PRESSURE TANK SAFETY VENT SYSTEM

摘要

In accordance with the present invention a pressure tank safety vent system is provided comprising a vent member mounted in a fixed housing. The vent member is hollow and is in fluid communication with the tank. It has at least one port adapted to vent the tank pressure. A resilient assembly is provided which restrains movement of the vent member within the fixed housing. The resilient assembly includes at least two chambers, at least one of which contains a vent controlling fluid. The chambers are in fluid communication by means of at least one vent controlling channel. In the event that pressure build-up within the tank lasts sufficiently long to transport at least a portion of the fluid from one chamber to the other chamber, the vent member will move sufficiently within the fixed housing to vent the tank pressure. In the event that an insufficient amount of fluid is transferred, such as during a surge in the tank, for example, caused by coupling impacts on a railway tank car, the vent member will not vent the system and in a preferred embodiment will return to generally its original position due to the spring constant of the resilient means and/or gravity and the fluid will return to the original chamber. The flow of fluid from one chamber to the other determines the time lapse between pressure build-up and venting. The time may be controlled by the viscosity of the fluid and the cross sectional area of the vent controlling channel. The spring constant of the resilient means, viscosity of the fluid, the size of the channel and the volume and pressure within the chambers may be varied to meet different pressure and/or surge conditions encountered in different applications. A piston and cylinder arrangement may be used to define the vent controlling channel. Displacement of the vent member can be controlled by providing a tapered piston, or providing ports between said first and second chambers which are closed off by a portion of the moving vent member. In one embodiment the vent member may vent the pressure build-up into a vent chamber and a burst disk is provided between the vent chamber and the atmosphere. In venting to atmosphere appropriate means, such as a cap, may be provided to direct the vented material away from personnel which may be in the area of the pressure tank.