Spring-Loaded and Pilot-Operated Safety Valves and Their Industrial Uses

Here's a detailed explanation of spring-loaded and pilot-operated safety valves and their industrial uses.

Spring-Loaded Safety Valves

• Description: These safety valves feature a simple, self-contained design consisting of a valve body, a valve seat, a disc (or poppet), a spring, and an adjustment screw. The spring actively exerts a force on the disc, keeping it pressed against the valve seat and the valve closed under normal operating conditions. You can adjust the spring tension using the adjustment screw, enabling customization of the set pressure of the valve.
• Operation: When the system pressure exceeds the set pressure, the pressure forces the disc away from the valve seat by overpowering the spring force, opening the valve, and allowing excess pressure to vent out. Once the system pressure drops below the set pressure, the spring forces the disc back onto the seat, closing the valve.
• Applications: Industries use spring-loaded safety valves in various applications such as boilers, pressure vessels, and different piping systems, especially where the fluid is gas or steam. These valves respond quickly to sudden increases in pressure.
• Advantages: Spring-loaded safety valves are self-contained, straightforward, and reliable. They operate without the need for any external control or power supply.
• Disadvantages: These valves have limited capacity, might not handle extreme pressure fluctuations effectively, and can suffer from issues like "chattering" (rapid opening and closing), which can damage the valve.

Pilot-Operated Safety Valves

• Description: Pilot-operated safety valves are more intricate than spring-loaded valves. They comprise two main components: a main valve and a pilot valve. System pressure and a smaller spring close the main valve, acting on a larger surface area. The pilot valve, essentially a small spring-loaded safety valve, controls the opening and closing of the main valve.
• Operation: When system pressure surpasses the set pressure, the pilot valve opens first, reducing the pressure on top of the main valve. This action opens the main valve, venting the excess pressure. As the system pressure drops below the set pressure, the pilot valve closes, and the main valve reseals.
• Applications: Industries commonly use these valves in high-capacity and high-pressure applications such as chemical processing plants, power plants, and oil and gas facilities. They are ideal for liquid-based applications because they can handle large pressure fluctuations and higher flow capacity.
• Advantages: Pilot-operated safety valves offer greater capacity, improved performance with liquids, and increased stability compared to spring-loaded valves. They can accommodate more significant pressure fluctuations and are less susceptible to chattering.
• Disadvantages: These valves are more complex and costly compared to spring-loaded valves. They might also need periodic maintenance to ensure proper functioning.

Both types of safety valves play a crucial role in maintaining safe operating conditions in industrial systems. They prevent equipment damage and protect workers from potentially dangerous situations. The choice between spring-loaded and pilot-operated safety valves depends on the application's specific needs, such as the fluid type, operating pressure, and flow capacity.

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Convenient Rupture Disc Selection Form from Continental Disc Corporation

CDC rupture disc.

Continental Disc Corporation is a leading manufacturer of rupture disc (bursting disc) devices for a variety of process industries, including chemical, petrochemical, petroleum refining, pharmaceutical, food and beverage, aerospace, industrial gases, transportation, and other markets worldwide.

They have a very convenient online form to assist in replacement of an existing rupture disc, or to specify a new installation. The form can be found by following this link. The form gives you the option to print it from its online page, or to email the form to Continental Disc sales department for a quotation.

In 2017, CTi Controltech was appointed the exclusive Continental Disc and Groth Equipment representative in Northern California and Nevada.

Rupture Discs - Designed to "Fail"

Rupture discs can be combined in series for additional functions.
Image courtesy Continental Disc Corp.

A rupture disc, sometimes known as a pressure safety disc, burst disc or bursting disc, is a one time pressure relief device most often used to protect a vessel, pipe, or container from over pressurization. As opposed to pressure relief valves, rupture discs are designed to function only one time by providing an instantaneous response to an over-pressure condition, providing sufficient venting flow to disallow any further pressure increase.

These sacrificial parts are designed to burst when pressure within production equipment exceeds a certain threshold by breaking down, stopping the process to prevent or mitigate hazardous events. Rupture discs are critical instruments utilized so that companies can ensure process safety as set forth by the International Safety Standards (IEC 61508/61511).

The safety devices prove most effective when they fail according to pre-established specifications. Inferior rupture discs may cause unnecessary and expensive production shutdowns by bursting at the wrong pressure. Adequate quality testing and manufacturing expertise assures performance in accordance with ratings.

Rupture discs are commonly used in chemical, petrochemical, nuclear, aerospace, medical, railroad, pharmaceutical, food processing and gas & oil applications. They provide primary or backup protection. Very often rupture discs are used in tandem with safety relief valves, protecting them from the process media and extending the life of the relief valve.

For more on rupture discs call CTi Controltech at 800-288-7926 or visit their website.

Rupture Disc Products For Industrial Process Safety from CTi Controltech

Components for Industrial Tank Venting and Flame Arresting

Flammable gas line flame arrester
Image courtesy Groth Corp.

Pressure and Vacuum Relief Valves are protection devices often mounted on a nozzle opening on the top of a fixed roof atmospheric storage tank. Their primary purpose is to protect a tank against rupture or implosion by allowing the tank to breathe, or vent, when pressure changes in the tank due to normal operations.

Pilot Operated Relief Valves serve the same primary purpose as pressure/vacuum relief valves, but with better performance characteristics than weight or spring loaded valves. Lower leakage and better flow performance make a pilot operated valve the solution when the focus is product conservation, expanded tank working band, and reduced fugitive emissions. A pilot operated relief valve provides the maximum available leakage control technology as specified in the Clean Air Act of 1990.

Emergency Relief Valves protect tanks against excessive pressure caused by external fire exposure or flashes within the tank. Emergency relief valves provide higher flow capacity than standard pressure/vacuum relief valves.

Deflagration Flame Arresters are fire safety devices used to protect stored or process media from deflagrations. A deflagration flame arrester can be used on the top of a tank or as an in-line safety device where combustible gases are transported through low pressure pipe lines.

Detonation Flame Arresters provide flame protection in cases where the ignition source pipe lengths are greater than what can be protected with a deflagration arrester.

Blanket Gas Regulators can provide both pressure and fire protection for storage tanks by supplying a blanketing gas which maintains a constant positive pressure in the vapor space of a storage tank. In addition to preventing outside air and moisture from entering the storage vessel, a blanket gas regulator reduces the evaporation of the stored product to a negligible amount, resulting in product conservation and greatly reduced emissions.

Matching the function and capacity of each of these safety valves requires engineering expertise to assure proper operation. Share your requirements with product application specialists, combining your own process knowledge and experience with their product application expertise to develop an effective solution.

Flame control products for industrial fluid operations from CTi Controltech