Patent ID: 9482354
Filing Date: 2016-11-01
CPC Classification: B60P,F16K

Claim Text:
1. A pressure relief valve for a railroad tank car, comprising: an upper housing defining a housing internal chamber and comprising at least one window between the housing internal chamber and atmosphere; a lower housing operatively associated with the upper housing and comprising a housing opening; a pallet disposed within the housing internal chamber; and a pair of nested springs disposed within the housing internal chamber and configured to bias the pallet toward the lower housing and thereby form a seal between the housing opening and the housing internal chamber when a pressure in the housing opening is below a start-to-discharge pressure, wherein when the pressure in the housing opening is at a full discharge pressure that is greater than and within fourteen percent of the start-to-discharge pressure, the pair of nested springs is configured to permit the pallet to travel a sufficient distance to expose a flow area of the at least one window that is at least greater than a flow area of the housing opening.