Comparison: 11-ksi Pulsed Jet vs. 40-ksiContinuous Waterjet

Removal of coating from Marine SampleVLN 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 hydraulichorsepower almost the same (27 hp) for both systems. We used single-orifice nozzle (thisis because we do not have twin-orifice rotating nozzle for the 40,000 psi system). Weconducted 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 paintremoved. 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 the40,000-psi jet. Then we conducted tests to find out how many adjacent paths we need toremove 1-in wide swath. These are identified as Test#2 (pulsed jet) and Test #4 (40,000psi jet). To remove this 1-in swath, the pulsed jet took 8 adjacent passes, while thenumber of passes required for the 40,000 psi jet was 32. Based on this observation thearea 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’s pulsed waterjet removes almost 4 times the rateachieved with the 40,000-psi system at identical power input. Therefore, if the samekinematics of moving the jets over the surface are used with the pulsed waterjet, it willincrease the rate of removal from 600 sq-ft (this is the figure quoted, although it was notclear whether the coating was weathered or, new), the pulsed waterjet would removealmost 2,400 sq-ft/hr.

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.

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

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

Figure 3 Non-skid sample after coating has been removed

Figure 4 New development: TGR Twin-gun rotating pulsed jetting device