst behind your system’s last line of defense; without it, complications can occur, and other functional elements can falter.

While incredibly durable, these relief valves require maintenance and proper care. Luckily, our expert team at Backflow Direct proudly carries the perfect equipment for your system protection needs. Aside from valve technology, we offer backflow preventer repair tools for troubleshooting various plumbing and pipeline complications. Contact us today to learn more about backflow prevention and how our solutions can benefit you and your business.

Why Your Relief Valve Should Have a Sensing LineWhy Your Relief Valve Should Have a Sensing Line