Table of Contents

1. definition”>Definition of Fixed Ball Valve and Fire Safe Design
2. principle”>Working Principle of a Fixed (Trunnion Mounted) Ball Valve
3. fire-safe-concept”>Fire Safe Design Concept for Ball Valves
4. standards”>Main Fire Safe Standards for Fixed Ball Valves
5. design-features”>Key Fire Safe Design Features
6. materials”>Typical Materials and Construction
7. benefits”>Advantages of Fire Safe Fixed Ball Valves
8. applications”>Typical Applications and Industries
9. spec-table”>Typical Technical Specifications Table
10. selection”>Selection Guidelines for Fire Safe Fixed Ball Valves
11. installation”>Installation and Maintenance Considerations
12. faq”>FAQ on Fire Safe Fixed Ball Valves

1. Definition of Fixed Ball Valve and Fire Safe Design

1.1 What Is a Fixed Ball Valve?

A fixed ball valve, commonly called a

trunnion mounted ball valve, is a quarter‑turn shut‑off valve in which

the ball is held in a fixed position by trunnions (upper and lower stems or journals).

The line pressure pushes the seat rings against the ball to achieve tight sealing.

In contrast to a Floating ball valve, in a fixed ball valve the ball itself does not

move axially under pressure. The seat rings are spring‑loaded or pressure‑assisted

to maintain contact with the ball. This configuration is widely used for:

• Medium to large diameter pipelines
• High pressure services
• High differential pressure conditions
• Critical isolation in hazardous fluid systems

1.2 What Is Fire Safe Design for Ball Valves?

Fire safe design refers to a construction concept for valves that ensures

the valve can still provide a minimum level of sealing during and after exposure to a fire.

A fire safe fixed ball valve is designed so that:

• Soft sealing materials (such as PTFE or elastomers) may be damaged or completely burned in a fire.
• Once these materials are degraded, secondary metal‑to‑metal sealing surfaces

  come into contact.

• The valve continues to limit leakage both to the atmosphere and downstream, according to the

  fire test standard requirements.

Fire safe design does not mean the valve is indestructible; instead, it means that

leakage is controlled to a safe, predefined level during and after a fire

scenario, protecting people, property and the environment.

2. Working Principle of a Fixed (Trunnion Mounted) Ball Valve

2.1 Basic Operation

A fixed or trunnion mounted ball valve is a quarter‑turn valve:

• When the handle or actuator rotates the ball 90°, the valve changes from fully open to fully closed, or vice versa.
• The ball is supported by the upper and lower trunnions/stems and is constrained from axial movement.
• Seat rings are energized by springs or line pressure to maintain tight contact with the ball.

Because the ball is fixed, operating torque is lower than in floating ball valves under

high pressure, and sealing performance is more reliable for larger sizes.

2.2 Main Components

Although designs vary, a typical fixed ball valve consists of:

• Body (one‑piece, two‑piece or three‑piece)
• Ball (fixed by trunnions)
• Upper stem (drive stem)
• Lower trunnion
• Spring‑loaded or pressure‑energized seat rings
• Stem seals and packing
• Body gaskets
• Anti‑static devices
• Fire safe secondary metal seals
• Actuator interface (lever, gear, pneumatic or electric actuator)

2.3 Difference Between Fixed and Floating Ball Valves

3. Fire Safe Design Concept for Ball Valves

3.1 Purpose of Fire Safe Design

The purpose of fire safe design in a fixed ball valve is to:

• Limit the escape of flammable or toxic media during a fire.
• Maintain pressure boundary integrity as long as reasonably possible.
• Provide a secondary sealing mechanism when soft seals are destroyed.
• Reduce the risk of fire escalation and environmental contamination.

Many process plants, offshore platforms, tank farms and pipeline installations require

fire tested and fire safe certified ball valves in order to comply with

safety regulations, insurance requirements and international standards.

3.2 Fire Scenario Considered

Fire safe standards for fixed ball valves assume a realistic fire scenario:

• High temperature flames enveloping the valve for a defined period (usually 30–60 minutes).
• Rapid temperature rise leading to burning or melting of non‑metallic components.
• Possible thermal shock due to sudden cooling, for example when fire fighting water is applied.

Under these extreme conditions:

• Soft seats, O‑rings and gaskets may be heavily damaged.
• The valve body and ball remain, forming a metallic pressure boundary.
• Metal‑to‑metal contact between seat and ball, and between body and bonnet or body joints,

  must still limit leakage to defined values.

3.3 Primary vs Secondary Sealing

In a typical fire safe fixed ball valve design:

• Primary seal: Soft materials (PTFE, RPTFE, PEEK, elastomers, graphite‑filled

  compounds) are used for low operating torque, bubble‑tight shut off, and corrosion resistance

  under normal operating conditions.

• Secondary seal: Metallic contact surfaces, often supported by fire resistant

  graphite seals, create a backup seal when the primary soft materials are destroyed by fire.

This dual sealing philosophy is one of the key aspects of fire safe ball valve design.

4. Main Fire Safe Standards for Fixed Ball Valves

Several international standards describe how to design and test

fire safe ball valves. For fixed (trunnion mounted) ball valves,

the most commonly referenced standards include:

4.1 API 607

API 607 is a widely used fire test standard for

quarter‑turn valves and other valves with non‑metallic seat and

seal materials. Although originally applicable to soft‑seated valves up to a certain size,

it has been broadly adopted as a reference for fire safe testing of

fixed ball valves in many industries.

API 607 specifies:

• Fire temperature and duration.
• Valve pressurization requirements during fire.
• Allowable internal and external leakage rates.
• Cooling and post‑fire test procedures.

4.2 API 6FA

API 6FA is the fire test standard specifically oriented to

valves used in petroleum and natural gas pipeline and production systems.

Many fixed ball valves for pipeline service are tested according to API 6FA.

Compared with API 607, API 6FA focuses more on high pressure applications and larger sizes,

which are typical for trunnion mounted ball valves in critical pipeline duties.

4.3 ISO 10497

ISO 10497 is an international standard for

testing of valves — fire type testing requirements. It is broadly

equivalent in intent to API fire test standards but developed as part of the ISO framework.

Many global projects allow compliance with ISO 10497 as evidence of

fire safe design.

4.4 Other Relevant Standards and References

• BS 6755 Part 2 (historical, often referenced in legacy specifications).
• ISO 14313 / API 6D for pipeline valves (including trunnion mounted ball valves),

  which may reference fire test requirements.

• Industry or project specifications that adopt API 607, API 6FA or ISO 10497, sometimes

  with additional or stricter acceptance criteria.

4.5 Fire Safe vs Fire Resistant

In industry terminology, fire safe valves are those that have been

successfully tested according to a recognized fire test standard

and comply with leakage limits. The term fire resistant may refer more loosely

to materials or designs that have good resistance to high temperatures, but this

does not necessarily guarantee full compliance with a standard fire test.

5. Key Fire Safe Design Features

5.1 Fire Safe Seat Design

The design of the seat assembly is critical for a

fire safe fixed ball valve. Key characteristics include:

• Soft sealing material (PTFE, RPTFE, PEEK, etc.) for normal operation,

  located in a recess in the metal seat ring.

• Metal seat ring lip that is capable of contacting the ball directly

  when the soft seat material has disappeared due to fire.

• Spring or pressure energizing mechanism that presses the seat ring

  towards the ball, both in normal and post‑fire conditions.

• Optional graphite insert or metal‑graphite composite seal behind the

  seat to enhance fire performance.

During a fire, as the soft material burns, the seat ring travels further towards the ball,

allowing metallic contact to form the secondary seal.

5.2 Fire Safe Stem Sealing

The stem seal is another critical leakage path.

Fire safe fixed ball valve designs typically use:

• Multiple rings of packing, often combining graphite with other

  high temperature materials.

• Secondary O‑rings or lip seals for normal low‑torque sealing.
• A backseat feature that allows the stem to seat against the bonnet

  or body in a metal‑to‑metal contact during fire, reducing external leakage.

Graphite packing is commonly used because of its excellent fire resistance

and capability to maintain sealing at elevated temperatures.

5.3 Fire Safe Body and Bonnet Joints

For two‑piece and three‑piece body fixed ball valves, the body joints

are potential external leakage paths during fire. Common fire safe design solutions include:

• Spiral wound gaskets with graphite filler for body joints.
• Metal‑to‑metal contact shoulders that come into contact if the gasket

  is destroyed by fire.

• Careful design of gasket groove geometry to ensure compression and secondary sealing

  after fire exposure.

5.4 Anti‑Static and Blow‑out Proof Design

Although not exclusively a fire safe feature, anti‑static devices and

blow‑out proof stem design are commonly integrated in fire safe fixed ball

valves to address additional safety aspects:

• Anti‑static spring or ball devices ensure electrical continuity between ball, stem and body,

  preventing static charge accumulation that could ignite flammable fluids.

• Blow‑out proof stems are inserted from the inside of the valve body and cannot be expelled

  by internal pressure, even when gland components are damaged.

5.5 Fire Safe Operation Under Automation

Many trunnion mounted fire safe ball valves are operated by

pneumatic or electric actuators. For fire safe performance:

• Actuators may be coupled with fail‑safe functions (spring return or fail‑last),

  depending on project requirements.

• In high temperature fire conditions, actuator integrity is often compromised; however,

  the valve’s internal fire safe features aim to maintain sealing even if operational control

  is lost.

6. Typical Materials and Construction

6.1 Body and Ball Materials

The body and ball materials for fire safe fixed ball valves must withstand

high pressures, corrosion and elevated temperatures. Common materials include:

• Carbon steel (e.g., ASTM A105, A216 WCB) for general oil and gas pipeline service.
• Low temperature carbon steel (e.g., ASTM A350 LF2) for cryogenic or low temperature duty.
• Stainless steel (e.g., ASTM A351 CF8M, A182 F316) for corrosive media or offshore environments.
• Duplex and super duplex stainless steels for aggressive chloride‑containing environments.
• Alloy steels and nickel‑based alloys for high temperature or highly corrosive services.

6.2 Seat and Seal Materials

Typical soft seat and seal materials for fixed ball valves include:

• PTFE (Polytetrafluoroethylene) and reinforced PTFE (RPTFE).
• PEEK (Polyether ether ketone) for higher temperature and pressure capabilities.
• Nylon or other engineered plastics for specific media or temperature ranges.
• Elastomeric O‑rings (Viton, NBR, HNBR, FKM, etc.) for stem and body seals.
• Graphite rings and packing for fire resistance, especially in stem and body joints.

For fire safe ball valves, elastomers and plastics are carefully selected

to balance sealing performance with thermal resistance up to the anticipated service conditions.

6.3 Fire Safe Metal‑to‑Metal and Graphite Components

To ensure secondary sealing in a fire, the following materials are often used:

• Graphite packing around the stem for high temperature sealing.
• Graphite based gaskets for body and bonnet joints.
• Hardened or coated metallic seat and ball surfaces for metal‑to‑metal contact

  after soft seat degradation.

For severe service, metal‑seated fire safe ball valves may be specified with

hard coatings (such as tungsten carbide or chrome carbide) on the ball and seats.

6.4 Coatings and Surface Treatments

Fixed ball valves used in fire hazardous environments often include protective coatings:

• External painting or powder coatings for corrosion resistance.
• Internal coatings or overlays for specific media (e.g., corrosive gases or slurries).
• NACE‑compliant materials and treatments for sour service (H₂S containing environments).

7. Advantages of Fire Safe Fixed Ball Valves

7.1 Enhanced Safety

The primary advantage of a fire safe fixed ball valve is improved safety:

• Reduced risk of uncontrolled leakage during fire.
• Mitigation of fire escalation by limiting fuel release.
• Protecting personnel, process equipment and the environment.

7.2 Regulatory and Standard Compliance

Many industrial facilities and pipeline systems require

fire tested ball valves to meet:

• National and international safety regulations.
• Project‑specific specifications (often referring to API 607, API 6FA, ISO 10497).
• Insurance and risk management policies.

7.3 High Reliability in Critical Service

Fixed (trunnion mounted) ball valves with fire safe design offer:

• Reliable sealing at high pressures and large diameters.
• Lower operating torque and better control with actuators.
• Stable performance across a wide range of temperatures and media.

7.4 Long Service Life and Reduced Maintenance

When correctly specified and installed, fire safe fixed ball valves can

deliver long service life with:

• Durable metal body and ball materials.
• Replaceable seat and seal components in many designs.
• Predictable maintenance intervals and lower total cost of ownership.

8. Typical Applications and Industries

8.1 Oil and Gas Production and Transportation

Fire safe fixed ball valves are widely used in:

• Onshore and offshore oil and gas production facilities.
• Gathering lines, trunk lines and export pipelines.
• Block valves in pipeline networks and compressor stations.
• Crude oil, gas and multiphase flow applications.

8.2 Refining and Petrochemical Plants

In refineries and petrochemical complexes, many process units handle:

• Highly flammable hydrocarbons.
• Toxic and hazardous chemicals.
• High temperature and high pressure media.

Fire safe fixed ball valves are typically specified for:

• Unit block valves.
• Tank inlet and outlet isolation.
• Flare systems and emergency shutdown systems.

8.3 Chemical and Power Generation Industries

In chemical plants, power plants and industrial utilities,

fire safe ball valves are used where:

• Potential fire hazards exist due to flammable gases or liquids.
• Critical isolation is required for safety systems.
• Compliance with process safety management (PSM) is essential.

8.4 Marine, LNG and Storage Terminals

Fire safe fixed ball valves are also found in:

• LNG liquefaction and regasification terminals, where cryogenic and fire safety

  requirements must be harmonized.

• Marine loading arms and shipboard piping for hydrocarbon transfer.
• Bulk storage terminals handling gasoline, diesel, jet fuel and chemicals.

9. Typical Technical Specifications Table

The following table summarizes typical specification ranges for

fire safe fixed ball valves. Actual values depend on the specific design,

material selection, applicable standards and project requirements.

10. Selection Guidelines for Fire Safe Fixed Ball Valves

10.1 Define Service Conditions

When selecting a fire safe fixed ball valve, consider:

• Design pressure and operating pressure.
• Design temperature and operating temperature.
• Type of fluid (gas, liquid, multiphase, slurry, corrosive, toxic, flammable).
• Required flow capacity and valve size.
• Line connection type and layout constraints.

10.2 Compliance with Standards and Regulations

Selection should always align with:

• Applicable design standards (API 6D, ASME B16.34, ISO standards).
• Fire test standards (API 607, API 6FA, ISO 10497).
• Local safety laws, codes and insurance requirements.

10.3 Seat and Seal Selection

Choose seat and seal materials based on:

• Chemical compatibility with the medium.
• Operating temperature and pressure range.
• Required shut‑off class and cycle frequency.
• Special requirements such as low‑temperature or high‑temperature operation.

10.4 Manual vs Automated Operation

For critical safety functions, actuated fixed ball valves are often preferred:

• Automatic shutdown in response to fire or process alarms.
• Remote operation for hazardous or inaccessible areas.
• Integration into plant control and emergency shutdown systems.

10.5 Additional Fire Safety Considerations

In addition to valve design, the overall system must consider:

• Fire proofing of supports and actuators when required.
• Drain and vent arrangements to safely depressurize lines.
• Use of double block and bleed configurations where zero line leakage is critical.

11. Installation and Maintenance Considerations

11.1 Installation Best Practices

Proper installation is vital for the performance of a

fire safe fixed ball valve:

• Ensure correct orientation when flow direction is specified.
• Use appropriate gaskets and apply the correct bolting torque at flanged joints.
• Verify proper alignment of the pipeline to avoid excessive stress on valve body.
• Install supports to prevent vibration and mechanical overloading.
• Confirm actuator stroke adjustment and limit switch settings where actuated.

11.2 Commissioning and Testing

Before placing a fire safe ball valve into service:

• Perform pressure tests according to the relevant standard (API 598, API 6D, ISO 5208).
• Cycle the valve several times to verify smooth operation.
• Check for external leakage at the stem and body joints.
• Validate the correct function of any emergency shutdown or interlock systems.

11.3 Routine Inspection and Maintenance

Routine maintenance activities may include:

• Visual inspection for corrosion, damage, or external leakage.
• Torque check and occasional manual cycling to prevent sticking.
• Inspection of actuator and control accessories (solenoid valves, limit switches, positioners).
• Replacement of packing or seals after extended service or when leakage is detected.

Fire safe features such as graphite packing and metal‑to‑metal seats should also be

inspected during overhaul or major shutdowns.

12. Frequently Asked Questions (FAQ) on Fire Safe Fixed Ball Valves

12.1 Does a Fire Safe Ball Valve Prevent All Leakage in a Fire?

A fire safe fixed ball valve is designed to limit

leakage during and after a fire to specified maximum values defined in the fire test standard.

It does not guarantee absolutely zero leakage under fire conditions, but aims to reduce leakage

to a level that minimizes the risk of fire escalation.

12.2 How Do I Know If a Ball Valve Is Fire Safe?

A valve is considered fire safe when:

• It has been tested by a recognized laboratory according to a fire test standard

  such as API 607, API 6FA or ISO 10497.

• The test report confirms that leakage and structural integrity requirements were met.
• The valve documentation and marking indicate fire safe certification.

12.3 Is Fire Safe Design Required for All Ball Valves?

Not all ball valve applications require fire safe design.

Fire safe fixed ball valves are typically specified for:

• Handling flammable, toxic or hazardous fluids.
• Critical isolation functions in process and pipeline systems.
• Areas where potential fire exposure is identified in risk assessments.

For non‑hazardous services, standard non‑fire safe valves may be acceptable.

12.4 What Is the Difference Between Fire Safe and Fire Tested?

A fire safe design indicates that the valve has been engineered

with features intended to maintain sealing performance under fire.

A fire tested valve means that an actual valve sample has undergone

full‑scale fire testing according to a specific standard.

In practice, fire safe valves should be fire tested to demonstrate compliance.

12.5 Can Fire Safe Fixed Ball Valves Be Used in Cryogenic Service?

Yes, fire safe trunnion mounted ball valves can be designed for cryogenic

service, such as LNG, provided that:

• Special low‑temperature materials (such as austenitic stainless steel) are used.
• Seats and seals are suitable for both cryogenic temperature and fire exposure.
• Extended bonnets and appropriate insulation are provided as needed.

In these cases, both cryogenic testing and fire testing may be required.