EN IEC 61810-2-1 Electromechanical Basic Relays - Part 2-1: Reliability - Procedure for Verification of B10 Values

The standard "EN IEC 61810-2-1 Electromechanical basic relays - Part 2-1: Reliability - Procedure for verification of B10 values", which has its basis in a European standard and was subsequently published by the International Electrotechnical Commission (IEC), describes the reliability test procedures for electromechanical basic relays when the requirements developed for verification of reliability are applied. This standard contains specific provisions for relays incorporated in safety-related control systems of machines in accordance with IEC 62061 and ISO 13849-1. The B10 values for dangerous failures (B10d values) for such relays are derived from the tests specified in this standard.

For the purposes of this standard, the terms and definitions given in IEC 61810-2 as well as the following definitions apply:

Hazardous failure refers to a failure that has the potential to place the safety-related portion of a control system in a hazardous or dysfunctional state.
Type testing refers to conformance testing performed on a representative sample of production to obtain essential performance data for production or to verify that these relays comply with specified requirements.
Routine testing refers to conformity testing performed on a sample with specified repetitions without any modifications or specification changes during or after mass production. The results obtained from routine testing are used to verify that the technical performance level is maintained.

This standard includes the requirements for the evaluation and verification of the reliability of the relay (verification of B10). This procedure is valid for relays where wear mechanisms prevail. Measures must be taken for relays where random failures occur. The principles of this standard are also applied for relays intended for use in safety-related control systems of machines.

According to this standard, the following failure modes can occur:

Relay contact cannot be opened
Failure to close relay contact
Unwanted bridging of the changeover contact
Insulation failure of relay

From the type test, the B10 value is obtained, which indicates the probability of relay failure. The B10 value is given as the number of cycles. By knowing the operating frequency (cycle ratio) of the relay in a particular application, the number of cycles can be converted into the corresponding times. Verification that this B10 value is valid for production series relays should be done by routine testing.

The requirements in this standard are given as follows:

Test samples: Tests are carried out in accordance with the IEC 61810-2 standard.
Test circuit: Unless otherwise specified by the manufacturer and clearly stated in the test report, the test circuit described in Annex C of the IEC 61810-1 standard should be used. Whenever possible, one of the circuits conforming to Annex D of the IEC 61810-1 standard should be used.
Contact loads: Contact loads must be determined by the manufacturer and stated in the test report. It is recommended to select suitable resistive loads according to IEC 61810-1 standard or inductive loads according to IEC 61810-1 standard Annex B.
Environmental conditions: The conditions in the table given in the IEC 61810-1 standard are valid. However, an extended ambient temperature range of 18 degrees to 40 degrees is allowed.
Operating conditions: The provisions of standard IEC 61810-2 apply. Unless otherwise specified by the manufacturer, each cycle of coil energization shall be 1 second on and 9 seconds off. Unless explicitly stated otherwise, the test is performed without coil bias.
Failure criteria: In general, testing is continued until all test specimens fail. When the test is interrupted at a certain number of cycles, all relays that have not yet failed are considered to have failed at that number of cycles. However, at least 2/3 of the tested relays fail or each test specimen reaches a life of 10 M cycles. In the evaluation of recorded failures, severity B is applied according to the IEC 61810-2 standard.

Dielectric testing is performed at the following points:

Between coil and contacts
Between adjacent contacts
Between open contacts

A non-opening contact cannot be tested for compliance with the requirements for open contacts. The insulation requirements are verified according to the IEC 61810-1 standard. This can be achieved in one of the following ways.

During the test, the dielectric test is performed periodically with a certain number of cycles. When the relay fails the dielectric test, the number of cycles that have previously passed the dielectric test is considered as the failure cycle value for this relay.
If periodic monitoring is not performed in the manner described above, the dielectric test is performed when the relay under test fails due to a functional contact failure. If the relay fails the dielectric test, it is deemed to have failed the entire test. The same applies if the test is interrupted for a certain number of cycles.

The type test is performed with a sample of 10 relays. Each fault is recorded. The B10 value is evaluated according to the procedure given in the IEC 61810-2 standard. For routine testing purposes, the shape parameter and characteristic life are evaluated according to the IEC 61810-2 standard. After the type test is completed, the first routine test is started for verification in accordance with the specified periodicity.

Routine tests should be performed at specific intervals specific to the manufacturer.

This standard specifies the requirements for relays designed for use in safety-related control systems of machines in accordance with IEC 62061 and ISO 13849-1. This procedure is valid for relays where wear mechanisms predominate. The following failure modes may occur in these tests:

Relay contact cannot be opened
Failure to close relay contact
Unwanted bridging of the changeover contact
Insulation failure of relay

For a specific application, these are evaluated strictly in terms of the listed failure modes and hazardous failures are taken into account.

By using forcibly guided (mechanically linked) contacts, which offer a high diagnostic coverage, simultaneous closing of the opening and closing contacts is prevented. Electromechanical basic relays with forcibly guided contacts are specified in the IEC 61810-3 standard.

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