Referring to Problem 1.7D,
(a) Sketch a tub hay grinder and label a guarding device, power source, point of operation, and danger zone.
(b) List general methods used to guard known tub grinder hazards.
(c) Write a paragraph explaining the procedure of lockout/tagout for the tractor and tub hay grinder.
(d) Develop a warning sign/label(s) that could be applied to the tub grinder shields (guards) on the tub grinder.
(e) Sketch a device that could be used to "immediately" stop a rotating hammer mill if the tractor PTO is "turned off."
Problem 1.7D
An incident occurred on a cattle ranch that resulted in an injury to the operator of a tub grinder. The tub grinder was being used to grind hay bales. The grinder was powered from a tractor by means of (i) hydraulic fluid pressure (that powered a hydraulic motor that turned the tub) and (ii) a power take off (PTO) shaft that powers a spinning hammer mill that rotates to "grind" the hay bale. The discharge spout of the tub grinder became clogged during operation. The operator exited the cab of the tractor, "turning off" the tractor PTO while leaving the tractor engine running. He walked to the tub grinder spout area, removed pins and opened the tub grinder shields (guards). The operator reached into the unguarded opening and at some point his right hand contacted the still rotating hammer mill of the tub grinder. At issue are (a) whether the tub grinder contained proper warnings, (b) whether the tub grinder hammer mill was properly guarded, and (c) whether the hammer mill should be allowed to "coast down" to a stop, or the hammer mill should stop rotating immediately once the tractor PTO is "turned off." Search the OSHA regulations http://www.osha.gov and specifically review the regulations 29 CFR 1910.212, General requirement for all machines, 29 CFR 1910.147, The control of hazardous energy (lockout/tagout), and 29 CFR 1910.145, Specifications for accident prevention signs and tags. Write several paragraphs explaining how each regulation would apply to a tub grinder.