Frequently Asked Questions
Below are answers to the most frequently asked questions. If you can’t find what you are looking for, please get in touch with us.
What is a rupture or bursting disc?
A non re-closing pressure relief device designed to relieve excess over-pressure or vacuum conditions at a pre-determined
pressure or temperature.
Do rupture discs replace safety relief valves?
Not always. Increasingly, engineers are using a rupture disc in combination with their traditional valve to enhance the pressure relief solution and achieve the most cost effective explosion protection. Using a rupture disc in addition to a valve means the system benefits from the unique advantages of each individual solution, whilst maintaining a reasonable cost.
Process leakage into the atmosphere is kept to a minimum and valve life is extended by isolating corrosive fluids from internal valve parts. As secondary protection, discs also offer a back up in case of downtime and can enhance the SIL level of the system by adding layers of protection. For safety-critical applications, ‘doubling up’ in this way not only offers greater protection to the infrastructure of a process plant, but also to its people.
What different types of disc are available?
There are two main categories of disc designs:
- Forward acting (tensile loaded).
- Reverse acting (compression loaded).
However, graphite and custom design (OEM) discs are also available.
What information is needed in order to be able to specify the correct disc?
The specification variables to consider when choosing a disc include required burst pressure, burst temperature, nominal bore size, medium, whether it must be a non-fragmenting design, and whether the disc has to withstand full vacuum. There are several other factors as well. As a disc is safety-critical part of the plant equipment, we would always recommend you speak to an Elfab specialist to specify the correct disc for any application.
What size discs are available?
Elfab can supply discs from 1/8” (3mm) up to 32” (800mm) in diameter.
What is ‘working pressure to burst pressure ratio’?
This is the margin between the Maximum Recommended Working Pressure for the disc design and the bottom limit of the burst
pressure for the disc.
How does temperature affect the burst pressure of the disc?
The burst pressure will generally reduce as the temperature increases, and vice versa. However, this is dependent on the disc type and the material used. Please contact us for further information.
Can the disc be used on Oxygen clean duty?
Discs can be supplied cleaned for use in Oxygen Service at a nominal extra charge.
Does Elfab have experience with discs in exotic materials?
Yes. Elfab can manufacture discs in Inconel, Stainless Steel, Nickel, Hastelloy, Tantalum and Monel. The most suitable materials will depend on the specific operating conditions.
Will a disc withstand back pressure or vacuum?
This depends on the disc design being used. Reverse acting discs such as Opti-Gard will withstand full vacuum without the need for
vacuum support, but other designs may require it. Vacuum conditions should be specified with the request for quotation.
Can a rupture disc be used in applications other than pressure relief?
Yes, you can use discs as pressure switches, for example, to enable the controlled activation of propellant systems by bursting and
therefore allowing the two mediums to mix.
What if I can’t find what I need on the website?
Alongside its standard range, Elfab design and offer customised solutions to meet your exact specification requirements. If you can’t see anything suitable, please contact us directly to discuss your individual application in more detail.
My discs are bursting too often, what could be the problem be?
A number of factors come in to play which can affect the performance of the disc. Possible issues could include the following:
- Deteriorating condition of the disc
- Incorrect installation of the disc and/or holder
- The installation could be exceeding the specified maximum operating ratio
- Damage to the disc
We are happy to assist you investigating the cause of unwanted bursting.
How does the rupture disc fit into my system?
Discs are generally fitted into a holder and mounted between pipe flanges. However, they can also have screwed connections or a variety of custom-designed mounting arrangements depending on the particular application. Please refer to the specific installation instructions when fitting. Elfab can offer training to help your teams understand the importance of correct installation.
How do I know I have the correct disc?
The disc will carry a tag that displays all the relevant performance details of the disc. As an absolute minimum the disc will carry the Elfab contract number, which can be traced to the test certificate and checked for the correct specification. Additional markings can be added to the disc tags to identify its unique location within your plant.
Can I fit an Elfab rupture disc into another manufacturer’s holder?
No. As specified by the Pressure Equipment Directive, one manufacture’s rupture disc cannot be placed into another manufacture’s rupture disc holder. All Elfab product certifications relate to the Rupture Disc Device, comprising of an Elfab disc in an Elfab holder only. Installing product in alternative holders will invalidate the CE marking, warranty and insurance.
How do I know I have the correct holder for the disc?
The disc should be marked with the reference of the holder in which it should be used.
How do I know that the holder is fitted into the pipe work in the correct orientation to flow?
Elfab uses a fixed bracket (System-loc) on the flange inlet, which forces the holder orientation. Each Elfab holder is also laser etched with a flow arrow to enable correct installation within the system.
How do I know when the disc has burst?
Depending on the installation and complexity of the control system, the easiest solution is a rupture disc with integrated burst detection. The disc comes complete with a small magnet, which is pulled away from the sensor upon burst giving an open circuit signal if installed with the Flo-Tel™ detection system.
Can I reuse the holder and just replace the disc after it has burst?
Some applications are more suited to an integral holding device, which is also discarded following a burst. However, in most cases, the holders are reusable and it is only the disc which needs to be replaced. In the case of a disc with an independent holder and integrated burst detection (as above), only the disc itself has to be replaced after it functions, also eliminating the need to hold stock of detectors.
Are the disc materials used traceable?
Yes. All disc materials used are traceable and certificates (EN 10204:3.1) can be supplied on request for a nominal charge will be applied.
Should I keep spare discs?
Yes. Although Elfab offers an industry-best lead time on all its products, it is always recommended that you hold spare discs to avoid costly downtime in the event of a burst. If no spares are available and the discs are required immediately, Elfab also offers a Fast-Track express manufacturing service at an additional cost.
Does Elfab keep discs in stock?
No. Every batch of discs is manufactured specifically to order. However, we do stock a large range of raw materials to minimize leads times
What is the standard warranty on Elfab products?
Elfab offers a unique 3-year warranty for its high performance reverse-acting rupture disc, Opti-Gard™. For other products, standard warranty is 12 months in service and 18 months in storage.
What do the part codes on each quote mean?
Due to the technical nature of our products, our quotes contain a lot of information about our products. To help you better understand our quotes, below is an example of what some of our part codes symbolize. REMEMBER – this list is not exhaustive and Elfab provide several part-code variations for individual/specific applications. All sizes are in mm.
Category (First three letters of the part code)
– DSC = Rupture Disc
– VNT = Explosion Vent
– ACC = Accessory
– DET = Detection
– OE = OEM
– HLD = Holder
– HAL = Hastelloy Fluoropolymer Liner
– HAU = Hastelloy Underlined
– INL = Inconel Fluoropolymer Liner
– INU = Inconel Underlined
– MOL = Monel Fluoropolymer Liner
– MOU = Monel Underlined
– NIL = Nickel Fluoropolymer Liner
– NIU = Nickel Underlined
– SSL = Stainless Steel Fluoropolymer Liner
– SSU = Stainless Steel Underlined
– TAL = Tantalum Fluoropolymer Liner
– TAU = Tantalum Underlined
– GRL = Graphite Fluoropolymer Liner
– GRU = Graphite Underlined
Disc Support (Last three figures of the part code)
– XXX = Without vacuum support
– NVS = Non-Opening vacuum support
– OVS = Open vacuum support
– 2WS = Two-way burst – same burst pressure both directions
– 2WD = Two-way burst – different burst pressure in opposite directions
This information is correct at the time of publishing. If you are unsure about anything, please do not hesitate to get in touch with us.