# Engineering Controls Database

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## Stump Cutter Machine safety – Developing an Operator Presence System

| Problem:                | Stump cutter safety involves many elements of machine design and safe operating practices. Manufacturers and dealerships provide extensive documentation on the proper operation and safe use of stump cutter machines. ANSI Z133.1-2006 requires that stump cutters be equipped with enclosures and guards to reduce the risk of injury. It also states that operators shall keep the enclosures and guards in place when stump cutters are operative [ANSI 2006].                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
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| What this means to you: | In some cases, operators involved with stump cutters have been injured. American Rental Association (ARA) Insurance Services reported in 2007 [ARA 2007] that since January 2000, six claims have involved people injured while using rented stump cutters. Incidents involving stump cutters can result in serious injuries with workers missing multiple days of work.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
| Description of control: | Machine safety is critical for worker safety, because machines have many ways to injure workers.  Many machines have moving parts, sharp edges, and hot surfaces with the potential to cause severe workplace injuries such as crushed fingers or hands, amputations, burns, or blindness. Safeguards are essential for protecting workers from these preventable injuries. Any machine part, function, or process that might cause injury must be safeguarded. When the operation of a machine may result in a contact injury to the operator or others in the vicinity, the hazards must be eliminated or controlled.In 2001, the National Institute for Occupational Safety and Health (NIOSH) became interested in developing a passive operator presence system that did not require the operator to engage a separate handle or switch.  The system was to be designed based on capacitive-sensing components and would automatically detect an operator around a machine and shut down the equipment if the operator entered a danger zone.  NIOSH entered into collaboration with Vermeer Corporation to investigate the possibility of applying capacitive-sensing technology to detect an operator at the controls of a hydraulic stump cutter.  Few hydraulic stump cutters have operator presence systems due, in part, to practically and operator concerns. Such systems could help prevent injuries that can occur when an operator approaches the cutter wheel with the clutch still engaged.Working together, NIOSH and Vermeer designed a capacitive sensor which would be placed inside the control handles, since an operator typically has both hands on the handles while using the machine. Vermeer took the basic technology and developed it into a prototype handle (Photo 1).  The company then incorporated the handle into a working prototype machine (Photo 2).**Photo 1. Prototype handle****Photo 2. Working prototype stump cutter** |
| References:             | ANSI [2006]. Safety requirements for arboricultural operations. New York: American National Standards Institute, Inc. ANSI Z133.1-2006.ARA [2007]. American Rental Association. Yard work accidents are common this time of year: Here are 7 tips to stay safe. [http://landscaping.savvy-cafe.com/yard-work-accidents-are-common-this-time-of-year-%E2%80%93-here-are-7-tips-to-stay-safe-2007-11-29/]. Date accessed: September 2009.Powers JR, Ammons DE, Brand I [2009].  Machine safety – developing an operator presence system. Professional Safety: November 2009/54(11):28–31.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
| NAICS Codes:            | 561730                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
| Keywords:               | capacitive-sensingcapacitive-sensinginjury preventioninjury preventionlandscaping serviceslandscaping servicesmachine safetymachine safetystump cutterstump cutterstump removalstump removaltraumatic injuriestraumatic injuriestree removaltree removal                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |

November 16, 2018
National Institute for Occupational Safety and Health