Fusible plug device

Caution No attempt should be made to repair used fusible plug devices because of the possibility of the wrong fusible metal being used, the absence of a qualified repair procedure, and the possibility of destroying the bond... 

A fusible plug device is a nonreclosing device. Therefore, when it functions it releases the entire contents of the cylinder. 

R. This fusible plug device may be used at pressures up to the maximum service pressure of the cylinder for which the device s use is intended, but no more than 6000 psig (41 400 kPa). When cylinders are over 65 inches (1651 mm) long, exclusive of the neck, this device is required at both ends. For shorter cylinders, the device is required in one end only. 

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... 

Cautions No attempt should be made to repair fusible plug devices that have been returned from service by melting out the alloy and recasting. Used fusible plugs that are not leaking may be cleaned externally, reinstalled, and subjected to the prescribed leak tests. 

Fig. 7-5. Illustration of a fusible plug device (TVpe CG-2 or CG-3) threaded into a cylinder valve body.

Fig. 7-6. Combination rupture disk/fusible plug device (Type CG-4 or CG-5) factory-assembled as a complete unit.

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. 

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]... 

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