Have you ever purchased a hygienic tank for a food processing application and found outafter delivery that the spray device included with the tank was not suitable for yourapplication? There were shadows behind the baffles or agitator shaft? It didn’t clean yourproduct residues or left soil streaks? The flow rate was not sufficient to clean the outletpiping? Or the spray device was not sanitary?
Selecting a spray device to clean process equipment is much more than simply putting asprayball in the top of the tank and hooking up the CIP system. For cleaning vessels, thetype of spray device, location(s), flow rate / pressure are the critical criteria for successfulcleaning of the process system. The proper spray device(s) must first be selected and thenthe CIP supply pump must be specified based on the flow rate and pressure required.
When selecting a spray device, there are many factors to consider:
There are many sanitary spray devices available to meet the needs of the applications.Spray devices may be static sprayballs, single axis rotary sprays, or multi-axis orbitalsprays. There is no ‘one size fits all’ device that will work for every application, andsome spray devices are designed for specific applications, such as drop-in tanker sprays.
Fixed spray devices are the most common type of sprays, developed at the advent of CIPcleaning. They are best suited for light residues such as fluid milk, whey, beverages, andother easy-to-remove soils. These devices clean by cascading action combined with thechemical breakdown of the residues, to erode the soils from the equipment surfaces. If asilo is sprayed at the top with a suitable flow rate, all the water will flow down thesidewalls to the outlet. Provisions must also be made for spray coverage of the tankoverflow, vent, agitators, and baffles.
The minimum flow rate required to clean vertical tanks or ductwork with fixed sprays is2.5 GPM per foot of circumference. For rectangular tanks or vessels with flat tops, theminimum flow rate should be 0.25 GPM per square foot of surface area. And forhorizontal round tanks or ductwork, the minimum flow rate should be 0.12 GPM persquare foot of surface area.
Advantages of fixed spray devices:
Disadvantages of fixed spray devices:
Single-Axis Rotary Sprays are devices that spin due to the reaction of the solutionsflowing out of the orifices. They provide higher impact than fixed spray devices, andprovide complete coverage within the range of the spray pattern. They can be specified tohave 360° coverage, top coverage, bottom coverage, or some range in between,depending on the needs of the application. The spray can have drilled holes or may haveslots to create a rotating ‘fan’ of CIP solution, and several models are available with 3-Asymbol authorization.
The typical minimum flow rate required to clean vertical tanks or ductwork with single-axis sprays is 1.9 GPM per foot of circumference, but the manufacturer’srecommendations should always be followed, as spray devices vary in their coverage,spray range, and impact.
Advantages of single-axis rotary spray devices:
Disadvantages of single-axis spray devices:
Multi-Axis Rotary Sprays are machines devices that rotate by the flow of fluid througha turbine or by an external drive, rotating internal gears. The spray nozzles rotate in anorbit, like a ball of yarn, to provide high impact across longer distances, and at a lowerflow rate and high pressure. They provide high impact for soils that are difficult toremove and can cover large areas with a single device with a 360° orbit. For criticalapplications, the rotation can be verified with pressure sensors located where the spraystream must pass during each orbit.
The typical minimum flow rate required to clean vertical tanks or ductwork with multi-axis sprays is 1.25 GPM per foot of circumference, but the manufacturer’srecommendations should always be followed, as spray devices vary in their coverage,spray range, and impact. The minimum flow rate required to clean the discharge pipingfrom the vessel must also be considered.
Advantages of multi-axis rotary spray devices:
Disadvantages of multi-axis rotary spray devices:
Regardless of the spray device selected, the CIP supply system must have a suitable strainer to prevent particulates from plugging or stopping the rotation of the devices.
Multiple sprays are required when there is an agitator, baffles, or blind areas in top ports to prevent ‘shadowing’. To ensure complete coverage of spray applications, a ‘riboflavin test’ can be conducted to confirm that the spray device is providing complete coverage of all surfaces by direct impingement, cascading flow, or secondary impingement. This does not confirm cleaning performance with the actual product residues, but it does verify that all surfaces have CIP solution coverage.
As noted previously, there are many factors to consider when selecting spray devices for food processing equipment. Some equipment cleaning is well documented with a long history of successful cleaning. However, if you have an application with unknown variables, it is recommended to test the application in advance to ensure that the spray devices selected will provide the necessary coverage, and confirm the cleaning performance under the actual conditions of operation and CIP.
* Gabe Miller has 30 years of experience in cleaning and sanitizing equipment and is the owner of Process Innovation – Food Safety, LLC, providing sanitary design guidance, training, sanitation audits, and 3-A CCE Third Party Verification (TPV) inspections.