How To Select A Tank Washer
Selecting the correct tank washer is a vital part of any process system. By selecting the most appropriate tank washer, other parameters of the process can be optimized along with the complete CIP cycle. Turn around times can be shortened, and productively can be increased.
Ultimately this can lead to increased profit, and can increase the companies’ competitive advantage in the market place.
Selecting a tank washer is not difficult, but the information requirements can be varied and not always readily at hand.
Follow the guide in this section in order to learn what parameters are important and where to start from.
There are five sides to the information requirements:-
The first is to know exactly what the result of the cleaning is required to be.
The second is to know what product is being cleaned and its characteristics.
The third is to know what cleaning fluid is intended to be used.
The fourth is to know the vessel parameters and design.
The fifth is to know the CIP system set up and what resources are available.
This is the first place to start when selecting a tank washer. The cleaning requirement means –
What do you want to achieve?
How quickly do you want achieve this?
Health and Safety of staff
In most cases this would translate to:-
A total clean of the vessel as quick and safe as possible.
However, in some cases this is not always true. There are other factors to consider such as:-
Passive Flushing between batches
Cleaning part of a vessel such as the nozzles
How much cleaning media to use
You are making blue paint in a process vessel, and always make the same blue paint in the same vessel, batch after batch, with very little time between batches.
In this example you may not need to fully clean the vessel in between batches, as the odd bit of paint residue would not affect the next batch. Therefore you might simply rinse out excess paint. Turn around time might be more critical.
However, if the example was of a paint manufacturing process that switched colours every batch, and therefore colour contamination would affect the next batch, it would therefore be vital to ensure a 100% clean in between batches.
Another example might be a pharmaceutical/chemical product that is of high value, but also has the problem of becoming explosive once it dries out. Whilst in a damp or wet state the product is stable.
In such a circumstance it might be that product recovery of the high value residue left in the tank is very important. It might also be vital to ensure that after the initial production process is finished, the cleaning device needs to use very low volumes of liquid to keep the remaining residues damp to prevent any explosion risk. The low volumes of liquid are to prevent the recovered product from becoming too diluted and create excess re processing, as well as keeping the residue damp to prevent an explosive risk.
The tank washer can therefore have a dual purpose of not only cleaning in place, but also of product recovery or even sterilisation in place after the CIP cycle is finished.
As you can see, the concept of “What do you want to achieve?” is very important to understand before you actually begin to select the tank washer. Once this concept is understood, then you can move on to step 2.
It is important to know about the characteristics of the product to be cleaned. It is not always important to know the product name although this can often help. However, for reasons of confidentiality this is not necessary.
The product characteristics will identify what sort of cleaning power will be required. Together with the cleaning fluid (step 3), this will give a good indication as to what the ideal tank washer should be. Some of the main considerations are:-
Is the product easily soluble?
How Toxic ?
How Corrosive (Acid/Alkali)?
Is the product Explosive?
How Valuable is the product?
Does the product change properties when wet/dry?
How quickly does it need to be removed from the tank?
Most of these requirements are obvious. For example, if the product is easily soluble then the requirements might be for a passive tank washer, where as if the product was very sticky and viscous, the requirements might be for a jetting tank washer.
However, some are less obvious. For example, the speed of product removal might be very important due to the nature of the product. If the product dries very hard (the product is a coating such as resin) then once dry it might be impossible to remove. It would therefore be vital to remove the product as quickly as possible.
It is therefore very important to consider the product characteristics before moving on to step 3.
The cleaning fluid chosen will also affect the selection of tank washer. If the cleaning fluid is going to be a solvent, then this could cause an explosive atmosphere inside the vessel. This would then require an Atex exempt tank washer.
If the cleaning fluid has a high viscosity, then this will affect the flow and pressure requirements, and so affect the tank washer selection.
If the cleaning fluid will remove the soiling/contamination on contact, then only a low power cleaning unit is required. However, if the cleaning fluid will need some power to do its job, then a jetting unit will be more appropriate.
The cleaning fluid may need to be used at high temperature, and again this might affect the selection of tank washer.
Different cleaning fluids might be used at different stages of the CIP cycle, and therefore it is important that the tank washer chosen can function correctly with all the different types of fluid used.
It is also important to consider the materials of construction, as some chemicals can affect seals, bearings and other components/materials. For Example, a highly acidic atmosphere will affect stainless steel. Hastelloy would therefore be more appropriate.
Which ever cleaning solution is used, it could potentially have an affect on the tank washer chosen.
Vessel Design & Attributes
This area is split down into the actual vessel dimensions and tank shape as one area, and then any attributes/accessories fitted to the tank such as baffles, mixers, dip pipes, inlets, stirrers, scrapers, ladders, outlets etc.
The two main dimensions required are the tank Diameter and the tank Height.
The tank diameter is important to ensure that the tank washer chosen can physically propel the cleaning fluid far enough with sufficient energy to clean the walls of the tank. The tank height is also required to make sure the slant angle and distance from the tank washer to the tank wall is not too great. Two vessels with the same diameter, but with different heights may require completely different tank washers to clean them.
The shape of the tank is also important as this will also affect the tank washer chosen and its means of operation as the cleaning range and angle may change on the different shaped surfaces of the vessel.
The interior attributes and accessories of the tank such as baffles or mixers will also have implications on the type and number of tank washers chosen. CIP fluid can not pass through a solid surface, and therefore any obstruction inside the vessel needs to be taken into account to avoid any blind spots or shadow areas. Also these internal attributes will affect the locations and height of installation of the tank washer.
If a central agitator is fitted, it is important to have at least two tank washers inside the tank either side of the agitator. This ensures that the shaft does not cause any blind spots or shadows. It might also be necessary to consider retracting units to clean the bottom of the agitator.
Where there are baffles fitted, blind spots might be caused by deflection of liquids from the baffles (if they are thick or misshapen) or if the tank washer is not centrally mounted, there might be some increased blind spots created. Where baffles are present, it is always best practice to use multiple tank washers to ensure good angles of attack for the liquid and no blind spots.
Anything fitted inside the tank will affect the shadow areas in the tank and should be considered carefully when looking to select a tank washer.
The number of inlets and the potential CIP inlets can have a significant impact on the tank washer chosen. If due to internal accessories, multiple units are required, but only one CIP inlet is available, then this can cause problems. In these circumstances, there are a number of options available.
When considering the individual fitment of each tank, always consider everything from the prospect of “How are we going to clean that?”
The size of the inlets and access to the tank also needs to be considered. If no access other than the CIP nozzle inlet is suitable for physically installing the tank washer into the tank then this will play a significant part in selecting the tank washer. If an inlet size has a maximum opening of 90mm, then it may not be possible to install a tank washer that is physically larger than this, and this might restrict the type of unit which can be used.
In an ideal world, the size of CIP inlet and its location will be altered / modified to take the most suitable tank washer.
Once all the potential cleaning issues inside the tank have been identified, then you can move on to step 5.
CIP System Set Up.
Step 1, 2, 3 and 4 will have identified what sort of tank washer is ideally suited, and in an ideal world the flow and pressure requirements of the “correct and most appropriate unit” should then be made available.
However, unfortunately in the real world this seldom happens. Typically the FLOW and PRESSURE parameters have already been limited by the plants existing CIP set.
If this is the case the flow rate and pressure at the cleaning head needs to be specified. This should not be based on the pump, or the theoretical flows and pressures. This should be physically measured at the head. Unfortunately, in some cases this is not possible, and it may need to be “Guestimated”.
If this is the case the pump output needs to be specified, along with the pipe lengths, diameters etc. This will give a good indication of what is reaching the head, but is no substitute for real measurements at the cleaning head.
If there is insufficient flow and pressure to use the optimum cleaning head or heads, then alternative solutions will be required.
It may be possible to simple change the delivery pump, or add in a buffer tank for increased delivery, or it may be that a different tank washer or multiple units can solve the problem.
However, changing the tank washers in an existing set up, or changing the delivery pump for inlet flow may also have consequences on the outgoing flow. If a scavenge pump is used to remove liquid from the tank, then the settings on this pump need to be changed in accordance with the inlet flow. If not excess pooling may occur in the tank and inhibit the cleaning action of the tank washer.
What is the existing or planned CIP cycle?
This will highlight areas of changing chemicals which could affect the flow rate and pressure due to changes in liquid viscosity. It will also highlight any re-circulation steps. If CIP fluid is being re-circulated, then adequate filtration must be provided. 500 to 1000 micron filters are ideally suited, but they must be of a sufficient size as to not impede flow and pressure to the tank washer. Cleaning of these filters must also be taken into account.
It is important to consider all the information from steps 1 through to 4 in order to make the correct selection of tank washer. All too often simple spray balls or rotating spray balls are installed without any thought for the above parameters.
Dasic Tank Clean will work with you at every stage to help you find the most practice solution to optimize your CIP and cleaning requirements, and if necessary supply pumps and complete CIP systems to optimize the total system.
The following is a list of information that needs to be considered when choosing a tank washer. If all of this information is gathered correctly, the correct tank washer can be specified relatively easily.
1. What TYPE of RESULT is required from the CIP process?
2. What is the PRODUCT to be cleaned?
3. How QUICKLY does the vessel need to be cleaned?
4. What CLEANING FLUID/FLUIDS are going to be used?
5. What are the vessel DIMENSIONS?
6. Are there any INTERNAL vessel ATTRIBUTES?
7. What INLETS are available for CIP?
8. What is the FLOW RATE available at the tank washer?
9. What is the PRESSURE at the tank washer?
10. What is the intended CIP CYCLE?
11. Are there any RE-CIRCULATION stages?
12. Is there adequate FILTRATION in the system?
13. Are there DRAWINGS of the tank available?