This is a story of materials designed to be destroyed versus supersonic jets. Water jetting has advanced rapidly in the last four decades, and the design and use of personal protective equipment (PPE) has had to change significantly to keep up with developments.
Ultra high pressure water jetting (UHP) systems can now operate at 3,000 bar (43,500psi) and above. New robotic (semi-automated) systems allow water jetting to be carried out more safely and in hostile or constrained environments, contributing to a greater number of applications for the technology.
Both high pressure water jetting (HPWJ) and UHP jetting are essential maintenance processes in the oil and gas exploration and petrochemical. Arguably, these industries, in their modern form, could not exist without them.
Water jetting is used to clean a huge range of pipes and tanks, including sewer systems. It removes coatings and prepares surfaces for new ones. It is ideal for cleaning the hulls of ships. Combined with abrasives, it is used for cutting metals. Hydrodemolition is often the safest and quickest method for removing or preparing concrete.
It stands to reason that systems needed to protect operatives and others during water jetting have also had to advance, and that includes the use of personal protective equipment (PPE).
However, as with other high risk processes, PPE must always be seen as a last line of defence. Codes of Practice developed by the Water Jetting Association, a member organisation for the water jetting industry based in the UK, state that systems of work should seek to eliminate or reduce to ‘acceptable levels’ risks associated with water jetting and that use of PPE should be a ‘last resort’.
Water jetting risks and hazards
Water jetting can be carried out with hand-held lances, flexible lances or with robotic semi-automated systems, which allow operatives to stand away from the water jet and so, in many respects, improve safety.
PPE is used to reduce the many different risks and hazards associated with all these systems of work. These include:
- High pressure fluid injection – the puncturing of the skin by water jets
- Physical trauma from the force of an uncontrolled water jet or water jetting equipment striking the body
- Toxic material coming into contact with the skin, eyes or ears
- Inhalation, through the nose or mouth, or ingestion of toxic materials either in the form of particles, fluids or aerosols
Of these, high pressure fluid injection of water is, perhaps, the injury most commonly associated with water jetting. Water at 7 bar of pressure, or 100psi, has the potential to puncture the skin. Water from a tap, when put under additional pressure with a thumb, can cause a serious eye injury.
Consider, then, that UHP water jets are leaving nozzles at over twice the speed of sound, or Mach 2, and the challenges in protecting operatives against them becomes significant. A WJA study carried out by a team of eminent trauma physicians, and published in the European Journal of Trauma and Emergency Surgery in 2019, found that the two most common causes of serious injury or deaths associated with water jetting were high pressure fluid injection injury and trauma, as described above.
Fluid injection injuries carry with it a specific set of hazards. Particles and chemicals, some potentially toxic, can be carried into the body, increasing the risk of infection. The injury may not be properly identified or taken seriously straight away, because the entry point is usually small. As part of the emergency medical response, water needs to be drained from the 26 body, and the wound carefully cleaned. This can be overlooked.
The study has led to the development of far-reaching new water jetting health and safety guidelines that, for the first time, provide clear and precise step by step advice on how first responders and emergency doctors should treat fluid injection injuries to reduce fatalities and significant long-term injury and disability.
The guidelines are now incorporated in the newly-revised version of the WJA’s Code of Conduct for HPWJ and UHPWJ – the Blue Code – published in 2021. Another key issue for water jetting PPE is the risk associated with actually using it, largely related to thermal stress. This is a particular concern for water jetting in hot and humid climates, for example in the Middle East and Africa.
“high pressure fluid injection of water is, perhaps, the injury most commonly associated with water jetting”
Types of water jetting PPE
Water jetting PPE falls into two main types. One uses interlocking plates, not dissimilar to body armour once worn by medieval knights, to form a tough barrier against water jets.
The other uses a multi-layered system of sophisticated textiles, prepared in woven and needle felt forms, that together provide an effective barrier against water jets.
All water jetting PPE systems make use of these sophisticated textiles, also used in police and military body armour. For water jetting, key characteristics include:
- Water resistance – involving water striking an operative’s suit with very high force and in potentially large volumes
- Strength – the PPE must be able to withstand the force of a water jet and being struck by particles, small and large, dislodged by the process
- Ability to take treatment – to provide other characteristics, such as resistance to toxic chemicals
Water jetting PPE is a modular system that fits together to provide protection as a whole, depending on the type of water jetting being done and the specific nature of the work. For example, there may be an apron to protect the body, gaiters for legs different types of helmets and neck guards.
The WJA makes clear, in its Codes of Practice, that these elements must be considered as an ensemble, with a clear understanding of how they work together to minimise risk.
Water jetting PPE development
Development of the textiles and materials and the PPE systems of which they form a part, are extremely costly.
A key trigger that has justified the investment, said Per-Arne Andersson at manufacturer TST in Sweden, was the introduction in 1995 of the CE Mark, short for Conformité Européenne.
This is an administrative marking that indicates conformity with health, safety, and environmental protection standards for products sold within the European Economic Area.
Per-Arne Andersson explained: “The CE mark system required PPE to be manufactured to specified standards for the first time. Before 1995, water jetting technology had raced ahead of PPE development. Afterwards, there was a process that allowed PPE capability to catch up, with rapid innovations in material design. The CE Mark gave manufacturers who invested in research and development a commercial advantage.”
Another game changer in the UK, which has influenced the use of PPE in other territories, was the release by UK health and safety agency the Health and Safety Executive (HSE) in 2002 of advice on the use of protective footwear and clothing when carrying out UHPWJ.
The advice, related specifically to pressures above 1,700 bar (24,650psi) with typical flowrates of 20 litres/min (4.5 UK gallons/min), was developed in conjunction with the WJA. It identified the PPE that should be worn and how HSE inspectors should ensure compliance with the advice.
“water jetting PPE may include an apron to protect the body, gaiters for legs different types of helmets and neck guards”
Steve Williams, director of a WJAregistered training provider that delivers training in the Middle East, and a member of the WJA’s Training and Safety Committee, said: “From that moment, there was clarity on what the HSE expected to see with specific criteria. The advice was aligned with the WJA’s Blue Code, and because the WJA’s standards are widely recognised in the Middle East, it has significantly influenced practice in that region as well.”
Key to the success of modern water jetting PPE has been the development of highly sophisticated man-made materials, such as Dyneema and Kevlar. They are many times stronger than steel but much lighter. Ironically, the material’s success depends on its ability to fail.
“The key objective is that you want the material to be destroyed by the water jet,” says Per-Arne Andersson. “If the water jet can cut through the material it won’t work. Instead, the fibres are damaged in a controlled way, a process that rapidly dissipates the force of the jet, preventing it from getting through to the operative’s skin.”
Key PPE protection areas
It is useful to consider which areas of the body are most at risk from water jetting injury. These are the foot, lower leg and hands.
A hand-held water jetting lance should not be short enough for an operative to position the nozzle over the foot. However, where this is not the case, the risk of foot swipe injuries increases.
Swipe injuries over the lower leg can occur if the operative slips and falls, losing control of a lance. To counter these risks, special boots and gaiters are worn, protecting feet and legs. Hand injuries are most often caused when an operative tries to move an obstacle while water jetting. As a result, gauntlets are available that protect the forearm and fingers.
Injury risk can be exacerbated by technical malfunction, for example a hose burst or a rotating nozzle failing to work. However, says Per-Arne Andersson, their analysis indicates that up to 90% of all injuries are caused by operator error.
Indeed, incident and near miss analysis is one of the most important drivers of PPE innovation. Behaviour and environment also influence the use of PPE and its effectiveness. In the Middle East and Africa, a key factor in this process is climate.
Steve Williams says: “Despite advances in modern materials and design, water jetting PPE is heavy and restrictive, and gets more so when soaked with water. Therefore, it can get very hot, and that’s before you factor in the high temperatures you’re working in.”
The temptation would be to limit the PPE to the bare minimum required, or even to do without it. However, Steve Williams is impressed by compliance levels among contractors, clients and operatives.
He adds: “Water jetting health and safety standards have improved greatly in recent years in the Middle East in the face of significant challenges caused by climate. Risks are minimised in a range of different ways, including frequent rest periods, working at cooler times of day, and providing shaded and cooled workstations.”
Contractors in the Middle East and Africa can also take advantage of the latest PPE cooling systems, including the provision of additional venting, especially across the back where there is less risk.
PPE systems can also be supplied with cooling by compressed air, which pumped through tubes inside the suit. The first of these was created for use in the Gulf of Mexico and proved so popular operatives wanted to keep them on during rest periods. The additional cost of such systems can be offset by the greater productivity they allow.
“behaviour and environment influence the use of PPE and its effectiveness. In the Middle East and Africa, a key factor in this process is climate”
On a general level, issues such as ease of use is important for water jetting PPE (as it is for all tasks). PPE components are designed to be as easy as possible to put on and take off, with the help of a colleague, or there is a risk they will not all be used for shorter tasks. They must also allow the full range of movement needed.
Minimise risk first
It is vitally important, however, that the point made at the beginning of this article is emphasised. PPE must always be a last resort, in water jetting perhaps more than other industrial processes.
Water jetting PPE systems are designed to a specific performance standard, usually based around the swipe test. A particular boot or leg gaiter will be designed to prevent penetration of a water jet defined by specific criteria. These are commonly pressure, flow rate, distance to PPE, swipe speed, angle and nozzle type.
If any of these variables change, the performance of the PPE will be affected, warns John Jones, the WJA’s Vice President, and Chairman of its Training and Safety Committee.
He adds: “If you have a fine pencil jet, say 1mm in diameter, under 3,000 bar of pressure, it will go through anything. It’s just a matter of time. That’s why PPE will only provide limited additional protection.
“The use of PPE must be incorporated in a thorough risk assessment of the task at hand. Risks must be eliminated, reduced and isolated before you consider the appropriate use of PPE.”
Robotic water jetting
Central to this process with water jetting is the increased use of robotic, or semiautomated, systems. These allow the operative to stand away from the water jet to control the process from a safer distance, though PPE is still a critical component of operative safety.
Robotic systems are increasingly used for concrete hydrodemolition, tube and pipe cleaning, refractory removal, cutting and surface preparation, defouling and cleaning of tanks.
It is essential for abrasive water jetting, where additional cutting agents are added to water, as there is no PPE that will protect against such a jet.
Also critical to the use of PPE is the knowledge, experience and behaviour of the water jetting team. This comes down to training, operational control systems, standards and health and safety culture.
In this context, the point of works risk assessment is critical. This is the last opportunity anyone has to ensure the selected process, which includes the use of PPE, is safe.
This is why the WJA’s City & Guildsaccredited training courses, both the class-based Safety Awareness course our the four practical modules, cover the use of PPE at length.
New competency training
It is also why the WJA has just launched a new competent water jetting qualification, a Level 2 Water Training Technician Certificate, accredited by ABBE, which is regulated by Ofqual, the UK’s qualifications and examination regulator.
John Jones explains: “The qualification, for the first time, rigorously assesses the competence of a water jetting operative, giving them, their employers and their clients greater confidence that their work will be carried out to a safe and high standard. For the water jetting industry, it represents a game changer.”
Candidates must pass the Safety Awareness course and two practical modules, one of which must be Surface Preparation, equivalent to 52 hours of structured learning. They must then undergo at least 122 hours of workbased assessment, including preparation, use and care for PPE.
As water jetting has evolved rapidly, and continues to do so, the use of protective equipment is also changing. The WJA will be looking closely over the coming months at the use of respiratory protective equipment (RPE). Potential “if you have a fine pencil jet, say 1mm in diameter, under 3,000 bar of pressure, it will go through anything. It’s just a matter of time” 33 risks associated with pathogens and particles released by water jetting in aerosols are of particular interest.
The WJA’s Codes of Practice, the Blue Book and, for drain and sewer water jetting, the Red Book, both reference the need to consider the use of RPE, if necessary. However, we will be taking a fresh look at this issue based on an assessment of latest scientific studies and practice.
What might be termed Environment Protection Equipment (EPE) is also coming onto the market. This includes protective curtains and booths to contain jets, debris and aerosols, safeguarding other members of the water jetting team or nearby colleagues.
These may be particularly relevant in the oil, gas and petrochemical industries, where water can be mixed with volatile and hazardous chemicals and compounds.
Such systems can also control harmful noise levels and support the collection, processing and reuse of water, making water jetting more viable and sustainable, especially in territories where water is scarce.