Machine Safety: Does adding a hard guard always make your machine safer?

Machine guarding is sometimes approached with the methodology that says lets first add a hard guard to protect the operator from the hazard. Does this always mitigate the hazard, reduce the hazard to an acceptable level, or achieve “safe enough”?

12/29/2011


Machine guarding is sometimes approached with the methodology that says lets first add a hard guard to protect the operator from the hazard. Does this always mitigate the hazard, reduce the hazard to an acceptable level, or achieve “safe enough”?

   In my opinion this approach only works some of the time. More often, it not only doesn’t solve the problem but it also adds another hazard.

   The required practice today begins with a risk assessment per the local jurisdiction or safety standard governing your application or machine. Having said that, adding the hard guard may have been an appropriate next step, however, it’s only the next step. The safety standard will also say that having added the hard guard you will need to update your risk assessment. One of the driving reasons for this step is to hopefully identify any new hazards created by the addition of the hard guard. Reference; Annex G, Risk Scoring Matrix System, ANSI B11, 2008, below.

Control Engineering Machine Safety blogger J.B. Titus says: Identify any new hazards created by the addition of a hard guard. Reference; Annex G, Risk Scoring Matrix System, ANSI B11, 2008.

   For example, I’ve seen machines that occasionally require an operator to almost work “in” the machine to clear a temporary jam which would otherwise result in lost production or extensive downtime. To reduce the “very likely to occur” hazard of the operator getting caught by the machine and the resulting “catastrophic” potential injury, a hard guard has been added to the machine. But, all too often I’ve seen where this guard has created another hazard if this guard has to automatically open and close to eject a completed product. The updated risk assessment requirement should document this new hazard and mitigation steps should follow. The new guard may protect the operator while the guard is in the closed position, however, what could happen if the operator gets caught by the machine while the guard is open. It seems to me that the operator is still exposed to the catastrophic hazard of the machine and the new hazard of the guard closing. The operator is certainly better protected by the closed guard but potentially in greater harm’s way because of the new hazard.

                                   So, is the machine safer?

   This example suggests the importance of the risk assessment process as a “living” document and the best practice to continually look for machine safety hazards. Adding a hard guard is not always the best answer! And, often it’s recommended to go through this exercise prior to making any changes to the machine because the decision might be made to choose a different machine guarding solution.

   Your comments or suggestion are always welcome so please let us know your thoughts. Submit your ideas, experiences, and challenges on this subject in the comments section below. Click on the following text if you don't see a comments box, then scroll down: Machine Safety: Does adding a hard guard always make your machine safer?

   Related articles:

How To Integrate Safety

Machine Guarding & The Hierarchy of Measures for Hazard Mitigation

Risk assessment - A best practice for sustainable performance

Machine Safety – Hard Guarding Is Best – Right?

Updating Minds About Machine Guarding

 

Contact: www.jbtitus.com for “Solutions for Machine Safety”.



No comments
The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by...
The System Integrator Giants program lists the top 100 system integrators among companies listed in CFE Media's Global System Integrator Database.
The Engineering Leaders Under 40 program identifies and gives recognition to young engineers who...
This eGuide illustrates solutions, applications and benefits of machine vision systems.
Learn how to increase device reliability in harsh environments and decrease unplanned system downtime.
This eGuide contains a series of articles and videos that considers theoretical and practical; immediate needs and a look into the future.
Salary and career survey: Benchmarks and advice; Designing controls; Remote data collection, historians; Control valve advances; Hannover Messe; Control Engineering International
System integration: Best practices and technologies to help; Virtualization virtues; Cyber security advice; Motor system efficiency, savings; Product exclusives; Road to Hannover
Collaborative robotics: How to improve safety, return on investment; Industrial Internet of Things, Industrie 4.0: World views; High-performance HMI, Information Integration: OPC and OMG
This article collection contains several articles on the Industrial Internet of Things (IIoT) and how it is transforming manufacturing.
PLCs, robots, and the quest for a single controller; how OEE is key to automation solutions.

Find and connect with the most suitable service provider for your unique application. Start searching the Global System Integrator Database Now!

Getting to the bottom of subsea repairs: Older pipelines need more attention, and operators need a repair strategy; OTC preview; Offshore production difficult - and crucial
Digital oilfields: Integrated HMI/SCADA systems enable smarter data acquisition; Real-world impact of simulation; Electric actuator technology prospers in production fields
Special report: U.S. natural gas; LNG transport technologies evolve to meet market demand; Understanding new methane regulations; Predictive maintenance for gas pipeline compressors

(copy 5)

click me