Rupture, disk Graphite

Rupture Disks A rupture disk is a device designed to function by the bursting of a pressure-retaining disk (Fig. 26-15). This assembly consists of a thin, circular membrane usually made of metal, plastic, or graphite that is firmly clamped in a disk holder. When the process reaches the bursting pressure of the disk, the disk ruptures and releases the pressure. Rupture disks can be installed alone or in combination with other types of devices. Once blown, rupture disks do not reseat thus, the entire contents of the upstream process equipment will be vented. Rupture disks are commonly used in series (upstream) with a relief valve to prevent corrosive fluids from contacting the metal parts of the valve. In addition, this combination is a reclosing system. 

A rupture disk is a non-reclosing thin diaphragm (metal, plastic, carbon/graphite (non-metallic)) held between flanges and designed to burst at a predetermined internal pressure. Each bursting requires the installation of a new disk. It is used in corrosive service, toxic or leak-proof applications, and for required bursting pressures not easily accommodated by the conventional valve such as explosions. It is applicable to steam. 

Figure 7-13A. Installation of graphite rupture disk. Adapted by permission, Falls Industries, Inc.

The service life of a rupture disk is difficult to predict, since corrosion, cycling pressures, temperature and other process conditions can all affect the useful life and cause premature failure. A graphite-type disk is shown in Figure 7-9. In some processes it is safer to replace disks on a schedule after the life factor has been established, as a planned shut-down is certainly less costly than an emergency one. 

Zook Graphite Rupture Disks, Bull. 6000-2, Zook Enterprises. 

K,j = coefficient of discharge, K = 0.62 for rupture disks, except some coefficients are different. For example, the Zook graphite standard ASME disks when tested mono-style, Figures 7-9B and 7-13A have a KD of 0.888, and when inverted, Figure 7-13B have a KD of 0.779. Consult manufacturer for special disks. 

Runaway reactions, 405 Runaway reactions, DIERS, 521-523 Rupture, disk, 401, 418, 435, 455 Burst pressure, 456 Calculations, non-explosive, 455, 459 Code pressure levels, 410 Effects of temperature, 458 Graphite, 418-420, 424 Installation, 422, 423 Liquids, 462 Low pressure, 418, 421 Manufacturing range, 434, 456 Metal, 411 Non-fire, 465 Quick opening, 414, 415 Reverse buckling, 413 Selection features, 434... 

The available rupture disk (RD) materials and temperature limitations are listed in Tables 3.152 and 3.153. Their rupture tolerance (error) is 2% of set pressure, which can be up to 8,000 barg (100,000 psig). The RD in its simplest form is a metallic or graphite membrane that is held between flanges. It bursts at some predetermined pressure and relieves the pressure in the protected equipment before the system components fail. Another common use of an RD is as single use, fast-acting valves used in fire suppression systems. Table 3.152 lists some RD design variations and their features. 

Other mechanical applications of molded graphite include glass-lehr roll bearings, roller bearings for jet-engine exhaust nozzles, metering seats for gasoline pumps, vane pumps for air compressors, rupture disks, and many others. 

For rupture disk u.sed at PRV inlet, it should be non-fragmenting design to avoid damaging PRV. Rupture disks, such as forward-acting solid metal disk and graphite rupture disk are of fragmenting design, should not be used at PRV inlet. 

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