NCCER Hydroblasting cheat sheet

At 10,000 psi, water jet impact pressure can exceed 30,000 psi; skin penetration occurs at pressures as low as 100 psi, causing injection injuries requiring immediate medical attention.

Water jet velocity (ft/s) ≈ 12.4 × √(pressure in psi / fluid density in lb/ft³); for water at 10,000 psi, velocity ≈ 1,240 ft/s.

Reaction force (lbf) on a straight nozzle ≈ 0.0526 × flow (gpm) × √(pressure in psi); for 10 gpm at 10,000 psi, reaction ≈ 52.6 lbf.

Noise levels often exceed 100 dBA at the nozzle; use dual hearing protection (earplugs + earmuffs) when levels exceed 100 dBA.

Minimum PPE: impact-rated face shield over safety glasses, hard hat, heavy-duty waterproof gloves, steel-toe boots, and waterproof suit; never wear loose clothing near rotating equipment.

Use a 4:1 safety factor for whip checks and restraints; inspect hoses for cuts, bulges, or exposed wire before each use, and tag defective hoses out of service.

Never point a lance at anyone; treat all hoses as pressurized until the pump is locked out and pressure is bled to zero.

Confined space entry requires atmospheric testing (O2 19.5–23.5%, LEL <10%, H2S <10 ppm, CO <35 ppm) and a standby attendant with retrieval system.

Triplex plunger pumps are rated by flow (gpm) and pressure (psi); brake horsepower (bhp) ≈ (gpm × psi) / 1714 × pump efficiency (typically 0.85–0.95).

Nozzle orifice size is designated by a number: size = flow (gpm) at 4,000 psi; flow at other pressures = size × √(pressure/4000).

Fan nozzles produce a flat spray pattern for surface cleaning; rotating nozzles (rotary or turbo) increase impact for pipe and tube cleaning.

High-pressure hoses are rated by burst pressure (typically 4:1 over working pressure); minimum bend radius and temperature limits are marked on the hose.

Accumulators dampen pressure pulsations and protect the pump; precharge pressure is typically 60–80% of operating pressure.

Safety relief valves must be set at or below the pump's rated working pressure and tested regularly; never plug or disable a relief valve.

Foot pedal or remote control valves allow the operator to depressurize the lance instantly; deadman controls are required for safe operation.

Before start-up: confirm all connections are tight, hoses are restrained, relief valve is functional, and all personnel are clear of the nozzle path.

Start the pump at low pressure, then gradually increase to working pressure while monitoring gauges and listening for cavitation or knocking.

Use a lance with a minimum length of 4 feet for hand-held operations; keep both hands on the lance and maintain a stable stance.

When cleaning pipes or tubes, use a back-out or rotating nozzle and control the rate of insertion; never exceed the hose manufacturer's recommended pull force.

Shutdown sequence: reduce pressure to zero, stop pump, lock out/tag out, bleed residual pressure, and secure the lance before disconnecting hoses.

In cold weather, drain hoses and pump after use to prevent freezing; store hoses coiled at a diameter larger than the minimum bend radius.

Communication: use hand signals or radios; the pump operator must maintain visual contact with the nozzle operator or have a dedicated signal person.

Water jet cleaning removes coatings, scale, and debris; surface profile depends on pressure, standoff distance, and traverse rate.

For concrete removal, pressures of 10,000–20,000 psi are typical; for paint removal, 3,000–10,000 psi may suffice depending on coating adhesion.

Standoff distance: closer distance increases impact but reduces coverage; typical standoff is 6–12 inches for fan nozzles.

Traverse rate: slower movement increases cleaning but may damage substrate; test on a small area to determine optimal rate.

Use fan nozzles for broad surfaces and rotating nozzles for pipes, tubes, and heat exchanger bundles.

After cleaning, inspect surface for remaining coating or damage; use a profile gauge or visual comparator to verify cleanliness.

Wastewater from hydroblasting may contain contaminants; contain and dispose of according to environmental regulations.

Daily inspection: check hoses for cuts, bulges, or abrasion; check nozzles for wear or blockage; inspect couplings and fittings for leaks.

Pump maintenance: check oil level and condition, packing or plunger wear, and valve condition; change oil per manufacturer's interval.

Nozzle wear reduces impact; replace nozzles when flow increases more than 10% above rated or spray pattern becomes uneven.

Common troubleshooting: low pressure-check relief valve, worn nozzle, or pump internal leak; pulsation-check accumulator precharge or valve wear.

Hose failure signs: pinhole leaks, bulging, or exposed wire; remove from service immediately and tag.

Record inspections and maintenance in a log; include date, equipment ID, findings, and corrective actions.