ABB Electronic Safety Relays Catalog

Electronic

7

Safety relays

Personnel safety and machine protection

Risk category according to EN 954-1

Classifi cation of a machine into categories to EN 954-1

Pursuant to the Machinery Directive 89/393/EEC, every machine must

comply with the relevant directives and standards. Measures must be taken to
keep the risk to persons below a tolerable extent.

In the fi rst step, the project planner performs a risk evaluation to
EN 1050 "Risk Assessment". This must take into consideration the machine's
ambient conditions for instance. Any overall risk must then be assessed. This risk
assessment must be conducted in such a form as to allow documentation of the
procedure and the results achieved. The risks, dangers and possible technical
measures to reduce risks and dangers must be stipulated in this risk assessment.
After stipulating the extent of the risk, the category on the basis of which the safety
circuits are to be designed is determined with the aid of EN 954-1 “Safety-Related
Components of Controls”.

This determined category defi nes the technical requirements applicable to the
design of the safety equipment.

7

There are fi ve categories (B, 1, 2, 3 and 4), whereby B (standing for basic
category) defi nes the lowest risk and, thus, also the minimum requirements
applicable to the controller.

Possible selection of categories pursuant to EN 954-1

Starting point for the risk assessment of the safety-related component of the
controller.

S- Serious injuries

S1 Slight (normally reversible) injuries,
S2 Serious (normally irreversible) injuries,
including death

Safety
category 1 achieving safety

B The safety-related components of controls and/or their protection The occurrence of a fault may lead
devices and their components must be designed, constructed, to loss of the safety function.
selected, assembled and combined in compliance with the
applicable standards, such that they can withstand the anticipated Predominantly characterised
infl uences. by selection of componentsl

1 The requirements of B must be complied with. The occurrence of a fault may lead
Time-proven components and time-proven safety principles to loss of the safety function but the
must be applied. probability of occurrence is less than
in category B.

2 The requirements of B and the use of the time-proven safety principles • The occurrence of a fault may lead
must be complied with. to loss of the safety function between
The safety function must be checked at appropriate intervals the inspection intervals.
by the machine control.

• The loss of the safety function is
detected by the check/inspection.
3 The requirements of B and the use of the time-proven safety principles • If the single fault occurs, the safety
must be complied with. function is always retained.
Safety related components must be designed such that:

• a single fault in any of these components does not lead to loss • Certain faults but not all faults are
of the safety function and detected.

• the individual fault is detected, wherever feasible in an • An accumulation of undetected faults
appropriate manner. may lead to loss of the safety function.
Predominantly
characterised
4 The requirements of B and the use of the time-proven safety principles • If the faults occur, the safety function by the structure
must be complied with. is always retained.
Safety related components must be designed such that: • The faults are detected in good time to

• a single fault in any of these components does not lead to loss prevent loss of the safety function
of the safety function and

• the individual fault is detected at or before the next requirement
applicable to the safety function or, if this is not possible
an accumulation offaults may then not lead to loss of the

safety function.

This mandatory classifi cation runs likes a red thread from selection of the smallest limit switch through to the overall concept of the entire
machine, whereby it is necessary to grapple with the permanent confl ict between what is technically feasible and what is permitted on the basis
of “pure theory”.

Thus: Depending on application, not every technically feasible safety category is also permitted. For instance, in the case of contactless
protection devices (light barriers etc.) only categories 2 or 4 are permitted. By contrast, in the case of tread mats, categories B to 4 can be used,
depending on risk assessment, provided these categories can be reached at all owing to the design.
The 2-hand control C575 would technically also comply with the lower categories but it cannot be connected in categories 1-3.

Summary of requirements System behaviour 2

F- Frequency and/or duration of the risk exposure

F1 Rare to frequent and/or short duration of exposure
F1 Frequent to sustained and/or longduration of exposure

P- Options for risk avoidance

(Generally referred to the speed and frequency at which the
dangerous components moves and to the clearance from
the dangerous component).
P1 Possible under certain conditions
P2 Hardly possible

Categories

B12

S1

P1

F1

P2

S2

P1

F2

P2

B1-4 Categories for safety-related components of controls

● Preferred category

● Possible category requiring additional measures

Disproportionately extensive measures by comparison

with the risk

Principles for

3

4

1 The categories are not intended to be applied in any specifi c order or hierarchical arrangements with respect to the technical-safety requirements.
2 The risk assessment will indicate whether full or partial loss of the safety function(s) as the result of fault is acceptable.

7.38 Low Voltage Products & Systems

AC 1000 - 11/03

Selection table

Electronic

7

Safety relays

Selection table for ABB safety relays in accordance to risk category (EN 954-1):

Category C 570 C 571 C 572 C 573 C 574 C 575 C 576 C 577 C 578 C 6700 C 6701 C 6702

B
1 x x x x x x x x x x
2 x x x x x x x x x x
3 x
4 x

Selection table for ABB safety relays in accordance to device characteristics

Characteristics
suitable for device C 570 C 571 C 572 C 573 C 574 C 575 C 576 C 577 C 578 C 579 C 6700 C 6701 C 6702

EMERGENCY STOP yes yes yes yes yes — yes yes — 3 yes yes yes

7

Safety gate monitoring yes yes yes yes yes — yes yes — 3 yes yes yes
Tread mats — — — — — — — — — — — — ­Two-hand control — — — — — yes — — — — — — -

e.g. presses
Feedback loop for moni- yes yes yes yes yes yes yes yes — — yes yes yes

toring of external contactors
Single channel yes yes yes yes yes — — — — — yes yes yes
Two channel — yes yes yes — yes yes yes — — yes yes yes
Cross-short circuit monitoring — — yes — yes — yes yes — — — yes yes
24VDC at the EMERGENCY — — yes — — yes yes yes yes — yes yes yes

STOP limit switch
Operating voltage at the yes yes — yes yes — — — — — — — -

EMERG. STOP limit switch
No. of safety outputs 4 2 3 3 2 2 2 2 — 4 2 4 2 1
No. of time delayed — — — — 1 — — — — — — — 1

safety output contacts
No. of signalling contacts 2 — 2 1 2 2 — — — — — — 5 — 5
Enclosure width in mm 75 22.5 45 22.5 45 45 22.5 22.5 45 22.5 22.5 22.5 22.5
Monitoring overtravel — — — — — — — — yes — — —

e.g. presses
Auto-start yes yes yes yes yes — yes — — — yes yes yes
Controlled/monitored start — — yes — — — — yes — — yes yes yes

1

x x x x x x x x x

1

x x

1 x2

x x x x x x

1 Possible with additional external measures.
2 Applies only to undelayed contact. Category 3 applies to delayed contact.
3 Contact extension
4 Solid-state outputs requirements of safety in acc. to 954-1 only in combination with positively guided contactors.
5 Solid-state outputs could also be used as safe messaging outputs.

7.40 Low Voltage Products & Systems

AC 1000 - 11/03