Gate valves are an important component in pipelines that transport flammable materials such as oil, gas, chemicals, etc. They allow flow to be stopped or adjusted by sealing the pipeline. Standard gate valves can be dangerous in a fire as the seals may burn and allow flammable material to escape, spreading the fire. Using fire safe gate valve mitigates this risk. This article will provide an overview of what fire safe gate valves are, how they work, their key components, benefits, and applications.
What Are Fire Safe Gate Valves?
Fire safe gate valves, sometimes called firewall gate valves, are designed to automatically seal off in the event of a fire. They prevent the spread of flammable liquids and gases that could intensify a fire. The main feature that makes them fire safe is a replaceable fusible link positioned between the gate and valve body. The link is made of an alloy designed to melt at temperatures typically seen in fires around pipelines. When exposed to fire, the link melts and releases the gate. Springs then force the gate into the sealed position, stopping flow through the valve. This happens even without any operator intervention.
How Do Fire Safe Gate Valves Work?
Fire safe gate valves work by both mechanical and thermal means. Here are the key steps in their operation during a fire:
The valve is open and allows normal flow during regular operation. The gate is raised and held open by an actuator or manual handwheel.
When a fire occurs near the valve, the heat melts the fusible link between the gate and valve body. This link is designed to melt at temperatures between 160-220°F.
With the link melted, springs force the gate to rapidly close against the valve seat. Common spring types used are compression or tension.
The valve is now sealed, stopping flow through the pipeline segment and containing the flammable material. This helps prevent the fire from spreading.
Once the fire is extinguished, the valve must be inspected and likely replaced. The melted fusible link will need to be replaced at minimum.
Key Components
Fire safe gate valves have all the typical components of a standard gate valve, along with some additional fire-safe parts:
Valve body – the main pressure vessel that directs flow through the valve. Usually made of carbon steel or stainless steel.
Gate – a solid wedge that seals against the seats to stop flow. Common gate materials are cast iron, ductile iron, or stainless steel.
Seats – pressed into the body to provide a tight seal when the gate contacts them. Typically made of bronze, stainless steel, or other alloys.
Stem – connects the gate to the handwheel or actuator for operation. Usually stainless steel.
Fusible link – a special alloy insert designed to melt at fire temperatures. This is the main fire safe component.
Springs – steel compression or tension springs that force the gate closed once the link melts.
Benefits of Fire Safe Gate Valves
There are several important benefits that fire safe gate valves provide:
Automatic shutoff without power or operator action needed. This gives added safety.
Prevent flammable liquids/gases from escaping and enlarging a fire. Limit damage and safety hazards.
Require no special controllers, operators, or power systems. Work through fail-safe mechanical design.
Applicable in both new installations or retrofits of existing systems.
Available in a full range of standard valve sizes: 1-48 inches or more.
Can be fabricated from various materials like carbon steel, stainless steel, and cast iron depending on the service.
Applications
Fire safe gate valves are mandated or highly recommended for use in pipelines carrying flammable substances. Typical applications include:
Oil refineries, pipelines, production rigs, storage tanks, and transport vessels
Gas processing plants, transmission lines, compressor stations, and LNG facilities
Chemical, petrochemical, and fuel plants, loading racks, and storage tanks
Offshore oil & gas platforms and pipelines
Mining and mineral processing plants
Power plants
Military fuel depots and transportation vessels
Anywhere that flammable liquids or gases could intensify fires
Standards
Several standards define fire safe requirements and testing procedures for gate valves. These include:
API 607 – Fire Test for Quarter-turn Valves and Valves Equipped with Non-metallic Seats
API 6FA – Fire Test for Valves
ISO 10497 – Fire type-testing requirements
BS 6755 – Fire Safety of Valves
API 607 and API 6FA are the most widely used standards in the oil & gas industry.
Valves certified as fire safe by these standards give added assurance of safety and reliability. Be sure to look for verified fire safe testing and certification when selecting gate valves for flammable services.