Note: Descriptions are shown in the official language in which they were submitted.
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PU~l~IN~ ~Y~ M~
This invention relates to pumping systems
particularly ~ut not exclusively for handling such
materials such as slurry or sludge having high
content of solids, particularly but not exclusively
the transfer of such materials over substantial
distances utilising high pressure small bore pipelines.
Under practical conaitions the volume of material
to be handled by a pumpiny system may vary widely
at different times as may the consistency and other
1~ properties of the material, for example the ratio
of solids content and fluid content and this will
affect the flow characteristics of ~he material
in the particular pipeline. For maximum efficiency
and safety of operation it is desirable that the
pipeline is kept fully char~ed at all times with
delivery from the output end of the pipeline taking
place at a substantially constant rate ana pressure
regardless of fluctuations in input. Where the
pumping system is part of a water treatment plant
or sewage or effluent disposal plant voids in the
pipeline flow may become filled wi~h flammable
gases such as methane giviny rise to danger of
explosion.
The~obJect of the invention is to provide
~S a pu~ping system which will substantially meet
the above desirable requirelnents and which will t
operate automatically and reliably under service
conditions In a wide range of applications.
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~ ne kind of ~ump known for the purposes referred
to above such as handling slurry or sluage comurises
a ram-ty~e piston or other displacement member
mounted for reciprocation in a cylinder having
inlet and outlet ports for admission and discharge
of material to be pumped, and power actuated drive
means, commonly a hydraulic ram, linked to the
displacement member and actuated to effect reversal
of the latter at the end of each stroke. ~aid
1~ ram is usually operated by a hydraulic pressure
system whose prime mover is an electric motor driving
a hydraulic power pump. While the ram-type pump
may be double-acting utilisin~ the displacement
member to define a variable volume chamber at each
end of the cylinder, a single acting arrangement
is more commonly employed particularly for heavy
duty high pressure applications. Double or single
actiny pumps as defined above are hereinafter referred
to as Ureciprocating pump units of the kind described#.
~U A plurality of such units may be operated
in a pumping system in parallel with each other
and controlled for sequential operation of their
displacemen~ members a~ ~esç~ibed in our co-pending
Canadian Patent Application No. 482,812 and to which
reerence is made for further details.
According to one aspect of the present invention
we provide pumping apparatus comprising one or
more reciprocating pump units of the kind described,
a delivery duct through which outflow from the
unit or units passes in use, control means operatively
connected to regulate operation of drive means
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~f the unit or units, sensing means responsive
to a property or properties of outflow within the
delivery ~uct in use, and feedback means applyiny
a signal or si~nals wllich are a function or functions
of said property or pro~.-erties to the control means
to maintain the power output frorn the pump unit
or units developed in said outflow at a substantially
.constant level duriny operation.
Conveniently said sensing means include a
pressure transducer providing a direct reading
of the pressure at any given time in the delivery
dùct and a flow rate recorder monitoring the rate
of flow therethrough, si~nals therefrom being applied
in the control means to regulate the drive means
of the pump unit or units by maintaining the power
a~plied therein at said constant level.
In one example of the invention, as applied
to a puTnping system of the kind described in our
said co-pendiny patent application, said signals
~U will be applied to a microprocessor based programmable
logic controller (PL~) and which also provides
other control functions of the system, for servo
control of a flow regulator in the hydraulic power
drive circuit whereby the wattage exerted by said
drive means is maintained at a substantially constant
level.
According to a further aspect of the invention
we provide a method of o~eratin~ pumping apparatus
in which the pressure and flow rate at the output
3U from the apparatus is automatically monitored and
applied to regulate the power applied by the apparatus
in use to said output whereby the power so applied
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is held at a substanti411y constant predeter~in2d
level.
It will be appreciated that the invention
may be applied t~ various types of pumping systems
and is not restricted to the reciprocating pump
units of the kind described.
One example of a pumping ~ystem incorporating
the invention is illustrated by the accompanying
diagrammatic dra~ing.
1~ In the drawing three single ~cting reciprocating
pump units of the kind described, Pl, P2 and P3
are shown which are connected in parallel between
a ~uction or inlet duct 10 ~nd a common outflow
or deliv~ry duct ll, the latter extendins to ~
lon~ distance small ~ore pipeline. The pumping
~ystem in this example is used for long distance
transfer of slu~ge, ~he hydraulic ram drive~ of
the three units being controlled and operated ~equentially
in the man~er descr.ibq~ i~ our said co pending Canadia'n .
Patent Applicati-on No. 482,812. The rams of each unit
are connected to a common hydraulic drive and control
module 12 which is powered by a hydraulio drive
pump 13 driven by an electric motor 14.
Po~itioned in the delivery duct 11 adjacent
25 to the common output f rom the pump unit~ i~ a pre~sure
~ransducer 15 and, immediately downstrea~n of this,
a flow rate transducer 16.
Thes~ tran~ducers operate to con~t~ntly monltor
the pressure and flow r~te~ in duct 11 providing
3t) ~i:gnal~ which are ed to an automatic control unit
17 which incorpor~te~ ~ microproce~or ba~ed pro~ral~unabla
logic controller (PLC) . Control unlt 17 regulates
the operation of the hydraulic control module 12
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t`o provide said sequential operation of pump units
~1-3 as described in greater detail in our said
co-pendin~ application.
Control unit 17 also functions to apply the
signals derived from the transducers 15 and 16
to provi~e an output signal which is a function
of the pressure and flow rate sensed in duct 11
and this is fed back to the hydraulic module l~
to regulate the power applied thereby to the actuating
lU ra~s of the pump units, in this example by adjusting
a flow control ~evice in the hydraulic circuit.
Where P is the power needed to drive the pump
uni~s, F is the flow rate and P is the pressure
then
P_~_ F x P x Constant.
The PLC of control unit 17 is pre-programrned
to maintain the power output at a substantially
constant preset level and this will be maintained
despite any variations in input rate to the pu~p
units and/or the consistency or other physical
characteristics of the material being pumped, for
example variations in solids/liquid content.
Control in this way ensures that the pipeline
is always kept fully loaded and operates with optimum
~5 efficiency and substantially constant material
output at the delivery end.
As the actual useful work done by the pum~
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units, i.e. the delivery through duct 11 is being
directly monitored and the power requirement is
being automatically adjusted by control of the
hydraulics which are applied directly to the pump
rams a very efficient and accurate closed loop
feedback system is provided. This is much more
responsive, reliable and accurate than known power
consumption monitoring systems which "read" the
current consumption of the electric drive motor
1~ and attempt to regula~e operation accordingly.
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