Safety in compressed air abrasive blasting

Compressed air blast pots are pressure vessels and, as such, demand high manufacturing and maintenance standards. They must meet design, manufacturing and testing requirements under ASME or ASTM standards and keep control tests up to date at the corresponding intervals. Failing to meet these standards not only breaches current regulations but also exposes personnel to a high health risk.

Any deformation or mechanical work on the vessel voids its manufacturing and testing certification. For that reason, pressure vessels must never:

• Be struck, dented or ground on any of their components.
• Have parts re-welded or new elements added.
• Be handled carelessly during transport: a minor drop or knock can cause irreparable damage and dangerous failures during pressurisation.

It is also essential to use proper covers to prevent severe corrosion when the equipment is left outdoors on site.

The Dead-Man system is a primary safety device: it cuts off the flow of air and abrasive the moment the operator releases the trigger or loses control of the hose. This prevents exposure to the abrasive jet, which can exceed 300 km/h (186 mph).
A dangerous and common practice is to disable the system with a by-pass on the control hoses to gain freedom of hand movement at the expense of safety. It must be prevented through proper training and strict, ongoing control to ensure the Dead-Man works correctly.

On the control system power supply:

• Always use 12 or 24 V, without exception. Never use mains voltage.
• Pay special attention in damp areas or water puddles, especially where extension couplings are used.
• Maintain the system per its schedule: it works reliably only with proper maintenance.

Before unloading the equipment, inspect the site and identify, repair or mark every risk element —obstacles, pits, electrical boxes—, which prevents accidents both during assembly and throughout the job. Assembly begins only once the area is clear and organised.

The blast pot is the centre of the installation: the other equipment is arranged around it, so its location is planned in advance. Small pots (up to 0.5 m³) are easy to move; higher-capacity units usually require a fixed installation.

During assembly:
• Carefully check the compressor, the power source for the whole installation: it must be in perfect condition and located away from the dust zone and, if possible, upwind.
• Verify that collector tanks and filtering elements have current certificates and tests.
• Fence off the hose run —between compressor, pot and blast operator— to keep vehicles from driving over them.
• Link hoses joined by couplings with safety cables, which prevent hose whip if a coupling fails.
• Keep the blasting area free of combustible or flammable materials: the process generates sparks with a risk of fire or explosion.
• Run a second check of hoses, couplings and nozzles when deploying the abrasive line (the first check is done before loading the equipment).

Many incidents in compressed air abrasive blasting originate in failures of hoses, couplings or nozzles that, when worn or detached, can project abrasive at high speed toward areas where people pass. Periodic inspection of these elements is therefore one of the most important safety measures. Use only hoses, couplings and nozzles specifically designed and manufactured for abrasive work.

Hoses
• Make sure the inner lining is top-quality virgin rubber and that the hose is rated to dissipate static build-up.
• Check that it has no soft spots or excessive outer wear.
• Continuously inspect tight bends and marks from crushing by vehicles or equipment: these are the most common failure points.
• Replace the rubber rings daily, at the end of each shift.

Couplings
• Use external-clamp couplings with special screws that do not pierce the hose's inner tube.
• Before fitting, cut the hose end square so it seats against the coupling's internal backing; CYM Materiales recommends applying sealant to that end.
• Fit the coupling so the hose is firmly clamped, and use couplings and nozzles matched to the hose diameter.
• Always install the safety lock fully engaged and link couplings in pairs, adding safety cables at each joint to prevent hose whip if a coupling breaks or comes loose.

Nozzles
• The nozzle consists of a hard-metal core, an elastic jacket and an anchoring element; threaded anchoring is the safest system.
• Check that it is firmly screwed to the coupling before use, and periodically inspect the thread on nozzles and couplings: replace immediately at any sign of wear or cracking.
• Use the correct rubber ring, which must seat perfectly against the hose end; clean off all dirt or abrasive before screwing on.
• Replace the nozzle when the tungsten or boron carbide core has enlarged to the equivalent of the next nozzle size up.
• Avoid striking the nozzle's outer guard, which can cause internal damage.

Before any maintenance task, fully depressurise the equipment. Protective equipment is mandatory during depressurisation, as the equipment expels small abrasive particles together with the air.

• Periodically check the components under the highest pressure and wear: if they fracture or puncture, they can project abrasive toward the sides, where personnel are usually present.
• Inspect all wear elements daily and replace them at the first sign of wear.
• Never operate broken or fractured equipment, and never expose hands or body to direct contact with the abrasive jet.

The operator must always have suitable clothing and protective equipment. The personal protective equipment in detail —helmet, eye and hearing protection, clothing and breathing air— is covered in our dedicated article.