Alternative Methods as energy control
Compliance for Alternative Methods
When it comes to reducing risks on automated machines the hazard controls hierarchy is very useful to follow as it serves as a good base.
When applying risk mitigation measures, we should aim to achieve an acceptable risk. Acceptable risk can be achieved by applying various risk reduction measures from design out measures, engineering measures and administrative measures.
Hazardous energy can be either isolated, dissipated or controlled. When energy isolating devices are properly implemented and documented for a task/hazard(s), they provide acceptable level of risk and there will always be task/hazards that are best reduced, by depending on energy isolating devices.
On the other hand, there are tasks/hazards that can be best performed by relying on alternative control methods and still achieve an acceptable risk; when properly applied and maintained.
Compliance with ANSI B11.26 and ANZI Z244.1 is required to apply engineering control devices as alternative methods as a form of hazardous energy control (See ANSI Z244.1). In addition, the following shall be complied with when using engineering control devices as alternative methods:
- Acceptable risk must be achieved for the specific task/hazard by relying on the engineering control device as an alternative method,
- Engineering control devices selected must be designed to withstand the environment, temperature, etc., to which it would be expected to be exposed to on the machine/plant floor,
- Alternative control shall be under exclusive control and machine unexpected startup, must be in the control of personnel,
- The safety function covering the alternative method should not be capable of manual suspension (not in hardware nor software); it should have priority over other safety functions,
- Consideration should be given to personnel exposed to risks from unexpected machine state such, mode change, power loss, etc.
- Qualification and training should be provided to personnel performing the required tasks mitigated by engineering controls and alternative methods,
- The safety requirements specification needs to be documented,
- The safety function should be designed to the required control circuits reliability as indicated in the risk assessment,
- Fault exclusions for engineering control devices needs to be documented and inspected periodically,
- Periodic inspections need to be performed on engineering control devices being used as alternative methods to ensure their reliability, operational condition, wear/tear, defeat, etc. See article on inspection of risk reduction measures
- See ANSI Z244.1 clause 8 for further information and details on requirements