Fire Protection of Flangeless Valves

Kris Thorsteinsson Delta-P Risk Inc.

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Objective

Identify flangeless valves Assess fire loss potential Provide cost-effective protection

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What Are Flangeless Valves?

Also called long bolt valves or sandwich valves Devices such as control valves, butterfly valves,

wafer check valves, etc. with no integral flanges for bolting to the pipe or vessel flanges

Single long bolts extend from one pipe flange to the other across the device

used due to space and cost savings

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Long bolt valve A – LPG Service

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Long bolt valve B – Gas Service

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What is the fire concern?

when exposed to hydrocarbon fire the exposed tie bolts expand faster than the valve body

this leads to loosening of the connection and leakage around the pipe flange-to-valve body seals

the leakage adds to the fire this may lead to escalating of an otherwise

controllable fire situation

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Has the risk been verified?

Tests conducted by an oil refiner in late 1970s confirmed the potential for bolts exposed more than about 3” (76 mm) to leak seriously after 5 to 10 minutes

Flange leakage due to thermal expansion and loss of bolt strength at elevated temperature

Spiral wound gaskets used in tests

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Published Industry Experience

a flangeless valve leaked when exposed to a hydrocarbon fire in a refinery

“Flixborough” disaster investigation cited a possible contributing factor

Two flangeless valve fires in 6 months in one ammonia plant

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Related risks

Long bolts on a check valve in hot refinery service broke when subject to sudden cooling from heavy rain

Weather shields were later installed on similar valves to protect against cyclic cooling

Vents on shields allow for vapour testing for flange leakage

Some companies now call the protection system Heat / Weather shields for flangeless valves

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Protection Method 1 – Rigid Shielding

Consider any CUI (corrosion under insulation) effects and enhanced exposure of studs to process conditions

31 gauge (0.010”) stainless steel sheet wrapped around the valve and banded to outside of the mating pipe flanges (one company specs .06” to .075” thickness type 304 SS.)

cut 3” longer than valve body, to extend beyond each pipe flange

trim to overlap around bonnet (one company also inserts a ceramic fibre gasket between the

flanges and steel sheet) use stainless banding and clips (one company specs .020”

banding, four for flanges over 1.75-in thickness) 13 mm drilled hole at low point (one company specs one 1-in

vent to safe location and one ½-in drain or steam snuff connection for higher hazard service)

risk of leakage is now comparable to flanged valve

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Protected valve A

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Protected valve B

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Protection Method 2 – Flexible Shielding some plants install pre-fabricated flexible fireproofing covers

instead of steel sheet on critical long bolt flanges for ease of inspection, and greater fire protection

There are manufacturers of both flexible and rigid systems

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Site specific risk factors

process operating conditions – pressure, temperature, toxicity

physical plant layout, drainage valve function – e.g. emergency isolation emergency depressuring emergency response – firewater cooling

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Code requirements

no known “code” restriction on flangeless valves API 2510A, ‘Fire Protection Considerations for LPG Storage

Facilities’ – “2.7.1.2 g. Use flanged valves or valves with bodies that cover the flange bolts. Flangeless wafer-type valves that are clamped between flanges by long bolts shall not be used because in a fire they quickly begin to leak, and the connection may fail.”

API RP 553 ‘Refinery Control Valves’ - "3.1.6 Flangeless valves have no flange connections as part of the valve body and are simply bolted or clamped between the adjoining line flanges. Long bolts used with flangeless valves can expand when exposed to fire and cause leakage. A fire deflection shield and/or insulation is recommended. In addition, high-tensile strength bolting is required."

identified in Gas Processors Association “Safety Inspection Checklist”

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References

“Do flangeless valves & petroleum fires mix?” David Blomquist, Fire Protection Engineer, Standard Oil, 1977

“API Safety Digest of Lessons Learned Section 1 – General Safety Precautions in Refining” 1986

“Some Problems with Valves” J. Bond, 1986 API 2510A “Fire Protection Considerations for LPG

Storage Facilities” API RP 553 “Refinery Control Valves” “Preventing Ammonia Plant Fires” R. Watkins, EI

Dupont, 1969