Steps to a More Effective
UHP Waterjetting Operation
Presented by: Rick Dupuy
UHP Projects, Inc
Learning Outcomes
– Describe the purpose of surface preparation
and what it includes
– Using SSPC VIS 4/NACE VIS 7, determine the
initial condition of a surface and assess the
level of cleanliness
– Using SSPC SP-WJ/NACE WJ standards to
demonstrate ability to achieve the level of
waterjet cleanliness required for a given job
– Identify the components of the waterjetting
• 3 Viewpoints required for successful
coatings application
1. Owner / Inspector
2. Contractor
3. Coatings Manufacturer
• 3 Performance Criteria needed for
successful coatings
1. Visual – SSPC standards
2. Profile – based on coatings manufacturer
requirements for the coatings specified
3. Non-visible contaminants
UHP Waterjetting Surface
Preparation Processes
• Pre-Cleaning
• Cleaning
• Post-Cleaning – before coating
• Pre-cleaning may involve:
– Removal of grease/oil,
gross contaminants
– May require the use of
degreasers or other
solvents and low
pressure water cleaning
– Repair of defects in steel
Pre-cleaning - SSPC SP 1 Solvent Cleaning
• Always performed first if necessary,
regardless of which surface preparation
method is selected
• Requires removal of all visible oil, grease,
drawing compounds, and other
contaminants from steel prior to surface
Surface Imperfections May Need to be
Corrected Prior to Surface Preparation
Sharp edges
Weld spatter
SSPC PA Guide 11
• This guide discusses the technique called
“stripe coating” or “striping” as a way of
providing extra corrosion protection
measures on edges, outside corners,
crevices, bolt heads, welds, and other
irregular steel surfaces, including optional
surface preparation techniques for sharp
edges to improve coating performance
Surface Preparation
• Actual surface preparation involves:
– Preparing the surface to accept the coatings
– Ensure that the surface is cleaned to the
standard specified and for the coatings
– Removing existing coatings, rust and other
unwanted materials from the surface
– Waterjetting surface to a stated visual
cleanliness level
Common Surface Preparation
Methods and SSPC Standards
– Degreasing (SP 1)
– SP WJ-1 Clean to Bare
– SP WJ-2 Very Thorough
– SP WJ-3 Thorough Cleaning
– SP WJ-4 Light Cleaning
Visual Guides for Cleaned
SSPC VIS 1 (Dry Abrasive Blast Cleaning)
SSPC VIS 3 (Hand and Power Tool Cleaning)
SSPC VIS 4 (Waterjetting)
SSPC VIS 5 (Wet Abrasive Blast Cleaning)
NSRP Flash Rust Guide
• Post-cleaning prior to coating application
involves verifying that the surface is:
– Dry
– Still free of contaminants, including dust and
dirt that could have accumulated since
surface preparation
– Still at the required cleanliness level
– Ensure that the surface is an acceptable level
of flashrust for the coatings specified
Advantages of UHP Waterjetting
• Used where profile is already established
• Does a good job of reducing/eliminating surface
• Used where solid particles will cause harm - controls
unwanted emissions
• Can reduce disposal costs particularly on hazardous
• Can minimize containment requirements
• Can be used to remove coatings layer by layer
• Less interference with other trades and activities
• Removes elastomeric coatings effectively
Pressures for Cleaning
with Water
• Low-pressure water cleaning (LP WC):
less than 5,000 psi (34 MPa)
• High-pressure water cleaning (HP WC):
5,000 to 10,000 psi (34 to 70 MPa)
• High-pressure waterjetting (HP WJ):
10,000 to 30,000 psi (70 to 210 MPa)
• Ultra High Pressure waterjetting (UHP
WJ): above 30,000 psi (210 MPa)
Top Coats
Types of UHP Tools
• Manual Guns
• Manually operated vacuum attached
– Floor, Deck, Wall (“Lawnmower”)
• Automated / Robotic
How do You Decide Which
Equipment to Use?
• Size of project and project requirements
• Project time constraints or productivity
• Knowledge level of personnel doing the work
• Jobsite requirement for water collection
• Full removal or partial removal of coatings
• Hazardous coating removal and
personnel/environmental protection
Typical Equipment Setup for
Manual Gun Operation
Hand activated
on/off – double
Correct Stance and Hose Placement
Recommended PPE
Standard PPE – Safety glasses, hard
hats, Hearing protection, FRC
Cut resistant gloves
Metatarsal Boots
Full Face Shields
Heavy rain suits
Task specific PPE – Safety harnesses,
respirators, H2S monitors, etc.
Cut Resistant
Clothing is
Becoming More
Operator Friendly
Automated / Robotic Equipment
• Vacuum Recovery removes both coatings
and effluent water from the nozzle (Keeps
water from pooling on the surface)
• Closed Loop (Water filtered and
• Open Loop (Water used once)
Automated UHP Equipment
Vacuum System
Remote-Control System
Horizontal Large Surface Robot
Manually Operated Vacuum
Attached Equipment
Primary Components of the
Waterjetting System
• Pump – Positive Displacement or Intensifier
• Pressure and volume are considerations
• Type of power source
• Gun – Dry shut off or Dump
• Rotating or non-rotating
• Hose
• Vacuum system if required
• Nozzle
• Accessories
Skid-Mounted UHP Pump
Skid mounted UHP Pump
Typical Single
User Pump
Pump with Vacuum Recovery
Vacuum Systems
• Sized to the flow and the application.
– Venturi nozzle to drum
– Skid mounted vacuum systems
– Large vacuum truck
• How is the effluent from the vacuum
going to be handled
• Multiple tools from same system
• NEVER put your hand in front of the
vacuum hose.
Vacuum System
•Vacuum equipment is
often integrated into a
skid package. This unit
can be mounted on the
back of a pickup truck
with a 220 gallon tank
40-55,000 psi Hose
Hoses and Connections
• Burst rating should be a minimum of 2.5 times
working pressure of the hose
• Test high-pressure hoses at 1.5 times working
• Fittings should be rated for the working
• Inspect hoses for shroud abrasion, leaks, and
flow restrictions (such as squashed fittings)
before each use
Hose Accessories: Bend Restrictors, Containment Grips
(Whip Check)
Proper UHP Hose Care
• Never run hoses over sharp edges – use
softeners and suspend hoses
• On long vertical runs don’t let the hose
connectors bear the full weight of the hoses
• Don’t let vehicle traffic run over hoses
• Store hoses in a protected location with
ends connected
• Always clean and lubricate ends before
Handheld UHP tools
• Attached to the UHP pump by
• Incorporates a control valve,
guard, lance (barrel), usually a
rotation device and nozzle
• Comes in various lengths,
normally with dual triggers. May
also have a support handle and
a shoulder stock
• The control valve used to relieve
the pressure further defines the
gun type
UHP waterjetting using handheld tools
UHP waterjetting
used handheld tools
hand activated
Handheld UHP tools
Dump gun:
– Moves pressure to the atmosphere, i.e.
water continues to flow but at low pressure
when the valve is released
Dry shut-off gun:
– Pressure is retained in the system with a
shutoff control valve, i.e. you see no water
at the gun, but it is re-circulated to the
Dump Gun
• Dump gun:
– Designed with a tube for depressurization (dump
mode) at the nozzle
– May be used alone or in a multi-gun operation with
an adjustable constant pressure valve to ensure
that pressure does not change abruptly
– When the dump gun valve is closed, the gun is
blasting with free passage of water through the
– When the valve is released the water is “dumped”
at the gun
– The operator can modulate the pressure
Dump Gun
Dry Shut-Off Gun
– Designed for use with a pressure regulator (or
tumble box) for single or multi-gun applications
– When the internal valve is open, water flows through
the nozzle. When the operator closes the valve,
there is no flow through the gun
– The shut-off gun is either “on” or “off.” The
operator cannot modulate the pressure at the trigger.
This can slightly improve productivity
– Pressure is relieved away from the operator
– The tumble box is designed to maintain constant
pressure in the hose and gun.
Dry Shut-Off Gun
Fan or zero-degree
Self-propelled or air-propelled
Number of orifices and size
Wear guards available
UHP Nozzle Assemblies
 Nozzles are usually multiorifice configurations
 Use sapphire or diamond
orifices for UHP WJ.
UHP Waterjetting is a Proven
Technology with Proven Benefits
Write good specifications
Choose an experienced UHP contractor
Use the correct equipment for the project
Follow good quality practices