Hydroblasting vs high-pressure washing: pressures, uses and what to ask a South African contractor

No. Both use water under pressure, but hydroblasting works at far higher pressure: one maker's industrial pressure washers deliver 150 to 250 bar, while a local water jetting supplier's hydroblasting units start at 1,000 bar and run to 2,800 bar, with flows of 100 to 150 litres a minute and motors of 190 to 260 kW.^[12][11][10]

Sources:^{[12][10][11][9]}

In South Africa, a hydroblasting job falls under the general duties of the Occupational Health and Safety Act and, when anyone enters a tank, vessel or pipe that counts as a confined space, under regulation 5 of the General Safety Regulations.^[1][2]

Under section 8(2)(d) of the Act, the employer must, as far as is reasonably practicable, establish "what hazards to the health or safety of persons are attached to any work which is performed", decide the precautionary measures and "provide the necessary means to apply" them.^[1]

A hydroblasting contractor is a mandatary of the plant that hires it, and section 37(2) extends to the client the presumption that it committed the contractor's offences, "except if the parties have agreed in writing to the arrangements and procedures between them to ensure compliance by the mandatary" with the Act.^[1]

The General Safety Regulations define a confined space to include "any chamber, tunnel, pipe, pit, sewer, container, valve, pump, sump" in which a dangerous liquid or a dangerous concentration of gas, vapour, dust or fumes may be present (regulation 1), so a tank, vessel or pipe that held process fluids can qualify.^[2]

Regulation 5(1) allows entry only after the air "has been tested and evaluated by a person who is competent to pronounce on the safety thereof, and who has certified in writing" that the space is safe and will remain safe for the work.^[2]

Where that cannot be done and the space holds, or is likely to hold, a hazardous gas, vapour, dust or fumes or less than 20 per cent oxygen, it must be purged and ventilated and isolated from pipes and ducts "by means of effective blanking other than the shutting or locking of a valve or a cock", or valves must be chained and padlocked where blanking is not practicable (regulation 5(2)).^[2]

In South Africa, every holder of the scale and sludge that hydroblasting removes must, within the holder's power, take "all reasonable measures" to manage it so that it "does not endanger health or the environment", under section 16(1) of the National Environmental Management: Waste Act.^[3]

The Waste Classification and Management Regulations require a waste generator to have its waste classified within 180 days of generation (regulation 4(2)), and transporters and waste managers may not accept unclassified waste unless the regulations exempt it (regulation 6(1)).^[4][5]

For waste classified as hazardous, the generator completes a waste manifest for each consignment sent to a waste manager, and the transporter may not accept the load unless the manifest goes with it (regulation 11(2) and (4)).^[4][5]

Run-off to a sewer falls under the municipality's by-law: in Cape Town, for example, the City may permit industrial effluent into the sewer on conditions, and no one may "increase or vary the quantity, nature, content or composition" of effluent discharged without its written permission (section 3(3) and (4)).^[6]

1. Equipment to be cleaned (exchanger bundle, tank, pipe run, cooling tower), with tube count, diameter and length, straight or U-tubes, and the deposit (scale, slag or other build-up) and how hard and adherent it is.^[10][11]
2. Bundles pulled and cleaned on a wash pad, or cleaned in place, and the tube orientation.^[10]
3. Pressure washing (a 250-bar washer, for example) or hydroblasting (a 1,000-bar jetting unit), with the working pressure in bar and flow in litres a minute if known, or the result needed.^[12][11]
4. Manual or hands-free (semi-automated or automated) tooling, priced as separate options.^[10]
5. Water on site: the supply point and its flow, and whether it is potable, brackish or recycled.^[11]
6. Tanks or vessels that need entry, who will test and certify the atmosphere in writing, and how lines will be blanked.^[2]
7. Operator training records against SAQA unit standards 377722, 377761 or 377740, plus the contractor's risk assessment, barricading plan and PPE list.^[7][8][9]
8. Waste: who classifies the sludge and wash water, who completes the waste manifest, which facility receives it, and whether the municipality allows discharge to sewer.^[4][6]
9. Shutdown dates the work must fit, and a written agreement on safety arrangements under section 37(2) of the OHS Act.^[11][1]