How to Select Nozzle？
How to Select Nozzle？
1) Introduction of Nozzle There are many kinds of nozzles and a wide range of choices. Generally speaking, the specific types of nozzles include: narrow-angle nozzle, wide-angle nozzle, combined sector nozzle, single sector nozzle, self-cleaning sector nozzle, flat sector nozzle, dovetail sector nozzle, clip-on sector nozzle, quick-release sector nozzle, side-spray sector nozzle and universal sector nozzle.
The factors of nozzle selection include flow rate, pressure, spray angle, coverage, impact force, temperature, material, application, etc. These factors are often interrelated and mutually restricted. Flow rate is proportional to pressure, spray angle is proportional to coverage. The injection purpose of any nozzle is to keep the bath liquid in contact with the workpiece continuously. Flow rate is more important than pressure. The temperature of the liquid will not affect the spray performance of the nozzle, but it will affect the viscosity and specific gravity, and also affect the choice of materials. The material of the nozzle should also be determined according to the chemical characteristics of the bath liquid. For non-corrosive bath liquid, bronze casting or plastic die casting can be used according to the difficulty of processing. In order to prevent corrosion, nonmetallic materials can be used. Nylon plastic can be used for strong corrosive bath liquid such as sulfuric acid and hydrochloric acid. The nozzle material for phosphating bath solution is generally acid-resistant stainless steel, and the nozzle for preventing corrosion can also be directly made of stainless steel or nylon.
For nozzles with certain impact force, small angle nozzles should be selected, with liquid column flow (i.e. jet flow) as the best; Fan-shaped nozzles are suitable for cleaning, degreasing, cooling, etc. Cone-shaped nozzles are suitable for rinsing, surface coating, phosphating, humidification, dust removal, etc. Venturi stirring nozzles shall be installed in paint storage tanks and tank bodies. Take “H” type namely stirring nozzles (also called Venturi nozzles) as an example. The tank liquid is mixed with the liquid sucked at the inlet port at a flow rate of 1: 4 under a certain pressure and then diffused and sprayed out, so as to achieve the effect of solute mixing and stirring without air, thus preventing sedimentation, because stirring ensures uniform mixing of chemical solutions.
Installation of nozzles:
A plurality of nozzles are arranged in a certain arrangement on an annular pipeline formed according to the outer profile size of the workpiece to surround the workpiece, so that all surfaces of the workpiece can be sprayed and washed by tank liquid when passing through a spraying area, and nozzles are uniformly arranged in the whole spraying area to ensure the spraying process time and effect. The distance between the nozzle and the workpiece should be within the optimal diffusion range of the jet, so the arrangement of the nozzle and nozzle should be reasonable. The distance between the nozzle and the nozzle is 250mm to 300 mm, and the distance between the nozzle and the workpiece is preferably not less than 250 mm when the nozzles are arranged crosswise.
Immersion coating pretreatment stirring device from pump to pipeline to stirring nozzle forms a complete tank liquid spraying system. The mixing nozzle uses Venturi principle, the tank liquid enters the pipeline under the action of a certain pressure, forms a high-speed jet through the spray hole of the mixing nozzle, and generates a low-pressure area at the inlet opening around the nozzle, forming a siphon phenomenon, and the tank liquid is sucked into the mixing nozzle under the action of the pressure difference, so that a large amount of liquid can be circulated. The distance between the stirring nozzle and the bottom of the tank is 25 mm to 75 mm, and the distance between the stirring nozzle and the workpiece is 200 mm to 380 mm. The angle of the spray hole should be determined according to the size of the workpiece. When the width of the workpiece is small, the spray hole can be designed to be vertically upward, and when the workpiece is large, the spray hole can be designed to be 35-45 degrees with the vertical plane; When the width of the workpiece is large, in order to improve the stirring effect, the spray hole can be designed to be vertically downward, but this will stir up the sediment, so it is only suitable for stirring the tank liquid without sediment.
2) why fan nozzle is selected: during the process of rolling strip steel, a large amount of heat will be generated. if the roller temperature is not uniform, the rolled strip will have defects. therefore, a key factor to ensure the quality of the strip is to ensure the control of the roller shape. Using an effective roller cooling system can not only control the shape of the working roller, but also play a role in lubrication, cleaning, etc. Nozzle is the core component of the roller cooling system. Choosing the appropriate nozzle arrangement and nozzle type can make the coolant spray onto the roller accurately and evenly, transfer the heat of the roller body to the greatest extent and lubricate the nip. At present, flat and fan-shaped spray nozzles are widely used in industry. Compared with other cleaning nozzles, fan-shaped nozzles have their unique advantages. They can form flat and uniform jet, with good jet compactness, and the diffusion angle can vary in a large range, and varies with the flow rate, flow rate, jet angle and coverage. Through partial cross overlapping, uniform coverage of the ejection surface can be realized.
3) fan nozzle features:
Fan nozzle Fan-shaped spray form, the edge of the spray shape is clearly defined, and the guide plane processed by fine technology provides a uniform and high-impact spray shape. The spray channel is large and smooth, reducing blocking. Due to the influence of the earth’s gravity, the fan-shaped spray with various angles will have “edge effect”, i.e. the fan-shaped section of the spray will produce gradually thinner edge spray particles that are fine and uniform, and the size of the spray particles is medium. when multiple nozzles are arranged, 25%~30% overlap is required to make the arrangement uniform in the whole direction. Fan-shaped spray with multiple angles can be produced with uniform spray water flow, medium droplet size adopts unit combined connection mode, which is convenient to install and replace, can be equipped with filter screen, and is easy to clean. Can be installed or replaced on most piping systems. NPT or BSPT (external) thread type nozzles are available. Generally, 1/4-4 inch nozzles can be made of Cu, 304SS, 316SS, 316L, PVDF, PP or silicon carbide materials respectively. Rust steel (SS304, 303, 316, 316L), BRASS (Brass), silicon carbide, plastic (PVC, ABS, FUD), ceramics and other materials.
4） Attention should be paid to the selection of nozzles 1. System conditions:
The power and lift of the pump (determines the rated pressure), the total flow rate of the system (determines the rated flow rate), and the pressure drop designed by the piping system (determines the actual working pressure of the nozzle).
2. Spray conditions:
The spray angle of the nozzle (determines the number and problems of cross-arrangement), spray shape (determines the flow distribution characteristics), spray particle size (determines the actual effect of atomization), and spray flow (determines the aperture and shape of the nozzle).
3. Effect conditions:
Injection pressure (which determines the structure and flow rate of the nozzle), impact force (which determines the cleaning effect of the spray), and counter impact force (which determines the type and destructive force of the nozzle).
4. Media conditions:
Density, viscosity, surface tension (determines the actual effect of spraying), temperature, pH (determines the material of nozzle)