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Rotary Lobe pumps
Hygienic and aseptic design
Over the last 25 years, the main issue to provide cleaner Rotary Lobe
pumps has been to reduce entrapped product within the pumps. Most pumps
developed since the beginning of the 90’s have had the clear ambition to
be cleaner and in some cases even tried to combine clean, high clean
with cost over time. A view on present and future developments by
Johnson Pump AB.
All started in the early 30’s when the dairy association in the United
Kingdom gave an assignment to some pump companies in the UK. They wanted
a pump for gentle handling-not whipped cream or butter coming out-and at
the same time the pump should be easy to clean. The perception of clean
at this time was visually clean.
The concept of RotaryLobe Pumps was spread among several manufacturers
in the 60’s in Europe as well as overseas. In the US the concept of hand
cleaning was developed into a standard known today as 3A. This standard
is a certification guiding the design of pumps to be accepted by visual
inspection at all critical hazard areas. This means that you have to
obtain minimum radius, tapped threads, etc. to be able to see that they
are visually clean.
In Europe the hand cleaning process was questioned due to fact that the
human hand is one of the biggest hazards; you never know where the hand
has been before it enters the pump. In the end of the seventies there
were tests for automatic cleaning that ended up as a standard for C.I.P
(Clean In Place) in the 80’s.
Contamination problems
During this time all saw a dramatic reappraisal of many of the
standards and practices previously regarded as acceptable within the
dairy industry. This was following incidents, both at home and overseas,
of contamination of products by micro-organisms. Up tot hen these
problems had rarely ever been encountered other than in raw milk
supplies and these problems had only affected the average dairyman in
earlier years. Problems of salmonella, listeria and yersinia
contamination in finished products have all played their part in
accentuating the need for stringent food hazard assessment in every
field activity, cleaning technology being not the least among these.
In the beginning of CIP cleaning, huge systems were built involving both
raw material handling as well as the process. Today CIP cleaning is
split up into many small cycles targeting specific products and their
significant problems. In the end this also influenced the design of
pump manufacturers and if we look specifically at lobe pumps all are
hunting entrapments within the pumps so as to have less bacteria growth
over time in the pump. At present suppliers of pumps have possibilities
to prove designs of pumps via EHEDG Certificates tested and judged by
independent testing units such as TNO.
Reducing entrapped product
Over the last 25 years, the main issue to provide cleaner Rotary
Lobe pumps has been to reduce entrapped product within the pumps in
areas such as a-ring groves, free space holes for retainers in front
covers, retainer design, splints in between the rotor and the shaft,
rotor hydraulic design in combination with volumetric efficiency, back
covers, etc.
In the beginning of the 90’s the first real attempt came on developing
high clean as well as aseptic pumps. Pump manufacturers had learnt how
to develop pumps that were accepted both for 3A standard as well as
capable of CIP, SIP cleaning in one and the same design. They had learnt
about the most difficult part-the seals of the pump: moving them into
the movement of the pumped product in the heart of the pump instead of
its original position in between the wet (product part) and the gear box
that has always worked as a dead end. This has not only improved the
clean part, it has had tremendous impact on the function as well as for
maintenance and service.
This also gave the possibility to design self draining pumps that today
often are required; the ambition from production is to have totally self
draining systems in a near future, again to avoid or reduce entrapped
product with bacteria growth within the system.
At the beginning these pumps became quite sophisticated and self
draining came in the same design as aseptic. This meant that these
extreme pumps, providing safe, protected interfaces in between the front
cover, port connection as well as at the seal areas towards the outside
to avoid cross contamination, became very expensive. To this add several
other factors: demands on the external design and demands to minimize
risk avoiding areas on a pump where liquid could remain. This impacts
also the total design of a system also from an external design. If you
have extreme demand or may have in the future you should also consider,
base plats, framework, hoods over drive units, etc.
Example: cheese production
Today there are Rotary Lobe Pumps suitable for all type of demands.
Everything from traditional lobes with low demand, quite easy
application to high clean or in some cases where even aseptic pumps are
needed, it is important to discuss and understand or anticipate future
needs together with the present. The reason for this is to pinpoint the
need in this application. For example: normal life time for a lobe pump
in clean areas is 10 to 15 years. It is up to the supplier as well as
the customer to find out the need for this coming years. It would be
stupid to invest in traditional pumps if the consensus is that the
demand on self draining will be implemented in the next coming 5 to 6
years. In the end this means that the customer would have to change out
perfectly good pumps due to the fact that the tandem supplier/customer
didn’t make a good analysis of present as well as of future needs
resulting in higher cost.
A perfect illustration for the need of partnership between supplier and
customer is the case of a cheese manufacturer who needed to invest in
new pumps. His first question was that he wished to have an offer for
exactly the same pumps he had (these pumps were installed 12 to 14 years
ago). He was happy with them and the people within his organization knew
the pumps regarding performance and maintenance, as well as being well
trained in service for these pumps. We started to discuss future demands
on his area of cheese manufacturing, as well as process needs. I asked
which were the most common discussions at the moment and he immediately
told me about securing safety of production, improved demands on clean,
clean in process, external etc. He also started to talk about cuts of
cost in production but he didn’t see any possibility to implement this
on his pump selection. We discussed external design as well as need of
self draining systems in the near future as well as cost of production.
I informed him about the life time as he knew but didn’t think of, we
discussed new modern design, how to position the pumps in the system as
well as ownership cost over time and in an hour we could see that he
really needed new modern pumps.
Related to self draining:
If he invested in the old design the possibility of self draining was
not possible meaning that when the demands came, he would have to invest
in new pumps, estimation in time 4 to 6 years. This would mean new pump
investment, high cost and loss of money.
Related to Clean & Cost:
If he invested in the old design, no improvements could be made on
securing the product quality due to entrapment of product with the
result of more, quicker problems with bacterial growth over time. No
cost reduction, probably increasing cost over time due to increasing
demand on hygiene (needs to clean more frequent).
External demand on clean:
Should be discussed to avoid problems on future demand where normal
base plates are not considered as clean enough and frame work in
hygienic design is preferred as well as a hood over drive unit and
coupling is needed to be able to secure the external demand on clean.
Cost of ownership
To this can be added cost of ownership. At the same time as they
developed new hygienic pump, suppliers have spent tremendous amounts in
developing pumps that are cheaper to own over time so that maintenance
and service becomes more cost effective. So we also talked about higher
demand CIP as well as SIP cleaning, manual disassembly and assembly of
pumps on daily basis demand cleaning critical parts in an autoclave.
These procedures put more and more strain on articles of consumption
such as a-rings, elastomers and gaskets that have to be changed more
frequently.
Pump overhauling
If we compare time to be spent on an old designed pump with a new pump
it is quite dramatic. A complete strip down on an old pump and restoring
it with new articles of consumption, checking all shims areas including
bearing change takes around 1 to 1,5 days in time. On new modern
designed pumps this will take about 1 to 2 hours.
Mechanical seal maintenance or replacement was more or less impossible
to do earlier in production. This meant that the entire pump had to be
exchanged with a spare pump or service had to be planned together with
another stop in production with the result of a completely destroyed
seal at a high cost and long time leaking at high cost instead of a
quick stop and fixed in a matter of minutes as possible today. Estimated
stop for old design 1 hour to change and 1 to 1,5 hours at service
department and to reinstall an extra 1 hour; in total 2 to 3 hours
causing interruption of production. Today with modern pump changing
o-rings or the total seals requires only 5 to 10 minutes.
In the end there are a lot of cost savings on modern designed pumps not
only in the matter of cleanliness.
Conclusions
Modern pumps are in some cases more expensive to purchase but the
cost of ownership over time is continually dropping. Less time is spent
with the pump (maintenance and service). Cleaner pumps with fewer
entrapments within the pump mean longer time intervals between CIP
cleaning sessions, which gives more production time. Self draining
systems / processes with built-on CIP cleaning valves (integrated in the
front cover of the pump) instead of old by-pass design with separate CIP
seat valves with the same result in longer time between the CIP cleaning
sessions decreasing lost production. Less parts to be maintained, more
and more standard details used and stable compact design decreases cost
even when mistakes are made.
We have in existing systems refitted old pumps to new including the
built-on CIP valves and taken the old valves and by-pass away and we can
see that in the old updated system we have decreased the CIP cleaning
sessions 2 to 4 times per week resulting in increasing the production
time between 90 to 180 minutes/week. This is in general; in some cases
more time is realized and in some less but approx. 1,5 to 3 hours more
production time per week.
What about the future?
Future developments in lobe pumps will be in material; a combination
of different materials using the different specific effects will provide
more efficient as well as cleaner pumps as well as smooth clean
surfaces.
Hunting down entrapped product in the pumps will continue, minimizing
them or excluding them totally if possible. This might mean that we will
find other solutions in the design of seals, sealing of shafts - perhaps
mag-drive etc. It is for instance possible to build pumps without the
geax box using individually driven asynchrony motors. This will create
opportunities to provide cleaner as well as higher efficiency on low
visceous medias, resulting in gentler handling.
Specially designed pumps in both design and materials will be developed
for specific duties. This is something that some of the suppliers
already are doing today with good results. However, the main problem
with these pumps is that they become quite expensive to produce even
though the total cost over time can go down.
During my 30 years in or close to the pump business I have experienced
the pump manufacturing time when we pump manufactures developed pumps
that we believed were the best solution without asking any customers for
advice. This was the trial and error period for customers buying on flow
and pressure without any guarantees for function. Sometimes it worked
and sometimes it didn’t-if not, followed by new purchases and new tests.
Customers were creating their own experience.
Today we have learned a lesson: we as pump manufacturers are not
developing any pump without a deep study of what will be the demand from
the market. We are looking closely at specific segments that we wish to
target, anticipating the changes in specific segments following the
development in processes, applications as well as in technology to be
able to develop next generation to pin point the need from the market.
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Information courtesy of Johnson Pump AB
BOX 1:
The Rotary Lobe Pump Market
At present the Rotary Lobe pump market is a defined and mature market.
There are approximately 25 producers manufacturing more than 50 ranges
of Rotary Lobe Pumps. The total market demand is between 32 000 and 36
000 pumps / year at a value of approx. 225 -265 MEuro. The breakdown is
that Europe takes approx. 12 000 pumps, US and connected markets 12 000
pumps and the rest of the world 12 000 pumps. The spread today is from
easy common applications / pumps to high demanding clean and in some
cases aseptic applications / pumps where the main numbers of ranges
still are represented by what we call ‘traditional’ rotary lobe pumps
(improved in clean as well as more cost effective over time). Food is
the single largest market at 40%, the total hygienic market at 65% and
the non hygienic market at 35% is spread over all types of industrial
segments from raw material handling through the process, as well as in
the final product handling. <<
BOX 2:
Sterilizing In Place SIP
Equipment components may need sterilizing, i.e. heating to high
temperature (up to 140°C) to kill organisms still remaining on the
surface of the equipment, taking to an autoclave (a sterilizing
machine), sterilizing, removing and bagging. Reassembling and then
running. A long, costly process which represents all sorts of problems
to personnel and can cause much accidental damage. The trend now is to
pass steam through the system and sterilize the internal surfaces
without dismantling. It is important to steam through for a period long
enough for the coldest part of the system to reach the temperature
required for the time period required to kill off the organisms.
Equipment components may need sterilizing, i.e. heating to high
temperature (up to 126°C) to kill organisms still remaining on the
surface of the equipment, sterilizing, removing and bagging. Using hot
water in the same way as steam, by pressurizing the system is able to
run water at 126°C, flushing through for a period long enough for the
coldest part of the system to reach the temperature required for the
time period required to kill off the organisms.
Aseptic and bio-technological processing
An aseptic process, or part of a process, is one that requires the
avoidance of the ingress of microorganisms into a process that might
contaminate the product. Typically processing of food into aseptic
containers, of fermentation processes where a stray organism could spoil
the fermentation. In food processing a typical example is the processing
of low acid foods containing particulate matter.<<
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