Waterblasting and 'The Hierarchy of Safety'

When it comes to waterblasting safety, PPE should be your last line of defense.

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Waterblasting is dangerous work with several inherent risks. The best way to keep workers safe is to put as many obstacles as possible between the danger and the worker, according to Gary Toothe, training manager for Federal Signal’s Environmental Solutions Group. He calls it the hierarchy of safety.

“If an accident is going to happen, it has to make it through all my layers of safety instead of just one,” says Toothe. After all, there is usually a confluence of conditions that happens at just the right time that turns an event into an accident or a close call into an injury. “You want to put in as many safety components as possible, all working together. The higher up you are on the hierarchy, the safer you are.”

The Hierarchy of Safety

1. Elimination or substitution

Waterblasting is not always the best answer. There may be alternatives that are safer, such as chemical cleaning or the new robotic systems. “A lot of people are coming out with automated waterblasting systems that eliminate the human element,” he says, noting that Dow Chemical now requires hands-free waterblasting and BASF will require it later this year.

2. Engineering controls

Anti-withdrawal and anti-reversal devices, trigger locks and rupture discs serve as mechanical barriers from the risk. “Engineering controls take the danger out of the system and don’t rely on the individual,” says Toothe. But they can be bypassed or disabled. “Nothing is foolproof to a sufficiently talented fool.”

Even when properly used, such controls still may not be enough. “I know of an incident where a guy was cleaning hardened polymer out of a line,” says Toothe. “He had the valve properly locked out, but unbeknownst to him, the valve was leaking. When he broke through the hardened polymer he got to the really hot polymer and there was a steam explosion.”

The worker suffered third-degree burns down his back from steam and molten plastic. That’s why Toothe recommends going beyond lockout/tagout requirements and using best practices like double blocked (lockout the valve and the next one upstream), block and bleed (lockout both valves and bleed whatever is left in the line), or blind (a metal sheet that physically blocks flow through the pipe).

3. Warnings

“Pressure-relief devices and pressure gauges provide a warning and allow reaction time to fix the problem,” Toothe says. “Proper barricades and permits warn you about the dangers so you can react and prevent danger.”

Toothe stresses that there is no set distance for barricades. “The proper distance is where the water no longer presents a danger. You have to calculate pressure and flow to see where that is. If I can’t use distance for a proper barricade, I have to put up a barrier to make sure the energized water or any debris doesn’t exit the area.”

4. Training and administrative controls

“Training for both knowledge and skills is absolutely required before anyone puts something that can kill them into their hands,” says Toothe.

Additionally, administrative controls such as company policies and the WaterJet Technology Association recommended practices empower workers to take charge of their own safety.

5. Personal protective equipment (PPE)

Protective suits, safety shrouds and body protection serve as a temporary obstruction between the worker and the hazard. While readily available and cost-effective, PPE won’t always prevent injury. “It should never be your first line of defense,” says Toothe. “It does not eliminate the danger.”

Safety, he stresses, is a team sport. “Everybody has to be involved in creating standard operating procedures, hazard analysis, checklists, understanding the permits and doing the pre-operational equipment inspections. They are the ones at risk if they don’t.”


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