Vacuum Relief Valve

1
Vacuum Relief Valve

• Vacuum Relief Valve device which releases a
  vacuum in a tank car.
• Considered a non-safety device

2
Vacuum Relief Valve

• Designed for cars containing HOT commodities
  that create a vacuum when they cool.
• Manway covers of cars under a vacuum are very
  hard to open
• Used as device to protect cars with bottom outlet
  valves.
• Will activate if unloader fails to open valve or
  manway to equalize pressure when unloading

3
Vacuum Relief Valve ReleasesPercent of
Applicable Tank CarsBNSF Railway
4
Issue with VRV

• No way for the unloader to determine if valve is
  in good order without pressure being on the car.
• Loader/unloaders damage the valve by
  depressurizing the car by stepping on the VRV.

5
Accidents and the VRV

• Many of the VRV are placed unprotected on top of
  the manway.
• Others are offered minimum protection when placed
  under the top unloading fitting cover.

6
Accidents and the VRV

• In a derailment when the car rolls the valve can
  either leak due to
• Dirt pushing the valve open
• Liquid leaks around O ring

7
Recommendations

• Review the AAR Data for industry wide data on
  VRV, if data is consistent with BNSFs data
• Redesign VRV
• Phase out VRV
• Eliminate VRV