ISO/DIS 21260:2018 | Sicurezza contatto tra macchine o organi mobili e persone
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ISO/DIS 21260:2018 | Sicurezza contatto tra macchine o organi mobili e persone
ID 9304 | 18.10.2019
Il presente documento è un estratto della norma tecnica ISO/DIS 21260:2018.
La norma analizza i casi in cui i contatti degli operatori con gli organi mobili o con macchine mobili non possono essere evitati (ad esempio: rulli di carico, macchine utensili, porte dell’ascensore) e definisce i valori per i limiti relativi il contatto, da considerare in fase di progettazione.
Lo scopo della norma è stabilire dei valori che possano essere usati per soddisfare il criterio di “progettazione intrinsecamente sicura” definita dalla norma tecnica EN ISO 12100:2010 (rif. 6.2.2.2). Inoltre, introduce il concetto di gruppi per tenere conto della complessità delle condizioni che si verificano quando le macchine e le persone operano insieme per consentire un equilibrio tra la frequenza di contatto, il possibile rischio e i benefici che derivano dall’uso della macchina.
EN ISO 12100:2010 6.2.2 Considerazione di fattori geometrici e aspetti fisici
[…] 6.2.2.2 Aspetti fisici
Questi aspetti comprendono quanto segue:
a) limitazione della forza di attuazione a un livello sufficientemente basso in modo che la parte azionata non generi un pericolo di natura meccanica;
b) limitazione della massa e/o della velocità degli elementi mobili e pertanto della loro energia cinetica;
c) limitazione delle emissioni agendo sulle caratteristiche della sorgente […]
Nella norma vengono trattati solo gli effetti meccanici diretti sulla persona a seguito del contatto con parti in movimento della macchina. C’è però anche la possibilità di avere effetti secondari o indiretti sulla persona causati da:
- temperatura della parte di macchine con cui si ha il contatto;
- spinta consequenziale al contatto che potrebbe causare la caduta della persona (la norma ISO/DIS 21260:2018 analizza il caso nell’Allegato E);
- scosse elettriche.
La norma analizza solo il rischio “meccanico” diretto dovuto al contatto con l’organo o la macchina mobile.
ISO/DIS 21260:2018| Norma tecnica di tipo B
Comitato tecnico: ISO/TC 199
Excursus
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Methodology
If a type-C standard exists for the machine that includes contact limits, the limits specified by that type-C standard shall be used.
NOTE Type-C standards can specify limits directly or by reference to this document.
If there is no type-C standard or it does not include contact limits, the contact limits shall be determined using this document.
For a given machine a number of different human contacts may be possible. These may be by different moving parts of the machine or due to different modes of operation or other use conditions. To apply this document all possible contacts shall be taken into account.
For each contact the following steps (shown in Figure 1) shall be followed:
a) Identify human contact by a moving part of the machine.
b) If the contact could be with the eye or within 50 mm of the eye it is not permitted and shall be prevented or eliminated.
c) For other contacts, determine the contact classification group (see Clause 6).
d) Determine the allowable contact condition for the contact (see Clause 8).
e) Compare the actual or design contact condition with the allowable condition. If the allowable condition is not satisfied the design shall be revised until the contact condition is met. Design changes are allowed to also affect the risk assessment which should be reviewed and if necessary repeated.
f) Repeat the process for each contact under foreseeable use and misuse conditions.
b) If the contact could be with the eye or within 50 mm of the eye it is not permitted and shall be prevented or eliminated.
c) For other contacts, determine the contact classification group (see Clause 6).
d) Determine the allowable contact condition for the contact (see Clause 8).
e) Compare the actual or design contact condition with the allowable condition. If the allowable condition is not satisfied the design shall be revised until the contact condition is met. Design changes are allowed to also affect the risk assessment which should be reviewed and if necessary repeated.
f) Repeat the process for each contact under foreseeable use and misuse conditions.
Figure 1 - Flowchart for application
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Classification of machine-human contact
General
The acceptability of a contact by a moving machine or parts of a machine varies depending upon the contact circumstances.
For practical purposes contacts have been divided into the following groups.
One classification group could define all of the contact situations but typically there are multiple classification groups.
In single contacts it is possible to also include dynamic (G1, G2 and G3), static (G4) and sliding (G5) elements all of which shall be taken into account.
Group 1 (G1) — High frequency contact
Group 1 comprises dynamic contacts on the same individual more than once every hour, averaged over a period of eight hours.
Group 2 (G2) — Occasional contact
Group 2 comprises dynamic contacts on the same individual, less than once per hour averaged over a period of eight hours but more than once a week, or rare dynamic contacts, less than once per week, that the person being contacted does not expect.
Group 3 (G3) — Rare contact
Group 3 comprises dynamic contacts on the same individual less than once per week.
Group 4 (G4) — Static or quasi-static contact
Group 4 comprises any contact where the energy transfer rate is less than 2 J/s or where the contact force is applied for more than 500 ms.
Group 5 (G5) — Sliding contact
Group 5 comprises any contact that includes sliding directly on the surface of the skin.
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Contact thresholds
General
The following paragraphs specify the threshold values for each of the previously defined contact groups.
NOTE Current limit values are based on size, energy, force and pressure. Future research is permitted to suggest alternative units for limiting thresholds, e.g. momentum [kg ∙ m/s].
Threshold values — Group 1, group 2 and group 3 contacts
For a dynamic contact to be acceptable the conditions given in Table 1 shall apply.
Table 1 - Dynamic threshold values
Where contact frequency exceeds once per minute the following additional requirements apply:
- a protective barrier in the form of protective clothing or similar shall be used at the contact location to prevent localized skin damage; or
- for direct skin contact the acceptable conditions are reduced by 50 %.
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Certifico Srl - IT | Rev. 00 2019
©Copia autorizzata Abbonati
©Copia autorizzata Abbonati
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