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Ergonomic Dead Man Switch on Blast Nozzles

Description:

TECHNOLOGY AREA(S): Materials 

OBJECTIVE: R&D an ergonomic dead man switch design for use with Hill AFB PMB equipment 

DESCRIPTION: Abrasive blast operators within 576 PSS need an ergonomic replacement for the blast activation dead man switch currently used on plastic media blast (PMB) nozzles for paint removal on F-16, C-130, and A-10 aircraft. Currently, PMB operators activate hoses by squeezing a large dead-man switch affixed to the PMB nozzle. The grip forces required to initiate and maintain trigger activation are 16-lbf and 8-lbf, respectively. Pre-activation and activation tangential grip distances are 3.75-in and 3-in, respectively. PMB operators can be expected to hold these trigger grips in activated position for up to four hours per shift. Due to the poor ergonomic qualities of the current switch, 576 PSS operators experience abnormally high rates of chronic shoulder injuries and carpal-tunnel syndrome (CTS) corrective surgeries costing the Air Force an estimated $340,000 per year in workman’s compensation, operator time off-work, or alternate work assignments. The replacement design must meet OSHA dead man switch requirements and reduce or eliminate the fatigue and injuries associated with the current switches. The design shall meet performance, interface, and form-factor requirements of 576 PSS’s PMB systems. To reduce the risk of CTS and shoulder injuries, the design shall meet or exceed requirements in OSHA Standard 1910.244(b) and its two accompanying interpretations, and MIL-STD-1472G. The maximum allowable activation and maintaining grip pressures shall be 5-lbf and 3-lbf respectively. The design shall be adjustable, to provide ergonomic benefit regardless of the individual operator using it, and shall not exceed 12 oz. in weight. The design shall be equally useable by operators lying prone in F-16 intakes and by users standing up straight. Maximum switch deactivation time shall be 0.3 seconds. The switch shall be designed to mitigate risks to the aircraft being worked on, primarily that of contact damage. The switch shall survive 100 repeated 48-in vertical drops onto concrete in its operational configuration and remain functional for at least 500 hours of cumulative use. The design shall be resistant to un-commanded activation through drops, bumps, or electromagnetic interference (EMI). The design, when engaged and allowing flow of media, shall reliably disengage in 0.5-sec or less to de-activate media flow in user-unconscious, nozzle-drop, and other physical failure scenarios. The design shall interface with 576 PSS’s pneumatically controlled PMB systems, and shall be able to be exchanged from the blasting hose in under 6 minutes using common tools. The design must be self-contained (i.e. no interface to systems other than the user and PMB system), and shall not interfere with the operator’s personal protective equipment (PPE), stands, or equipment. The allowable physical envelope for the design is within 5 inches radially from the blast hose, with at least 2 inches of clearance from the opening of the blast nozzle, and length not to exceed 8 inches. The design shall meet or exceed OSHA requirements for equipment used in Class II Division 1 locations. 

PHASE I: R&D solution that meets the above requirements and conduct preliminary business case analysis (BCA) to determine implementation costs, including a return-on-investment (ROI) calculation that compares anticipated savings to expected costs. Proof-of-concept prototype(s) shall be developed to demonstrate conformance to the requirements. 

PHASE II: Initiate and complete the test plan developed in Phase I. Proof-of-concept prototype(s) shall be refined to installation-ready article and shall undergo testing to verify and validate all requirements. This process may require multiple iterations before a final design is selected. Refine BCA/ROI based on the final design. 

PHASE III: If developed technologies are cost effective, passes verification / validation and qualification testing, then it shall proceed to transitioning and implementation of the technologies. With possible application to other AFSC sites. 

REFERENCES: 

1. OSHA Standard 1910.244(b) – Occupational Safety and Health Standards; 2. MIL-STD-1472G – Human Engineering; 3. OSHA Standard 1926.449 – Safety and Health Regulations for Construction

KEYWORDS: Ergonomic, Bead Blast, Fatigue, Safety, Carpal Tunnel, Chronic Shoulder Injuries, Trigger Grip 

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