Ergonomic Exposures And Controls For Production Line Work:
Compressed Gas Cylinder Filling

Description Of Work Tasks

Employees place empty cylinders, with the caps removed, into a manifold rack for filling. A hose is connected to each cylinder by inserting and screwing the hose fitting to the cylinder. After all hoses have been attached, the valve of the cylinder is manually opened, the cylinder is filled, and the valve is closed. After the valve has been closed, the filling hose is unscrewed and then removed, and the cap manually screwed back onto the cylinder. The cylinder is then “walked” to the loading dock for shipment to customers. The walking procedure involves rolling the cylinder on its bottom edge by twisting the cap with one hand, and “kicking” or “rolling” the base with the toe and instep of the foot, which propels it forward. The cylinder is also kept upright by balancing it using the hand that propels it. Two cylinders are generally moved at one time.

EXPOSURES

• Risk of injury is increased as duration of static posture or repetitions of movement are increased.
• Frequent forceful finger exertions with the wrists in a deviated posture are required when opening and closing valves, removing and replacing caps, and attaching or detaching hoses during the filling process.
• Overall muscular fatigue is an issue.
• Prolonged periods of holding the arms in an elevated posture.
• Considerable force is exerted with the fingers and palms of the hands to initiate cylinder movement. Force is also exerted upon the lower leg when contacting the instep of the foot with the base to propel the cylinder forward.
• Forearm rotations and shoulder strength are required to roll and support the cylinder
• Risk of strain or sprain if the cylinder falls

CONTROLS

• Any moves farther than 10 to 15 feet should be performed with mechanical assistance. Purchase or develop a mechanical system that can be used to move cylinders from the filling stations to the dock. Ideas include using hand carts or hand trucks to move the cylinders over longer distances. An overhead trolley system might also be feasible.
• Provide a powered tool that can be used to remove and tighten cylinder caps as well as open and close cylinder valves. It should be set with a torque-sensitive sensor such that valves are not opened or closed with such force that they are damaged. Use of a tool should be less damaging to valves since they could always be closed to the same tightness and would not be subject to operator variability.
• Initially loosen the valve cap with one hand, then use both hands parallel to each other with the cap in between to rotate the cap off and on.
• Frequent rest breaks may be warranted.
• Hose hook-up fixtures should be designed with large handle adapters for hose end fittings instead of using a hand wrench flat fitting.
• Determine the number of turns needed to fully open the cylinder for proper filling. The hazard of this task could be reduced if several turns of the valve handle were eliminated since the hazard of a task is partially determined by the number of repetitions performed.
• Place caps on cylinders prior to moving them to the loading racks.
• Ensure that preventive maintenance is performed on the caps and cylinder neck threads such that the force required to place and secure caps is kept to the absolute minimum.
• When manually rolling cylinders, employees should be instructed to let cylinders fall if they lose their balance instead of trying to catch a falling cylinder and risking a back injury.
• Jobs should be classified by the nature and extent of exertion and a rotation schedule should be created that allows for as much variation as possible in the distribution and frequency of musculoskeletal activity.
• Work-rest schedules should be developed and enforced. Generally, a minimum of a 15-minute rest break at least every two hours is recommended.
• Employees should understand the nature of the hazard of the task they perform such that they can attempt to perform the task in the safest possible manner. The wrist should remain in a straight neutral posture most of the time and the elbow should remain close to the torso.
• Cylinders should only be “rolled” if employee is wearing metatarsal-guarded shoes.

XL Environmental • Risk Control Division • 520 Eagleview Boulevard, PO Box 636, Exton, PA 19341 • Phone: 800-327-1414 • Fax: 610-458-7285 • xlenvironmental.com

XL Environmental is a division of XL Specialty Insurance Company.