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Focusing on the importance of chamber guards, this single-page guidance is intended for all operators, supervisors and quarry managers. Produced by the Plant Sub-Committee of the Quarries National Joint Advisory Committee (QNJAC), the guidance addresses the BS EN Standard; the problems faced; and ways of reducing the risk of rock ejection. Particular emphasis is put on the necessity to REPLACE guards after they have been raised, removed or repaired

With mobile processing plant being employed more frequently within the extractives industry, particularly within crushing operations, QNJAC would like to remind all operators, supervisors and quarry managers of the importance of chamber guards, predominantly on mobile jaw crushers.

The Standard

BS EN 953:1997+A1:2009 specifies the general requirements for the design and construction of both fixed and removable machine guards that protect persons from mechanical hazards.

Problems faced

The main purpose of chamber guards is two fold; not only do they prevent anyone from falling from the access platform into the crushing chamber, they also prevent material from being ejected from the crusher.


Generally, chamber guards are manufactured and supplied as standard. However, these are frequently removed and not replaced or crushers are operated with the guard in the raised position.

Reducing the risks

Remember – always replace guards whenever they have been removed or raised, for whatever reason.

A safe system of work should be in place and made clear to all operators who may be required to clear blockages or remove/replace guards.

If appropriate, larger guards can be fabricated with ram opening operations to reduce manual handling issues. This will also reduce the chances of the guard not being replaced.

Hydraulic arms can then be used to deal with any blockage, eliminating the need for operatives to enter any ‘danger areas’.


Other types of crushers should have their own arrangements for controlling risk from rock ejection.


'Protect persons from mechanical hazards’