SAFE WORKING PROCEDURE FOR ABRASIVE BLASTING

OBJECTIVE To define and promote safe working procedures for abrasive blasting operations, which must be adhered to by personnel and contractors.

1 INTRODUCTION 1.1 Abrasive blasting involves the utilisation of hand-held or automatic equipment

which directs a blast of abrasive material (wet or dry) against a surface in order to clean the surface, remove burrs and excess surface material or develop a surface finish.

1.2 Common abrasives vary from metal shot and clipped wire to non-metallic

abrasives such as aluminium oxide, garnet, glass beads, metallic slag, plastic media, silicon carbide, crushed pips and most commonly mineral slag.

1.3 The two types of abrasive air blast cleaning systems to be considered in this

procedure are: 1.3.1 Portable blast cleaning machines consisting of a source of compressed air in the

7 bar range, a pressure vessel or container to contain the abrasive, a metering device to control the air-to-abrasive ratio and flow, a flexible hose to deliver the abrasive, a hand-held nozzle to direct the abrasive onto the blasting surface, and fitted with the approved safety devises.

1.3.2 Manual units within blast cleaning rooms. These units are similar to the portable

units except that the operation is confined to a chamber especially designed for the purpose.

2 HAZARDS Hazards associated with abrasive blasting can be divided into two classifications,

namely safety hazards and health hazards.

2.1 Safety hazards

2.1.1 Poor housekeeping and mechanical hazards These include;

Unsafe equipment due to mechanical wear, Incorrectly fitted units, General negligence, i.e. leaving obstructions in blast room doorways.

2.1.2 Personal protective equipment hazards These may result from the incorrect use or lack of use of personal protective

equipment or the use of inadequate equipment.

List of safety equipment:- Air fed Blast Helmet, including spare visors for the helmet, Ear Muffs / plugs Operators Breathing Equipment for cleaner air, Blast apron (ankle length), Complete blast suit, Leather gloves, Safety shoes, N.B. The pot operators should also be wearing appropriate safety clothing and dust masks

2.2 Health hazards 2.2.1 The principal hazards associated with abrasive blasting are the vast amount of

airborne dust usually generated during operation. The dust originates from broken-down abrasives as well as pulverised surface

coating and abraded material from the object being blasted. The health hazard is related to the concentration and particle size of the dust as

well as its composition. Remembering differing blasting media have differing compositions and therefore differing health risks.

As far as composition is concerned the greatest hazard lies with dusts containing

silica (quartz). The inhalation of this dust over an extended period causes the serious, disabling lung disease known as silicosis. The most common source of silica dust is the use of silica-containing materials such as silica sand as an abrasive. Other forms of media can carry other types toxicants, be aware of the risks and prepare accordingly.

Dust originating from the component being blasted can also pose a health

hazard. Metal dusts, such as lead, cadmium and manganese are extremely toxic upon inhalation.

Paint coatings may also contain lead or chromium pigments which may also

present a health hazard if inhaled. 2.2.2 A second health hazard connected with abrasive blasting is that of excessive

noise. Noise originates from the abrasive blast discharge nozzle as well as from the impact of the abrasive on the surface being cleaned. Compressors may also contribute to high noise levels.

3 CONTROL MEASURES

3.1 Safety hazards 3.1.1 Hose lines which are subject to deterioration from abrasive materials must be

examined daily for any signs of mechanical and wear damage. 3.1.2 All metal pipes, lines, valves, pressure vessels and other parts should be

periodically tested and inspected for internal deterioration. Proof of statutory inspections (pressure tests etc.) must be available for perusal should the owner be requested to do so.

3.1.3 In a blast-cleaning chamber the ventilation and exhaust system, as well as the

filter system, should be inspected regularly to ensure correct functioning. 3.1.4 The filter unit should be cleaned regularly. This will be dependant on the type of

unit being used. If not extraction filters this is referring to OBE filter.

3.1.5 In order to reduce the possibility of static electricity discharges all hose lines should be manufactured from an approved rubber anti-static material.

3.1.6 Blast operators and assistants must wear personal protective equipment

whenever performing blasting work. This equipment should consist of the following: Heavy canvas or leather gloves, gauntlets and leggings where appropriate, heavy canvas or leather aprons, safety shoes and suitable eye protection as well as ear muffs.

3.1.7 For personal health reasons, respiratory protective equipment should be

assigned to individual workers for their exclusive use. 3.1.8 Respirators should be checked routinely to ensure safe and effective operation. 3.1.9 All manual abrasive blasting units should be equipped with positive abrasive shut

off or deadman's controls which cannot be activated by dropping the nozzle or hose.

3.1.9 The air pressure should not exceed the manufactures specifications

3.2 Other Safety and Health hazards 3.2.1 Since silica dust poses the most serious hazard, the use of abrasives containing

free silica should preferably be avoided wherever possible. 3.2.2 Whenever possible blasting operations being carried out with a portable unit

should be isolated from other personnel in the area. This can be done by erecting suitable screens or tarpaulins where practicable.

3.2.3 If abrasive is to be recycled it is preferable that some method be available for

separating the fines before re-use. This will reduce the amount of dust produced during blasting.

3.2.4 Blast chambers shall be cleaned of dust and waste material daily to prevent dust

build up. Vacuum or wet methods of dust removal are preferred. 3.2.5 All spent abrasive media must be captured and removed to the approved

dumping site as soon as possible after blasting operations are completed.