PNR Tank Washing Technology

TANK WASHINGTECHNOLOGY

CTG TT20 BR

Tank Cleaning TechnologyVersion: 456B (Abridged)

Index

Preface page 3

Common Tank Cleaning Methods page 4

Tank Cleaning Devices page 4

Cleaning Dynamics page 11

CIP (Clean In Place) Systems page 16

Cleaning Validation and CIP Optimization page 17

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01 - Preface

PNR is active in the tank washing business since 1968 anddeveloped since then a quite wide product range to cope with theever increasing requirements of the industry. The success of eachcleaning process inside a tank depends upon a number of differentfactors, each one of them requiring to be carefully considered.While PNR sales personnel will always give their best advice andassistance to our Customers, we considered it would be usefulto publish this booklet in order to give our Customers acomprehensive view into this fascinating technology.

The Science of Tank Cleaning Technology is a culmination ofvarious disciplines and includes but is not limited to the applicationof mechanical function, hydraulics, physics, chemistry, andinstrumentation. The application of these various disciplines for agiven Tank Cleaning requirement will also vary from the simplisticto the very complex.

The safe, efficient, and economic cleaning of tanks and vessels hasbecome a major consideration for a number of industries. Today,less than adequate cleaning can result in...• Off-Spec Products• Lost production• Excessive waste• Excessive energy consumption• Unsafe working conditions

All of these factors can result in lost revenues and in some casesloss of consumer confidence. The purpose of this paper is to makeyou aware of the factors to be considered when analyzing a tankcleaning requirement. This paper should not be consideredconclusive as the available technologies are ever changing. Youwill, however, receive information about various types of cleaningdevices, CIP Design Considerations, Cleaning Dynamics, ValidationMethodologies and more.

Cleaning of vessels and tanks is not a new requirement. In ancientEgypt, manual cleaning of large wine amphorae was very common.However, it is amazing that today this method of cleaning is stillquite prevalent. It is estimated that approximately 40% of the tankcleaning accomplished worldwide today is manually achieved andanother 15%-20% is accomplished inefficiently compared to thetechnology available. The primary reason is due to insufficientknowledge and understanding of today's cleaning technologies.

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02 - Common Tank Cleaning Methods

Most all Tank Cleaning Methods fall into the following categories:• Manual

The process whereby a human being is placed in the tank orexternal to the tank and cleaning is accomplished by eitherhand/brush or with wash hose (high and low pressure).

• Fill and Dump (Floatation)The process whereby a tank or process vessel is filled with therequired cleaning fluid. Agitation and heat may be applied.

• Automated - PortableThe process whereby an automated cleaning device is placed inthe tank; either static or dynamic; then removed after thecleaning process has been completed.

• Automated - Fixed In PlaceThe process whereby an automated cleaning device is placedpermanently in the tank; either static or dynamic; and is notremoved during process, storage or transportation.

03 - Tank Cleaning Devices

The most optimal cleaning process is the one which brings backthe tank or vessel into satisfactory operatingcondition by using:• the shortest possible time• the least volume of cleaning liquid• the least amount of chemicals• the least amount of energy

while at the same time being..,• Reliable• Safe• Economical

To accomplish this, a properly engineered and installed systemalong with the proper selection and placement of theautomated cleaning device is imperative.

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03.01 - Types of Automated Cleaning Devices

Automated cleaning devices fall into the following primarycategories:• Static• Dynamic

Static Devices

Static devices are any cleaning device that does not move and hasno moving parts (Figure 1). Devices within this category are:• Spray Balls• Spray Rings• Static Nozzles

There are variations of these devices in that they can be directionaland vary in their pressure and flow rates. Primary advantages anddisadvantages of these devices are as follows:• Advantages

- Mechanically they are not complicated- Low purchase cost- Little to no maintenance required- Disassembly and inspection process by regulatory authorities is

easy

• Disadvantages- High flow rates compared to other technologies- Low transference of energy to tank surfaces- Blockage of cleaning ports more prevalent- Limited tank size capability- Validation of device operation is difficult compared other

technologies

Dynamic Devices - RJH Non-Integrated Fluid Drives(Auxiliary)Non-Integrated fluid driven rotating jet-heads (RJH) and spheresare those which require a power source to operate the gearmechanism other than the cleaning media (Figure 2). In otherwords, to rotate the head or sphere a pneumatic, electric, orhydraulic power source is required.A rotating jet-head lays a cleaning pattern by rotation of its mainbody axis (the horizontal plane) while at the same time rotating itsnozzle hub (the vertical plane). A full 360 degree or directionalindexing can be accomplished (Figure 3).

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Figure 1

Figure 2

Figure 3


Dynamic Devices - Rotating Spray Head (RSH)

A rotating sphere is either a rotating ball or disc with strategicallydrilled ports or slots for the expulsion of the cleaning fluid (SeeFigure 4). An RSH is normally set into rotation by reaction of thefluid flow against the sphere or disc. As the fluid is dischargedthrough the device, the reaction of the fluid force will set the ballof the RSH or disc in rotation. Some rotational values on sometypes are controlled; but in most cases it is not.• Advantages

- Good transfer of energy to tank surfaces- Lower flow rates- Reduced cleaning times compared to static devices- Reduced chemical usage compared to static devices- Normally improved cleaning results compared to static

devices- Broader range of tank sizes compared to static device

• Disadvantages- Mechanically more complicated- Higher purchase cost- Self cleaning can be more difficult to accomplish

Dynamic Devices - Integrated Turbine Fluid Drives

An Integrated Turbine Fluid Drive is powered by the cleaning fluidthat flows through it. In the case of a rotating jet-head (RJH),normally a turbine is set in rotation by the passing of fluid acrossthe turbine vanes (See Figure 5). This in turn rotates the turbineshaft and associated gears. The device is then set into rotation.• Advantages

- Excellent transfer of energy to tank surfaces- Low flow rates; relative to tank size capabilities- Reduced cleaning times- Reduced chemical usage- Improved cleaning results- Validation of operation is easy- Broadest range of tank sizes- Normally offers the best cost-to-benefit ratio in terms of

cleaning cost.

• Disadvantages- Mechanically more complicated- Highest purchase cost of all dynamic devices- Unless properly designed, self-cleaning is difficult6

Figure 4

Figure 5


03.02 - How Automated Cleaning DevicesFunction

Static DevicesStatic devices predominantly clean the host tank or vessel bycascading the cleaning media on the surfaces of the subject structure.This is commonly referred to as sheeting. The most common deviceused is a spray ball. A spray ball atomizes the fluid flow within a fewcentimeters of the device and a dense mist is projected onto a portionof the subject structure. Solubility of the soil in water or the CIPsolution is relied upon to provide the cleaning action required. Thereis little to no impact values onto the surfaces as a whole. Staticnozzles basically accomplish cleaning in a similar way except that theycan offer increased impact and cleaning radius due to nozzle design…but is usually very localized. These devices rely more heavily on fluidflow, chemical assistance, time, and temperature than dynamiccleaning devices. However, in many cases, this is all that is required toplace the subject tank or vessel back into a satisfactory operatingcondition. Installation of these devices can be accomplished in anumber of ways. The most common for the hygienic industry is theslip-joint or tri-clamp fitting (See Figure 7). Placement of the staticdevice is predominantly located in the upper areas of the vessel (SeeFigure 6) so that the fluid flow will come in contact with these uppersurfaces, thus allowing gravity to assist in dispersing the media to theother portions of the vessel. Directional units are available if only aportion of the vessel is desired to be cleaned. This is many times thecase for open-top tanks or process vessels.

Dynamic Devices - Rotating Jet-Heads (RJH) and RotatingSpray Heads (RSH)As the basic cleaning operation of Auxiliary and Integrated TurbineFluid Drives are similar, we will not segregate the two in this section.Rotating Jet-Heads clean the host tank or vessel by projecting a pre-programmed or programmable cleaning pattern on to the internalstructures of the tank (See Figure 3). This pattern is a series of jetprojections onto the vessel structures. Pattern build-up and densitycan vary from one manufacturer of the device to another. Completecleaning patterns can be developed in as little as 5-6 minutes or aslong as several hours. It is many times not necessary to complete apattern in order to render a tank clean. Shielded (shadow) areas2 tothe cleaning device can many times be cleaned with a deflective jet(See Figure 8). Automatic indexing and the deflective quality of thejet is the primary advantage of the rotating jet-head over that of thestatic device and that of the rotating sphere or disc. The track width3

is cleaned by the jet spread that occurs upon impingement. Rotatingspheres and discs do not develop patterns in the same way as theRJH. In most cases, these devices project either a vertical or horizontalsheet or stream of cleaning fluid. The sphere or disc rotates 360

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Figure 6

Figure 7

2 A shielded or shadow area is thesurface within a tank or vessel thatcannot be projected upon directlyfrom a given position of the cleaningdevice.

3 The track width is the area betweenwhere the center of the jet impingesupon the tank surfaces and the nextadjacent jet track.


degrees and projects the cleaning fluid throughout the structure.Rotating jet-heads, spheres and discs can project onto only a designatedportion of the subject vessel (directional devices) or offer 360 degreecoverage.

Principal factors to be considered in the success of a Rotating Jet-Head are:▲▲ P (Delta P) across the cleaning device.The differential pressure loss from the entry of the cleaning media to itsexit at the nozzle is an important factor. Should the device consume aninordinate amount of the hydraulic energy, jet impacts and distances willbe negatively affected. An easy way to check this is to note the start-uppressure and flow. A lower start-up is a good indication of the RJHmechanical efficiency and hence less mechanical losses through themachine. When evaluating input values the following example mightoccur:RJH 1Pressure @ discharge pump: 6.9 BARGPressure @ inlet to RJH: 6.55 BARGPressure @ nozzle entrance: 5.17 BARG▲▲P across machine: 1.38 BARGRJH 2Pressure @ discharge pump: 6.9 BARGPressure @ inlet to RJH: 6.55 BARGPressure @ nozzle entrance: 6.2 BARG▲▲P across machine: 0.35 BARG

In this case RJH 2 with it’s lower ��P would result in a more efficient transfer of energy. It does notnecessarily mean that RJH 2 would offer an overall better cleaning ability over RJH 1… as numberother factors must be considered.

Machine and nozzle design.The internal design of the machine and nozzleshas a direct effect on achieving laminar flow whenthe fluid exits the nozzle as the jet stream. Laminarflow will result in a high density jet-stream withlonger distance and impact capabilities… resultingin the reduction of cleaning devices, flowrequirements, and enhancing the ability to clean shielded areas. Themore turbulence created within the cleaning device, the more difficultthe task of achieving optimized laminar flow values. Within an RJH;turbulence is created but can be minimized with proper design criteria. Inmost all designs… turbulence is abated primarily within the nozzle hub(Figure 10) and the nozzle (Figure 9). In the case of smaller nozzle designs(Figure 11) little to no turbulence reduction will be achieved. This nozzlebody (Figure 10) employs a tangential offset design as opposed to 180°opposite angles. This allows for reduction of turbulence prior to nozzleentry. The nozzle (Figure 9) employs a tubular bundle or flow straightenerto further reduce turbulence and hence improve laminar flow values.

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Figure 8

Figure 9

Figure 10

Figure 11


Today, the two most common gear mechanisms used in a RotatingJet-Head are the Worm Wheel and Planetary Gear. Both areeffective and proven designs… However the external appearanceand production requirements are reasonably different. The WormWheel Design (Figure 13) will typically use approximately 30%+fewer parts in the construction of the machine compared to the In-Line or Planetary Gear (Figure 12) methodology and will typicallyhave less pressure drop (▲▲P) across the machine. However,externally the bottom of the machine will require enlargement (bellshape) to allow for a horizontal shaft in the process of transferringtorque to the drive mechanism. As a result, the Planetary or In-LineGear design allows for a smaller profile… taking on a cylinder typeof construction and many times reduces the size opening requiredfor entry of the RJH in to the tank.

The machine designs shown in Figure 13 and Figure 12 areconsidered pre-programmed machines. In short this means that agiven cleaning pattern will be developed for a given XYZ locationwithin the tank being cleaned. Depending upon the gear ratio ofthe Fixed Gear (the gear attached to the inlet connection) and themoving gear… typically the one attached to the hub… a setpattern matrix will be developed within the tank. For example;should the fixed Gear employ 65 teeth compared to the hub gearthat has 63, it will take 65 axial revolutions to make one completepattern. After the 65th revolution, and for a given XYZ locationwithin a tank, the pattern matrix will begin all over again… tracingback over where it originally began. The pattern matrix of a twonozzle for both a 65/63 and 45/43 gear ratio can be seen below inFigure 14.

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Figure 13

Figure 14

Figure 12


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Figure 16

Programmable Tank Cleaning Machines typically will use a singlenozzle design; similar that seen in Figure 15 below.The cleaning patterns are mechanically programmed to start at agiven point in the tank and indexed based on a chosen degreeinclination per revolution.

A computer controlled tank cleaning machine does exist today inthe form of a product called the CyberJet. The cleaning jet, whichtakes the form of a single nozzle machine with retractable downpipe, is controlled by servos that operate via software workingfrom a geometrical representation of the tank being cleaned. SeeFigure 16 for a visual representation of this device.

Figure 15


04 - Cleaning Dynamics - The Science ofTank Cleaning

Jet Peripheral Velocity - JPV (RJH Devices)The peripheral speed at which the jet-stream is traveling at thefarthest distance from the device is a critical factor, particularly inlarger or more difficult to clean tanks. See the formula in Figure 17and illustration in Figure 18.

This is the most critical factor to consider when selecting andapplying an RJH to a given tank cleaning requirement.As a general rule, the following peripheral speeds should beobserved:Maximum impact requirements 0.15 to 0.45 m/secStandard impact requirements 0.45 to 1.5 m/secLow impact requirements 1.5 to 2.5 m/secGood washing and rinsing requirements 2.5 to 3.5 m/secGood wetting requirements 3.5+ m/secAs the speed of the jet-stream increases, the duration time of the jeton the surfaces is reduced. Additionally, the jetshear becomes moreprevalent. This serves to degrade the jet-stream and reduce its impactand distance abilities.

Jet Density + Velocity = Impact.The density of the jet is controlled by the volume of fluid in the jet andto an extent by the specific gravity of the cleaning media. Velocity isrelative to the fluid pressure upon entrance to the nozzle and theachievement of adequate laminar flow upon exiting the nozzle. As weare dealing with a liquid, too great of a jet velocity will serve todegrade the jet-stream prematurely. For example, a pressure of 10 barat the nozzle entrance where surface impact is 10 m from thecleaning device will result in a higher impact than that of 30 bar atthe nozzle. Correspondingly, as the surface becomes closer to thedevice, impact values will normally increase and higher pressurevalues at the machine will become more efficient.

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Figure 17 Figure 18


Locating The Cleaning Device

Placement of the Rotating Jet-Head is not accomplished in thesame way as placement of the Rotating Spray-Head or disc. Therotating sphere or disc is positioned in much the same way as thestatic devices. Although these cleaning devices overcome distanceand impact limitations imposed by static devices, it is advantageousto benefit from the cascading effect when installed in the upperportion of the tank or vessel. When determining the position of therotating jethead, a geometrical study of the host vessel isrecommended.

As the rotating jet-head overcomes limitations of the other devicesmentioned, an improper location can result in less thansatisfactory results. A study of the jet-stream impact angles anddeflection requirements should be made. In doing this the numberof units, time, and flow rates required to accomplish the desiredcleaning can be optimized. See Figure 19, Figure 20, Figure 21and Figure 22.

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Placeent Drawing - Profile View

Figure 19

Placeent Drawing - Plan View

Figure 22

Figure 20

Figure 21


Validation of Cleaning Device Operation

Validation of operation for static devices and rotating spheres ordiscs are for the most part limited to the monitoring of flowmeters, pressure gauges, or ultrasonics. It is difficult to validate thatall the ports of a spray ball are clear or that a rotating sphere or discis in rotation. Visual inspection by means of a sight glass is areasonably good method. However, in addition to the sight glassmethod, a rotating jet-head can have its operation validated by therotation of the jet impinging upon a pressure sensor (See Figure23). This signal can then be interpreted in various ways, subject tothe facility's requirements.

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Figure 23


Selection Of The Appropriate Cleaning Device

The selection of the appropriate cleaning device can involve anumber of factors. However, if due consideration is given to theapplication, the process can be quite simple. When selecting thecleaning device consider the following with regards to theapplication at hand:

Dimensions and internal structures of the tank or processvessel?The size and number of internal structures of the tank or processvessel will be a major factor in determining the type and quantityof devices required.

Type of surfaces to be cleaned?Electropolished stainless steel and glass lined vessels are far easiersurfaces to clean than carbon steel or certain types of coatedtanks. The condition of the lining can also be a factor. This is dueto the frictional resistance of the surface to the cleaning mediaand its ability to absorb the product.

Are sanitary conditions required?Sanitary cleaning devices, in most cases, are more costly and willutilize more flow than a device that does not consider thisrequirement. If you require a 100% self-washing device, make itknown in your cleaning design.

What openings are available for the installation of thecleaning device?In the case of new equipment, this consideration is more flexible.A review of the vessel design can be made prior to constructionand the cleaning requirements determined. Installation is madeeasier and usually less costly. However, in the case of existingequipment, the desired location for the cleaning device may notbe available. This will have a bearing on the device selected andits operating parameters.

What percentage of shadow4 areas are acceptable?At present, there are no regulations governing the percentage ofshadow areas for any industry other than marine.However, it is a factor that should not be overlooked whenselecting the proper cleaning device. This consideration is aprincipal factor in determining the number of devices to be used,the type, or both.

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4 See footnote 1. A shadow area is thesame as a shielded area.


Desired cleaning time?As production requirements may be a primary factor, the speedat which the selected device or devices will render the tank orvessel clean, would be a consideration.

Reason for cleaning?What required the subject tank or vessel to be cleaned? Toprevent cross-contamination, sterilization, preparation formaintenance, product recovery, etc.

Is it desired that the cleaning device be permanentlyinstalled or portable?5

The installation assembly and cleaning device can be of differentnatures if portable rather than fixed placement is desired. Forexample, you may not normally require the device to be fully self-washing if it is to be installed only for the cleaning process andthen removed.

Type of soil to be removed?The device selected is largely influenced by the type andcondition of the soil to be removed. As a simple example,consider the removal of methanol versus the removal of latex.The methanol can be removed with simple cascading of the fluidover the surfaces. A spray ball or rotating sphere/disc could beemployed, subject to tank size and capacity.However, in the case of the latex you would be cleaning a longtime if you used a spray ball or rotating sphere. For latex, it wouldbe more prudent to use a rotating jet-head at the requiredpressures and flows.

Budget considerations; capital cost and operational?The cost of cleaning devices and their associated systems for agiven application can cost from $150.00 to $1,000,000.00+. Thepurchase of the device is only part of the cost. In many cases, ifthe proper cleaning system and device are selected, operationalsavings can result in a favorable return on investment.

Operating parameters?Pressure, flow rates, tank/vessel evacuation rates, cleaning media,operating and at rest temperatures of the cleaning device are allconsiderations in the selection process. These criteria willdetermine, among others, the construction requirements of thedevice.

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5 A portable cleaning device is anydevice that is placed into the tank orvessel for cleaning then removedonce cleaning has been accomplished.The device does not remain in thevessel during process or storage ofthe product.


05 - CIP (Clean In Place) Systems

CIP Systems fall predominantly into the following three categories:• Single Use/Single Pass• Single Use/Recirculatory• Multi-Tank Solution Recovery

As this is an abridged version of this paper… we will not go intothe depth required concerning CIP Systems.However, in general it should be understood, that the CIPSystems should never be designed until the cleaningrequirements have been determined. It should also be noted thatin addition to the cleaning of the lines, valves and otherassociated wetted areas must be considered. This in many casescould require multi-pumps or multiple pumps to achieve thisrequirement. On determination of the in-tank cleaning design,the in the CIP design process is the formulation of the P&ID(Piping and Instrumentation Diagram).

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06 - Cleaning Validation and CIP Optimization

Cleaning Validation is the process whereby the desired cleaningis verified by means acceptable and repeatable for the givencleaning requirement. CIP Optimization is the process ofstreamlining the cleaning process so that operationally thehighest level of efficiency is achieved.

In brief, cleaning validation is accomplished today by thefollowing means:• Sight• Time and Temperature• Conductivity• Plate Counts• ATP (Adenosine Tri-Phosphate)

Prior to any Cleaning Validation Process, it is generally goodpractice to validate coverage by means of establishing rinseprotocols so as to insure that all surfaces that require cleaningreceive the minimal fluid flow requirements. One of the bestmethods is the Riboflavin Rinse Validation Process. This methodemploys the spraying of a Riboflavin mixture onto the surfacesto be cleaned and then validating coverage with a long-waveultraviolet light. On validation of that coverage the prescribedcleaning arrangement is started and at set time intervalschecked and recorded until the surfaces are free of theRiboflavin mixture. Riboflavin is readily miscible with water atambient temperatures and very accurately reveals if fluid flowreaches the required areas of the tank, valves, pipes, and otherareas within the tank or process structure.

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Figure 24 Figure 25

Application of Riboflavin Mixture


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Validation of Coverage with Long-Wave Ultra Violet Light

Figure 26 Figure 27

Figure 28 Figure 29

Photos After Rinsing


Once sufficient rinse coverage is established, validating cleanlinessby the taking of a rinse sample can then be considered viable.Conductivity is a reasonable good way to monitor the absence ofcertain fluids within the rinse water but is limited to those fluidsthat possess a reasonably good conductivity value. Biologically, oneof the best methods is to measure bio-mass using the ATPdetection method. All organic matter possesses ATP (Adenosine Tri-Phosphate). When ATP is properly mixed with Lucifern Luciferase achemical light is produced that can be accurately read andrecorded by a properly balanced luminometer.

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PNR Tank Washing Technology