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EN 13555 Data


EN 13555 Vocabulary

The creep relaxation factor (PQR-value) is the ratio between initial and residual surface pressure of a gasket from installation to operation. It is determined by mounting the gasket with an initial surface pressure and measuring the remaining surface pressure after a defined time of exposure to the surface pressure and the (test or operating) temperature. This ratio can be used as a factor to draw conclusions about the remaining surface pressure in the case of an installation surface pressure.

Intrusion into the inner diameter is when, after the test to determine QSmax or PQR, the inner diameter of the tested gasket is reduced to such an extent that it intrudes into the inner diameter of the pipe, which is representative of the tested size. For DN40/PN40 this is 43.1mm. In EN 13555-2014, the intrusion of the gasket into this bore was introduced for the first time and specified there as a failure criterion when determining the maximum surface pressure (QSmax). On data sheets according to EN13555 2014 and earlier, no values may be included where intrusion has occurred (even if these are identified as intrusion values in some form). In the 2021 version of EN 13555, the weighting of intrusion has been weakened and is now no longer one of the failure criteria, and values where intrusion has occurred may be included on an EN 13555-2021 data sheet. It must be taken into account that these intrusion values are marked as such in a suitable manner.

The QSmax value is the surface pressure up to which the gasket material may be loaded. The QSmax-value is only valid for the corresponding temperature. If the gasket is subjected to a higher load, this will lead to failure of the gasket element typically due to mechanical failure.

Qmin(L) is the minimum surface pressure on the gasket during assembly, at room temperature (ambient temperature) and a specified internal pressure, in order to achieve the required tightness class (L). Leakage values and thus also the value Qmin(L) are also discussed in a separate help article on leakage data.

QSmin(L) is the minimum surface pressure on the gasket under service conditions to achieve the required tightness class (L). Leakage values and thus also the value QSmin(L) are also the subject of a separate help article on leakage data.

The tightness classes LN (L1.0, L0.1, L0.01, ...) represent the maximum limit for a specific leakage. If a tightness class is to be complied with by a gasket, the leakage under the defined conditions must not be higher than permitted by the tightness class.

QA is defined as the surface pressure of the gasket in the assembly condition.

ΔeGc is the thickness change of the gasket determined by creep and or relaxation from initial surface pressure to final surface pressure in the test PQR. The value was included in EN 13555 2014. It can be calculated from existing data using the following formula:
ΔeGc(K,QI,T) = (AG × QI  × (1 - PQR(K,QI,T))) / K

Note: In the data on gasketdata. org the calculated δeGc should be used.

QA is the surface of the gasket that experiences surface pressure. It is therefore the area that is in contact with the flange surfaces and is compressed. This area refers to the tested size and is different for other sizes and different flanges. It is calculated from the largest inner diameter of the flange (raised face) or gasket and the smallest outer diameter of the flange (raised face) or gasket. The part of the gasket is taken into account that is actually in contact with the sealing surfaces of the flange.

Force per area with which the seal is pressed against the sealing surfaces

EN 13555 Data and Testing

Seals according to standard series EN1514 or EN12560 will be tested on flange sealing surfaces acc. to EN1092-1, DN40/PN40 or EN1759-1, NPS 4 Class 300

Gasket data according to EN 13555 is determined either with gaskets of the dimension DN40/PN40 or NPS 4"/Class 300. The test-flanges must have a size accordingly, chosen from the standard EN 1092-1 (DN40/PN40) or EN 1759-1 (NPS 4"/Class 300). All values for one gasket have to be determined with one size, mixing values determined by using different dimensions is not allowed.

Currently there is no possibility to determine values for RTJ-Gaskets according to EN 13555. Therefore a calculation according EN 1591-1 is also not possible. See help topic on metallic seals for more detailed info.

The basis of each data sheet is a complete data set of the gasket to be published. The Gaskets Workgropu (AK Dichtungen) has defined the following minimum requirements for data sheets to be published:

  • Determination of leakage at a test pressure, preferably at 40 bar
  • Mechanical characteristic values (EG, QSmax, PQR) must be given for room temperature and two elevated temperatures. The temperatures must be chosen equally for the mechanical parameters. If the highest temperature is <= 80°C, room temperature and one elevated temperature shall be sufficient.
  • For at least two initial surface pressures and the maximum surface pressure QSmax, PQR values shall be provided for each test temperature. If at one temperature the maximum surface pressure QSmax is <= 50 MPa, the specification of two PQR-values for this temperature - at QSmax and another initial surface pressure - is sufficiant.
  • Double tests must be carried out, from which the arithmetic mean is calculated and published.

The revision number is a unique number of the data revision of each gasket. The revision number always starts with 1. With every change of the data or even editorial changes the revision number is incremented by 1. There is no change in data without change of the revision number. Every data-revision has a corresponding revision date. The revision date (or sometimes refered as creation date of the datasheet) is defined as the date the data is published on There was a minor change from the Pre-2021-Database, please see the corresponding FAQ-topic.

As a rule, the revision numbers have remained the same after transfer to the reprogrammed database in the 2021 database structure. In the early days of the database, versioning of data was not yet assumed and therefore no revision number was noted on the data sheets. When revision numbers were introduced, all first revisions of a gasket were given revision 1. Existing revisions without a revision number were treated as revision 0. The versioning of the new database structure also uses revision number 1 for the first version of the data and it is not intended and possible to use revision number 0. Therefore, it may happen that a gasket with the same revision level has a revision number 1 higher.


Use 'Filter Results' when on the database page to show the filter options. At the top of the filters you will find the slider for the operating temperature range. Move the dots from outside to inside to adjust the temperatures. If the respective slider is all the way outside, it will not be applied.If only the lower temperature (left) is set, then only gaskets with characteristics at temperatures <= the set temperature and characteristics at >= temperatures are displayed. If the right slider is set, then only gaskets are displayed that have characteristic values with at least the temperature.

Gaskets from this category have a geometry that deviates from the standard geometry or a material combination that is not specified in the standard. However, the characteristic values are determined according to standard EN 13555 in the respective standard status and can be used for calculations.

Recent Changes feature

There are several ways to see the recent changes made to gaskets, gasket data, certificates and further admissions. If you open the item Database in the website-menu you already see a shortcut to the last changes. Open the menu Service you will find the item Recent Changes which will show a more extensive list of recently changed data. Also there is a RSS-Feed and a Newsletter - there are special FAQ-items describing those features.

We implemented different features how you can get updates on the changes happening to the database. The most common things are the Newsletter and the RSS-Feed. A more sophisticated way is to use the API for staying up-to-date. Please see the FAQ-items below.

We offer a RSS-Feed service for new and updated Gaskets or gasket data as well as updated documents like certificates and admissions. The feed is free of charge an can be polled using a RSS-Feed-Reader App. Use as the address for your feed reader.

The RSS-Feed we offer is in a standardized scheme so literally speaking every RSS-Feed App should do the job. For iPhone and iPad you can use NetNewsWire, on Android devices Feeder to name but a few. For your PC you can use RSS-Reader plugins for your favorite browser. The mentioned Apps are published under a open-source licence at time of writing. We are not affiliated to the persons or companies offering the Apps

If your App does not automatically set a polling interval for the RSS-Feed we recommend to set it to a value of 1 hour to 24 hours. That way you will get an update at least once a day. If there is no update to the database there will be no update to the RSS-Feed.

Yes. Please enter your email in the newsletter-form on the bottom of this page. You will be periodically informed about changes. The email on changes will only send to you if there are any.

Of course the API can used to obtain the updates to the database. Because this is a very sophisticated way to use the database, the use of the API is described on this extra page.

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