Pulse jets , waterjets

1. Comparison: 11-ksi Pulsed Jet vs. 40-ksi
Continuous Waterjet
Removal of coating from Marine Sample
VLN Technologies Inc. performed tests to compare the performance of ultra-high
pressure (40,000 psi) with our pulsed waterjet at 11,000 psi, keeping the hydraulic
horsepower almost the same (27 hp) for both systems. We used single-orifice nozzle (this
is because we do not have twin-orifice rotating nozzle for the 40,000 psi system). We
conducted the tests on our X-Y gantry, at a traverse rate of 2,000 in/min (166.7 ft/min),
the standoff distance being 1.5-in.
This sample was obtained from the US Navy and consisted of:
2 Coats anti-corrosive paint / 2 Coats Devoe Bar rust - average 5 mils each coat
The top layer is International Intervirion Antifoulant BRA 640 – Red – 3 coats,
average dry thickness of 5 mils. Blasted profile on substrate is 2-4 mils.
First, a single pass test was conducted to find out the width of the swath of paint
removed. In the photograph below, these are identified as Test#1 (pulse jet) and Test#3
(40,000 psi jet). It is quite clear that the pulsed jet removes a much wider swath than the
40,000-psi jet. Then we conducted tests to find out how many adjacent paths we need to
remove 1-in wide swath. These are identified as Test#2 (pulsed jet) and Test #4 (40,000
psi jet). To remove this 1-in swath, the pulsed jet took 8 adjacent passes, while the
number of passes required for the 40,000 psi jet was 32. Based on this observation the
area removal rate achieved with these jets are:
Pulsed Waterjet: 104.2 sq-ft/hr
40,000-psi jet: 26.0 sq-ft/hr
This clearly shows that VLN’ pulsed waterjet removes almost 4 times the rate
s
achieved with the 40,000-psi system at identical power input. Therefore, if the same
kinematics of moving the jets over the surface are used with the pulsed waterjet, it will
increase the rate of removal from 600 sq-ft (this is the figure quoted, although it was not
clear whether the coating was weathered or, new), the pulsed waterjet would remove
almost 2,400 sq-ft/hr.

3. Coating Removal Using High Frequency Forced Pulsed Waterjet
VLN Advanced Technologies Inc. has performed numerous tests on non-skid samples
using the unique forced pulsed waterjet.
VLN’s pulsed machine has the ability to turn on and off the pulse function easily. Thus
quite some tests have been done to compare pulse and non-pulse waterjet’s performance.
Observations have been made in those tests that the performance of the pulsed waterjet is
at least 5 times of that of non-pulsed waterjet at the same pressure and same other
conditions.
So far, the overall best performance obtained with dual-orifice rotating nozzle (see Figure
1, Figure 2, and Figure 3) is about 60 ft2/hr. The best performance on the non-skid sample
with single nozzle pulse waterjet is about 100 ft2/hr. This gun only use 40 hp energy and
8 usgpm water.
Based on single-orifice pulsed waterjet gun, a lawnmower type waterjet machine has
been developed (see Figure 4). This machine (with two guns built in it) is expected to
double the performance of a single pulsed waterjet gun.

4. Figure 1 Dual orifice rotating nozzle works on non-skid sample
Figure 2 Dual orifice rotating nozzle works on non-skid sample

5. Figure 3 Non-skid sample after coating has been removed
Figure 4 New development: TGR Twin-gun rotating pulsed jetting device