Packed type cylinder valve

Valves must be either a nonperforated diaphragm type (with outlets sealed with a solid metal cap or plug) or a packed type provided the assembly is made gas-tight by means of a seal cap to the valve body or to the cylinder. 

Cylinders must be filled so they are not liquid full at 130°F (54.4°C). Valves utilized for cylinders of phosphine are usually of the diaphragm type. When shipped, the outlet must be sealed with a threaded cap or threaded solid plug. If shipped with a packed type valve, the valve must be fitted with a seal cap to contain leakage around the stem, or the complete valve must be sealed to the cylinder with a gasketed gas-tight cap. See 49 CFR 173.40 and 173.192 for general packaging requirements for Poison gas. Hazard Zone A materials [7]. 

Cylinders require the installation of a valve that will permit the withdrawal of the mixture. The valve used on a cylinder for a given mixture must be selected so the materials of construction are compatible with ail mixture components. The type of valve, packed or diaphragm, is chosen based on the integrity and regulatory requirements of the mixture. The outlet connection is selected based on the physical and chemical characteristics of the components. CGA V-7, Standard Method of Determining Cylinder Valve Outlet Connections for Industrial Gas Mixtures, is a guide for the selection of outlet connections for mixtures. It includes numerous examples of how to apply the selection procedures [12]. 

Cylinder valves are generally of two basic types, the packless (diaphragm) type and the packed t3q)e. These two types are described in detail below. 

---