Page 259 - Valve Selection Handbook

246 Valve Selection Handbook

Accessories

The following lists a number of accessories that are being supplied by
manufacturers in connection with rupture disc holders.

Jackscrews. These are used as a means for separating the flange carry-
ing the disc holder from the flange of a separately supported discharge
pipe. The Jackscrews must be properly spaced to allow the disc holder to
be removed or reinstalled.

Eyebolts. These are used primarily to hoist heavy rupture disc holders
into position.

Baffle plates. These are primarily used in connection with free-venting
rupture disc assemblies in which deflection of the discharging fluid
would protect personnel. The deflection of the discharging fluid absorbs,
in addition, the discharge reactive force.

Burst indicators. These give an instantaneous indication of a rupture
disc failure by actuating a visible or audible signal that may be locally or
remotely located. These can be designed to be intrinsically safe within an
explosively hazardous environment.

Double Disc Assemblies

Double disc assemblies, such as shown in Figure 6-34, are being used
in corrosive services to warn of product leakage due to corrosion damage
of the disc on the process side. In another application, double disc assem-
blies are used as a quick-opening device.

Product leakage warning devices. Figure 6-33 shows a double disc
assembly used for warning of product leakage due to corrosion damage
of the disc facing the product side. To prevent pressure build-up in the
space between the rupture discs due to pinholes from corrosion in the
first disc, the space between the discs must be provided with a telltale
device, consisting commonly of an excess flow valve and a pressure indi-
cator. Should the first disc fail prematurely, the second disc is likely to
fail also. If this mode of failure cannot be accepted, the burst pressure of
the second disc must be raised. This matter should be discussed with the
rupture disc manufacturer.