Graphite Rupture Disk (Discs) for vacumm and pressure relief

FAQs About Graphite Rupture Disks

Q:Why should I use a rupture disk?
A:A rupture disk is a non-reclosing relief device with an instantaneous opening used for overpressure and vacuum relief. Rupture disks reduce the risk of chemical incidents, thereby protecting employees, the public and the environment, minimizing economic consequences.

Q:Why should I use a graphite rupture disk?
A:Graphite rupture disks are used in a variety of applications. The biggest advantage to SAF-T-GRAF® rupture disks is very low burst pressure capabilities, high temperature resistance, and compatibility to many corrosive materials.

Q:What is the maximum temperature and pressure at which I can operate a graphite rupture disk?
A:BS&B SAF-T-GRAF® disks may be used in applications up to 800ºF with the use of a High-Temperature Assembly (HTA). The maximum pressure is 1000psi in small sizes.

Q:What is the service life of a graphite rupture disk?
A:This is a difficult question. Graphite rupture disks are very application sensitive. As long as the disk is operated within recommended limits it may last indefinitely. However, we do recommend that SAF-T-GRAF® disks be changed on a preventive maintenance schedule, usually 1-3 years.

Q:What is the "binder" in graphite rupture disks?
A:Actually, the term "binder" is misused. What is referred to as "binder" is the chemical "sealant" or "impregnation compound" which is used to seal the porosity of the raw graphite from which graphite rupture disks are manufactured. The "impregnation compound" used by BS&B SAF-T-GRAF® disks may be a high temperature epoxy resin, a phenolic, or a combination of both.

Q:Does one type of "impregnation compound" have an advantage over the other?
A:Not necessarily. Once the impermeability of the graphite is achieved, any advantage of one over the other would be associated with process compatibility. Although very similar in their resistance to chemical attack, one material may be better in some processes than another. Due to the extreme variables in processes, experience is the best teacher.

Q:What are the advantages of graphite rupture disks over metal rupture disks?
A:Certainly each has its place in the process industry. Conventional graphite rupture disks do not require a holder. Graphite rupture disks can be manufactured to operate at very low pressures. Since graphite is functionally inert, graphite rupture disks may be used in applications that would require very expensive anti-corrosive alloys in a metal rupture disk.

Q:Can I use a graphite rupture disk to isolate safety relief valves like I do with metal rupture disks?
A:Although it can be done and is suggested by some manufacturers, we discourage the practice since graphite rupture disks fragment when opening. Although a fragmentation chamber may be installed, some of the abrasive graphite will pass through the SRV with the process media potentially scarring the valve seat creating a leak path. We suggest using BS&B Metal Rupture Disks when fragmentation is an issue.

Q.What size of graphite rupture disk do I need?
A.The size of the SAF-T-GRAF® disk depends on the process conditions. Contact Us with the process information and we'll be happy to make a recommendation.

Q:Why does BS&B provide graphite rupture disks with gaskets attached by the manufacturer?
A:The inside diameter of gasketing on a MonoBloc™ disk can significantly elevate the burst pressure of a graphite disk over the rated pressure if the inside diameter is too small. Other manufacturers include instructions on the inside diameter which must be used should you not purchase gasketing with the rupture disk. BS&B understands that common-sized ANSI gaskets will be used more often than not if we do not attach gaskets at the factory. Very few facilities will take the time to hand cut gaskets to the required dimensions. For that reason, we use our own rule dies to punch the gaskets used on SAF-T-GRAF® disks to provide the end user with an extra margin of safety.

Q:Why should I request all my SAF-T-GRAF® disks with "armor"?
A:Although designed to do so, most often the flanges into which a SAF-T-GRAF® disk is installed are rarely parallel. Impregnated graphite is quite brittle. As the disk is torqued into the flanges, the stresses on graphite rupture disks can cause the graphite to "craze" or break. At a minimum, the uneven stresses can cause the disk to fail prematurely. The heavy armor makes the disk far more "forgiving" of uneven or excessive torque loading and rough handling during installation and significantly extends the service life of the disk.

Q:We like to have all our rupture disks equipped with sensors. Can sensors be provided on graphite rupture disks?
A:Yes. SAF-T-GRAF® disks can be equipped with a Graphite-Alert™ sensor as an integral part of the delivered disk which may be connected to a BS&B Burst-Disk™ monitor or into the facility’s existing PLC or DCS.

Q:I would like to use SAF-T-GRAF® disks in applications that would expose the disk to significant backpressures. Can I do this?
A:Depending upon the magnitude of the back pressure, SAF-T-GRAF® disks can usually be equipped with a "back pressure support" which is fit inside the counterbore of a MonoBloc™ type disk. The user is cautioned to remember that a rupture disk is a "differential pressure" safety device and backpressures should be taken into consideration during calculations to determine the requested pressure. Contact BS&B with the application details to determine if we can satisfy your back pressure application requirements.

Q:I’ve heard that graphite rupture disks aren’t suited to cyclic or pulsing service. Is this true?
A:Typically graphite rupture disks do not cycle as well as metal disks when exposed to the same cyclic environment. However, the effects of cycling or pulsing on the performance of a graphite rupture disk is a function of the frequency and magnitude of the cycling. If the system operating pressure is typically less than 80% of the burst pressure of the SAF-T-GRAF® disk, and the frequency of cycling is reasonably low, a SAF-T-GRAF® disk may very well provide satisfactory service.

Q:Can I replace my "other" graphite rupture disks with SAF-T-GRAF® disks without major modifications to my piping scheme?
A:Yes. Typically, the overall face-to-face dimensions of BS&B’s SAF-T-GRAF® will allow it to be installed where graphite rupture disks of other manufacturers have been used. For a nominal charge, we will adjust the face-to-face dimensions of the SAF-T-GRAF® product to meet your specific needs. Custom-sized SAF-T-GRAF® disks are a specialty at BS&B.