Spray Nozzle Selection

Spray Pattern The most common spray patterns are “vee”-shaped flat spray, full cone, and hollow cone. Each pattern offers its own advantages with respect to atomization, impact, and other properties.

Flow Rate Flow rate refers to the amount of liquid (typically water) that a nozzle will spray within a defined time period (minutes or hours). BEX spray nozzles are capable of handling flow rates from as low as 0.45 US Gallons per Hour (GPH) to as high as 968 US Gallons Per Minute (GPM).

Atomization Atomization is the breaking apart of a water droplet into a mist. The degree to which a spray is atomized depends primarily on pressure, viscosity and surface tension, and varies from point to point within a nozzle’s spray distribution. Any nozzle can produce a wide range of droplet sizes, depending on the operating conditions, such as temperature and pressure. If your application requires a specific droplet size profile, we can supply a droplet size measurement using our in-house LaserDopplerAnemometryInfoSheet equipment.

Spray Angles Spray angle is the angle of coverage of the spray pattern. Spray angles can change with pressure because as droplets accelerate due to gravity, spray patterns become less narrow. The SprayCoverageTable can help you determine this amount. Many other factors can also contribute to spray angle. Contact us to have a BEX technical representative guide you through the selection process.

 

BEX manufactures spray nozzles and eductors in many different materials. Some product groups are used frequently in certain industries, and are made with materials specific to that industry. The best resource for a material selection decision is your chemical supplier or system designer. If your application requires a material not shown, feel free to ask us about it.

The most common materials of construction are brass, 303SS, and 316SS. Our full list of materials includes:

• Steel
• Cast Iron
• Hastelloy®
• Titanium
• Monel®
• Carpenter 20®
• PVC
• CPVC Teflon®
• Polypropylene- Natural and Pigmented
• Acetal (Delrin®)- Natural and Pigmented
• PVDF (including Kynar®)

Nozzles can be attached to piping in different ways. The most common is a threaded connection – either male or female.

Most spray nozzles and eductors are made with tapered thread pipe connections, but are available with a wide range of connections.

Most nozzles are available with a NPT (National Pipe Thread)

The BSPT (British Standard Pipe Thread) is used mostly in Europe and the U.K.

Pipe threads are generally determined by the amount of fluid that has to flow through the nozzle. The greater the flow rate – the larger the connection has to be. When selecting a pipe size, or determining the pipe size of an existing nozzle, please refer to the Measuring Chart or Pipe Thread Sizing Diagram.

National Pipe Thread Sizing Chart

Notes:

• Male NPT is denoted as either MPT or MNPT Female NPT is either FPT or MNPT Pipe thread sizes do not refer to any physical dimension.
• The outside diameter of each pipe fitting must be measured and compared to the table for size identification.

To use the Measuring Chart, print out on 8.5 x 11” paper without scaling and stand the beginning of the thread on the corresponding sized circle.

BEX Standard Threads

Most threaded connections are available in both male and female.

NPT (Tapered)

BSPT (Tapered)

BSPP (Parallel)

UNF (Parallel)

UNC (Parallel)

Sanitary (With a hitch pin)

Clip-on (K-Ball Series)

Zip-Tip Quick Connect

 

Pressure
Higher pressure will usually result in finer spray droplet sizes, greater spray impact, and greater spraying distance.

Viscosity
Spraying liquids with a higher viscosity than water can result in reduced atomization, impact, and spray angle.

Specific Gravity
Fluids with a different specific gravity will yield a different flow rate than water.

Surface Tension
An increase in surface tension will generally result in larger droplet sizes (less atomization) and a reduced spray angle.

Droplet size refers to the degree of atomization that a spray has undergone. High atomization results in a small droplet and low atomization results in a relatively large droplet. They can range anywhere from 5 microns (a fine fog) to 5000 microns (a very heavy rain).

The most widely used value for spray impact (or impingement) affecting nozzle performance is “impact per square inch”. The impact is primarily dependent on spray pattern, spray angle, and operating pressure.

Next, find the relevant percent impact per square inch of the theoretical total impact on the chart and multiply this by the theoretical total. The result of this calculation is the impact per square inch.

Spray nozzle distribution and pressure have a significant effect on impact. The greatest impact in pounds per square inch obtained by a solid stream nozzle can be calculated by the formula:

1.9 X (nozzle operating pressure, psi)

Atomization
The degree to which a spray is atomized depends primarily on pressure, surface tension and viscosity, and varies from point to point within a nozzles spray distribution. Any given nozzle can produce a wide range of droplet sizes, depending on operating conditions, such as temperature and pressure.

We measure droplet size using our in-house Laser Doppler Anemometry equipment to help customers achieve optimal set ups for their applications.

Spray Angle
Spray angle is the angle of coverage of the spray pattern. Spray angles can change with pressure. Droplets accelerate due to gravity, causing spray patterns to change. The spray angle table can help determine how much change might occur, however, there are other factors which can affect spray angle.

Spray Coverage
Spray nozzle coverage is affected by factors that are unique to each installation. The table and illustration provide an approximate idea of the difference between the theoretical and actual coverages. Factors such as liquid pressure and droplet size can have a significant effect.

Chemical Compatibility
Not all materials are compatible with all chemicals. For example, polymers engineered for particular applications may not perform as expected in other applications using other chemicals. And high temperatures or operating pressure can reduce the mechanical integrity of plastics. The table provides some general guidelines to consider in consultation with chemical suppliers and system designers.