volume valve controls vtc oil control solenoid valve air control valve spa

What is fire safe ball valve?

loader control valve problems

mac valve boost control

modulating control valve cdl

Fire-safe ball valves are valves designed to reduce downstream leakages and fugitive emissions in case they are exposed to high-temperature fires. Because most of the valves are made up of non-alloy materials for sealing, they have to maintain functionality even at high temperatures or fail in a predictable way that differentiates fire-safe ball valves and other types of ball valves. There are certain design and test standards considered in fire-safe ball valves. These standards are followed by the fire safe ball valve manufacturers to ensure the valve can work as required. Fire-safe ball valves are operated manually using a hand lever or using an actuator. The actuator that can be used for fire-safe ball valves is electric or pneumatic. A fire-safe ball valve should be able to maintain its ability to contain pressure during and after a certain duration of fire exposure. A fire safe ball valve is used because of possible flammable or hazardous fluid leakage from the valve in case of a fire outbreak. If a ball valve that is not fire safe is used and fire occurs, it will cause fluid leakage from the valve stem. The fluid leakage will support the fire and make it grow bigger than before. As such, a fire safe ball valve is needed so that it will not leak fluid when it gets exposed to fire. Fire safe ball valves are mostly used in refining and chemical processing plants to help in handling flammable fluids. Fire-safe ball valve manufacturers are tasked to ensure a tight shut-off of the valve during and after fire outbreaks.

How does a fire-safe ball valve work?

Two types of fluid leakages are avoided by using a fire safe ball valve that is before the fire and after the fire. The leakage could occur from the stem and or the seat. The two methods are used to achieve a fire-safe ball valve design. One method is by using a fire-proof component and the other method is by using non-fire proof component supported by a special design that prevents leakage after the material melts. The method of using a fire-proof component uses a metallic seat, graphite seat insert, and graphite packing on the stem. In a fire-safe ball valve with a stem packing and seat insert, the graphite remains even when the valve is exposed to fire. The other method uses a thermoplastic stem packing and thermoplastic seat material like PTFE. In the seat design, the thermoplastic melts in case of high temperature and the valve seal is obtained by use of a body machined to serve as a secondary seal. In the stem packing, the thermoplastic seal material is supported by the use of graphite seal as the secondary packing in case of fire.

Figure: Fire safe ball valve components.

The normal operation of a fire safe ball valve that is opening and closing fluid flow is also maintained. The working of a fire safe ball valve to allow fluid flow depends on a ball with a bore at its center. To open a fire-safe ball valve, the handle is rotated for 90^o. This makes the handle which is connected to the ball via a valve stem to rotate the ball. When the ball is rotated for 90^o it becomes in line with the pipeline and thus allows fluid to flow. To close the fire safe ball valve, the handle is turned for another 90^o opposite to the direction turned when opening the valve. This makes the ball bore rotate and become perpendicular to the pipeline and thus block fluid flow.

Figure: Working of a fire safe ball valve.

Types of fire safe ball valve

Forged fire safe ball valves

This is a fire-safe ball valve that is manufactured through the forging method. The forging method of making a fire-safe ball valve involves shaping a metallic material while it is in solid form. In this method, industrial tools and heat are used to deliver compressive force to bend the metallic material. Dies are used to shape and cut the materials to create the required fire-safe ball valve. Forged ball valves are advantageous in that they have high strength making them suitable for high temperature and high-pressure applications. When a forged fire safe ball valve is being manufactured the grain structure becomes refined which increases the overall impact strength of the final product. In addition, through the forging method, fire-safe ball valves produced have less thickness which helps to minimize thermal fatigue when the valve is in operation.

Casted fire safe ball valves

These are fire-safe ball valves that have been made through casting method. The casting method uses molten metal to form the ball valve. The metallic material is heated to a high temperature so that it melts. The molten material is poured into molds. The molten material is given time to cool and solidify after which it is ejected from the mold. The casting method can create fire-safe ball valves with complex patterns, shapes, and sizes. Casted fire-safe ball valves are more cost-effective and make the valves cheaper as it reduces machining costs, unlike the forging method.

Single-piece fire safe ball valve

This is a fire-safe ball valve with one solid cast body. The single cast body helps to reduce the risk of fluid leakage. Single-piece fire-safe ball valves are the cheapest. Single-piece fire-safe ball valves cannot be cleaned or repaired since they cannot be opened. These valves are disposed of when they develop a problem.

Figure: Single-piece fire safe ball valve.

Two-piece fire safe ball valve

This is a fire-safe ball valve that is made up of two pieces are one-piece consisting of the body and one end connection and the second piece consisting of the trim and the second end connection. A two-piece fire safe ball valve is advantageous in that it can be opened for cleaning, repair, and inspection as necessary. A two-piece fire safe ball valve needs to be removed from the pipeline for the two pieces to be separated for repairs or cleaning.

Figure: Two-piece fire safe ball valve.

Three-piece fire safe ball valve

This is a fire-safe ball valve that is made up of three pieces that is body and two end joints. The three pieces are clamped together by use of bolts and nuts. A three-piece fire safe ball valve makes it possible to remove seats, ball, and stem from the pipeline for inspection, cleaning, or repairs. Three-piece fire safe ball valves are very convenient for repairs but they are more expensive compared to single piece and two-piece counterparts.

Figure: Three-piece fire safe ball valve.

Three-way fire safe ball valves

This is a fire-safe ball valve with three ports. A three-way fire-safe ball valve can have an L-port or T-port configuration. A three-way fire safe ball valve works by turning the handle which then turns the ball to align the holes in the ball with the valve inlet and outlet ports as necessary. The L-shaped configuration of a fire safe ball valve delivers fluid through 90^o from the inlet port to the outlet port. The L-shaped fire safe ball valve is used to divert fluid flow and for on/off applications. The T-shaped three-way ball valve is used to mix fluid streams or divert fluid flow. When used to mix fluid flow, two streams from the two inlet ports are mixed and exited through one outlet port. When the T-shaped three-way fire safe ball valve is used to divert fluid flow, it diverts one fluid stream from the inlet to form two fluid streams through the two outlet ports.

Figure: Three-way fire safe ball valve.

Design standards for a fire-safe ball valve

API 608 standard

This is a fire-safe design standard applicable to chemical and refineries industries

API 6D standard

This is a design standard applicable to natural gas and petroleum plants.

NACE MR-0175

This is a design standard followed in constructing materials in regards to hydrogen sulfide exposure which can occur naturally in natural gas and crude petroleum.

Testing standards for fire safe ball valves

API 607 test standard

This is the main fire test standard. This standard explains the parameters used in the test and performance evaluation.

API 6D test standard

This standard serves as a test and design standard. As such, in some documents, it is likely to see “with reference to API 6D” in API 6D design or test standard.

Applications of fire safe ball valves

Fire-safe ball valves are used in saturated steam applications.
They are used in high-temperature media.
They are used in chemical process lines.
They are used in applications with fugitive emissions.
Fire-safe ball valves are used in petrochemical industries.
They are used in oil and gas industries.
They are used in pharmaceutical applications.
Fire-safe ball valves are used in food processing industries.
They are used in the cosmetics industry.

Advantages of fire safe ball valves

They are quick to operate.
They can be manual or automatic as per the user’s preferences.
Fire-safe ball valves are durable.
They are versatile as they can be used in different industries.
They are fire-proof.
They are of high strength.
They have perfect seals.
They can be disassembled and repaired easily.

Disadvantages of fire safe ball valves

Fire-safe ball valves are expensive compared to other ball valves.
Fire-safe must be designed and tested according to the laid out standards otherwise they will not be reliable in case of a fire outbreak.
Fire-safe ball valves are not suitable for throttling applications.

Troubleshooting fire safe ball valves

Fluid leakage when the fire safe ball valve is closed

Damaged ball sealing surface. Replace the ball.
Damaged seat. Replace the seat.

Unsmooth operation of the ball

Foreign objects between the body and seat or between ball and seat. Disassemble the fire safe ball valve and clean the ball, seat, and body.

Difficult to operate the fire safe ball valve

Seat damaged. Replace the seat.
Very high internal temperature or pressure. Verify the valve is working at the recommended pressure and temperature ratings.
Foreign objects obstruct the body cavity. Clean the interior of the fire safe ball valve.

Steam leakage

Loose flange bolts or thread connection. Tighten the bolts or thread connection.
Stem damaged. Replace the stem as necessary.

Pipe leakage

Foreign objects in the pipe. Remove the foreign objects.
Damaged pipe threads. Replace the pipe.

Summary

Fire-safe ball valves are valves that are meant for reducing downstream leakages and fugitive emissions when they are exposed to high-temperature fires. Fire-safe ball valves are designed and tested according to certain laid-out standards to ensure they can be relied on. Some of the standards followed in the design of fire-safe ball valves are API 608, API 6D, and NACE MR-0175. One of the standards used to test-fire safe ball valves is API 607 standard. Fire-safe ball valves can be automatic or they can be manually operated. A fire-safe ball valve works by using a ball with a bore at its center. Fluid in a fire-safe ball valve flows through this bore when the valve is rotated for 90^o degrees. There are various types of fire safe ball valves which include forged fire safe ball valves, casted fire safe ball valves, single-piece fire safe ball valves, two-piece fire safe ball valves, three-piece fire safe ball valves, and three-way fire safe ball valves. These valves are used in different applications such as petrochemical, chemical industries, oil and gas, pharmaceutical applications, cosmetics, food processing, and high-temperature media among others. Advantages of fire safe ball valves are quick to operate, fire-proof, high strength, perfect seal, versatile, durable, manual or automatic operation, repairable, and high strength.