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Rethinking MicroRethinking MicroRethinking MicroRethinking Micro----Travel ShowerTravel ShowerTravel ShowerTravel Shower

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D K [email protected]

Rethink? But WHY?� Micro-travel showers are being used since decades.

� These are proven to be more effective than conventional showers.

� All machinery suppliers (almost) are supplying machines with micro-travel showers only.

June 2014Rethinking Micro-Travel Shower2

with micro-travel showers only.

� Micro-travel showers have already been well documented.

� We are aiming towards 23rd century, why should we think something that is decades old, obsolete?

Reasons to Think…..� Any technology is most suitable only for a particular set of

operating conditions.� Problem starts when we use new technology with old

machines.� If you run latest software on your old laptop, this may run,

but not very efficiently (and vice versa). Maybe much older


If you run latest software on your old laptop, this may run, but not very efficiently (and vice versa). Maybe much older version works better satisfying most of your needs.

� Furthermore, thinking does not cost a capital investment, does not risk our operating equipment or does not deteriorate product quality.

� However, it may give some clues for further improvement.

Back to the Basics…..� You might have already seen the

following pattern in the literature of micro-travel shower suppliers.

� The black lines are areas cleaned by the showers and the white area represents


showers and the white area represents part of fabric that is not clean.

� Nobody would like fabric cleaning in this way. Right?

Look at the Pattern� Look at the white area in the figure.

� You get unclean areas on fabric in the shape as in the shape given below.

� This shape can be characterized by the vertical and horizontal dimensions.


vertical and horizontal dimensions.

� Vertical dimension is in machine direction, while the horizontal one is in cross direction.

Typical Dimensions� As obvious, the horizontal dimension (size in cross direction)

cannot exceed distance between nozzles. Say it is 100, 125 or 150mm.

� Similarly, the vertical dimension (size in machine direction) cannot exceed length of fabric.


cannot exceed length of fabric.

� But, what is the minimum limit of this length we can achieve?

� The vertical dimension can be reduced only if the shower makes a rotation faster than the two rotations of fabric.

Increase Shower Speed� Yes. To get a smaller vertical dimension in the

figure, you need to increase shower speed, but that is not practically possible.

� 10-12 rpm is very high for showers.

� So, can such a pattern really exist on our paper


So, can such a pattern really exist on our paper machines really?

� Should we not start recalculating dimensions according to our running machines?

� By the way, if you had an experience of using conventional shower, did you see such pattern on your fabric anytime?

Machine Direction Strips� If you are using a micro travel shower, do you, sometimes,

notice different dirty and clean strips across the full length of fabric?

� If yes, let us rethink micro-travel showers.


Micro-Travel Showers� The speed of micro-travel shower can be calculated by the

following formula-


� This looks very fine. By this one can be sure that each and every point on fabric will get cleaned by the high pressure water jet on its turn.

Possible Problems� The biggest problem on slower speed machines is that the

shower needs a long time to complete one revolution. That means complete cleaning after a caustic wash takes long time this increasing downtime.

� Some mills have installed two HP showers, a micro-travel for normal operation, and another standard HP shower for faster


normal operation, and another standard HP shower for faster fabric cleaning after a caustic wash. However, officers from ‘Pollution Control Board’ often object to this saying that the mill seems uses both showers almost all the time and thus water consumption increases.

� Some other mills have started depending on LP showers for fabric cleaning after a caustic wash.

Possible Problems� Another practical problem is that the speed of micro-travel

shower is so low that it often appears stationary to the operators.

� In developed countries, you can trust equipment; but in our area, where frequent power cuts and voltage fluctuations


area, where frequent power cuts and voltage fluctuations causing electrical tripping is common; a tripping of micro-travel shower motor goes unnoticed, and it often gets too late when you detect a problem.

Possible Problems� The micro-travel shower design speed calculation does not

take care of the fabric guiding effect.

� If fabric is being guided towards drive side and the shower is also moving in the same direction, uniform fabric cleaning will NOT take place.


will NOT take place.

� If both are moving in opposite directions, uniform but inadequate cleaning will take place.

� Have you noticed machine direction strips of clean and unclean area easily visible just by looking at a glance?

Thinking Out of the Box� The basic idea behind the micro-travel shower is that the

shower should move equal to its nozzle diameter in one fabric revolution.

� But, on slow speed machines this results in increased time to cover the complete fabric.


cover the complete fabric.

Typical Micro-Travel Pattern� A typical pattern showing micro-

travel shower cleaning is given here.

� If the nozzle diameter is 0.7mm, each cleaning line is 0.7mm apart.

� Well, this means shower speed to be


� Well, this means shower speed to be very slow, say less than 0.05rpm.

� Can we get a similar pattern even after increasing shower speed?

Imagine of Another Pattern� Suppose, the shower moves equal to

twice of shower displacement plus nozzle diameter, the pattern could be something like given here.

� In fact, here, there is no difference in


� In fact, here, there is no difference in cleaning of fabric compared to conventional micro-travel one.

� But, here again, the fabric cleaning time will be high.

Another Case� If we consider shower movement only

equal to the shower displacement at one fabric rotation, we may get something like shown here.

� This is not acceptable. Right?


� This is not acceptable. Right?

� But, overall, what is the main difference between all these concepts?

Summing up Information� At shower movement equal to shower displacement at each

fabric revolution, we are supposed to get ‘X’ pattern with clean and unclean areas.

� If shower movement is increased to ‘nozzle diameter’ plus ‘integer times the nozzle spacing’ in every fabric rotation, the


‘integer times the nozzle spacing’ in every fabric rotation, the cleaning can be made similar to theoretical micro-travel shower.

Case Study� Here, one can see that the

micro-travel effect can be obtained at different shower speeds.

� One can calculate that the


� One can calculate that the cleaning would be identical and same if we operate shower at any of the 0.016, 2.25, 8.95, or15.6rpm.

Is There Something Missing?� Yet, a significant point to consider is still missing.

� That is effect of fabric guiding.


Fabric Guiding� In conventional micro-travel shower design, we assume that

the fabric is stationary with respect to machine center line, i.e. cross direction movement is ZERO.

� But, that is not the case generally.

� Fabric moves to and fro in cross direction during run.


� Fabric moves to and fro in cross direction during run.

� In this way, some areas may remain unclean and have to wait long for their next turn.

� This can easily be seen on most fabrics as a band of clean and dirty machine direction strips.

Showering with Guiding� One can understand that a grid pattern formed in

conventional showers will shift its position due to movement of fabric due to guiding.

� So, it is unlikely that we may see such clear demarcation of clean and dirty areas on any fabric.


clean and dirty areas on any fabric.

Making Use of Guiding� This hints a new concept for efficient cleaning.

� If we are able to alter the shower speed with time, the grid pattern formed by one speed will overlap with the pattern formed earlier, and you get a cleaner fabric.

� For better results with this approach, the shower speed


� For better results with this approach, the shower speed should be properly chosen.

� But the results will be same as in conventional micro-travel, except that the whole cycle will repeat fast, thus minimizing the problems caused by guiding.

� Let us name this as Floating Speed Micro-Travel.

Floating Speed MicroFloating Speed MicroFloating Speed MicroFloating Speed Micro----TravelTravelTravelTravel� For a VFD, it is generally considered better if we operate the

same at speeds between 60%-100%. Conventional VFDs may work at speeds as low as 10%, but torque limitations may create problems of current overload in some situations.

� So, for any speed of shower, we may work above 60% of


� So, for any speed of shower, we may work above 60% of rated with VFD controlled system easily.

� In this way, if the nozzle displacement was 0.7, 100.7, 200.7…700.7…; and we try to operate at 0.7mm (conventional micro-travel), we won’t be able to get to another regime of micro-travel like results.

Floating Speed Micro-Travel� But, suppose you are operating at 400.7 or 500.7mm nozzle

displacement and reduce speed of shower to 60%, you will cross previous nozzle displacement figures of 300.7 and 400.7.

� So, the shower will continuously float between one micro-


� So, the shower will continuously float between one micro-travel condition to the other, thus ensuring your fabric will be regularly cleaned at all positions.

Result� In other words, you will have an overlap of different fabric

cleaning patterns like shown in figure.

� For this system, a PLC controlled VFD can be used.


Another Approach� There could be another approach for shower operation that

overrides the guiding action.

� Let us name it Intelligent Micro-Travel.


Intelligent MicroIntelligent MicroIntelligent MicroIntelligent Micro----TravelTravelTravelTravel� If we are able to provide speed of shower as a sum of the

following two in every fabric rotation-�Movement of nozzle diameter

�Movement of fabric itself

� We’ll end up in a situation where effect of fabric guiding will


� We’ll end up in a situation where effect of fabric guiding will be compensated by the shower.

� I consider this as “micro-travel shower of future”.

� It works as if a shower nozzle is ‘following’ the fabric itself to ensure best cleaning of fabric.

Intelligent Micro-Travel� The overall system will include a fabric position sensor, a

computer to evaluate the differential change in cross direction position of fabric (CD speed), which finally sums up the target shower speed with fabric CD speed and govern the shower speed accordingly.

� Today, fabric position sensors are easily available, and such


� Today, fabric position sensors are easily available, and such computation is also not very difficult.

� The only problem that may appear with conventional micro-travel is the range of speed change.

� But, we may be required to run shower at very slow and very high speeds.

Intelligent Micro-Travel� We already know by operating micro-travel at higher speeds

according to approach of floating micro-travel, we can get rid of too low showering speed without affecting micro-travel performance.

� In this way, intelligent micro-travel may make use of floating


� In this way, intelligent micro-travel may make use of floating micro-travel technique.

� The system may be named as-

Showering of the Future

� Intelligent Floating Micro-Travel (IFµT)


� Intelligent Floating Micro-Travel (IFµT)

Thank You.


Thank You.

About the Author:

Born in 1968, D K Singhal is B.E., M.E. (Pulp & Paper, 1993) from Dept. of Paper Technology, University of Roorkee (now IIT, Roorkee, India). He is Certified Energy Auditor and Chartered Engineer also.

With nearly 7 dozen publications on slideshare.net, energymanagertraining.com and paperonweb.com, he has been constantly contributing to IPPTA(Indian Pulp & Paper Technical Association). He is also serving IPPTA as a member of Editorial Board and had been a member of Executive Committee.


An initiative by D K Singhal, a cyber campaign initiated against unjustified targeting of paper industry by “Idea” mobile, in their “Sirjee” advertisement campaign, after which this advertisement was taken off air.

He also moderated a Yahoo group, “PaperTechnology” with nearly 360 members from India and abroad to discuss problems related to pulp & paper making for five years.

He can be contacted at [email protected]

Happy Showering!


Please send your comments and feedback to:

D K Singhal

[email protected]