Cylinder Valve Solution for gases
Gases can be stored in high-pressure cylinders under different conditions and at different pressures.
The exact pressure depends on the gas type, state, and storage conditions.
Gases are stored in compressed cylinders with pressures of up to 104 pounds per square inch at 129.2 degrees Fahrenheit or 40 pounds per sq. inch at 70°F.
Most compressed gas cylinders require the installation of at least one cylinder valve.
This valve allows the cylinder to contain gases and gas to be filled or emptied from the cylinder.
The cylinder valve is the most vulnerable part of the compressed gas package and requires a thorough understanding to maximize its performance.
Types of Cylinder Valve
There are four basic valve types: the pressure seal valve, the packed valve, the O ring valve, and the diaphragm valve.
There are several versions or designs within each of the four basic types. This pamphlet will address the more common valves in today’s industry.
Pressure seal valve
Products: inerts, oxygen, hydrogen
Operating principle: The pressure seal valve is a handwheel-operated valve using a two-piece valve stem.
The upper and lower stems interface with each other.
The threads are located on the lower stem, and the upper limb is free-floating.
A Teflon@ material packing ring that makes contact with a ridge on the upper stem provides the seal around the valve stem.
The force that provides this contact is gas pressure and the spring in the handwheel.
This spring provides upward force to the upper stem and pulls the stem’s sealing ridge into the packing ring.
The spring-loaded diaphragm valve
Products: Highly toxic noncorrosive gases, high-purity gases, rare gases, and pyrophoric gases
Operating principle: The diaphragm valve is handwheel‑operated, using a two‑piece stem separated by nonperforated diaphragms. These diaphragms prevent leakage along the valve stem. The lower limb is
encased in a spring, which forces the branch away from the seat when the valve is opened. The upper limb is
threaded into the diaphragm retainer nut. When the handwheel is rotated to the closed position, the upper limb pushes on the diaphragms, which defect downward, forcing the lower limb against the valve seat. When the handwheel is rotated toward the open position, the upper limb is moved away from the diaphragms, allowing the spring to push the lower limb away from the seat. Replacing elastomeric seals with metal diaphragms gives this valve superior leak integrity to the atmosphere.
O ring valve
Products: inerts, oxygen, hydrogen
Operating principle: The O ring valve is similar in design to the pressure seal valve, except that O achieves the sealing rings(s) instead of a washer for the upper stem.
They identify features: 1. The design requires no spring, so the handwheel has no wriggle. The handwheel does not rise due to the handwheel rotation position, but the user can sense a rise of the handwheel when the valve is initially opened and the gland area subject to high pressure.
Recommended opening procedure: The valve does not require to be back‑seated during opening.
Wrench-Operated Packed Valve
Identifying features
1. This valve does not have a hand wheel. The top of the stem is machined square to accommodate a wrench.
2. The top of the valve has a large, internal‑threaded nut screwed onto the body, where the valve’s stem exits. This is the packing nut.
Recommended opening procedure:
The wrench‑operated valve has a considerable flow capacity. It is unnecessary to open this valve to the fully open position to provide full flow to the Process. Opening this valve entirely poses serious problems. The first problem is safety‑related. In many applications, cylinders with these valves are used in tight quarters (e.g., gas cabinets) or behind barricades. These space constraints often prevent the stem from being fully rotated when the valve operates.
This valve requires approximately three full turns from full open to full close. In the case of an emergency, it can take 15 to 30 seconds to close the valve, depending on
space and operator stress. However, if the valve is opened to the recommended ¼ to ½ turn, the valve can be quickly closed with minimal operator
exposure. The second benefit of only opening the valve the recommended ¼ to ½ turn is the protection of the up-per-section of threads.
Working knowledge of cylinder valves
Working knowledge of cylinder valves can improve processes, save time and money, prevent problems, maintain the life and integrity of the valve, and improve the safety of your operation. This document must not be used as a valve modification or repair guide. No changes to valves are permitted, and any repairs shall only be made by or under the direction of the supplier.
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