Pressure relief devices fusible plugs

Type CG-2 and CG-3 (fusible plugs), A fusible plug is a thermally operated pressure relief device that affords protection against excessive pressure developed by exposure to excessive heat. Once sufficient heat melts the fusible metal, the contents of the cylinder will be vented. The CG-2 fusible metal has a nominal melt temperature of 165°F (73.9°C) the CG-3 fusible metal has a nominal melt temperature of 212T(100X). 

Type CG-4 and CG-S (combination rupture disk/fusible plug). A combination rupture disk/fusible plug pressure relief device requires both temperature and pressure in that order for it to operate and therefore provides for maximum retention of the cylinder contents. Sufficient heat is required to first melt out the fusible metal, after which the device will afford the same protection as the CG-1 rupture disk device. 

Type CG-2 (fusible plug device). This type of device is described earlier in this chapter under compressed gas cylinder pressure relief devices. Only the CG-2 fusible plug with a nominal melt... 

Chlorine is authorized for shipment in ton containers with 2000-lb (907-kg) capacity that comply with DOT specification 106A500X. The pressure relief device is a fusible plug. These are installed on each end of the container. Ton containers conforming to older specifications may still be used. Valve outlet connections are the same as for cylinders except the ton container... 

Fusible plug A nonreclosing pressure relief device designed to function by yielding or melting of a plug of material at a predetermined temperature. 

TB-13 Rupture Disk Fusible Plug Type Pressure Relief Devices Correct Assemblies Installation. Description of Rupture Disk (CG-1) and Fusible Plug (CG-2, CG-3, CG-9) Pressure Relief Device including correct assemblies and installation. (5 pages)... 

Authorized pressure relief devices on acetylene cylinders are Type CG-3 fusible plugs with a nominal yield temperature of 212°F (100°C). [15]... 

Pressure relief devices authorized for use with ammonia cylinders are the Type CG-2 fusible plug device with a nominal yield temperature of 165°F (73.9°C). No pressure relief device is required for cylinders under 165 lb (74.8 kg). [12]... 

Pressure relief devices authorized for use on argon cylinders are the Type CG-1 rupture disk, CG-4 and CG-5 combination rupture disk/fusible plug devices, and the CG-7 pressure relief valve. Refer to CGA S-1.1, Pressure Relief Device Standards—Part I— Cylinders for Compressed Gases, for further information. [4]... 

As previously stated, the valve must be equipped with a Type CG-1 pressure relief device equipped with a rupture disk. A backed pressure relief device, that is, a combination rupture disk/fusible plug device, must not be used on a carbon dioxide cylinder valve. 

Carbon tetrafluoride is authorized for shipment in DOT specified cylinders as identified in 49 CFR 173.302 and equivalent Canadian regulations. [1] and [2] Authorized pressure relief devices include the Type CG-1 rupture disk, the Type CG-4 or CG-5 combination rupture disk/fusible plug device, or the Type CG-7 pressure relief valve. [3] The rupture disk must have a bursting pressure not exceeding the minimum prescribed test pressure of the cylinder. 

The most common cylinder valve used for dichlorosilane is a stainless steel diaphragm valve with a Connection CGA 678 outlet. The cylinder valve body has a combination CG-4 type pressure relief device consisting of a fusible metal plug, melting about 165°F (74°C), which is protected from the cylinder contents by a frangible metal disk, i.e. a rupture disk, rated at 250 psig (1724 kPa). 

Cylinders must be equipped with a CG-4 type pressure relief device. This device must be in both ends of the cylinder when the cylinder is over 30 inches (76 cm) in length. This type of device is a combination rupture disk/ fusible plug, utilizing a fusible alloy with a yield temperature not over I70°F (76.7°C). 

Authorized pressure relief devices for use on silane cylinders are the IVpe CG-4 combination rupture disk/fusible plug device wherein the fusible metal has a nominal yield temperature of 165° F (74 °C). Consult CGA S-1.1, Pressure Relief Device Standards— Part 1—Cylinders for Compressed Gases, for further information and requirements. [11]... 

Authorized pressure relief devices for use on sulfur dioxide cylinders are Type CG-2 fusible plugs. 

Chlorine is stored and transported as a liquefied gas in cylinders of 45.4-kg or 68-kg capacity that are under pressure and equipped with fusible-plug relief devices. Quantities in the range of 15 to 90 t are transported in tank cars having special angle valves on the manhole cover on top of the vessel. Tank barges of the open-hopper type having several cylindrical uninsulated pressure vessels are used for amounts ranging from 600 to 1200 t. Road tankers are used for capacities of 15 to 20 t. 

A boiler rupture occurs if steam flow output is prevented or restricted and the temperature and pressure in the boiler increases. If some form of safely device is not provided or is inadequate to limit the pressure to a safe value, the boiler will rupture. Boilers are required to be equipped with safety valves to relieve pressure if they exceed set values. Low points in some boilers are provided with fusible plugs. During normal operations, the plugs are covered with water which keeps them cool. If the water level drops and they are exposed, the plugs melt and create another vent for pressure relief. Boilers also have low-water shutoff devices which block in the burner fuel when the steam drum water drops below a certain level. 

Mechanical equipment that performs an action to relieve pressure when the normal operating range of temperature or pressure has been exceeded. Physical relief devices include pressure relief valves, thermal relief valves, rupture disks, rupture pins, and high temperature fusible plugs. 

Pressure relief valves are generally more susceptible to leakage around the seal formed by the seat than rupture disks or fusible plugs. These devices may be affected by the environment and/or lading, which may cause freezing, sticking, or otherwise improper operation. 

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