Less strain on moving monorail

DISMANTLING and removing a monorail poses severe musculoskeletal risks to workers. A Coal Services Health & Safety Trust-funded study into the task has come up with some simple design and administrative solutions to combat some of that risk.

Angie Tomlinson

The paper, “Participative ergonomics for manual tasks in coal mining”, presented at the 2005 Queensland Mining Industry Health & Safety conference, examined the removal of a monorail. The task was selected because of its routine nature and because removing each monorail rail section involves both large forces and awkward postures.

Awkward postures of the back and shoulders can occur when leaning backwards over the rail to remove the locking pin and chains and when lifting and lowering the rails. In particular, hyperextension and twisting of the spine and

overhead reaching postures are currently required to perform the task as the platform is not directly under the monorail.

Large muscular exertions are required to hammer out the locking pin and to lift, lower and carry the heavy (34kg) rail sections.

The primary concerns raised by each of the three crews which analysed this task were: the large forces required to move the heavy rails, the awkward postures required as the platform is almost always not positioned under the monorail, and the unresolved issue of carrying the rails up to 100m to the out-bye cut-through instead of having a bucket that is more conveniently located.

Following a risk assessment, the work teams presented several design control options including:

Make the platform hydraulically adjustable both in and out and up and down. Being able to vary the position of the platform under the monorail will significantly reduce the

awkward postures involved in the task, while varying the vertical position of the platform will cater for the varying standing heights of the miners and reduce stress on the shoulder by minimising the overhead work performed by the arms. The hydraulic platform could also be used to raise the rails up while removing the chains via a lifting ram with a roller on top that couples to the underside of the rail and is attached to the edge of the platform.

The platform at the in-bye end could be extended to enable the rails to be removed after the second main gate push. This would reduce the time constraints placed on the miners to remove the first rail between the first and second pushes.

A long crowbar with a hook could be used to raise the monorail to remove the chains and lower the rail once the chains are removed, thus reducing the force required to lift

and lower the rails.

Look into purchasing a new locking pin design (eg a split pin) that doesn’t require a forceful blow by a hammer to remove the pin.

If the current pins are retained, a hammer with a longer handle would reduce the force required to remove the pin and also reduce the incidences of hands being pinched against the rails.

Look into the possibility of reducing the weight of the rails by drilling holes in them or alternately purchasing lighter weight rails.

Build a monorail cassette storage bin that travels along the out-bye end of the monorail so that each rail section doesn’t have to be carried back to the cut-through. The cassette will have to carry at least 50 rails, and a full design was developed in the workshop session.

The team also identified some administrative control options:

Training for those involved in moving the storage pods for the rails should be conducted to reduce unnecessary distance that the rails have to be carried.

The dismantling of the monorail task should always be conducted by at least two crew members.

Story based on ‘Participative ergonomics for manual tasks in coal mining’ by Robin Burgess-Limerick, Gary Dennis, Leon Straker, Clare Pollock, Sue Leveritt, and Suzanne Johnson.

More information available from AProf Burgess-Limerick - robin@hms.uq.edu.au