A high-pressure water injury often looks harmless from the outside — usually a small entry wound with little bleeding. In reality, fluid is forced into the tissue under pressure, which can cause deep-reaching damage, compartment syndrome, and infection. Any high-pressure exposure to the body must therefore be treated medically without delay, irrespective of the external appearance, with a note of the pressure, the medium, and the time of exposure. This information belongs in every set of work instructions.
Safety-relevant threshold values
| Parameter | Threshold | Legal consequence |
|---|---|---|
| Permitted operating gauge pressure | from 25 bar | Brings DGUV Rule 100-500, chapter 2.36, into scope |
| Pressure-flow product | from 10,000 bar·l/min | Also brings the scope into effect, even at lower pressure |
| Hand-held reaction force | above 150 N | Only jetting lances with additional measures are permitted |
| Hand-held reaction force | 250 N | Upper limit for forces to be absorbed in the long axis |
| Operating pressure, product standard | above 350 bar (35 MPa) | EN 1829-1 applies instead of DIN EN 60335-2-79:2015-02 |
Figures per DGUV Rule 100-500, chapter 2.36 (issue March 2017), sections 1.1 and 3.7.5, and EN 1829-1:2021. The 35 MPa (350 bar) threshold applies under the currently valid edition DIN EN 60335-2-79 (VDE 0700-79):2015-02 (German version of EN 60335-2-79:2012, based on IEC 60335-2-79:2012, edition 3). Only the earlier IEC editions IEC 60335-2-79:1995 (edition 1) and IEC 60335-2-79:2002 (edition 2) set this boundary at 25 MPa (250 bar); the European version EN 60335-2-79:2009 (DIN EN 60335-2-79:2010-01) already stood at 35 MPa. The current official version governs.
The hierarchy under EN ISO 12100 applies unchanged: inherently safe design first, then technical protective measures, and only then user information and personal protective equipment. For waterjet systems, concretely: mechanical tool guidance takes precedence over hand-held operation, enclosure takes precedence over protective equipment, and choosing a nozzle with lower reaction force takes precedence over any organisational measure.
High-pressure water is treated as a hazardous working medium
The jet can penetrate tissue and cause serious injury. Depending on the application, this is compounded by reaction force, flying particles, noise, wet work areas, hose and line hazards, and possible hazards from the removed material. Simplified, generic "safe pressure limits" are therefore not a sound basis for operation.
Safety begins with the pressure system and machine concept
Suitable high-pressure components, pressure relief, safe valve states, protection against unintended start-up, emergency-stop functions, and defined access states are typical elements of a technical protection concept. Which measures are actually required follows from the specific risk assessment and the requirements that apply to the machine and the site.
For hand-held tools, reaction force is a design criterion in its own right
Spray guns and lances transmit reaction forces to the operator. Tool weight, posture, reaction-force absorption, control logic, and duration of use all affect ergonomics and controllability. Manufacturers offer two-hand controls, support aids, and mechanical reaction-force absorption for this purpose, among others. The permitted configuration must be derived from the relevant manufacturer documentation.
Enclosure and remote operation can reduce exposure
Enclosed processing cells, remotely operated carrier units, or robots keep personnel physically separated from the active jet. This introduces additional requirements for interlocking, access control, safe operating modes, and maintenance. Automation is therefore a possible risk-reduction measure, not a substitute for a complete protection concept.
Work instructions must be adapted to the machine and the site
Personal protective equipment, safety distances, authorisations, and operating sequences cannot responsibly be derived from a general website. They must be based on manufacturer documentation, the operator's own risk assessment, staff qualification, and the regulations that apply at the site.
Applicable rules and standards
DGUV Rule 100-500, ch. 2.36Working with liquid jetting equipment (March 2017)German operational rule with requirements for mechanically guided and hand-held jetting equipment, emergency-stop accessibility, reaction forces, briefing, and inspection.
OperationEN 1829-1:2021High-pressure water jet machines – Safety requirements – Part 1: MachinesProduct standard for high-pressure water jet machines above the scope of EN 60335-2-79 (currently valid: DIN EN 60335-2-79:2015-02, 35 MPa / 350 bar). Covers hazards over the entire life cycle, including servicing.
Product standardDIN EN ISO 12100:2011-03Risk assessment and risk reductionMethodology and hierarchy of protective measures. Basis for any machine-specific assessment. Based on ISO 12100:2010; a revision is in draft but not yet published.
MethodologyDGUV Rule 113-004Working in tanks, silos, and confined spacesApplicable to tank and vessel cleaning: safety watch, atmosphere testing, access, rescue.
EnvironmentThe complete picture, including the transition to the EU Machinery Regulation, is covered under Standards and Directives.
Frequently asked questions about safety
What personal protective equipment is required?
Selection follows the risk assessment and the manufacturer's specification, not a blanket list. Common items for hand-held work include penetration-resistant protective clothing, face and eye protection, safety footwear with appropriate protection, and hearing protection. The key point: no commercially available protective equipment stops a direct ultra-high-pressure jet indefinitely. It reduces the consequences; it does not prevent them.
Is an enclosure sufficient as a protective measure?
Only together with effective interlocking, pressure relief on opening, and a defined procedure for setup and maintenance operation. The critical states almost always occur outside normal operation: setup, fault clearance, nozzle changes, and cleaning of the catch basin.
How should residual pressure be handled during work on the system?
Before any intervention on pressure-carrying components, the system must be verifiably depressurised and secured against being switched back on. High-pressure lines can retain residual pressure even after the pump has been switched off. A defined procedure, described in the work instructions, with relief and verification, is part of the protection concept, not a formality.
What role does noise play?
A significant one. Ultra-high-pressure cleaning regularly reaches levels that trigger hearing-protection and further measures under the applicable noise and vibration regulations. The level must be determined at the actual workplace; manufacturer figures for the machine alone are not sufficient to assess workplace exposure.
- DGUV Rule 100-500, chapter 2.36 “Working with Liquid Jetting Equipment,” issue March 2017 – https://publikationen.dguv.de/media/pdf/27/3a/6a/R500_236.pdf
- DIN EN 1829-1:2021-04, High-pressure water jet machines – Safety requirements – Part 1: Machines – https://www.dinmedia.de/de/norm/din-en-1829-1/321847498