Fire Safe in Ball Valve

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What Is a Fire-Safe Ball Valve?

Fire-safe ball valves are capable of maintaining their pressure-holding capacity during and for an expected period of time after a fire. These ball valves are typically used in situations where hazardous or flammable liquids are likely to leak from the valve in the event of a fire.

 

How to Make a Ball Valve Fire Safe?

The use of fire-resistant components is the most common way to make a ball valve fire-safe. They are achieved by using secondary metal seats, graphite gaskets between the body and bonnet, and graphite packings on the valve stem.

The primary goal of fire safety is to prevent both internal and external leakage.

 

Internal Leakage Prevention

The internal leakage is to be avoided by providing a secondary metal-to-metal seat seal when the soft seat is destroyed by fire.

 

Floating ball valve

The floating ball valve’s fire-safe design is in accordance with API 607 and API SPEC 6FA standards. When non-metallic resilient seats are destroyed in a fire, the ball is pushed onto the downstream metal seat lip, cutting off the line fluid and preventing internal leakage due to a secondary metal-to-metal seal.

 

Relia Fire Safe Design Floating Ball Valve with Secondary Metal to Metal Seat
Fire Safe Design Floating Ball Valve with Secondary Metal-to-Metal Seat

 

Trunnion ball valve

When fire burned out the primary O-ring seal between the floating seat ring and adapter, also the seat insert between seat ring and ball, the secondary graphite seal between seat ring and adapter, and seat ring and ball metal to metal contact reloaded by spring will minimize the internal process medium leakage.

 

Fire Safe Design Trunnion Ball Valve with Secondary Metal to Metal Seat

 

External Leakage Prevention

The fire-resistant gasket and packings are used to provide fire-safe sealing to avoid external leakage.

Floating ball valve

For a fire safe design floating ball valve, all the possible external leakage points between stem and gland flange , gland flange and body, body and adapter are sealed with a 316+graphite gasket (part no. 8 in drawing), or graphite packing (part no. 12-14 in drawing). The graphite is fire-safe material which can prevent the process medium from leaking to the outside.

 

Relia Fire-safe design floating ball valve drawing

Fire-safe design floating ball valve drawing

Trunnion ball valve
For a fire-safe trunnion ball valve, all the possible external leakage points between stem and gland flange , gland flange and body, body and adapter are sealed with a primary O-ring and a secondary graphite gasket. When fire burns out the primary O-ring seal, the secondary graphite gasket seal can still prevent the process medium from external leakage.

 

Relia Fire-safe design trunnion mounted ball valve drawing
Fire-safe design trunnion mounted ball valve drawing

 

How To Make A Fire-Safe Test?

Test Procedure

Fire-safe tests determine the resistance of a fire-safe ball valve to a burn under controlled conditions as defined in common industry standards like: API 607, API 6 FA.

The performance requirements in these standards are meant to set what is acceptable for parts during a time period that is similar to how long it takes to put out most fires.

fire safe test for ball valve
Fire Safe Test for Ball Valve

The complete fire test is performed in a steel-reinforced concrete bunker and is monitored from a safe distance. All relevant values are logged by our log and registration system.

The acceptance of the test results is based on how much the valve seat leaks from the inside and how much the valve leaks from the outside during the burn. The leakage from the inside and the leakage from the outside during the different steps of the test, both when it is hot and when it is cold, must not exceed the maximum values allowed by the standard.

 

Allowable Leakage Rate

Following the fire-safe test, the ball valve will be pressure tested. The allowable leakage rate is as shown in the below table.

Maximum Allowable Leakage Rate

    Through-seat Leakage External Leakage
DN NPS During Burn After Cool-down During Burn and Cool-down After Operational Test
Low Pressure Test High Pressure Test Low Pressure Test Low Pressure Test High Pressure Test High Pressure Test
8 1/4 32 128 13 8 32 8
10 3/8 40 160 16 10 40 10
15 1/2 60 240 24 15 60 15
20 3/4 80 320 32 20 80 20
25 1 100 400 40 25 100 25
32 1-1/4 128 512 51 32 128 32
40 1-1/2 160 640 64 40 160 40
50 2 200 800 80 50 200 50
65 2-1/2 260 1040 104 65 260 65
80 3 320 1280 128 80 320 80
100 4 400 1600 160 100 400 100
125 5 500 2000 200 125 500 125
150 6 600 2400 240 150 600 150
200 8 800 3200 320 200 800 200
>200 >8 800 3200 320 200 800 200

Note: All pressures in ml/min

 

Qualified Sizes

The qualified sizes are listed in the table below. For example, if a DN50 ball valve passes the fire safety test, then DN50 and below, DN65, 80, and 100 are qualified as fire-safe.

Valve Qualified by DN

Size of Valve to be Tested DN Other Valve Sizes Qualified DN
50 50 and below; 65; 80; 100
65 65; 80; 100; 125
80 80; 100; 125; 150
100 100; 125; 150; 200
125 125; 150; 200; 250
150 150; 200; 250; 300
200 200 and larger

Valve Qualified by NPS (Inch)

Size of Valve to be Tested DN Other Valve Sizes Qualified DN
2 2 and below; 2-1/2; 3; 4
2-1/2 2-1/2; 3; 4; 5
3 3; 4; 5; 6
4 4; 5; 6; 8
5 5; 6; 8; 10
6 6; 8; 10; 12
8 8 and larger

Valve Qualified by PN

Valve Tested PN Other Valves Qualified
PN Class Rating
10 10; 16 150
16 16; 25 150
25 25; 40 150; 300
40 40; 63; 100 300; 400; 600
63 63; 100 300; 400; 600
100 100; 150 600; 800; 900
150 150; 260 900; 1500
260 260; 420 1500; 2500
420 420 2500

 

Qualified Pressure

The qualified pressures are listed in the table below. For example, if a Class 150 ball valve passes the fire-safe test, then Classes 150 and 300 are qualified as fire-safe.

Valve Qualified by Class

Valve Tested Class Other Valves Qualified
Class Rating PN
150 150; 300 10; 16; 25; 40
300 300; 400; 600 40; 63; 100
400 400; 600; 800 63; 100
600 600; 800; 900 63; 100
800 800; 900; 1500 100; 150; 260
900 900; 1500 150; 260
1500 1500; 2500 260; 420
2500 2500 420

 

What Are Fire-Safe Valve Standards?

API 607

API 607specifies fire type-testing requirements and a fire type-test method for confirming the pressure-containing capability of quarter-turn valves and other valves with nonmetallic seating under pressure during and after the fire test.

API 6FA

API 6FA standard establishes acceptable levels for leakage through the test valve and external leakage after exposure to a fire for a 30-minute time period. API 6FA standard establish the requirements for testing and evaluating the pressure-containing performance of API 6A and API 6D valves when exposed to fire.

 

What Fire Safe Certificates Does Relia Offer?

Relia Valve has sent the ball valves to TUV for fire-safe test. All the valves passed the test and we earned API 6FA and API 607 Certificates.

 

 

Relia API 6 FA Fire Safe Certificate for Ball Valve

Relia API 607 fire safe certificate for ball valve

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