F.A.Q.

What size discs are available?

Depending on disc’s type, DonadonSDD can supply discs from 1/8” (3mm) up to 40” (1000mm) in diameter.

What information is needed in order to be able to specify the correct disc?

You can download here the RUPTURE DISC FORM that will guide You to collect all the data required, which can be also summarized as below specified:

  • required burst pressure & burst temperature
  • nominal size, flange rating & face finishing
  • disc and holder material
  • vacuum resistance (if requested)
  • Pressure Safety Valve protection (if requested)

There are several other factors as well, so DonadonSDD specialists are always at disposal to specify the correct disc for any application. Each and every rupture disc we design and deliver to our customers is scrupulously custom-built, so as to match the industrial plant's specific and unique needs.

What different types of discs are available?

Main Families: Forward / Reverse / Sanitary
The categories of rupture & bursting disks which we manufacture for our customers, are:

What is a Forward-Acting Rupture Disc?

Concave side of the dome faces the process media and functions when the weakest portion of the disc exceeds its tensile strength. Often has a finite fatigue life at higher operating ratios because the stresses are tensile in nature.

What is a Reverse-Acting Rupture Disc?

Convex side of dome faces the process media and functions when the pressure creates an instability in the dome, resulting in buckling of the dome. Often has a longer life cycle that forward-acting designs because they are compressive and do not promote crack propagation.

What is a Sanitary Rupture Disc?

Specifically designed to meet the stringent sanitary and hygienic requirements found in the biotech, pharmaceutical and food and beverage industries, and within ASME, CE and 3-A standards.

What is the standard warranty on DonadonSDD products?

DonadonSDD warrants that the products supplied are free from defects in materials or workmanship, for a period of 18 (eighteen) months from the date of the invoice, or of 12 (twelve) months from the date of installation, whatever starts first.
This warranty does not cover defects due to:

  1. improper use, storage or maintenance by the purchaser or third parties;
  2. repairs, alterations, modifications, replacements carried out by the purchaser or third parties;
  3. normal wear, corrosion and / or erosion;
  4. particular conditions of use (for example, operating pressure too close to the breaking point, vibrations, fatigue, severe thermal cycles or other events that require more frequent replacement);
  5. force majeure events.

What is Specified Set Pressure (also referred to as Burst pressure)?

This is the pressure, requested by the customer, at which the rupture disc opens (it is always associated with a specific temperature). It is selected in such a manner, that the rupture disc opens before there is any system damage. The burst pressure is above the prevailing pressure during normal operation (also referred to as working pressure or process pressure) and below the pressure resistance (MAWP) of the respective system.

What is Specified Temperature?

The temperature of the disc at the time it is expected to burst, and the temperature correlated to the marked burst pressure.

What is Marked Burst Pressure?

The pressure marked on the rupture disc’s tag, which may be shown as a:

  • single value without tolerance
  • single value with tolerance shown
  • min/max range

What is Rupture Tolerance or Burst Tolerance?

The tolerance associated with the marked set pressure within which the disc is expected to burst. Usually expressed as +/- X% or +/- X pressure clearly marked on the tag plate.

What is Operating Ratio?

It’s the margin between the Maximum Recommended Working Pressure and the bottom limit of the burst pressure of the disc.
The maximum operating pressure of the plant on which the disc is installed must not be greated than the value obtained by multiplying the minimum bursting pressure by the operating ratio indicated by DonadonSdd.

What is Manufacturing Range?

A pressure range within which the marked burst pressure must fall. The average of the burst tests must fall within this range. All individual test values must fall within the rupture tolerance. DonadonSDD applies always a 0% Manufacturing Range.

What is Zero Manufacturing Range?

An exception to the normal definition of “manufacturing range.” The disc is marked at the specified burst pressure, not at the average of the burst tests. All of the burst tests must fall within rupture tolerance.

What are Cyclic Conditions?

Large magnitude operating pressure fluctuations. The extreme case is full vacuum to the maximum operating ratio of the disc. The fatigue life of the disc is a function of the disc design, the magnitude of the fluctuations and the positive-to-negative fluctuations.

What is Cycle Life?

Generally, a function of the disc’s stress history (not necessarily the frequency of pressure fluctuations). Frequency may be relevant to the client’s ability to understand the peak pressures the rupture disc endures.

What is Capacity?

The amount of fluid flow that will pass through the device using the coefficient of discharge method.

What is Minimum Net Flow Area (MNFA)?

The discharge area sized using the coefficient of discharge method (Kd = 0.62).

What is Combination Capacity Factor?

The de-rating factor that is applied the rated capacity of a pressure relief valve when a rupture disc device is installed upstream. If a certified value is not available a value of 0.9 may be used.

What is KR?

A unit-less factor that describes the resistance (velocity head loss) the rupture disc device provides to fluid flow.

What is KRG?

The resistance factor determined by flow testing discs burst in compressible vapor. This value can be used for sizing when the disc is in contact with compressible vapor.

What is KRL?

The resistance factor determined by flow testing discs burst in liquid test stand. This value can be used for sizing when the disc is in contact with incompressible liquid.

What is KRGL?

The resistance factor determined by flow testing discs burst both in liquid and compressible vapor. This value can be used for sizing when the disc is in contact with either compressible or incompressible fluid.

What is Scoring?

The manufacturing of the “line of weakness” that may be used to control the rupture disc’s opening characteristics or burst pressure. Various types of scoring are available and include:

  • Laser Ablation – ultra-fast pulsed laser equipment removes material to create a consistent and repeatable line of weakness across an entire lot of rupture discs.
  • Milling – localized removal of material to create a line of weakness by machining processes. May be used in conjunction with other scoring methods on thicker, forward-acting discs.

  • Chemical Etching – the disc surface is masked, leaving the target areas unmasked. Immersion in an electrochemical bath under a controlled set of parameters removes material from the unmasked zones to create a line of weakness.

  • Coining – the disc material flows around the score blade that is pressed into the material, resulting in localized thinning of the material, high residual compressive stresses, and high-stress concentration. In general, the coining process does not cut the material but often does create microscopic mechanical damage to the material.

What if I can't find what I need on the website?

DonadonSdd, alongside its standard range, designs and delivers each rupture disc so as to match the industrial plant's specific and unique needs of each customers, so If you can’t see anything suitable in our web-site, please contact us  at +390290111001 or send a mail to: donadonsdd@donadonsdd.com to discuss your individual application in more detail.

How do I know I receive the correct disc and holder?

The disc will carry a TAG PLATE that displays all the relevant performance details of the disc. As an absolute minimum the disc will carry the DonadonSDD lot number, which can be traced to the test certificate and checked for the correct specification. Additional markings can be added to the disc TAG PLATES to identify its unique location within your plant.

How do I know I have the correct holder for the disc?

The disc should be marked with the same Lot number for new application while the Spare Discs should be marked with the TYPE number of the holder (ex: 230) in which it should be used.

How does the rupture disc fit into my system?

Discs are generally fitted into a holder and mounted between pipe flanges or in same cases can be mounted directly between flanges or clamp ferrules. 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.

How do I know that the holder is fitted into the pipe work in the correct orientation to flow?

To enable correct installation within the system, each DonadonSDD holder is 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 to use a rupture disc indicator (can be integrated in the bursting disc). As soon as the disc bursts, the indicator is broken too giving an open circuit signal if installed with a detection system. When a rupture disc is installed without a burst indicator, it can be checked with a visual inspection, but if this operation is not possible (because of installation site), it’s important to check that there is no flow passage.

How does temperature affect the burst pressure of the disc?

Depending on the disc type and material used for construction, the rupture pressure will generally reduce as the temperature increases, and vice versa.

Can rupture discs replace safety relief valves?

Not always. Rupture discs are safety devices used to protect pressurised systems and equipment from over pressure and/or vacuum. They are devices that perform the same basic function as safety valves. The main difference however being that they intervene as a result of the differential pressure to which they are subjected but then they cannot be re-closed (in fact, they must be replaced once opened). Safety valves and rupture discs can be used separately as primary safety devices or they can be used in combination, giving to the system benefits from the unique advantages of each individual solution but maintaining a reasonable cost.

Can the disc be used on Oxygen clean duty?

Yes. Discs can be supplied cleaned for use in Oxygen Service (please specify on request).

Can I fit a DonadonSDD rupture disc into another manufacturer's holder?

No, installing product in alternative holders will invalidate the CE marking (2014/68/UE), warranty and insurance. As specified by the Pressure Equipment Directive, one manufacture’s rupture disc cannot be placed into another manufacture’s rupture disc holder.

Can I reuse the holder and just replace the disc after it has burst?

In most cases, the holders are reusable and it is only the disc (and relevant burst indicator) which needs to be replaced.
During periodic maintenance, before installing the new rupture disc, always clean the holder surfaces and check to make sure that it’s not damaged (scratched, dented, smeared with foreign material).

Should I keep spare discs?

To avoid plant stops, it is suggested to keep 3 spare rupture discs in stock for each installation.

Does DonadonSDD keep discs in stock?

No. Every Lot of discs is manufactured against specific customer order. However, we keep a wide stock of different raw materials to minimize leads times wherever possible.

Does DonadonSDD have experience with discs in exotic materials?

Yes. The choice of material dependes of the specific operating conditions. DonadonSDD can manufacture discs in several raw materials, as: Stainless Steel, Nickel, Monel, Inconel, Hastelloy, Titanium and Tantalum.

Are the disc materials used traceable?

All disc materials used are traceable and certificates in acc. With EN 10204:3.1. The Material Certificates are always supplied together with the goods without any extraprice. P.M.I. test can be provided on request.

Will a disc withstand back pressure or vacuum?

This depends on the disc design being used. Only Family of “Reverse acting discs” will withstand full vacuum and back pressure without the need of vacuum support, but other designs may require it. Vacuum and/or back pressure conditions should be specified in the request for quotation.