Manufacturing AUTOMATION

Features Machine Safety Opinion
To lockout, or not to lockout, that is the question


May 26, 2015
By Franco Tomei

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Mar. 27, 2015 – When performing a pre-start review as per section 7 of the Regulations for Industrial Establishments, one needs to identify the measures to be taken to fulfill the requirements of the relevant provision of the regulations identified in the table. The decision that needs to be made is whether or not to provide a protective element that signals that apparatus to stop or to provide a protective element that does not signal a stop. It must be very clearly stated here that the protective elements that signal a stop are not to be considered lockout devices, as the lockout theme is a very broad subject. It should also be pointed out that this article is written within the context of machine guarding i.e. item 2 of the Table.

From a strict regulatory standpoint, the section that specifically identifies “lockout” requirements is section 40 of the Regulations for Industrial Establishments. Nonetheless, there are other sections (74, 75 and 76 in particular) where lockout (including but not limited to blocking, bleeding, discharging, etc.) is not cited but standards and best practice would dictate a full lockout is required. The standard CSA Z460 Control of Hazardous Energy – Lockout and Other Methods, as well as other standards, does recognize that while lockout is the preferred method of controlling hazardous energy, it is not always practicable to do so.

Referencing Oxford Dictionaries1, the definition of practicable (in part) as follows:

Able to be done or put into practice successfully: the measures will be put into effect as soon as is reasonably practicable.

I have at times encountered situations where people have identified lockout as “not practicable” because the switch is far from the machine, but inconvenience should not be confused with “not practicable.”

In applying this to machine safety, we can state that loading a workpiece onto a machine with powered holding device would not be practicable to lockout because the powered holding device would not be operable and the task could not be performed.
In a situation where (despite the optimal performance of a machine) jams do occur, it may not be practicable from an economic viewpoint to lockout each and every time the jam occurs. However, let us be very cautious here in that while a full lockout may not be practicable, it is still necessary for the employer to ensure that the risk the worker is exposed to is as low as reasonably practicable. Impracticable economic interest cannot be taken to imply that the safety of the worker is trumped.

Section 7.4 of CSA Z460 states that:

Traditional lockout to a full zero energy state is not practicable in all situations. When lockout affects the tasks that are integral to the production process by design or traditional lockout prohibits the completion of a specific task, other hazardous energy control methods shall be used control options such as those specified in clause 7.4.6 to 7.4.10 shall be used in accordance with the hierarchy specified in clause 7.4.5 to ensure effective protection.

Clause 7.4.6 to 7.4.10 identifies various engineered safeguards, such as individual personal controls, area scanners, fixed and moveable guards, hold-to-run devices, light curtains and single opto-electronic beams, pressure mats, safety rated switches, stop devices, and trapped key devices, etc.

I interpret this to mean that the identified safeguards can be used for controlling hazardous energy only for tasks that are integral to the production process. This, of course, begs the question as to what determines if a task is integral to the production process. The standard provides us with the answer in section 7.4.2 where it states that a task can be deemed integral if it exhibits most of the following characteristics:

1. The task is short in duration. Since CSA Z460 doesn’t define what “short” is, it is recommended that each situation be analyzed separately and the time be defined within the context of the situation.

2. The task is relatively minor in nature. Once again, this can differ, but a reasonable measure for “minor” tasks could be those requiring one specific tool or no tools at all.

3. The task occurs frequently during the production shift. In other words, if the jam occurs only every couple of days, it can be reasonably concluded that the jam is a result of some malfunction and not inherent in the production process.

4. The task is usually performed by operators or others functioning as operators. The message here is that if maintenance personnel need to be called then the task is no longer simple. We must be careful here since many operations personnel often act as maintenance workers. Adequate supervision must be provided to control the situation.

5. The task represents predetermined cyclical activities. An example of this could be where the welding tip of a spot welding machine needs to be changed every 5000 welds.

6. The task minimally interrupts the operation of the production process. Minimal interruption is not defined but I would suggest an assessment for each specific process.

7. The task exists even when optimal operating levels are achieved. If we take the case of where jams occur because a machine component is excessively worn then the jam is a result of poor maintenance and not integral to the production process. If the jam occurs because of the variances in the product that can result from the production process, then we have a different case.

8. The task requires task-specific personnel training. In this case, a worker is trained and given specific instruction on performing a particular task. If the problem is not resolved, then the supervisor should be called.

The worker must go beyond the specific instructions given during the training. What has your experience been? Any feedback you can provide would be appreciated.

Note:
1. “Practicable: definition of practicable in Oxford dictionary.” Oxforddictionaries.com, Oxford Dictionaries. Visit bit.ly/1CMvm2k.

This column previously appeared in the March/April 2015 issue of Manufacturing AUTOMATION.