Spring-loaded check valves

Both the discharge valve and the intake or suction valve are simply spring-loaded check valves. The discharge valve permits gas only to be forced out of the cylinder. The intake valve permits gas only to enter the cylinder. 

Spring-loaded check valve —Screw cap Rubber sealing ring... 

Since the ordinary type of spring-loaded check valve does not always reseat satisfactorily and as rupture discs have the disadvantage of allowing >/wa. 

Several in-room service panels are part of this system. Each patient room, and other locations where needed, are equipped with an in-room service panel. The panel consists of an isolation valve, a regulator hand valve (to reduce supply pressure from 250 psi to a usable pressure of 20-30 psi), a pressure indicator gauge, a pressure relief valve, a spring-loaded check valve, and a capped interface port (for maintenance operations only). 

The suction and discharge valves inside a cylinder are spring-loaded check valves, lliey require a small differential pressure m open them. Therefore, at.sactiDn stroke, the pressure inside the cylinder is less than the suction line pressure, and at discharge stroke, the pressure inside the cylinder is higher than the discharge line pressure. 

When this low RPV pressure is reached, the RPV water level is lower than the inlet nozzle of the reflooding line. This means that the emergency condenser headers are filled with steam. When the spring-loaded check valve opens, steam flows from the header to the core flooding pool and is condensed there by means of a device similar to a quencher. At this point in the process the check valves serve the same function as supplementary relief valves and the pressure drop in the RPV accelerates after the check valves open. This steam blowing phase is the only phase in which natural circulation is used. The warm water of the core flooding pool flows to the water surface and the quencher is always surrounded by cold water. 

In some cases, after careful evaluation, other valves may be considered for EBVs such as spring-loaded control valves that fail closed, back flow check valves (these are not normally considered reliable enough for EBVs by many engineers), and excess flow valves. Excess flow is the loss of material from the confined environment of a vessel or pipeline. Two approaches are available for the detection and valve action of excess flow valve systems (1) External, where excess flow is detected outside the valve itself, and (2) internal, which is within the valve unit and has limited applications. Excess flow conditions are detected more readily because of loss of resistance to flow than because of loss of pressure. All excess flow detection systems are based on product physical properties as well as flow rate. A change of products or process conditions may require a change in the excess flow detection system. For example, a number of excess flow valves are rated for low pressure and are made of materials not suitable for hydrocarbons. 

The check valves, C, D, E, and F, are the heart of the system. If they foul up, the best metering pistons or mixer cannot remedy an off-ratio condition. These valves range in complexity and cost from a simple spring-loaded check to expensive powered valves of either... 

A continuous flow reactor vessel contains a liquid reacting mixture with a density of 0.85 g/cm3 and a viscosity of 7 cP at 1 atm pressure. Near the bottom of the vessel is a I i n. outlet line containing a safety relief valve. There is 4 ft of pipe with two 90° elbows between the tank and the valve. The relief valve is a spring-loaded lift check valve, which opens when the pressure on the upstream... 

PVC spring-loaded ball-check valve 3/s" barb x 3/s" barb, Buna-N seal McMaster- Carr 7933K33 1... 

SS spring loaded poppet check valve %" tube OD, Yor-Lok fittings McMaster-Carr 45385K55 1... 

PVC spring-loaded ball-check valve /g" barb x 3/8" barb. 

The Chlorine Institute (P93) also describes a pneumatically operated valve (POV) for use on chlorine tank cars. This is a dual assembly including an angle globe valve with external bellows seal and a spring-loaded ball check valve. The main features of the POV that distinguish it from the standard manual angle valve are ... 

Figure 4.21 Diagram illustrating the operation of a single piston HPLC pump. A circular cam with an eccentric shaft is held tight against the piston. As the cam rotates it pushes the piston inwards as the larger side of the cam moves around to contact the end of the piston, and then withdraws the piston as the smaller dimension moves around. When the piston is moved inwards it creates a positive pressure in the mobile phase liquid in the body of the pump, and this opens the spring-loaded sapphire ball in the exit check valve and simultaneously forces closed that in the entrance check valve. In the next half cycle when the piston moves backwards, a negative pressure is created and the exit valve is forced to close while the entrance valve is opened allowing additional mobile phase into the body of the pump.

Single-unit tank cars are protected from excessive internal pressure by a spring-loaded pressure relief valve located on the manway cover plate. Excess flow-check valves are installed on the liquid eduction and vapor lines of many tank cars in compressed gas service. These excess flow valves are intended to contain the tank contents in transit, in a wreck environment if the valve is sheared off, or during other incidents when uncontrolled release of product may occur. 

Shutoff nozzles are used to prevent nozzles from leaking into empty molds or when the nozzle is retracted from the sprue bushings. Valves of all kinds —i.e., spring-loaded ball check valves, hydraulically and mechanically operated needle valves, and rotary valves —have been incorporated into nozzles. 

In terms of cost, the powered check valve is more expensive than the spring loaded ball check valve, not only because of design differences but also because of thcontrol devices required for operation. Regardless of the powered valve s cost, it is a comfort to know that the valve is going to operate regardless of the material or operating conditions. 

---