Safety FAQ - 17750


This section contains questions and answers on different safety topics related to the installation and use of UR robots.


For better understanding our TÜV certificate (TÜV Nord Certificate) a document called Safety description and functional safety details has been made to explain the different safety functions, what they involve and what is controlled when the function is activated.

Safety description and functional safety details


Topic: Definitions

Question

Answer

What is a “Stop Category”?

“Stop Category” is a classification of how robot motion is stopped in a safe way. There are three different types.
See the topic "UR Robots Safety" below.
(See IEC 60204-1 or EN 60204-1 for more details)

What is ”Cat 3” or
”Category 3”?

The term “Category” should not be confused with the term “Stop Category”.

“Category” refers to the type of architecture used as basis for a certain “Performance Level”. A significant property of a “Category 3” architecture is that a single fault cannot lead to loss of the safety function.

 (See ISO 13849-1 for more details)

What is ”PLd” or
”Performance level d”?

A Performance Level (PL) is a discrete level used to specify the ability of safety-related parts of control systems to perform a safety functions under foreseeable conditions. PL=d is the second highest reliability classification, meaning that the safety function is extremely reliable. (See ISO 13849-1 for more details)

What is SIL 2?

SIL (Security Integrity Level), like Performance level, is a measure of how likely it is that a dangerous failure will occur in a system. SIL 2 roughly equivalent to PL d (performance level d).
(See IEC 62061 or EN 62061 for more details)

Topic: Risk Assessment

Question

Answer

What is a risk assessment?

A risk assessment is the overall process of identifying all risks and judging if they are reduced to an appropriate level. It includes both risk analysis and risk evaluation.
A risk assessment must be documented. See UR user manual.
(See ISO 12100 or EN ISO 12100 for more details)

What is a risk analysis?

A risk analysis is a combination of the specification of the limits of the robot installation, hazard identification and risk estimation.
(See ISO 12100 or EN ISO 12100 for more details)

What is a risk estimation?

Risk estimation is defining likely severity of harm and probability of its occurrence.
(See ISO 12100 or EN ISO 12100 for more details)

What is a risk evaluation?

A risk evaluation is the judgment, on the basis of risk analysis, of whether the risk reduction objectives have been achieved.

What is a residual risk?

A residual risk is the risk remaining after protective measures have been implemented.
(See ISO 12100 or EN ISO 12100 for more details)

Topic: Standards

Question

Answer

Is it required for robots to comply with ISO 10218-1?

No, it is required to comply with the laws and regulations in the country and/or the state that the robot is installed in.
See UR user manual.

Do UR robots comply with
ISO 10218-1?

Not all guidance in ISO 10218-1 is clear and/or applicable for collaborative robots. At the time when ISO 10218-1 was written, collaborative robots was a new and developing field. Some features described in ISO 10218-1 assumes non-collaborative, big, heavy, dangerous and fenced robots. A Technical Specification with clarifications on the features described in ISO 10218-1 is published in February 15th 2016 under the name ISO/TS 15066. 

 Are UR robots designed for collaborative operation according to ISO 10218-1?

UR Robots comply with all requirements for collaborative operation defined in ISO 10218-1, particularly using the method defined in clause 5.10.5. ISO 10218-1 is harmonized under the European Machinery Directive 2006/42/EC and it specifically states that a robot can be used for collaborative operation (i.e. without safety guards between the robot and the operator) if it is in compliance with the clause 5.10.5. The risk assessment of the complete robot installation must conclude that risks are sufficiently reduced using the collaborative safety features.
See UR user manual.

Is it OK not to comply fully with
ISO 10218-1?

Not all guidance in ISO 10218-1 is clear and/or applicable for collaborative robots. At the time when ISO 10218-1 was written, collaborative robots was a new and developing field. Some features described in ISO 10218-1 assumes non-collaborative, big, heavy, dangerous and fenced robots.

A Technical Specification with clarifications on the features described in ISO 10218-1 is published in February 15th 2016 under the name ISO/TS 15066. 

What is the difference between ISO 10218-1 and ISO 10218-2?

- ISO 10218-1 is for manufacturers of robots. UR is the manufacturer of UR robots. A naked robot is considered partly completed machinery and not a complete machine.
- ISO 10218-2 is for integrators of robot systems. The company that installs a UR robot in specific application is the integrator. UR is not an integrator. An integrated and installed robot is considered a complete machine.
- ANSI/RIA R15.06 is a republication that includes both ISO 10218-1 and -2, published in the United States of America.
- CAN/CSA-Z434 is a republication that includes both ISO 10218-1 and -2, published in Canada.

What is ISO/TS 15066, Technical Specification on Collaborative Robots? 

ISO/TS 15066 is NOT a standard, but a Technical Specification with additional guidance for collaborative robots published on February 15th 2016. It contains valuable guidance on risk assessment for the integrators of collaborative robots. It also includes a presentation of a research study on pain thresholds which an integrator voluntary can choose to make use of.

What is ISO 13849?

These standards defines how a safety-related control system must be designed to achieve a specific performance level.
- ISO 13849-1 provides safety requirements and guidance on the principles for the design and integration of safety-related parts of control systems, including the design of software.
- ISO 13849-2 specifies the procedures and conditions to be followed for the validation by analysis and testing of the specified safety functions, the category achieved, and the performance level achieved by the safety-related parts of a control system designed in accordance with ISO 13849-1.

What is IEC 62061?

IEC 62061 is roughly equivalent to ISO 13849-1. The two standards defines safety-performance-levels using the same principles, but are developed by two different international committees. SIL levels from IEC 62061 can be directly translated to Performance Levels in ISO 13849-1 and vice versa.

Topic: UR Robots Safety

Question

Answer

What is a Stop Category?

“Stop Category” is a classification of how robot motion is stopped in a safe way. There are three different types:
  - Stop Category 0 : Robot motion is stopped by immediate removal of power to the robot. It is an uncontrolled stop, where the robot can deviate from the programmed path as each joint brake as fast as possible. This protective stop is used if a safety-related limit is exceeded or in case of a fault in the safety-related parts of the control system.
  - Stop Category 1 : Robot motion is stopped with power available to the robot to achieve the stop and then removal of power when the stop is achieved. It is a controlled stop, where the robot will continue along the programmed path. Power is removed as soon as the robot stands still.
  - Stop Category 2 : A controlled stop with power left available to the robot. The safety-related control system monitors that the robot stays at the stop position.
(see IEC 60204-1 and ISO 13850 for more details)

Which Stop Category is used for emergency stop in UR robots?

The UR robots emergency stop is designed as a Stop Category 1 stop.
See above.

Which Stop Category is used for safeguard stop in UR robots?

The UR robots safeguard stop is designed as a Stop Category 2 stop.
See above.

What is the difference between emergency stop and safeguard stop?

 - Emergency stop functions are to be used for emergencies only. Emergency stop is typically activated by the use of red button with a yellow background purposely designed for emergency stop. Activating emergency stop should be infrequent and not part of a daily routine.
 - Safeguard stop is used to pause robot movement in a safe way as a part of procedures and protection routines. Safeguard stop is typically used in conjunction with light curtains, door switches, safety PLCs etc. Resuming from a safeguard stop can be automatic or controlled by a push button.
Both stop functions are performance level d.
See UR user manual.

What is the Machinery Directive 2006/42/EC?

The European Machinery Directive (MD) is one of many Directives forming laws in the European Union (EU), and its official number is "2006/42/EC". Some countries outside EU also implements these Directives. The member states are not allowed to deviate from the MD and must implement it as national law directly. The benefit is, that when you design a machine that conforms to the MD, then you are allowed to sell that same version of the machine in all member stats. The number "2006/42/EC" begins with a year (2006) which is based on the date that the work on the directive started and notthe date it is implemented. The letters "EC" refers to the language (EC = English, EG = German etc.). New directives will use the end designation "EU" only. Directives begins with introductions, background and legally oriented information. The more technical requirements are often included in Annexes (E.g. Annex I in the MD is "essential requirements").

Some Directives are CE-marking Directives, including the MD. This means that if the robot is to be installed in a country covered by the MD, then the manufacturer (robot integrator) must add a CE mark to the robot installation as an indication that the overall installation is in compliance with the MD (See annex III in the MD). The manufacturer (robot integrator) also needs to make a Declaration of Conformity (See Annex II in the MD) and document the details (See Annex VII). Other requirements and other Directives might also apply.
2006/42/EC can be downloaded free of charge and in different languages from the official European homepage:

http://eur-lex.europa.eu/legal-content/EN/TXT/?qid=1426848262724&uri=CELEX:32006L0042

NOTE: Typically it is easy to find Directives by searching the number on Google.com (E.g. "2006/42/EC" ).

Also see the "Declaration of Incorporation" in the UR user manual.

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