Five Main Ways to Automate Tank Cleaning
To meet the needs of a variety of tank cleaning applications,
Spraying Systems Co. manufactures a variety of tank washing nozzles.
Whether your tank requires a light rinse or a high-impact wash,
we have the right nozzle for your application.
Types of tank washing nozzles available include:
High-Pressure (Motor-Driven) Tank Washers
 These tank washers use high-pressure solid stream
nozzles at pressures from 100 to 1000 psi (7 to 70 bar)
with a separate motor for driving the nozzle assembly.
Two to four nozzles rotate on a gear hub as they
revolve around the central axis of the nozzle assembly.
Both the liquid pressure for cleaning and the rotational
speed (i.e., cleaning cycle time) are fully independent
to optimize both the pressure and time needed for
completing the cleaning process.
The high-impact force delivered by the tank washer
reduces the water required for effective tank cleaning.
A range of nozzle sizes is available, which allows one
unit to be used in more than one application.
Lightweight in design, the unit is easily portable so it
can be moved to other process tanks as required.
Fluid-Driven (Reactionary Force) Tank Washing Nozzles
 Increasingly popular, these fluid-driven spray
nozzles use the reactionary force of the fluid exiting the nozzle orifices to rotate the spray head.
For improved cleaning, some of the nozzles are available with solid stream or with flat fan spray
patterns for gentle rinsing. Both spray patterns are offered in a variety of coverages.
The advantages of this type of design include higher impact, better overall coverage, and
reduced fluid requirements. Plus, some of the nozzles are offered in TEFLON®
fluoropolymer
resin, which is chemically resistant in many applications with models engineered for sanitary
clean-in-place applications.
Fluid-Driven (Constant Speed) Tank Washing Nozzles
 Fluid-driven (constant speed) nozzles use the momentum of the liquid flow to drive
the spray head while maintaining constant rotating speed. Unlike conventional fluid-driven
rotating nozzles where cleaning efficiency decreases as pressures increase,
these nozzles increase their cleaning impact as the fluid pressure increases. This
high-impact spray performance means that liquid consumption is minimized and
cleaning efficiency is improved. The controlled rotational speed makes these
nozzles highly useful for tank cleaning, sanitizing, and foaming applications.
Fluid-Driven (Turbine) Tank Washing Nozzles
 This type of nozzle utilizes fluid to spin a turbine, which in turn powers a gear set. This allows
two solid stream sprays to rotate as the hub revolves around the central axis to provide complete
coverage. The most common applications for this fluid-driven nozzle are those requiring
high-impact cleaning in larger vessels or tank cars.
Fixed Spray (Stationary) Tank Washing Nozzles
 The fixed spray nozzle segment includes multi-nozzle spray assemblies
and individual fixed position spray nozzles. The advantages of these
types of nozzles are many: simplicity of design, reliability (no moving
parts), and a wide range of spray coverages. They are ideal for a
gentle washing or rinsing of an entire vessel.
Designing the Best Automated Solution for Your Application
The primary objective of any tank cleaning project is to design
a system that will clean, maintain, and sanitize equipment
at appropriate levels to prevent malfunctions or contamination
that would alter the safety, identity, strength, quality, or purity
of the finished product.
The degree to which this objective is to be met is inherent
to a specific product or industry. For example, acceptable levels
of contaminate for a pharmaceutical application are much
lower than for a shampoo application.
To assist you in the design of a tank cleaning system for your
application, the following are some key tank cleaning terms.
Cycle Time
What is the minimum duration of each stage of the
cleaning cycle? In many cases, more effective cleaning
can be achieved by extending the time of a step.
Here’s a look at four of the typical cleaning stages.
- Pre-Rinse. This stage removes 90 percent of the soil. Tests should be run during this stage to determine if
debris and gross soil is being removed in the first cycle.
- Cleaning. It is important to work with your chemical supplier to establish how long the chemical needs to be in contact with the vessel walls during the cleaning cycle. Water temperature and spray impact may also be important factors in the duration of this cycle.
- Post-Rinse. During this stage, suspended residue and cleaning agents are removed. Rinse time should be adjusted so that no residue remains. Actual cycle time may be determined by nozzle selection, as tank wash devices with solid stream nozzles must complete a predetermined number of nozzle revolutions to complete one cycle. Depending on the corrosiveness of the cleaning agents used, a cold water rinse may be recommended.
- Sanitizing. Application of sanitizing agents to all surfaces, per chemical supplier instructions, occurs during this stage. Micro-organisms are killed to an acceptable level.
Flow Design
System flow design can take either of two forms:
- Total loss. This is where the sprayed liquid is used once and then discharged. In practice, this type of design is only applicable when cleaning is infrequent or very small volumes of liquid are needed. Single use of water may be considered in applications where cross contamination is an issue or soiling is very heavy.
- Partial or total recovery. This is where the detergent or final rinse liquid is recovered and a water make
up rate is determined for reuse. This maintains the effectiveness of the cleaning cycle while reducing water and chemical costs.
In addition, the amount of wastewater generated
during tank cleaning operations can be minimized by:
- Segregating waste streams to capture the clean water while the dirty water is properly disposed.
- Recirculating the wash water or cleaning solutions.
- Capturing the water at the end of the cleaning cycle. For example, one tank’s final rinse can be the next tank’s pre-rinse.
Impact and Cleaning Effectiveness
How much impact is needed to clean your vessel?
There are no firm guidelines as tank cleaning is application
specific. Many vessels require little impact force, relying
on chemical action, water temperature, and rinse down
provided by the nozzle. Other applications require some
level of mechanical force including high-pressure solid
stream nozzles for aggressive cleaning.
Points to Remember:
Spray Coverage and the Elimination of Shadows
Shadowing is the term used when the spray cannot directly
reach part of the vessel due to an internal obstruction,
i.e., a mixer, agitator, or filling tube. Additional nozzles may
be needed to clean the obstruction or the shadowed area.
Water Quality and Chemicals
The water supply should be evaluated for potential problems,
such as dissolved solids or suspended particulate, that
may interfere with the cleaning process. In some cases,
a chemical additive will increase wettability. Another
option is to condition the water with water softeners.
TEFLON is a registered trademark of E.I. DuPont de Nemours and Company.
|
