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High-pressure nozzles are equipped with interchangeable jetting inserts which help to extend the nozzles service life, and make it more versatile by being adaptable to different water flow and pressure rates. The inserts are easily screwed into the threaded bores of the nozzle. The nozzle inserts differ in:
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(Image: Ceramic nozzle inserts (JetMax, ceramic, max. 500 bar)) The cleaning nozzles inserts are made of
Ceramic and sapphire inserts show very low wear and have a high flow rate hence making them optimal in use with high-pressure cleaning vehicles with water reclamation technology. (Table: Nozzle inserts – Materials) |
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Sapphire and ceramic have proven to be very wear resistant materials, however, ceramics inserts have shown to have a longer life span when used with very contaminated flushing water.
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The nozzle inserts have a bore diameter of 0.3 to 4.0 mm or more. The number of nozzle inserts can be both even or odd. In the case of an odd number, only equally sized hole diameters are to be used to prevent the nozzle from drifting off in one direction. When using different hole diameters, their number has to be even and symmetrically placed. |
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Connection between cleaning and driving performance based on the number of nozzle inserts: (Image: Number of nozzle inserts) |
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(Image: Radial nozzle - Removal of loose deposits) (Image: Rotary nozzle - Rear and side jetting) (Image: Penetrator nozzle) |
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The placement of the nozzle inserts and the specific angle (exit angle β) of the rear discharging jets determine how efficiently the nozzle propels itself, and the HP hose, upstream through the sewer channel. (Image: Effects of the jet angle on the propulsion of the nozzle as per [FI-Mülle]) |
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The jet angle (also called exit angle) represents an essential parameter in high-pressure cleaning. It is the angle between the pressurised water jet and the pipe axis or longitudinal axis of the sewer, and may range between 0° and 90°. Equation: (Formula: Berechnung der Zugkraft) with: FZ = Pulling force FSt = Jet force β = Jet angle n = Number of jets (nozzle inserts) Equation: (Formula: Berechnung der Reinigungskraft) with: |
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From a mathematical point of view, the force of the nozzle jets can be split vectorially into cleaning and pulling force components (drive force), meaning that the energy distribution for these two reactions changes depending on the jet angle. (Image: Nozzle jets pressure output represented vectorially by propulsion and cleaning components) |
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(Image: Jet angle - Effect on driving force and cleaning performance) |
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(Image: Jet angle selection) Achieving the above results is dependent on the free jet length. |
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(Image: Beam Angle - Influence of the pipe diameter) |
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May 15, 2012 BE-05 Cleaning: Cleaning Nozzles Pulling force – Water jet force, Number of nozzle inserts, Jet angle The pulling force (drive force) generated by the high-pressure water jets is dependent on:
(Image: Nozzle jet pressure test) |
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May 15, 2012 BE-05 Cleaning: Cleaning Nozzles Pulling force – Water jet force, Number of nozzle inserts, Jet angle Correlation between cleaning and driving performance based on the number of nozzle inserts and the beam angle: (Image: Effect of jet angle and number of nozzles) |
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May 15, 2012 BE-05 Cleaning: Cleaning Nozzles Pulling force – Water jet force, Number of nozzle inserts, Jet angle The jet force at the nozzle is dependent on:
It can be calculated using the following equation: (Formula: Equation to calculate the jet force) pdyn = dynamic pressure at the nozzle opening ρwater = water density v0 = water velocity at nozzle opening [Geib2002] |
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May 30, 2012 BE-05 Cleaning: Cleaning Nozzles Pulling force – Water jet force, Number of nozzle inserts, Jet angle The cleaning performance and driving force can be further enhanced by mounting the nozzle onto a sleigh or skid, thus avoiding direct contact between the cleaning nozzle and the pipe wall. (Image: Centric positioning of the nozzle through the use of a sleigh) (Image: Mounted nozzle) (Image: Cleaning nozzle with a skid) |
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For an effective use of high-pressure cleaning, a precise knowledge of the occurring pressure losses is very important. A distinction is drawn between:
Both nozzle pressure and volumetric flow rate can be optimised by choosing the appropriate high-pressure flushing hose, nozzle and nozzle inserts. Given an equal pump output, the required … |
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In the line between the high-pressure pump outlet and the high pressure hose inlet on the reel, there exists a large number of valves and fittings. The pressure losses at the vehicle are therefore dependent on the particular type of set up, and are equal to 5 % of the total loss or 12 – 15 bar [Geib2002]. |
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The highest pressure losses can be found in the high-pressure flushing hose. According to [Geib2002] the calculation of these losses, resulting from the turbulent flow, is performed using the following equation: (Formula: Druckverluste im Hochdruckspülschlauch) with: hv = Friction loss height [m] or pressure loss [bar] l = Hose length [m] d = Internal diameter of the hose [m] vm = Average flow velocity [m/s] in the hose l = Pipe coefficient of friction [-] |
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