Safety Classifications

I have spent the last few days working on a fairly elaborate safety system that involves linking and unlinking safety zones. Usually I have used on machine as a “master” and the the other a “slave” or sub-zone, but this project requires a true peer relationship between the two systems. This is complicated by the fact that the two systems have to be able to disengage from each other via a plug and function entirely independently, they both have e-stop and guard circuits and they have a muted light curtain between them. Its been a challenge but I have a pretty nice circuit set up with about every kind of guard relay I have ever used in it. Next comes the documentation and justification part of the design which is much less fun than the design part. Here are some of the references and procedures I use for this:

The international standards are described below, along with the European EN number and the new JIS number for each set of standards.

(1) General Standards


Basic concepts, general principles for design
Part 1: Basic terminology, methodology
EN standards: EN ISO12100-1
JIS standards: JIS B 9700-1
● Description
This part of these standards defines the basic concepts of machinery safety and stipulates safety design procedures.

● Main Points
(1)Machinery hazards are classified as follows:Mechanical hazards, electrical hazards, thermal hazards, hazards generated by noise, hazards generated by vibrations, hazards generated by radiation, hazards generated by materials and substances, and hazards generated by neglecting ergonomic principles in machine design.

(2)Identify the preceding hazards and apply safety design procedures to reduce risks.
Step 1: Specify the operating range of the machine.
Step 2: Identify the hazards and assess the risks.
Step 3: Remove hazards and reduce risks as much as possible.
Step 4: Design guards, safety equipment, and other safeguards against any residual risks.
Step 5: Inform and warn users about any residual risks.
Basic concept, general principles for design
Part 2: Technical principles and specifications
EN standards: EN ISO12100-2
JIS standards: JIS B 9700-2
● Description
This part of these standards describes the safety design procedures stipulated in part 1 in greater detail.

● Main Points
This part of these standards takes step 3 (Remove hazards and reduce risks as much as possible.), step 4 (Design guards, safety equipment and other safeguards against any residual risks.), and step 5 (Inform and warn users about any residual risks.) given in part 1 and describes them in greater detail.
Principle of risk assessment
EN standards: EN ISO14121
JIS standards: JIS B 9702
● Description
These standards pertain to risk assessment in the safety design procedures described in ISO12100-1.

● Main Points
Assess risk is performed using the following systematic methodology:

A)Determine how the machinery will be used.

B)Check foreseeable hazards.

C)Identify risk elements based on hazardous events.

D)Assess the risk and design accordingly to reduce the risk.

Safety-related parts of control systems
Part 1: General principles for design
EN standards: EN ISO13849-1 (EN954-1)
JIS standards: JIS B 9705-1
● Description
These standards apply to control systems where safety is a concern.
● Main Points
(1)These standards consider the anticipated degree of injury (light to serious) and the probability of injury (rare to common) in determining the hazard level of machinery.

(2)These standards classify hazard levels in five safety categories and stipulates safety functions that control systems should have in every category.

Safety-related parts of control systems

Part 2 : Validation
EN standards: EN ISO13849-2
● Description
Regarding the verification of the applicability of claims in relation to ISO13849-1 (EN954-1) categories.
● Main Points
In order to verify applicability to the category claims, the following should be specified:

(1)Guidelines for validity testing and inspections

(2)General considerations at time of design

(3)List of failures and failure exclusion criteria

(4)Test and Test results or report

Electrical equipment of machines
Part 1: Specification for general requirements
EN standards: EN60204-1
JIS standards: JIS B 9960-1
● Description
This part of these standards applies to electrical equipment with a rated power supply voltage of less than 1,000 VAC or 1,500 VDC between lines or a rated frequency of less than 200 Hz.
● Main Points
This part of these standards stipulates all elements required in electrical equipment for machines including the control circuits, functions, devices, safety measures, and technical documents related to the installation, operation, and maintenance of electrical and electronic equipment in machines.

Indication, marking and actuation
Part 1 : Requirements for visual, auditory and tactile signals
EN standards: EN 61310-1
JIS standards: JIS B 9706-1
● Description
This standard sets out specific requirements regarding visual, audio and tactile methods for providing safety related information to operators and those that may be placed in dangerous situations.
● Main Points
(1)Separate signals into passive and active

(2)Visual spectrum, brightness, and contrast ratio

(3)Meaning of colors and the shape of markings, and examples of forms that can be discerned by touch alone

(4)Operating switch symbols

(5)Shape, color and dimensions of safety markings (Prohibitions, warnings, information etc.)

Indication, marking and actuation
Part 2 : Requirements for marking
EN standards: EN 61310-2
JIS standards: JIS B 9706-2
● Description
This standard sets out the identification of machines, and markings to ensure safe use and the reduction of danger from incorrect connections.
● Main Points
(1)Regulations regarding manufacturer information (manufacturer name, address etc.), and rating information (power supply range, maximum speed etc.)

(2)Regulations regarding necessary markings such as for AC, DC and grounding etc.

Indication, marking and actuation
Part 3 : Requirements for the location and operation of actuators
EN standards: EN 61310-3
JIS standards: JIS B 9706-3
● Description
Specifies safety issues for actuators that are operated by hand or by human control.
● Main Points
(1)Set up away from dangers, and avoid ambiguous operations. Also, be sure that operation does not create alternative risks.

(2)Design to increase the clockwise rotation of handles and lifting action for levers, so that the operator is better aware of the resulting operation.

(3)Two-handed operating controls and enabling devices where necessary.

Functional safety of safety-related electrical, electronic and programmable electronic control systems
EN standards: EN62061
JIS standards: JIS B 9961
● Description
This standard specifies those matters applicable to the machinery portion of the industry as included in the IEC 61508 Series Functional Safety Standards.
This standard applies to the design and verification of safety related control systems that use electric, electronic, or programmable electronic control systems.
● Main Points
Standards, including the following, for the allotment of SIL (Safety Integrity Level) and in order to achieve the allotted SIL, for safety functions performed by safety control systems.

(1)Functional safety management

(2)Create specifications for safety controls

(3)Control system design

(4)User information (Manual)

(5)Check Validity
(2) Standards for Safety Switches

Interlocking devices associated with guards – Principles for design and selection
EN standards: EN1088
JIS standards: JIS B 9710
● Description
These standards stipulate general design and selection principles for equipment that uses interlocking devices for safety.
● Main Points
(1)There are two types of interlocking devices: those with and those without a guard lock.

(2)The guard must not allow machinery to operate until it is closed and it sends a stop command if it is open.

Low-voltage switchgear and controlgear
Part 5: Control circuit devices and switching elementsSection one – Electromechanical control circuit devices
EN standards: EN60947-5-1
JIS standards: JIS C 8201-5-1
● Description
This part of these standards applies to control circuit devices and switching elements that are produced to control, signal, and interlock switching and control devices. It applies to control circuits with a maximum rated voltage of 600 VDC or 1,000 VAC (a maximum frequency of 1,000 Hz).
● Main Points
(1)This part of these standards consists of Chapter 1: General Requirements, Chapter 2: Special Requirements for Indicators, and Chapter 3: Special Requirements for Positive Opening.

(2)It contains provisions such as switching capacity, temperature rise, terminal strength, protective structures, and positive opening.

Low-voltage switchgear and controlgear.
Part 5-8 : Control circuit devices and switching elements.
Three-position enabling switches
EN standards: EN 60947-5-8
● Description
An IEC 60947-5 Series standard that stipulates 3-position enabling switches, for enable devices under the IEN60204-1 standard. This does not apply to devices that employ teaching pendants or grip switches etc., but only to those devices with built-in enable switches.
● Main Points
(1)Stipulates electrical properties such as withstand voltage and insulation, and operating characteristics for operating stroke and load etc.

(2)The 3-position enabling switch verification mark has been changed.

Two-hand control devices,
functional aspect – Principle for design
EN standards: EN574
JIS standards: JIS B 9712
● Description
These standards stipulate safety requirements related to the design and selection of two-hand control devices.
● Main Points
(1)Stipulates dimensions for prevention of defect.

(2)Output signal shall be designated only when both control actuating devices are actuated less than or equal to 0.5 s.

(3)Classify devices by type (type I, II, IIIA, IIIB and IIIC) and risk assessment results as the basis for selecting devices.

Basic requirements for testing of position switches with positive opening contacts for safety applications
● Description
These are German labor safety standards that were enacted to prevent industrial accidents. They apply to testing on positive opening position detector switches that are installed for safety.
● Main Points
(1)Limit and door switches are classified in two categories according to function.

(2)The switches must have a positive opening mechanism, a mechanical service life of 1,000,000 operations, and an enclosure rating of IP54, and must not operate with any tool except a special operation key.

Basic requirements for testing and certification of locking systems with electro-magnetic locking unit for safety applications
● Description
These are also German labor safety standards. They apply only to devices that have a lock monitoring mechanism in door switches that use a key lock for safety.
● Main Points
(1)The switches must use a mechanism like a solenoid for locking and unlocking.

(2)They must have a locking strength and positive opening mechanism, a mechanical service life of 1,000,000 operations, and an enclosure rating of IP54, and must not operate with a tool other than a special operation key.
(3) Standards for Emergency Stop Device

Emergency stop equipment,functional aspects – Principles for design
EN standards: EN418
JIS standards: JIS B 9703
● Description
These standards stipulate principles used to design emergency stop devices.
● Main Points
(1)Devices must have a positive opening mechanism.

(2)Devices must have a latching mechanism.

(3)The operative parts must be structured to allow easy access to the mushroom-shaped pushbuttons, wires, and ropes.

(4)The operative parts must be red on a yellow background.
(4) Standards for Safety Sensors

Electro-sensitive protective equipment
Part 1: General requirements and tests
EN standards: EN61496-1
JIS standards: JIS B 9704-1
● Description
These standards apply to devices, such as safety sensors/safety light curtains, that detect the presence of workers electrically and output a control signal for their protection. They stipulate items like fault detection performance, software design policy, heat resistance performance, EMC performance, vibration and shock performance, indicator colors, labeling details, and the content of operating manuals.
● Main Points
(1)Electro-sensitive protective equipment (ESPE) is classified as either type 4, which complies with category 4 requirements in EN954-1, or type 2, which complies with category 2 requirements in that same standard.

(2)The provisions in these standards stipulate that equipment displays the fault mode for electronic components in the equipment and they demonstrate that safety characteristics for the type of equipment are maintained in all fault modes.

Electro-sensitive protective equipment
Part 2: Particular requirements for equipment using active opto-electronic devices
EN standards: EN61496-2
JIS standards: JIS B 9704-2
● Description
This part of these standards applies to the type of ESPE protective equipment that in principle detect emitted or received light. They stipulate items such as detection performance for the minimum size object detected, effective aperture angle, extraneous light resistance performance, and mutual interference resistance performance.
● Main Points
(1)Directional angles are stipulated separately for type 4 and type 2 according to the distance between the emitter and receiver.

(2)Conditions that maintain ordinary operation and conditions that permit incorrect operation safely are stipulated for all extraneous light sources.

Electro-sensitive protective equipment
Part 3 : Particular requirements for Active Optoelectronic Protective Devices responsive to Diffuse Reflection
EN standards: EN61496-3
JIS standards: JIS B 9704-3
● Description
This part of these standards applies to electro-sensitive protective equipment that diffuse or reflect light. They stipulate items such as detection performance for the detection range, allowable errors, response time, detection capacity, resistance to extraneous light, and reflective detection capability as well as the influence of background interference.
● Main Points
(1)Only stipulated for Type 3. (not specified for types 1, 2 and 4)

(2)Conditions that maintain ordinary operation and conditions that permit incorrect operation safely are stipulated for all extraneous light sources.

The positioning of protective equipment in respect of approach speeds of parts of the human body
EN standards: EN999
JIS standards: JIS B 9715
● Description
These standards stipulate the minimum distance that must be provided between hazardous parts of machinery and protective equipment. Referred to as the safe distance, this distance is calculated from the worker entry direction, protective equipment response time, machine response time, and minimum object size detectable by the protective equipment.
● Main Points
(1)These standards apply when individual machine standards do not prescribe the method used to calculate safe distance.

(2)Protective equipment must be selected with a detection performance level capable of maintaining a safe distance so machines can be stopped before they pose a hazard to workers.

(5) Standards for Safety Relays

Relay with forcibly guided (linked) contacts
● Description
These standards apply to control circuit relays that are installed for safety and its provisions are for self-monitoring relays that have a forced guided mechanism that prevents normally open and closed contacts from operating simultaneously.
● Main Points
(1)If a normally open contact of a relay with forcibly guided (linked) contact is welded shut, the coil switches OFF and all normally closed contacts must maintain a gap of at least 0.5 mm. Even if a normally closed contact is welded shut, the coil switches ON and all normally open contacts must maintain a gap of at least 0.5 mm.

(2)Ideally, contact load switching must comply with the AC-15 (AC electromagnetic load) and DC-13 (DC electromagnetic load) utilization categories.

(3)The forced guide contact mark may be used on all class A relays (all relays with forcibly guided (linked) contacts).

Pretty dry stuff, but these are some of the regulations governing application of safety devices in industrial applications. Most of the major safety device manufaturers have pretty good documentation and application help on their devices and safety in general. Pilz, Allen-Bradley/Guardmaster, STI, Banner, and Phoenix are a few that come to mind.

Be safe!


Electrical Engineer and business owner from the Nashville, Tennessee area. I also play music, Chess and Go.

2 Comments on “Safety Classifications

    • Somewhat not related to the topic and a bit spammy, but at least related to automation so I’ll let it slide for now…