U.S. patent application number 10/536452 was filed with the patent office on 2006-06-22 for pressure regulated method for preventing cavitations in a technical system.
This patent application is currently assigned to Endress + Hauser GmbH + Co. KG. Invention is credited to Hartmut Breithaupt.
Application Number | 20060133941 10/536452 |
Document ID | / |
Family ID | 32308801 |
Filed Date | 2006-06-22 |
United States Patent
Application |
20060133941 |
Kind Code |
A1 |
Breithaupt; Hartmut |
June 22, 2006 |
Pressure regulated method for preventing cavitations in a technical
system
Abstract
A pressure regulated method for a technical system that serves
to prevent cavitations in a liquid medium, which is conveyed inside
a conduit section consisting of a pump, a pressure sensor, a
flowmeter and of a first valve. The pump pressure of the pump is
regulated by the pressure sensor and the flowmeter in such a manner
that the liquid pressure does not fall below the vapor pressure of
the medium.
Inventors: |
Breithaupt; Hartmut;
(Schwabisch-Hall, DE) |
Correspondence
Address: |
BACON & THOMAS, PLLC
625 SLATERS LANE
FOURTH FLOOR
ALEXANDRIA
VA
22314
US
|
Assignee: |
Endress + Hauser GmbH + Co.
KG
Haupstrasse 1
Maulburg
DE
|
Family ID: |
32308801 |
Appl. No.: |
10/536452 |
Filed: |
November 25, 2003 |
PCT Filed: |
November 25, 2003 |
PCT NO: |
PCT/EP03/13229 |
371 Date: |
November 16, 2005 |
Current U.S.
Class: |
417/28 |
Current CPC
Class: |
G05D 16/2066 20130101;
F04D 29/669 20130101; F04D 15/0022 20130101 |
Class at
Publication: |
417/028 |
International
Class: |
F04B 49/00 20060101
F04B049/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 27, 2002 |
DE |
102 55 514.1 |
Claims
1-3. (canceled)
4. A pressure control method for a technical system, for preventing
cavitation in a liquid medium which is transported in a section of
piping, the system comprising a pump, a pressure sensor, a flow
rate meter, and a first valve (4), the method comprising the step
of: controlling the pump pressure of the pump with the pressure
sensor and the flow rate meter such that the liquid pressure does
not sink below the vapor pressure.
5. The pressure control method as claimed in claim 4, wherein: a
second valve is arranged parallel to the first valve, said method
further comprising the step of: alternately opening and closing the
two valves.
6. The pressure control method as claimed in claim 4, wherein: a
buffer container, with the second valve and the pressure sensor, is
arranged between pump and flow rate meter, said method further
comprising the steps of: registering the headspace pressure in the
buffer container; controlling the head space pressure with the
second valve; and actuating the second valve by the flow rate meter
and the pressure sensor.
Description
[0001] So-called buffer tanks, or pressure equalizing containers,
are often used in technical systems to aid in the transfer of
liquid products between individual system components. The liquid
products can be foodstuffs, creams, oils, etc. Especially in the
area of foodstuffs, gases are frequently dissolved in the products
(champagne, beer, etc.). This dissolved gas can lead to foaming. In
the case of beer, the foaming is desired at the bar; however, in
the brewery, foaming is disruptive to the bottling process.
[0002] Closely associated with foaming is cavitation. "Cavitation",
as used herein, refers to a phenomenon in which gas bubbles are
produced in a liquid, and implode under pressure. In such case,
pressure spikes arise, which can lead to severe material damage of
the system components. This can bring an entire bottling plant to a
halt, and incur substantial costs. The availability of the plant is
thereby significantly compromised.
[0003] Cavitation is also disruptive in the case of sensitive
products.
[0004] Cavitation appears mainly in cases of large pressure
differences in pipelines, when the static pressure of the liquid
falls below the vapor pressure. These sudden pressure increases or
decreases can occur especially in the opening and closing of
valves.
[0005] In order to effect cavitation-free transfer of liquid
products in the case of a technical system, such as a processing
plant, buffer tanks are provided. These buffer tanks are charged
with the pressure of air or some other gas in their headspace.
Large pressure differences between system components are thereby
canceled, and the formation of gas bubbles in the liquid products
can be prevented.
[0006] The pressure control of the air or other gas in the buffer
tank is accomplished using a pressure sensor and a proportional
valve. Such buffer tanks are also used in bottling plants. Buffer
tanks are generally complex and expensive. They require a
significant amount of space, which is not always adequately
available. Furthermore, the pressure control for the buffer tank is
complex.
[0007] In addition, the use of air or some other gas for
pressurizing the headspace is not always desired in the case of
certain products.
[0008] An object of the invention is to provide a pressure control
method for preventing cavitation in a technical system, which
method does not have the above-listed disadvantages, and which is
simple as well as cost-efficient.
[0009] This object is achieved through the features given in claim
1.
[0010] Advantageous further developments of the invention are given
in the dependent claims.
[0011] An essential idea of the invention is, with the help of a
pressure sensor and a flow rate meter in a section of piping of a
technical system, to control the pump pressure of the supply pump
such that cavitation is prevented.
[0012] The invention will now be described in greater detail on the
basis of several examples of embodiments illustrated in the
drawings, the figures of which show as follows:
[0013] FIG. 1 schematic illustration of a technical system;
[0014] FIG. 2 schematic illustration of a section of piping of a
technical system, according to a first variant of the
invention;
[0015] FIG. 3 a section of piping of a technical system, according
to a second variant of the invention;
[0016] FIG. 4 a section of piping of a technical system with a
buffer container, according to a third variant of the
invention;
[0017] FIG. 5 a section of piping of a technical system according
to a fourth variant of the invention; and
[0018] FIG. 6 plots of pressure and associated flow rate, both as a
function of time t.
[0019] FIG. 1 shows a technical system for transferring liquid
media (e.g. beer, champagne, creams, oils, etc.) from a tank B1
into a containment B2, which, in turn, can be a tank, or also a
bottle, or the like. The medium is transported in a pipeline 10.
Arranged in the pipeline 10 are, in addition to a supply pump 1 and
a valve 4, various measuring devices, e.g. a pressure sensor 2, and
a flow rate meter 3.
[0020] FIG. 2 shows a section of the pipeline 10 in greater detail.
This section has a pump 1, a pressure sensor 2, and a flow rate
meter 3, as well as a valve 4, which are arranged in series. The
quantity of medium flowing through the pipeline 10 toward the valve
4 is controlled with the help of the flow rate meter 3 and the
valve 4. In the case of bottling plants, the valve 4 opens and
closes such that the desired fill quantity of medium M is available
on the downstream side of the valve 4. Pressure sensor 2 and flow
rate meter 3 are so-called intelligent field devices, with
appropriate microprocessors.
[0021] A control line L1 leads from the flow rate meter 3 to the
valve 4. Furthermore, a control line L3 leads from the flow rate
meter 3 to the pressure sensor 2. From the pressure sensor 2, a
control line L2 leads to the pump 1.
[0022] The control lines L1, L2, L3 transfer digital signals (e.g.
8-bit signals). It is important that the signal transfer occur
relatively quickly (<10 msec) in order to enable a meaningful
control. With limitations, this is also possible using the 4-20 mA
signals generally known in the field of automation technology.
[0023] The flow rate of the medium M through the pipeline 10 is
registered with the help of flow rate meter 3. The current,
measured value of flow rate is forwarded to the pressure sensor 2
via control line L3. Pressure sensor 2 determines the current
pressure in the liquid. In pressure sensor 2, the two measured
values, pressure and flow rate, are evaluated, and the pump 1 is so
controlled via the control line L2, that the fluid pressure does
not sink below the vapor pressure of the medium M. Through the
pressure sensor 2 and the flow rate meter 3, the danger of
cavitation formation is thus accounted for, and prevented, by
controlling the pump 1. The resolution of pressure sensor 1 alone
is not enough to effectively prevent cavitation formation. For
this, a quick controlling of the pump output, especially in the low
pressure region, is necessary. This pressure region is reached when
the flow rate is relatively low, that is, at the end of the closing
process, and at the beginning of opening process, of the valve. Per
the invention, this information is supplied by the flow rate meter
3.
[0024] Plots of pressure and flow rate versus time in pipeline 10
at the pressure sensor 2 are illustrated in FIG. 6.
[0025] On the one hand, the control provides that the pressure
increase at the closing of the valve 4 does not become too great.
At the same time, as a result of the moderated pressure increase, a
shooting of the medium is prevented when the valve is opened.
[0026] At the opening of the valve 4, the control provides that the
pump output is again quickly increased accordingly, in order to
ensure an adequate product supply, and to prevent a pressure
drop.
[0027] FIG. 3 shows a further example of an embodiment of the
invention, with two valves, 6 and 4, being arranged downstream from
the flow rate meter 3, which alternately open and close. A control
line L4 leads from the flow rate meter 3 to the valve 6. The
example of the embodiment in FIG. 2 functions essentially according
to the same principle as the example of the embodiment in FIG.
1.
[0028] FIG. 4 shows a further example of an embodiment of the
invention. In this example, a buffer container 5 is arranged in the
pipeline 10 between the pump 1 and flow rate meter 3. In the buffer
container 5, a gaseous medium (gas/air) is located above the medium
5. With the help of the pressure sensor 2, the pressure in the
buffer container 5 is registered, and controlled via a valve 6a. A
control line L3 leads from the flow rate meter 3 to the pressure
sensor 2. From the pressure sensor 2, a control line L2 leads to
the pump 1, and a control line L4 to the valve 6. Also here the
pressure sensor 2, in connection with the flow rate meter 3,
controls the pump pressure of the pump 1. The fill level in the
buffer container 5 is basically constant. The flow rate meter 3,
together with the pressure sensor 2, recognizes the ideal refill
quantity, and, for this reason, controls the pump output of the
pump 1. In order to keep the vapor pressure in the buffer container
5 relatively constant, the pressure sensor 2 and the flow rate
meter 3 control the valve 6, via the control line L4. On the basis
of the control according to the invention, the buffer container 5
can be considerably smaller than conventional buffer
containers.
[0029] In FIG. 5, a fourth example of an embodiment of the
invention is shown in greater detail. In the case of this example
of an embodiment, the section of pipeline 10 no longer has a flow
rate meter 3, for which reason an additional pressure sensor 7, and
a valve 6, are arranged after the valve 4. The pump 1 is controlled
via the pressure sensor 2.
[0030] The valve 4 controls the coarse flow of the liquid product.
The fine discharge is controlled with the valve 6. The pressure
sensor 7 supplies the coarse parameters, and the pressure sensor 2
supplies the fine parameters for the control. Also here the pump
pressure is adjusted such that no cavitation occurs.
[0031] FIG. 6 illustrates the behavior of pressure and flow rate in
the pipeline 10, at the opening and closing of the valve 4, as a
function of time t. The pressure is determined with the pressure
sensor 2, and the flow rate with the flow rate meter 3. For better
comprehension, an ideal plot is illustrated in each case.
[0032] At point in time t1 the valve 4 begins closing and the flow
rate decreases until point in time t2, when the valve 4 is
completely closed and no flow rate is available.
[0033] At point in time t3 the valve 4 begins opening again and the
flow rate increases. At point in time t4, the flow rate reaches its
maximum value.
[0034] In the accompanying pressure diagram, two curves, K1 and K2,
are illustrated, which reflect the uncontrolled and controlled
cases, respectively.
[0035] In the uncontrolled case (curve K1), when the valve closes,
an enormous pressure builds up, which suddenly drops when the valve
opens.
[0036] In the controlled case (curve K2), the pressure increase at
the closing of the valve is considerably smaller, and therefore
also the drop at opening of the valve is considerably less.
[0037] As seen from the two curves K1 and K2, the control is
applied at exactly the point at which, in the uncontrolled case,
drastic pressure changes occur.
[0038] Naturally, the supply pump 1 can also be replaced with a
controllable modulating valve, which controls the drainage e.g.
from an elevated container into a section of pipeline. In this
case, the modulating valve controls the product quantities and the
corresponding pressure in the section of pipeline.
* * * * *