Transcript The vacuum Pump - University of Wisconsin–Extension

MilkTech International
Web-assisted Training in
Milk Harvesting
An educational initiative by:
University of Wisconsin - Madison
(USA)
Milking Research and Instruction lab, and the
Babcock Institute for International Research in Dairying
University of Melbourne –
(Australia)
National Milk Harvesting Center
Milking and Pumping Trade Association
(New Zealand)
The UK Dairy Group
(UK)
Vacuum Production and
Control
This is an example from the course
Introduction to Milking Machines

MilkTech has drafted 14 ‘courses’ from introductory to advanced technical
levels. See the MilkTech intro presentation for this list.
The Introduction to Milking Machines Course contains 3 modules
Introduction to Lactation Physiology and Milking Procedures
Milking Machine Components and Basic Concepts
Integration of Components into a System
Each module contains multiple topics
This example topic “Vacuum Production and Control” is intended to


familiarize students with milking machine components
teach basic concepts necessary to understand how each of these
components work
This topic is intended for a beginning audience and contains many
animations to help visual learners picture the concepts. The
emphasis is on concepts not numbers.
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Learning Objectives
In this module, we will cover…
concepts of vacuum
what a vacuum is
how a vacuum is created in a milking machine
how a vacuum is controlled in a milking machine
the different parts of the vacuum
production and control system
vacuum pump
vacuum gauge
vacuum regulator
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What is Vacuum?
A pressure difference
Think of a box divided into two equal
parts by a flexible “balloon”.
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What is Vacuum?
If each side of the box contains the same number
of air molecules, the pressure will be the same on
each side, and the pressure difference between
the two sides will be zero.
There will be no differential force to move the
‘balloon’, and it will not be stretched.
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What is Vacuum?
If we take ½ of the air molecules out of one side
of the box, the pressure in that side will be less
than the pressure on the other side.
The full side will have a positive pressure relative to the
½ full side.
The ½ full side will have a partial vacuum, or lower
pressure, relative to the full side.
Vacuum
negative
pressure
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positive
pressure
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What is Vacuum?
When air is removed from one side:
the positive pressure will PUSH the balloon
The negative pressure will PULL the balloon
the balloon will bend towards the vacuum side
(the side with less air molecules)
Vacuum
negative
pressure
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positive
pressure
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Rules of Vacuum
A force is developed toward areas of
negative pressure or higher vacuum.
Because of this force, air moves toward
areas of lower pressure or higher vacuum.
Air moves to “fill the void” created by
fewer air molecules in areas of vacuum.
When the pressure is equalized, there is no
pressure difference—no force and no air
flow in any direction.
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Vacuum Gauge
A vacuum gauge is a device used to
measure the pressure difference between
the inside of the milking machine and the
atmosphere.
It may be a mechanical device or an
electronic device.
The next slide displays some different
types of vacuum gauges.
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Types of Vacuum Gauges
Permanently
mounted digital
gauge
Bourdon tube
mechanical gauges
Hand-held digital
gauge
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Vacuum Principles
Now let’s think about a
milking machine as a simple
jar.
•If the air density is the same
inside the jar as it is outside
the jar
•there is no pressure
difference between inside
and outside
• no positive pressure
• no vacuum in the jar
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Vacuum Principles
50 kPa
0 kPa
100 kPa
If half of the air in the jar
is removed, a partial
vacuum will be created
inside the jar relative to
the outside atmosphere.
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What is a Vacuum Pump?
A milking machine operates under a partial
vacuum.
This vacuum creates the pressure
difference to pull milk out of the cow’s
udder.
The vacuum pump removes air from the
milking machine to create this partial
vacuum.
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The Vacuum Pump
This is a lobe vacuum pump.
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There are several other types of
vacuum pumps but they all do the
same job
Water Ring Vacuum Pump
Turbine
Rotary
Vane Vacuum
Vacuum Pump
Pump
Vacuum pumps remove air from the milking
machine to create vacuum inside the
machine.
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Vacuum Production
50 kPa
0 kPa
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100 kPa
If this vacuum pump
removes half of the air from
our jar, a partial vacuum (50
kPa) will be created inside
the jar relative to the outside
atmosphere.
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Vacuum Production
•Air is admitted into the milking
fromthe
many
Note:machine
air is filling
places.
void and the vacuum
50 kPa
pump
is notjar
removing
•In this
example the milking
machine
begins with
any air so the vacuum
a vacuum of 50 kPa.
drops
the pressure
•Air is then admitted through
theand
milking
unit until the
difference
is equalized.
inside
and outside
is equal.
0 kPa pressure between
100the
kPa
Vacuum Pump
Milking Unit
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Vacuum Production
0 kPa
kPa
In50
this
example, the vacuum pump is
removing air from the jar at the same rate that
it is admitted by the milking unit so that the
vacuum in the100
jar kPa
is maintained.
Vacuum Pump
Milking Unit
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The Vacuum Regulator
Most vacuum regulators are valves that admit a controlled amount of air
into the milking machine.
If the vacuum gets too
low, the regulator
admits less air to
increase the vacuum
in the milking machine
If the vacuum gets too high,
the regulator admits more air
to reduce the vacuum in the
machine
Air admitted
by regulator
Air removed by
vacuum pump
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Air admitted to
milking machine
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The Vacuum Regulator
In most milking machines air is removed from the milking machine at a
steady rate by the vacuum pump.
The amount of air admitted to
the milking machine changes
during the milking process.
The regulator
makes up the
difference
Air admitted to machine
+ Air admitted by regulator
= Air removed by vacuum pump
Variable amount of air
admitted by regulator
Steady rate of air
removed by
vacuum pump
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Variable amount of
air admitted to
milking machine
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Here are some different
types of vacuum regulators
Spring actuated regulators use the same principle as weighted regulators except
that the closing force on the control valve is supplied by a spring. The tension of
the spring is adjusted by changing the length of the fully extended spring, usually
with a screw-type adjusting mechanism. Spring actuated regulators may be
damped
using an oil fill reservoir
or other
Modern servo-operated
regulators
use mechanism.
a feedback system consisting of a
Weighted regulators use a
sensing element and a mechanical
‘dead weight’
amplification system. These devices
are or a weight
mounted
a more sophisticated version of
spring on a lever system.
force
type regulators as the vacuumThe
level
is of the weight acting to
controlled by varying the forceclose
of a the control valve is
spring attached to the sensingbalanced
element.by the force of the
system vacuum acting to open
it. The rapid movement of the
valve stem or weight may be
impeded by a damping
mechanism.
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The Vacuum Regulator
Vacuum Regulator
The
vacuum
pump
isairremoving
this
In this
animation
will
see how
We
start
withwe
being
airvacuum
at theinto
same
it is
the
regulator
balances
admitted
an rate
openthat
teatcup
to to
keep
thethe
system
airadmitted
admission
keep
system
of the milking
machine.
vacuum
50 kPa.level.
vacuum
at a at
constant
50 kPa
0 kPa
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100 kPa
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Vacuum Regulation
Now
we
attach pump
the
milking
The
The
vacuum
regulator
opens
is and
stillunit
to
the cow
and
the
from
removing
starts
to admit
air
atstop
air
theatsame
theair
same
rate
entering
through
theremoved
teatcup.
rate that as
it isbefore.
being
by the vacuum pump to keep
the system vacuum at the set
point – 50 kPa.
50 kPa
0 kPa
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100 kPa
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Vacuum Regulation
In a real milking machine, the situation is
more complicated because air is admitted
from many sources both steady and
intermittent. However, the basic concept
is the same.
The regulator makes up the difference
between air admission and air extraction to
keep the system vacuum at a constant
level.
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Let’s Review
A milking machine operates under a partial vacuum.
This partial vacuum is created by removing air from the
milking system with a vacuum pump.
This vacuum level is kept steady by the vacuum regulator.
The vacuum regulator balances the air admission with the air
extraction to keep the system vacuum steady.
If the system vacuum drops as a result of more air being
admitted than extracted, the regulator will admit less air to
bring the system vacuum back up.
If the system vacuum rises as a result of less air being
admitted than extracted, the regulator will admit more air to
reduce the system vacuum.
Newer vacuum regulation technology uses a variable speed
control on the vacuum pump. This will be discussed in a
future module.
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Let’s Review
The Rules of Vacuum
Vacuum is a term used to describe a
pressure difference.
Vacuum refers to an area of negative
pressure relative to the atmosphere (or
some other reference point)
The vacuum pump is the prime mover of air
in the milking machine.
Air is admitted into the milking machine
from many sources, both steady and
intermittent.
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Let’s Review
The Rules of Vacuum
All of the air that is admitted is removed by the
vacuum pump.
Therefore, the path of air flow in a milking
machine is toward the vacuum pump.
A force is developed toward areas of negative
pressure or higher vacuum.
Because of this force, air moves toward areas of
lower pressure or higher vacuum.
The vacuum pump inlet must be the point of
greatest vacuum level in the milking machine to
keep all of the air moving towards it.
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Quiz
After the students have competed this module, they will be
eligible to take an online quiz testing their understanding
and comprehension.
If they fail the quiz, they will be instructed to study the
module in greater detail.
If, in subsequent lessons, we find that they do not
understand the concepts of vacuum production and control
they will be directed back to this module.
The following slide gives an example of an online quiz.
These online quizzes are automatically graded. The
instructor can monitor the progress of all of their students
as well as quiz questions that are the most difficult for
students – indicating a need for a better instructional
module.
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Quiz Example (from online
renewable energy course)
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