Foundries Sheet No 3 - HSE information sheet

Introduction

This information sheet is one of four prepared by the Foundries Industry Advisory Committee's Working Group on foundry machinery guarding. It is intended that the four sheets be read together. Essential introductory information is given on sheet 2.

Moulding machinery - Individual machines

Process

Individual moulding machines ('jolt squeeze' machines) use hydraulic or pneumatic power to consolidate and squeeze sand contained in moulding boxes. Different designs of machines have common elements:

• Compression
• Jolting motion
• Movement of head/machine
• Vacuum facility
• Explosion facility

Hazards and remedies

1. Trapping when the heads close account for the bulk of accidents which occur at individual machines. Interlocking guards are effective in preventing accidents as closing occurs and should be used on automatic and semi-automatic machines. When movement is manually initiated then a simple but substantial rubber skirt will suffice to prevent access.
2. Trapping can also occur from lateral movement of the head or rotation of the machine body. Interlocking perimeter guards will be necessary in this case.
3. Noise from vibration and jolting mechanisms can be considerable. Rotary valves significantly reduce noise from this source and can be retro-fitted.
4. Although silica is present, sand is usually used in a moist form for this process and, provided good housekeeping standards are maintained, inhalation of silica should not be a problem.
5. Care should be taken in devising work methods associated with these machines to avoid unnecessary lifting and awkward postures.

Moulding machinery - Automatic moulding machines

These machines are usually incorporated in fully automated lines with the following stations:

1. Sand box delivery;
2. Mould box delivery - not flaskless mould process;
3. Pattern section;
4. Core setting facility - manual or automatic;
5. Box closing station;
6. Moulds/box conveyance;
7. Metal pouring - manual or automatic;
8. Cooling line;
9. Knock-out.

Hazards

1. Trapping: All the hazards associated with the closing and rotating parts of individual elements of the line are still present and in addition further hazards arise from movement of transfer mechanisms which link the different sections.
   • Guarding should be achieved by perimeter fencing provided with interlocking access in the form of trapped key systems. This feature is essential for the safety of any person needing access to a part of the line since reliance by operators on visual contact with control stations is not in itself sufficient.
   • Where frequent access may be required for adjustment purposes, then close-fitting fixed guarding with the actual adjuster or control located outside the guard reduces the need for reliance on interlocking devices.
   • All interlocking devices should operate so as to remove any residual energy from pneumatic or hydraulic systems or other sources of stored energy.

   Example: A machine operator received a broken shoulder while clearing sand from a core belting machine. The machine started up without warning; there was no facility for dumping residual pneumatic power while the machine was isolated.

   Manual core setting facilities: These are often incorporated into automatic lines. The guard must be closed before the machine indexes. Automatic guards should be fitted with sensitive edges, or photo-electric systems should be used to avoid core setters becoming trapped by transfer movements.

   Consideration should also be given to the means of access provided to different parts of the line, eg via bridges, walkways.

1. Noise: Acoustic booths/control rooms should be an integral part of an automatic line.
2. Heat/molten metal: Where possible, protective screens should be provided to protect operators from these hazards. Recourse to suitable personal protective equipment should be a last resort.
3. Dust and fume: Local exhaust ventilation (LEV) will be required at pouring, cooling and knockout stages to control exposure to dust and fume. Assessments carried out under regulation 6 of COSHH will determine the level of control required to ensure that occupational exposure standards are not exceeded.

Core making systems

The process

A metered amount of sand mixed with resin and catalyst is blown or shot into a heated core box. The box is in two or more parts and is closed under pressure and maintained for a prescribed period until the core is cured. The pressure is then released and the core is removed mechanically by a core extraction system, or manually. In some cases a rise and fall conveyor belt will take the core away from the machine.

Hazards

1. Closing platens: The sections of the box are closed hydraulically or pneumatically under high forces. Access to these moving parts should be prevented.

   Even when machines purport to be fully automatic, frequent intervention may be required by the operator, eg to clear sand blockages; to clean dies; to make adjustments.

   The standard of guarding should reflect the need for intervening at any particular machine.

   Controls fitted at these machines will usually offer a variety of modes of operations:

   • Fully automatic: each element in the work cycle triggers the next.
   • Semi-automatic: each element follows in sequence but has to be initiated by the operator.
   • Manual: each element must be initiated by the operator and in a random sequence (eg backward and forward movement of the platens during setting processes).

   Setting: Particular attention should be paid to how setting is done, and to what degree movement is needed without guards in place, and how such movement is to be achieved. In addition to the trap between the closing platens, the possibility of entrapment between the moving and fixed parts of the machine also needs to be considered.

2. Heat: Contact with hot portions of the box will always be possible during cleaning, core removal and box removal. Suitable protective clothes should be worn. Arrangements should be made to segregate stored boxes which have been removed from the machine and which are still hot.
3. Fire: Highly flammable chemicals (eg amines) can lead to serious fires since they represent a ready fuel for sources of ignition. Maintenance of metering systems is important. Suitable fire precautions should be taken.
4. Chemicals: Contact with hazardous chemicals (eg certain resins and catalysts) should be avoided. Particular care is required during maintenance activities to ensure that systems are drained/purged before work begins.
5. Fumes: Fumes and gases will be evolved during the process. Local exhaust ventilation will be required to ensure compliance with COSHH and EPA requirements. Mechanical guarding requirements usually result in the machine being in an enclosure which makes the introduction of the LEV relatively easy.
6. Access: Sand metering/blowing/heating equipment is usually located on top of the machine cabinet. Good access and safe working places will need to be provided for any work requiring access to this equipment.
7. Noise: Noise mainly arises from pneumatic exhaust valves which can easily be fitted with silencers.

Useful reading and further information

See sheet 2.

This information sheet contains notes on good practice which are not compulsory but which you may find helpful in considering what you need to do.

This publication may be freely reproduced, except for advertising, endorsement or commercial purposes. The information it contains is current at 9/95. Please acknowledge the source as HSE.

Printed and published by HSE 9/95 NIS/11/03 C40

Added to the web site 24/4/98