A rupture disk is designed to open at a defined pressure, but “defined” does not mean every disk breaks at one mathematically exact number. In real engineering work, I separate the pressure requested on the purchase order, the pressure marked on the finished disk, and the pressure observed during a destructive burst test. Treating those values as interchangeable can reduce operating margin or create a conflict with the protected equipment's MAWP.
In short, rupture disk accuracy is controlled through a combination of specified burst pressure, manufacturing design range (MDR), marked burst pressure, burst tolerance, specified disk temperature, and production-lot qualification. MDR determines where the marked pressure may fall. Burst tolerance defines the permitted test variation around that marked pressure. Zero MDR does not automatically mean zero burst tolerance.
This guide explains those relationships in practical terms. It also shows why a “100 psi disk” needs more definition before an engineer can confirm the real pressure envelope. Final selection must always follow the applicable code edition, the selected disk model's qualified data, and the manufacturer's documented test basis.
What Does Burst Pressure Tolerance Mean for a Rupture Disk?
Burst pressure tolerance is the permitted variation around a rupture disk's marked burst pressure when representative samples from the production lot are tested at the specified disk temperature. It is not simply a purchasing allowance around the number entered in an RFQ. The reference point matters.
Marked Burst Pressure
The marked burst pressure is the rated value placed on the disk tag or device after production-lot qualification. It is tied to a specified disk temperature. When the applicable system uses an MDR, the marked value may differ from the specified burst pressure originally requested by the buyer.
Actual Burst Pressure
The actual burst pressure is the pressure at which a particular disk opens during a destructive test or service event. Small variation is unavoidable because a rupture disk is a thin, engineered membrane. Material properties, thickness, forming, scoring, temperature, installation, pressure cycling, backpressure, and the rate of pressure rise can all influence performance.
This does not mean rupture disks are uncontrolled. It means their performance is qualified within a defined range rather than calibrated one by one like reusable pressure transmitters.
How Accurate Are Rupture Disks in Practice?
A correctly selected and manufactured rupture disk is expected to perform within the tolerance stated for its marked pressure, temperature, model, size, material, and applicable standard. However, there is no responsible universal answer such as “all rupture disks are accurate to ±5%.”
ASME Burst Pressure Tolerances
For many ASME applications, a common rule is ±5% for marked burst pressures above 40 psig. In the 15–40 psig range, the tolerance is commonly expressed as an absolute value of ±2 psig. Very low-pressure products may use different product-specific limits. The exact boundary, units, code treatment, and available tighter tolerance should be confirmed against the current applicable code and the selected manufacturer's qualified data.
| Marked Burst Pressure Region | Common ASME-Oriented Treatment | Selection Note |
|---|---|---|
| Above 40 psig | Often ±5% of marked burst pressure | Confirm product data and applicable code edition. |
| 15–40 psig | Often ±2 psig around marked burst pressure | An absolute tolerance has a larger percentage effect at lower pressure. |
| Below 15 psig | Product- and manufacturer-specific | Request the exact minimum/maximum performance range. |
Manufacturer-Specific Tolerances
Some disk designs and manufacturing methods can provide a tighter performance band than the maximum allowed by a general code rule. A tighter value is useful only when it is documented for the exact product configuration. Never apply a premium model's tolerance to another disk type, size, material, or pressure range.
What Is the Difference Between Specified and Marked Burst Pressure?
Specified Burst Pressure
The specified burst pressure is the target pressure supplied by the user or design engineer for a defined disk temperature. It is an engineering input used for manufacturing and selection. A complete specification also states the pressure unit, gauge or absolute basis where needed, coincident disk temperature, required MDR, and applicable code.
Marked Burst Pressure
The marked burst pressure is the value assigned to the finished production lot and shown on the disk tag or nameplate. It is normally based on qualification testing and must fall within the agreed MDR. Therefore, a disk ordered at 100 psig may not always be marked 100 psig when a non-zero MDR is accepted.
The actual tag format depends on the product and certification route. During receiving inspection, compare the tag, purchase specification, test certificate, holder, and protected equipment data as one package.
What Is Manufacturing Design Range and Why Does It Matter?
Manufacturing design range is the agreed pressure range within which the marked burst pressure may fall for a requested specification. It accounts for the practical manufacturing range needed to produce and qualify a lot. MDR does not lower product quality; it defines the acceptable relationship between the requested value and the final marked value.
Standard Manufacturing Range
A standard MDR is the normal range offered for a particular disk design. Its direction and magnitude are product-specific. Many modern products use a range at or below the specified pressure, but older or specialized designs may differ. What changes is the possible marked pressure. What does not change is the need to meet the applicable burst tolerance around that marked value.
Reduced Manufacturing Range
A reduced MDR narrows the permitted marked-pressure window. This can help when the space between normal operating pressure and MAWP is limited. It may also affect price or lead time because manufacturing acceptance becomes more restrictive.
Zero Manufacturing Range
Zero MDR means the marked burst pressure is intended to match the specified burst pressure without an additional manufacturing-range shift. What changes is the relationship between specified and marked pressure. What does not automatically change is the burst tolerance used to qualify the lot.
Is Manufacturing Design Range the Same as Burst Tolerance?
No. MDR and burst tolerance act at different stages and use different reference points. I use the following distinction during a specification review:
| Parameter | Manufacturing Design Range | Burst Pressure Tolerance |
|---|---|---|
| Controls | Where the marked burst pressure may fall | Acceptable burst-test variation |
| Reference | Specified burst pressure or agreed range | Marked burst pressure |
| Determined by | Product design and agreed manufacturer option | Applicable code and qualified product performance |
| Can zero be specified? | Yes, when available for the selected product | Not implied by zero MDR |
| Used during | Specification and manufacture | Production-lot qualification |
Does Zero Manufacturing Range Mean Zero Tolerance?
No. With zero MDR, the specified and marked values can be the same. The production lot still needs an allowed burst-performance band unless a separately documented product specification states otherwise. Confusing these two concepts can make the minimum and maximum expected test pressures look much tighter than they really are.
How Does Temperature Affect Rupture Disk Burst Pressure?
Specified Disk Temperature
A burst rating is valid at its specified disk temperature. Material strength changes with temperature, so pressure must not be stated without the temperature basis. The National Board explains that the relevant value is the temperature of the disk when it is expected to burst, sometimes called the coincident temperature.
Process Temperature vs. Actual Disk Temperature
The disk may be installed in an uninsulated nozzle, dead leg, traced line, or location exposed to ambient weather. Its temperature can differ from the vessel design temperature and bulk process temperature. Upset conditions, a runaway reaction, flashing, steam-out, cryogenic cooldown, and solar exposure can change the governing case.
Why Re-Rating May Be Required
If the real disk temperature differs materially from the original specification, do not assume the old marked pressure remains valid for the new condition. Ask the manufacturer to review the disk material, construction, temperature correction, holder, gaskets, and certification requirements. A statement such as “100 psig ±5%” is incomplete unless the specified disk temperature is also known.
How Are Rupture Disk Burst Tolerances Verified?
A rupture disk is a non-reclosing device. Once it is burst-tested, it is destroyed and cannot be installed in service. For that reason, qualification is normally based on representative destructive tests from a traceable production lot, not individual calibration of every disk that will be shipped.
Rupture disks performance test
Production Lot Testing
A manufacturing lot groups disks made under controlled and traceable conditions. Representative samples are selected according to the applicable quality and code procedure. The tested samples must represent the released lot.
Destructive Sample Testing
The sample is installed in the correct test assembly and brought to the specified test temperature. Calibrated instrumentation records the pressure at opening. The results are evaluated against the marked pressure and required tolerance. The exact sample quantity and acceptance method depend on the applicable code, product, and manufacturing procedure.
Lot Traceability and Certificates
Traceability connects the material, production process, test samples, marked data, and supplied disks. A burst test certificate can document the lot number, disk type, material, size, test temperature, marked pressure, and test results as required. This record is also important when replacement disks are ordered.
What Does a 100 PSI Rupture Disk Actually Mean?
The following simplified examples show why the number on a purchase order is not enough. They are teaching examples, not a substitute for a project-specific selection calculation.
Example 1: Zero MDR
- Specified burst pressure: 100 psig
- Manufacturing design range: Zero
- Marked burst pressure: 100 psig
- Assumed burst tolerance: ±5%
Zero MDR keeps the specified and marked values aligned. The separate burst tolerance still creates an allowed qualification band.
Example 2: Non-Zero MDR
- Specified burst pressure: 100 psig
- Teaching MDR: −10% to 0%
- Final marked burst pressure: 95 psig
- Assumed burst tolerance: ±5%
The tolerance is applied around the final marked pressure of 95 psig, not automatically around the 100 psig entered on the order.
How Does Burst Pressure Tolerance Affect MAWP Protection?
MAWP is an equipment limit, not merely a convenient rupture disk ordering number. The marked burst pressure, MDR limits, permitted accumulation, other relief devices, backpressure, and the applicable code must be reviewed together. The National Board specifically warns that an MDR can produce a marked pressure above the vessel MAWP if the specification is not developed correctly.
Do not assume that specifying a burst pressure equal to MAWP always creates a compliant finished selection. Check the upper MDR boundary and final marked value. When a single device protects the equipment, the applicable code may restrict the marked set or burst pressure relative to MAWP. Multiple-device installations and special cases require their own review.
Does Burst Pressure Tolerance Affect the Operating Ratio?
Operating ratio is another separate parameter. It indicates how close normal operating pressure may run to the relevant burst-pressure basis for the selected disk design. It should not be calculated only as operating pressure divided by the nominal value typed into the purchase order.
A complete check may need to consider:
- Maximum normal operating pressure, including startup, shutdown, pulsation, and control variation
- Specified and marked burst pressure
- Upper and lower MDR boundaries
- Burst tolerance, especially for low-pressure disks
- The selected model's recommended operating ratio
- Temperature, phase, cycling, corrosion, vacuum, and backpressure
For a broader selection workflow, read BasCo's Rupture Disk Selection Guide.
What Should You Specify When Ordering a Rupture Disk?
A useful RFQ gives the manufacturer enough information to reproduce the intended pressure basis and check the complete application. At minimum, include:
Include units and gauge/absolute basis where relevant.
Use the expected disk temperature at the burst condition.
State the required range or ask for available options.
Include routine variation, cycling, startup, and shutdown.
Provide the governing equipment and code limits.
Fluid, phase, corrosion, vacuum, and backpressure.
Confirm the assembly and installation requirements.
Identify project, country, and documentation needs.
Provide it when ordering replacements.
List burst test, material, traceability, and inspection records.
Which BasCo Rupture Disk Design Fits the Application?
Burst pressure tolerance is only one part of selection. The disk construction must also match the operating ratio, pressure cycling, process phase, corrosion conditions, vacuum, backpressure, temperature, holder, and required relief path. The following BasCo products illustrate forward-acting, composite, and reverse-acting options. Click a product to review its dedicated page.
1110 Forward Acting Scored Rupture Disk / LC Type 
1120 Forward Acting Composite Rupture Disk / LF Type 
1310 Reverse Acting Scored Rupture Disk / YC Series 
1311 Reverse Acting with Groove Prefabricated Rupture Disk / YCP Series What Are the Most Common Burst Pressure Tolerance Mistakes?
- Assuming the ordered pressure is always the marked pressure. A non-zero MDR can allow the final marked value to differ.
- Confusing MDR with burst tolerance. MDR controls the marked-pressure range; tolerance controls variation around the marked value.
- Assuming zero MDR means zero tolerance. These are separate specifications.
- Ignoring specified disk temperature. A pressure rating without its temperature basis is incomplete.
- Comparing operating pressure only with nominal burst pressure. Include MDR, tolerance, operating ratio, cycling, and process conditions.
- Using ±5% as a universal rule. Lower-pressure disks and specific designs may use an absolute or tighter product-specific tolerance.
- Reordering only from the old nameplate. Use the original lot record and specification to preserve the intended design basis.
- Assuming every shipped disk was individually burst-tested. Burst testing is destructive; qualification relies on representative samples from a controlled lot.
Not Sure What Burst Pressure or MDR to Specify?
Send BasCo your maximum operating pressure, MAWP, expected disk temperature at burst, process medium, backpressure, required code, and operating conditions. Our team can review the pressure relationship and help identify an appropriate rupture disk configuration.
Request a Selection Review View Rupture Disks- ASME BPVC Section XIII — Rules for Overpressure Protection
- API 520 Part I — Sizing and Selection of Pressure-Relieving Devices
- National Board — Specification of Rupture Disk Burst Pressure
Disclaimer: This article provides general technical education. It does not replace the current applicable code, relief-system calculation, equipment design review, or written product data for the selected rupture disk and holder.
