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Reference

How to read
a gasket datasheet —
temperature, pressure, approvals

A gasket datasheet lists peak temperature, continuous temperature, max pressure, compressibility, leak rate and approval codes. Most engineers focus on only two or three of these. The important point is to know which ones are load-bearing for the actual duty.
This article explains what each property means, which ones are commonly misread, and how to use datasheet values correctly when selecting or specifying a flat gasket.
Kinetics Line Standards & Reference 9 min read
How to read a gasket datasheet — annotated example A mock gasket datasheet with the six key sections highlighted: identity, temperature, pressure, compressibility, leak rate and approvals. DATASHEET — WHAT TO READ FIRST GREENSEAL PRO 180 Cellulose-synthetic fibre · NBR binder · sheet 1.0–3.0 mm TEMPERATURE −40 to 180°C continuous · 220°C peak PRESSURE PN 40 (40 bar nominal, derate above 100°C) COMPRESSIBILITY · RECOVERY 9% / 50% (DIN 28090-2) SPECIFIC LEAK RATE (λ) ≤ 0.10 mg/(s·m) at 30 MPa (DIN 28090-2) APPROVALS · DOCUMENTATION FDA KTW/UBA DVGW (—) Issue 04 / 2026 · Verify against current technical data sheet before specifying 1 · IDENTITY Material family + binder + thickness range 2 · TEMPERATURE Continuous ≠ peak — design for continuous 3 · PRESSURE PN rating drops with temperature — check curve 4 · COMPRESSIBILITY Higher % = better seal on rough faces 5 · LEAK RATE (λ) Lower = tighter — only meaningful with test method 6 · APPROVALS Match jurisdiction to medium — gas, drinking water, food Dashed = not held / verify scope
Six rows decide whether a gasket is the right one for the job.

The structure of a flat gasket datasheet

A typical flat gasket technical data sheet contains four categories of information:

  • Service limits — maximum temperature (peak and continuous), maximum pressure, and the important note that these limits are not for simultaneous use
  • Mechanical properties — compressibility, elastic recovery, tensile strength, residual stress under load
  • Sealing performance — specific leak rate, thickness increase in oil or fuel
  • Approvals and certifications — which regulatory standards the material has been tested against

Each category serves a different purpose in specification. Service limits establish whether the material is broadly rated for the duty, while mechanical properties and sealing data help show whether it will seal reliably at the loads and conditions actually available in the joint. Approvals confirm compliance with relevant regulatory requirements for the specific medium.

Temperature — the most commonly misread property

Peak temperature ≠ continuous temperature. Specifying a gasket by its peak temperature when it will operate continuously near that figure is one of the most common causes of premature gasket failure.

Peak (Max Service) Temperature e.g. 180°C
The maximum temperature the material can withstand for short periods — typically during startup, shutdown, steam cleaning or transient pressure spikes. The gasket will not immediately fail at this temperature, but sustained operation at or near this limit will cause accelerated degradation.
⚠ This is not the operating limit. It is the survival limit under transient conditions.
Continuous Temperature e.g. 140°C
The maximum temperature at which the gasket can operate in sustained normal service. This is the operative limit for most applications. A gasket operating continuously near its peak temperature — rather than its continuous limit — will typically show accelerated compression set, loss of residual bolt load and earlier seal failure.
Steam Temperature e.g. 120°C
Where stated separately, the steam temperature limit is lower than the dry heat continuous limit. Steam penetrates fibrous gasket materials differently than dry gas or liquid, and the combination of moisture and heat degrades certain binder systems faster. If the application involves steam, this is the correct temperature limit to apply — not the general continuous limit.

Illustrative example based on the published GREENSEAL PRO 180 TDS: peak 180°C · continuous 140°C · steam 120°C. An application running at 150°C continuous on a heating circuit is above the continuous rating of this material. The peak figure (180°C) appears to have headroom, but the continuous rating does not. The correct material for that duty would be a higher-rated aramid grade.

Pressure — and why it cannot be combined with peak temperature

Datasheets typically carry a note: "Max temperature and max pressure ratings are not for simultaneous use." This is not boilerplate — it reflects a real limitation in how gasket materials behave.

At elevated temperature, fibre gasket materials soften and become more susceptible to creep under bolt load. At maximum pressure, the full structural and sealing capacity of the joint is already engaged. Combining both limits creates conditions beyond the basis on which either rating was established. In practice, applications close to either limit usually require additional margin and reference to the manufacturer's guidance or the relevant joint design basis, rather than treating the headline limits as directly usable design numbers.

The max pressure stated on a datasheet is also assembly-dependent. It assumes correct flange geometry, adequate bolt load and proper installation. An under-torqued joint or a damaged flange face will reduce effective pressure rating regardless of what the material is rated for.

Mechanical properties — compressibility and recovery

Compressibility ASTM F36 e.g. 9%
The percentage reduction in gasket thickness under a defined compressive load. A higher compressibility means the gasket conforms more readily to surface irregularities on the flange face — useful where face finish is variable or where the flange is not perfectly flat. A lower compressibility usually indicates a stiffer grade, which may be preferable on smoother flanges or at higher bolt loads, but extrusion resistance still depends on the full material system and joint conditions. Standard cellulose grades typically show 7–12% compressibility. High-compressibility grades may reach 20–30%.
Elastic Recovery ASTM F36 e.g. 60%
The percentage of compressed thickness the gasket recovers when the load is released. A higher recovery means the gasket better maintains contact with both flange faces when pressure fluctuations or thermal cycling temporarily reduce bolt load. A gasket with low recovery that has been compressed may not return to fill the sealing gap if load is momentarily reduced. This is particularly relevant in systems with thermal cycling.
Residual Stress DIN 52913 e.g. 20 MPa
The remaining clamping force in the gasket after prolonged exposure to elevated temperature under load. Tested at a defined temperature and time (e.g. 50 MPa initial load, 175°C, 16 hours). Higher residual stress means the gasket retains more sealing force after thermal exposure — relevant in high-temperature applications where long-term bolt load retention matters. A gasket that retains very little residual stress is more likely to lose sealing margin in high-temperature service, particularly where bolt load retention is already limited.
Tensile Strength ASTM F152 e.g. 8 MPa
The force per unit area at which the gasket material tears when pulled. Relevant where gaskets are cut to non-standard geometries, where narrow cross sections are used, or where there is risk of gasket blow-out under pressure. A higher tensile strength provides more resistance to mechanical damage during handling and to pressure-driven extrusion or blow-out in service.

Sealing performance — leak rate and media compatibility

Specific Leak Rate DIN 3535-6 e.g. 0.04 mg/s·m
The mass flow rate of test gas (typically nitrogen) leaking through a unit length of gasket under defined test conditions. A lower number means better sealing performance under the test conditions. This is one of the more direct sealing-performance indicators on the datasheet, but only within the defined laboratory test conditions. It is also referenced in TA-Luft and industrial emission compliance contexts. Note that leak rate is measured under specific laboratory conditions — actual field performance depends on flange condition, bolt load, and assembly quality.
Thickness Increase in Oil / Fuel ASTM F146 e.g. 10%
The percentage increase in gasket thickness after immersion in a test fluid (oil or fuel) at defined temperature and time. A lower percentage means the material is more resistant to swell in that fluid — relevant where the gasket is in contact with oils, fuels or solvents. Significant swell can cause the gasket to extrude from the joint or change its sealing characteristics over time.

Reading the approval codes

Approval codes on a gasket datasheet indicate that the material has been tested, listed or documented for a specific medium or application context. An approval does not mean the gasket is suitable for all media — it means it met the specific test or documentation requirements for that scope.

Code Body What it covers Scope
WRAS Water Regulations Advisory Scheme (UK) Contact with potable water — UK Extraction and migration testing for drinking water contact. Required for water supply fittings in the UK.
DVGW Deutscher Verein des Gas- und Wasserfaches (DE) Gas and water applications — Germany and EU Testing for gas-tightness, water compatibility and material suitability. Widely specified in European gas distribution.
KTW / KTW-BWGL Kunststoffe im Trinkwasser / UBA evaluation basis (DE) Plastics and elastomers in contact with drinking water — Germany; check current KTW-BWGL / UBA scope where applicable Migration testing for drinking water contact materials. German market requirement.
FDA 21 CFR Food and Drug Administration (US) Food-contact materials — United States FDA 21 CFR references specific food-contact regulatory sections, and only the cited section applies. It does not by itself imply suitability for every food medium, temperature or contact condition.
BAM Bundesanstalt für Materialforschung (DE) Oxygen-compatible materials Required for sealing materials in oxygen service. BAM documentation must be checked against the tested pressure, temperature, oxygen medium and report conditions.
TA-Luft Technische Anleitung Luft (DE) Fugitive emissions — industrial plant German clean-air regulation tied to defined fugitive-emission leak rates for industrial flanges. TA-Luft documentation is a leak-rate reference, not a general gas approval.
TZW Technologiezentrum Wasser (DE) Drinking water contact — Germany Independent testing institute for drinking water materials. TZW approval is required for some German potable water applications alongside or instead of DVGW W270.
CRECEP Centre de Recherche et de Contrôle des Eaux de Paris (FR) Drinking water contact — France French approval for materials in contact with potable water. Required for water supply applications in the French market.

Approvals are material-specific and grade-specific. Approvals should be checked against the specific grade, thickness range and product form actually being supplied, rather than assumed across nominally similar variants of the same material family. Always confirm the approval applies to the specific product being used, not just the material family.

Approvals also do not substitute for application engineering. A gasket carrying WRAS documentation is listed for potable-water contact only within its scope, listed conditions and maximum water temperature — and still needs to match the pressure and joint geometry of the actual installation.

An annotated example — GREENSEAL PRO 180

Illustrative example GREENSEAL PRO 180 — Cellulose + Synthetic Fibres + NBR — values from published TDS
Property
Value
What it means
Max Service Temperature (peak)
180°C
Short-term survival limit — not the continuous operating limit
Continuous Temperature
140°C
The operative limit for sustained service — use this for selection
Steam Temperature
120°C
Lower limit applies when the medium is steam — not dry heat
Max Pressure
40 bar
Assembly-dependent — not for simultaneous use with peak temperature
Compressibility (ASTM F36)
9%
Low compressibility — stiff grade, better for smooth flanges and higher bolt loads
Elastic Recovery (ASTM F36)
60%
Maintains sealing contact through moderate pressure fluctuations
Residual Stress (DIN 52913)
20 MPa
Adequate bolt load retention at the test conditions (50 MPa / 175°C / 16h)
Specific Leak Rate (DIN 3535-6)
0.04 mg/s·m
Low leak rate for standard industrial service at 2.0mm thickness
Approvals
FDA · KTW/UBA
Listed for relevant extraction tests per cited approval scope — not blanket approval for all media or conditions

Common specification errors

  • Using peak temperature as the operating limit. Peak temperature is a transient survival figure. Continuous temperature is the correct selection parameter for sustained service.
  • Assuming max temperature and max pressure can be applied together. Both limits cannot be simultaneously applied — the datasheet note is technically significant, not administrative.
  • Selecting by approval code alone without checking temperature and pressure. A documented material is not automatically suitable. The approval or compliance reference confirms only its stated test or regulatory scope. Temperature and pressure still need to be within the material's rated limits for the specific duty.
  • Treating one grade's approval as applying to the whole material family. Approvals should be checked against the specific grade, thickness range and product form actually being supplied, rather than assumed across an entire material family.
  • Ignoring the test standard behind each property. Compressibility measured by ASTM F36 and compressibility measured by DIN 52913 are not directly comparable. When comparing datasheets from different manufacturers, verify that properties are measured by the same test standard before drawing conclusions.

Treat continuous temperature as the primary operating limit and peak temperature as a short-duration excursion limit. Check pressure separately. Confirm the approval covers the actual medium and duty.

A gasket datasheet contains more information than most selections use. Peak temperature is not the operating limit. Max pressure is assembly-dependent and cannot be combined with peak temperature. Approvals are grade-specific and confirm media compatibility — not automatic suitability for all conditions. Reading these correctly is what separates a selection based on the datasheet from one based on its headline numbers.

Explore Kinetics Line gasket grades → Drinking water gasket selection →
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