How Fire Safe Butterfly Valves Work

Butterfly valves are effective flow control devices that use a rotational disk to regulate the flowing media in a particular process. The wide use of this type of valves is attributed to its tight shutoff and quarter-turn operation. For many industrial facilities, it has always been a concern if a butterfly valve will continue to function efficiently during a fire incident. When there is a valve failure during fire, it can result to further damages and can endanger human lives. Such concern has prompted manufacturers to create fire safe butterfly valves.

Fire safe butterfly valves are manufactured in various designs, all of which must allow them to function properly even during fire situation. The most common fire safety feature is focused on the valve's sealing capabilities. Usually, a butterfly valve with a fire safe feature comes witha two-tier sealing configuration. The main sealing seat provides positive shutoff and bubble tight sealing under normal circumstances. It is usually made of the material called polytetrafluoroethylene (PTFE) or Teflon. Although it offers some resiliency to temperature, Teflon still has a high tendency to burn during a huge fire. Once the first seating is burned, it is unable to conduct its main function. The secondary sealing seat then takes over the responsibility, enabling the valve to perform its sealing task despite the fire. The second seal is typically composed of indestructible metal materials like stainless steel, which demonstrate great tolerance to extremely high temperature.

Although the primary sealing seat guarantees a bubble tight leakage free sealing capability, the secondary sealing seat may permit minimal leakage when trying to withstand extremely high temperature during fire. The metal backup sealing seat can assume the sealing function during and after a fire. Both sealing seats are designed to make contact with a metal closure member, which is called a ball, plug or disk. This capability enables the secondary seat to perform the sealing function when the primary seat is disintegrated. Fire safe butterfly valves are high performing valves that conduct critical process line applications, which face a higher threat of fire occurrence. This type of valves is always in demand in petroleum facilities, chemical plants, hydrocarbon processing, power generation facilities and HVAC industries. They are most suitable for handling combustible fluids and gas in the process line.

Manufacturers cannot just claim that their butterfly valve products are fire-safe. They must subject their valves to reputable testing methods and standards, before they can sell them to clients. Testing of fire safe butterfly valves involves factors like determining the temperature during the fire as well as the particular process liquid that the valve is handling. When companies create butterfly valve products with fire safety feature, they also consider how tight the sealing capacity of the valve should be as well as its ability to function even after the fire. Fire safe butterfly valves usually have a higher operating torque than non-fire safe butterfly valve units. The additional torque is mainly requires to break loose the metal closure member from the second metal seat when necessary. Because a fire safe butterfly valve unit need higher torque , manufacturers typically use larger actuators or handles.

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