An informational site dedicated to process control education. Posts on this blog contain interesting and noteworthy information about process instrumentation, valves, and equipment used in industrial and municipal facilities. This blog is sponsored by Instrument Specialties, Inc. (ISI). For more information, please visit ISI.GROUP
Rupture discs are fixed setpoint devices designed to provide failsafe performance in venting gases or liquids in the case of excessive pressure. The precision made and certified disc is contained within a holder specially designed for the disc and to facilitate proper inspection and maintenance.
Fike is a globally recognized manufacturer of products that protect people and critical assets from dangers such as fire, explosion and over-pressurization. With over 60 years experience manufacturing products ranging from rupture discs and explosion protection systems, to fire suppression and fire alarm systems, Fike offers reliable solutions for customers around the world.
An integral part of the inclusion of a safety device in a process system is the manner in which it is installed. Documented product performance, upon which the user is depending, is predicated upon installation in a manner which duplicates the rating condition. Varying from the manufacturer's installation procedure or instructions can have an impact on the performance of almost any process measurement and control product, but adherence to procedure is especially important when safety devices are concerned. The video below demonstrates the proper procedure for installing Fike rupture discs.
Fike provides certified rupture discs to meet all applications for process industries including isolating pressure relief valves from corrosive materials, reducing involuntary emissions, insuring pressure relief in critical applications, rupture discs for sanitary/pharmaceutical processes.
Share your over-pressure safety requirements with a product specialist and select from the complete line of cost-effective rupture discs, holders and custom pressure relief devices which are compliant with global code regulations and designed to meet or exceed industry requirements for performance, reliability and quality.
Safety and pressure relief valves are common elements of any pressurized system. Their general purpose is to stop system pressure from exceeding a preset value, preventing uncontrolled events that could result in damage to personnel, environment, or assets. Their operating principle and construction are comparatively simple and well understood.
Long term exposure of a relief valve to any number of media can result in corrosion, material buildup, or other conditions which may shorten the useful life of the valve, or worse, impair its proper operation. This excessive wear will increase the ongoing cost of maintaining or replacing a prematurely worn valve. One other aspect of relief valves can be the reduction in their seal integrity or force as the system pressure approaches the setpoint. This could possibly lead to fugitive emissions, an undesirable condition.
A reasonable solution is posed by Fike, globally recognized leader in fire, explosion, and overpressure protection. Isolating a relief or safety valve from the process media through the installation of a rupture disc upstream of the valve inlet will eliminate exposure of the costly valve to effects of the media. It is necessary to establish proper rating and selection for the rupture disc to avoid any impairment of the overall operation of the relief valve, but the selection criteria are not complex. A number of benefits can accrue with this concept.
Avoid purchase of relief valves manufactured from exotic materials to accommodate exposure to corrosive media. Rupture disc provides isolation of the valve from the media.
Eliminate fugitive emissions at the relief valve. Rupture discs, when properly installed, are leak free and bubble tight.
Relief valve inventory can be evaluated for reduction.
Longer valve life.
Less downtime.
The additional cost for the rupture disc enhancement can have a reasonable payback period, with all factors considered. In any case, the rupture disc protection makes for a cleaner relief valve installation.
Rupture discs and holders are available in sizes and materials for most applications. Share your ideas with a product specialist, combining your process knowledge with their product application expertise to develop an effective solution.
The objective of this bulletin is to provide detailed guidance for sizing rupture discs using standard methodologies found in ASME Section VIII Div. 1, API RP520, and Crane TP-410. To assist in the sizing process, contact Instrument Specialties at 407.324.7800 for help.
Overpressure Allowance
When sizing pressure relief devices, the Code defines the maximum pressure that may build up in the pressure vessel while the device is relieving. This pressure varies depending on the application of the device. The following table defines the various overpressure allowances.
Rupture Disc Sizing Methodologies
There are 3 basic methodologies for sizing rupture disc devices:
Coefficient of Discharge Method (KD) — The KD is the coefficient of discharge that is applied to the theoretical flow rate to arrive at a rated flow rate for simple systems.
Resistance to Flow Method (KR) — The KR represents the velocity head loss due to the rupture disc device. This head loss is included in the overall system loss calculations to determine the size of the relief system.
Combination Capacity Method — When a rupture disc device is installed in combination with a pressure relief valve, the valve capacity is derated by a default value of 0.9 or a tested value for the disc/valve combination. See technical bulletin TB8101 for specific application requirements when using rupture disc devices in combination with PRVs.
Fike rupture discs are designed to provide instantaneous pressure relief at a predefined pressure and temperature. Installation is an important consideration that can affect the performance a ruptured disk. Installation instructions are included with all Fike ruptured disc shipments. These instructions should be followed carefully and completely.
Remember to place the rupture disc assembly where it will have sufficient clearance to operate unhindered. The rupture disc assembly should be vented to a safe area where people and equipment are not at risk, as a system discharge can be hazardous or cause injury. Baffle plates used on the end of outlet piping will redirect but not eliminate potentially dangerous system discharge. The piping near the rupture disc assembly should be braced to absorb shock caused by the opening up a rupture disk. Fike provides a danger sign with all rupture disc shipments and it should be placed in a conspicuous location near the zone a potential danger. Keep the danger sign clean and unobstructed for ease of viewing.
To install a new rupture disc remove the burst rupture disc assembly from its piping. Please use caution as a ruptured disk may have sharp edges. Remove pre-assembly screws or side clips and separate the holder components. If this is an existing installation, it is important at this point to do a visual inspection of the rupture disc holder. Inspect the holder seat area for nicks, scratches, corrosion, or deposits left by the process media. If necessary, hand polish the seat area with Scotch Bright, super fine steel wool, or a fine emery cloth. Before installing a new rupture disc into the rupture disc holder, clean the seat area with the solvent compatible with your media. To verify that the holder has not become deformed, place a straight edge on the flat flange mating surfaces of the base and hold-down. If the flat surfaces are not parallel with the straight edge, the holder should be replaced immediately.
Visually inspect the rupture disc for shipping damage. Read the complete information contained on the rupture disc tag. Verify that the disk size, type, pressure, and temperature are correct for your system. After verifying that you have the correct rupture disc, carefully place reverse acting rupture discs into the hold-down of the holder. Or if the rupture disk is forward acting, carefully place the disc into the base the holder. Checked the rupture disc tag and make sure that the side labeled "vent side" faces downstream. Rupture disc tags with flow arrows must point in the same direction as the flow arrows on the ruptured disc holder. Carefully place the hold-down on top of the disc.
Install the pre-assembly screws or side clips. Do not apply torque to the pre-assembly screws. Finger tight is sufficient. Check to be sure the gap between the base and the hold-down is equal all the way around the holder. If it is not, take the rupture disc holder apart and reassemble. After assembling the rupture disc and holder, you are ready to install the rupture disc assembly into your piping system. Place gaskets on the top and bottom of the rupture disc holder as needed. Gaskets that are subject to cold-flow are not recommended. Carefully place the rupture disc assembly between the piping flanges. Check to insure the holder flow arrows point downstream. Care should be taken not to damage the dome of the rupture disc, being particularly careful if it protrudes above the hold-down of the rupture disc holder.
Check to see that all studs and nuts are the correct size. Lubricate the studs with the light, free running oil, such as 20 grade. Studs and nuts that show evidence of galling should not be used. Insert the studs into the flange and finger tighten. Check to see that the gap is still equal. If it is not, loosen the studs and the nuts and adjust flanges until the gap is once again equal.
To determine the required torque, refer to the appropriate stud torque chart included in the written installation instructions. Find a nominal rupture disc size and ANSI rating of your flange. Follow the row across the column that contains your rupture disc type to determine what is required for your rupture disc in foot-pounds. Using a criss-cross pattern, apply torque in 25 percent increments. For example if the required torque is 100 foot-pounds, torque would be applied in 25 foot-pound increments using the criss-cross pattern. After each torque step, it is recommended that you checked the gap between the base and the hold-down to be sure that it is still equal. After the final torque step has been completed, make one revolution around the flange to be sure that each stud has received the correct amount of torque.
Fike rupture discs and holders come in many sizes and types. A common requirement of all designs is proper handling and installation. Please follow the instructions included in your Fike shipment to optimize performance and service life.
