Slide background




Il nuovo Standard ISO 24119 e il massimo PL raggiungibile in caso di serie di dispositivi di interblocco

ID 1610 | | Visite: 7945 | Documenti Estratti NormePermalink: https://www.certifico.com/id/1610




ISO/DTR 24119
Safety of machinery - Evaluation of fault masking serial connection of guard interlocking devices with potential free contacts.

This is currently under committee review, with an expectation that it will be available quite soon as ISO/TR 24119.

This TR has not been published but it will deal with.

The Technical Report illustrates and explains principles of fault masking in applications where multiple interlocking devices with potential free contacts are connected in series to one logic unit which does the diagnostics.

It provides also a guide how to estimate the probability of fault masking and the maximum DC for the involved position switches.

In simple terms, if we have more than one frequently opened guard (once per hour) the level of Diagnostic Coverage falls to zero, which in EN ISO 13849-1 results in a maximum PLc.

It remains to be seen exactly what ISO/PDTR 24119 has to say about the maximum PL achievable when several infrequently operated guards are connected, but it is very likely to be PLd where careful analysis is possible (for example, the number of guards, the type of switches, type of wiring, distance between guards, and accessibility of guards), otherwise it is more likely to be PLc.

It is definitely not possible to achieve PL e with more than one guard switch connected in series, at least not when using volt-free based interlock switch technology.

Early signs are that the technical report ISO/PDTR 24119 will provide two methods for evaluating the extent to which diagnostic coverage is impacted by masking:

1. Simplified method for the determination of the maximum achievable DC

Table 1 provides a simplified approach for the determination of the maximum achievable DC taking into account the probability of masking.

If the maximum achievable DC resulting from the application of this table does not meet the required level, the more detailed approach given in 2 may be more suitable - but this is not ideal.


2. Regular method for the determination of the maximum achievable DC

2.1 Estimation of the fault masking probability

The probability of fault masking is dependent on several parameters that should be considered, including:

  • Number of series connected devices
  • Actuation frequency of each movable guard
  • Distance between the movable guards
  • Accessibility of the movable guards
  • Number of operators

The maximum achievable DC depends on the fault masking probability level (FM) and the type of cabling used in combination with the switch arrangement and the diagnostic capabilities of the overall system to detect faults.

Tables 3 to 5 show the maximum reachable DC depending on those parameters.

In any case, if it is foreseeable that fault masking will occur (eg multiple movable guards will be open at the same time as part of normal operation or service), then the DC is limited to none.

It is beyond the scope of this article to go into the details of tables 3 and 5 referred to above, and it is recommended that, instead, the 'simplified method outlined in 2 above is used.

http://www.iso.org/iso/catalogue_detail.htm?csnumber=63160

http://www.machinebuilding.net/ta/t0402.htm

Fonte: Pilz

Pin It

Tags: Normazione EN ISO 14119

Ultimi archiviati Normazione

ISO 37123 2019
Feb 13, 2020 100

ISO 37123:2019

ISO 37123:2019 Sustainable cities and communities - Indicators for resilient cities This document defines and establishes definitions and methodologies for a set of indicators on resilience in cities. This document is applicable to any city, municipality or local government that undertakes to… Leggi tutto
Gen 29, 2020 268

Norme CEI: Status 2020

In attesa di prima pubblicazione Leggi tutto
Norme tecniche UNI  pubblicazioni mese
Gen 29, 2020 336

Norme tecniche UNI: Pubblicazioni mensili 2020

Norme tecniche UNI: pubblicazioni mensili 2020 Pubblicazioni mensili 2020 delle nuove norme tecniche da UNI. Allegati al presente articolo un elenco di tutte le novità di ogni mese. Gli elenchi intendono essere uno strumento di rapida consultazione dei titoli di nuove norme introdotte. 01 Gennaio… Leggi tutto
Gen 26, 2020 162

IEC TS 62998-1:2019

IEC TS 62998-1:2019 Safety of machinery - Safety-related sensors used for the protection of persons IEC TS 62998-1:2019 gives requirements for the development and integration of safety related sensors (SRS) and safety related sensor systems (SRSS) used for protection of persons with special… Leggi tutto
Radon 222
Gen 23, 2020 163

ISO 11665-8:2019

ISO 11665-8:2019 Measurement of radioactivity in the environment - Air: radon-222 - Part 8: Methodologies for initial and additional investigations in buildings This document specifies requirements for the determination of the activity concentration of radon in all types of buildings. The buildings… Leggi tutto

Più letti Normazione