Industry Insight How Can Relief Valves Keep Chemical Plants Safe?

From Shaji Arumpanayil*

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Critical components for plants and refineries, relief valves help operators avoid a variety of safety concerns related to system overpressurization – but only if they’re placed in the right locations. That includes in high-pressure systems, when toxic fluids or chemicals are used, and when sensitive equipment is involved. Placed strategically, relief valves can help facilities vent excess system pressure buildups due to procedural error, component wear, contamination, or loss of power.

Figure 1 – Though pressure regulators are designed to maintain pressures at appropriate levels, relief valves remain one of the most effective fail-safe measures to ensure the safety of a facility.
Figure 1 – Though pressure regulators are designed to maintain pressures at appropriate levels, relief valves remain one of the most effective fail-safe measures to ensure the safety of a facility.
(Source: Swagelok)

In most chemical plants and refineries, fluid systems are complex and the interwoven network of small-bore tubing can branch in multiple directions, with each branch designed to accomplish specific functions. One challenge presented by this inherent complexity is that safety threats may occur when and where you least expect them. Since comprehensive monitoring of these complicated systems is difficult, the best way to avoid creating potential hazards is to make smart design decisions up- front. This includes using pressure relief valves at crucial points within the fluid system. Allowing excess pressure to vent could prevent blowouts, damaged equipment, and system failures, which is why pressure relief valves are such critical components of a well-functioning, safe fluid system.

Why are Relief Valves Essential for Safe Operation?

Not only is maintaining the proper fluid system pressure critical to operational efficiency, it is also the most effective way to keep employees safe and secure. Most fluid systems have pressure regulators to keep precise pressures operating throughout the system, but no system is perfect. That is why fail-safe measures must be included in any well-designed fluid system.

Relief valves are one of the primary fail-safe measures that should always exist within the original fluid system design (Figure 1). They should automatically open when excess pressure is detected to allow it to be released, since they’re designed to detect higher-than-normal pressures. The pressure may be vented into the environment unless the system media is toxic, in which case the excess pressure should be captured instead.

Relief Valves May be Activated

Though overpressurization may occur due to any number of reasons, generally they can be grouped into four broad categories:

  • Procedural error: Human error is one common reason for overpressurization since the systems are operated and maintained by people. For example, an incorrect valve may have been opened upstream, which could lead to increased pressure downstream. Another possibility is that system conditions may have been improperly calibrated or the wrong pressure regulator may have accidentally been installed. Extensive fluid system training can minimize the possibility of human error, but relief valves account for these potential problems and allow for corrections to be made.
  • Component wear: Relief valves are critical to maintaining safe operations, because even the highest-quality fluid system components will deteriorate over time, especially in systems that handle aggressive chemicals. If the system is not designed with the proper material alloys, corrosion may threaten the components, which can compromise pressure control.
  • Contamination: Dirty or otherwise contaminated fluids can negatively affect pressure regulators. Particulates may compromise the regulator’s seal, which allows unwanted pressure to flow through the system and increase pressure downstream. A properly placed relief valve will allow operators to vent the unwanted pressure before it can cause problems farther along in the system.
  • Loss of power: As fluid systems have modernized, many of them are controlled electronically, which works perfectly well until an unexpected loss of power causes the controls to go down. A lack of electricity may prevent certain components from working as intended, meaning relief valves may be the most effective way to manage potential overpressurization.

Figure 2 – Installing relief valves in high-pressure systems helps to prevent accidents.
Figure 2 – Installing relief valves in high-pressure systems helps to prevent accidents.
(Source: © 2022 Swagelok Company)

Where Should Relief Valves be Installed?

For chemical plant and refinery safety, there are specific applications where installing relief valves is essential:

High-pressure systems: When the pressure rises within fluid system applications, it is crucial to include relief valves to avoid potential accidents (Figure 2). Using high-quality small-bore tube fittings is the best way to keep pressure under control, but relief valves add another layer of protection by preventing overpressurization.

Toxic fluid or chemical applications: If toxic or hazardous chemicals are flowing through the fluid system, relief valves are essential. Overpressurization under these circumstances poses threats not just to the system but to employees as well. Using appropriate relief valves allows chemicals to be vented and captured instead of releasing them into the environment. Once they are captured, they can be disposed of properly.

Sensitive equipment: Relief valves are important in protecting sensitive analytical equipment from overpressurization threats. After all, online analyzers are expensive and can be irreparably damaged if pressures rise higher than they are equipped to handle. It is particularly important because analyzers sample fluids from main processes. Optimally, each regulator should have a correctly rated and set relief valve to reduce the fluid pressure by the time the fluid is delivered to the analyzer to avoid damage.

Optimizing System Design for Chemical Plant Safety

Making sure pressure relief valves are part of the initial design of an industrial fluid system helps chemical plants and refineries remain safe, though it is not the only way to do so. Designers should also avoid tube fitting intermix, streamline the system to remove unnecessary complexity and account for operational issues like vibration. If these factors are considered from the beginning, the fluid system will be safer and more reliable.

Once components are selected from the same manufacturer, it is important to follow that manufacturer’s instructions for proper assembly and disassembly procedures. This may seem like obvious advice—but even the most experienced technicians should take care to give a close reading to specific directions from the manufacturer.

Even a perfectly designed system depends on its operators, which is why facilities that handle hazardous chemicals must establish a culture where accountability is encouraged. If a dangerous situation occurs, especially when it puts employees at risk, it should be reported instantly—and employees should have the authority to stop production immediately. If employees are engaged with the commitment to safety, they can help make a chemical plant or refinery a place where everyone can feel secure.

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Finally, working with a supplier who understands what it takes to design and build safe fluid systems for chemical plants and refineries is crucial. Find a supplier with the expertise and experience to shepherd the process from beginning to end, to keep all systems performing reliably, even in the most demanding environments.

* The author is a Product Manager at Swagelok Company