How Rotary Spray Heads Work
Process designers specify rotary spray heads when cleaning requires better coverage than static spray balls. As their name suggests, rotary spray heads turn while supplying pressurized fans of cleaning solutions or water against the interior surfaces of the tank or vessel during cleaning cycles.
Unlike static spray balls that supply streams in fixed arrays, rotary spray heads combine rotating motion and spray pressure to increase the effectiveness of cleaning cycles.
Advantages of Rotary Spray Heads
Because of the rotary design using flat fans of wash fluid, the spray heads produce increased impingement action during cleaning cycles. In CIP, impingement refers to the force of water under pressure and flow to remove soils from the interior surfaces of tanks.
Cleaning occurs when the concentrated fluid stream meets interior surfaces. Rotary spray heads increase impingement action while generally requiring a lower flow rate than static spray balls.
They rotate in a precise, repeatable 360-degree patterns to achieve full coverage inside the tank. Due to the detailed placement and design of the rotary spray head wash fluid slots, this action increase provides around a 30% reducing in time, water, and chemicals compared to static spray balls. As the spray head rotates, its fans produce a variable falling film, which has higher heat and mass transfer coefficients than the falling film produced by static spray balls.
Rotary spray heads can replace static spray balls when required, to improve cleaning coverage.
For example, tanks with an agitator and a single static spray ball will likely not clean well behind the agitator shaft. Replacing the single static spray ball with two rotary devices can meet cleaning requirements without having to change parameters on the CIP skid because rotary heads have similar pressure requirements at a lower flow rate than static spray balls.
As fans of water rotate during cleaning cycles, they create an impingement action on the tank circumference, which allows soaking and cleaning with a greater force than static spray balls.
Rotating spray heads operate under similar pressure requirements as static spray balls, so rotary spray heads are easy to retrofit into existing systems without needing to increase Clean-in-place (CIP) supply pressures or flows.
Selecting the Right Rotary Spray Head
Designed for a variety of applications, rotary spray devices are available in various sizes and different configurations covering most tank sizes. To comply with good manufacturing practices, rotary spray heads should be self-draining and self-cleaning, inside and out.
As Table 1 shows, specifications remain constant for all tank sizes, while only the model of rotary spray heads for CIP change to suit tank volume.
Table 1
| Tank A | Tank B | Tank C | Tank D | |
|---|---|---|---|---|
| Tank Size | Small ranging from 0.05m3 to 1m3 | Small ranging from 0.1m3 to 10m3 | Mid-sized ranging from 5m3 to 50m3 | Large ranging from 50m3 to 350m3 |
| Recommended Pressure | 30PSI | 30PSI | 30PSI | 30-45PSI |
| Working Temperature (max) | 203°F | 203°F | 203°F | 203°F |
| Ambient Temperature (max) | 284°F | 284°F | 284°F | 302°F |
| Spray Pattern | 360° 180° Down 270° Up | 360° 180° Down 270° Up | 360° 180° Down 270° Up | 360° 270° Up |
Typical pressure, temperature, and spray pattern specifications for rotary spray heads in CIP remain constant across small and mid-sized tanks. As tank size increases (Tank D), pressure requirements for rotary spray heads also increase.
Download Alfa Laval Tank Cleaner Selection Guide
Consider several factors when selecting spray heads and their configuration:
1. Types of soil
In general, static spray balls provide sufficient cleaning action for water-soluble soils because the balls use chemicals, heat, and water to create a cascading action that removes soils.
For more viscous or oil-based products, use rotary spray heads for their increased impingement action.
2. Vessel Size and Dimensions
Vessel diameter and shape determine the flow rate required to meet cleaning requirements, which must be calculated during CIP design. Consult with CSI engineering to ensure accurate needs analysis.
3. Number and type of internal obstructions in the tank
Because rotary spray balls rotate but don’t change location in the tank, their effectiveness diminishes with the presence of obstructions in a tank such as heating coils, agitators, baffles or ladders.
4. Port size
Port size determines spray head size that will fit into the tank and ultimately the flow required for the device. If the port is too small to accommodate a device suited to the cleaning application, an additional device may be required to provide the proper coverage.
5. Pressure and Flow
Since tank cleaners are calibrated to deliver a specific cleaning force to the tank surface, understanding your operating conditions is necessary to deliver the required cleaning performance for your application. It is, therefore, very important to know at what pressure and flow rate you plan to operate.
Pressure comparisons
A comparison of operating pressures illustrates the difference in impingement among various spray devices:
Device | Pressure |
25PSI | |
Rotating Spray Balls | 35PSI |
Working pressure: 15 - 45PSI | |
Working Pressure: 40 - 300PSI |
Because pressure is such an important factor in spray head performance, specifications for supply pumps and spray heads must be factored into system design. Centrifugal and twin-screw are among the most common supply pumps for CIP.
Cycle configurations that affect cleaning
In addition to spray head factors, four cycle factors affect the cleaning action of rotary spray heads during cleaning: time, action, concentration (chemicals), and temperature.
Time
The total amount of time required to run a complete cleaning sequence is the sum of a number of different steps (such as preparation, programming, wash and rinse, drying, etc.), but the critical “time” element of the cleaning process is the amount of time that cleaning solutions are in direct contact with the product soil.
Longer contact times can result in better cleaning, but increased impingement can also result in better cleaning in shorter cycles.
Your wash and rinse cycle times may each be as short as 10-15 minutes, or they may take up to an hour or more depending on system design.
Since the time spent cleaning reduces the time spent producing saleable product, the goal is to reduce cleaning cycle times as much as possible while still ensuring that the process system is sufficiently clean and safe.
An experienced cleaning expert can determine the right cleaning spray device and cycle times for a particular application based on product and system variables.
Action
The action in a cleaning process is the mechanical force of the cleaning solution that physically dislodges soil from the surface. The amount of impingement needed--and therefore the spray devices and pressure required--are important considerations.
Concentration
The right concentration of chemical cleaning agents make a significant difference in CIP efficiency. The main job of chemicals in any CIP process is to enhance cleaning. To maximize cleaning while conserving chemicals to minimize waste, consult a CIP specialist at CSI.
Temperature
Calculating the precise solution temperature is critical to effectively cleaning a system while at the same time reducing energy costs. Some studies have shown that for every one-degree reduction in CIP solution temperatures there will be nearly a 1% reduction in the energy needed to heat the fluid.
Higher solution temperatures can increase the effectiveness of chemicals and mechanical action, and they can also reduce the amount of time needed to clean properly.
Considering the cost of energy to heat cleaning solutions, accurately calculating and controlling temperature for each cleaning stage is an important cost consideration.
Spray patterns
Flow rate and spray pattern affect cost and cleaning efficiency--and therefore choice of rotary spray heads.
Cost comparison
Rotary spray heads from CSI provide exceptional cleanability, better end-product quality, greater overall output and reduced operating costs.
Although the initial investment cost of a rotary spray head is higher than alternatives such as static spray balls, rotary spray heads produce lower cleaning costs and cleaning time. The dynamic movement and higher impact force of rotary motion reduce water usage, acid, caustic and disinfection time.
Clean-in-place Buying Guide
This Buying Guide for Clean-in-Place Solutions is a comprehensive resource for anyone who designs, owns, or operates processing systems and wants information about all aspects of CIP Systems.
References
Frank, J. W. & Seiberling, D. A. (2008). CIP spray device design and application. In D. A. Seiberling (Ed.), Clean-in-place for biopharmaceutical processes (pp. 159-174). Drugs and the Pharmaceutical Sciences 173.New York, NY: Informa Healthcare USA.
ABOUT CSI
Central States Industrial Equipment (CSI) is a leader in distribution of hygienic pipe, valves, fittings, pumps, heat exchangers, and MRO supplies for hygienic industrial processors, with four distribution facilities across the U.S. CSI also provides detail design and execution for hygienic process systems in the food, dairy, beverage, pharmaceutical, biotechnology, and personal care industries. Specializing in process piping, system start-ups, and cleaning systems, CSI leverages technology, intellectual property, and industry expertise to deliver solutions to processing problems. More information can be found at www.csidesigns.com.