U.S. patent application number 12/221630 was filed with the patent office on 2008-12-11 for centrifugal pump casing relief system.
This patent application is currently assigned to Applied Drives and Systems, Inc.. Invention is credited to Louis G. Zacherl.
Application Number | 20080304955 12/221630 |
Document ID | / |
Family ID | 38319519 |
Filed Date | 2008-12-11 |
United States Patent
Application |
20080304955 |
Kind Code |
A1 |
Zacherl; Louis G. |
December 11, 2008 |
Centrifugal pump casing relief system
Abstract
In a fluid flow network including a centrifugal pump, a system
and kit for monitoring said centrifugal pump and relieving the pump
of fluid when the pump is operating at no-flow conditions. The
system comprises a fluid conduit connected to the pump, at least
one sensor for indicating when the pump is operating at no-flow
conditions. The sensor is selected from the group consisting of:
temperature sensors, pressure sensors, and motor current sensors.
The system has a fluid control means located in the fluid conduit.
An electric snap-action valve is included that has an inlet
connected to the fluid conduit and an outlet and a diaphragm. The
diaphragm is movable between a first position and a second
position. A power supply is included.
Inventors: |
Zacherl; Louis G.;
(Broomfield, CO) |
Correspondence
Address: |
Laura A. Dable;RYAN KROMHOLZ & MANION, S.C.
Post Office Box 26618
Milwaukee
WI
53226-0618
US
|
Assignee: |
Applied Drives and Systems,
Inc.
|
Family ID: |
38319519 |
Appl. No.: |
12/221630 |
Filed: |
August 5, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11341289 |
Jan 27, 2006 |
|
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|
12221630 |
|
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Current U.S.
Class: |
415/17 |
Current CPC
Class: |
F04B 49/00 20130101;
F04D 15/0218 20130101; F04D 15/0005 20130101 |
Class at
Publication: |
415/17 |
International
Class: |
F01D 17/08 20060101
F01D017/08 |
Claims
1. A method for monitoring a centrifugal pump within a fluid flow
network and relieving said pump of deleterious effects caused by an
increased pressure and/or temperature in said pump, said pump
communicating with a fluid release valve connected to a fluid
conduit, said method comprising: selecting a sensor to monitor a
variable of said pump; providing a fluid control device; providing
an electrical solenoid operated valve having an inlet connected to
said fluid conduit and an outlet and a solenoid operated diaphragm,
said diaphragm having a first position and a second position;
providing a power supply; attaching said sensor to said fluid
conduit or said network; attaching said fluid control device and
said solenoid operated valve to said fluid conduit; forming an
electrical circuit by attaching said sensor and the solenoid
operated valve to said power supply; and moving said diaphragm from
said first position to said position second position by completing
said electrical circuit to the solenoid of said solenoid operated
valve.
2. The method of claim 1 wherein said step of attaching said fluid
control device and said solenoid operated valve further comprises
attaching said fluid control device and said solenoid operated
valve to said fluid conduit at a distance of four inches or less to
one another.
3. The method according to claim 1 further comprising the steps of:
selecting a second sensor to monitor a second variable of said
pump; and attaching said second sensor to said fluid conduit or
said network.
4. The method of claim 1, wherein said step of moving said
diaphragm results in allows fluid flow through said solenoid
operated valve.
Description
RELATED APPLICATION
[0001] This application is a divisional of co-pending patent
application Ser. No. 11/341,289 filed 27 Jan. 2006.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to centrifugal pumps and, more
specifically, systems and devices to monitor operating parameters
of centrifugal pumps to prevent damage to the centrifugal
pumps.
[0003] Centrifugal pumps are relatively simple pumps used for fluid
movement within piping systems. The pumps operate efficiently
requiring only one moving part. However, care must be taken to
insure that the pump is being operated within proper parameters.
Specifically, care must be taken to insure that the pump is not
operating at a "no-flow" condition, which can lead to damage of the
pump and burning out of the motor driving the pump.
[0004] If a centrifugal pump is operating at a "no-flow" situation,
fluid flow will have stopped through the pump. A small amount of
fluid can remain in the pump and become trapped within the pump.
This fluid will be churned by the spinning impeller of the
centrifugal pump. Because there is only a small amount of fluid
within the pump, the temperature of the fluid can increase quickly,
and the fluid will begin to boil. The boiling fluid will increase
the pressure within the system. The increasing temperature and
pressure feed off of each other, and the pressure can quickly
increase to uncontrollable levels. Such increases will lead to
damage to the piping system and the pump, such as damage to the
seals located at the joints, and the rise of the fluid temperature
can lead to spontaneous tripping of "dry pipe valves" in fire
protection systems. Other components, such as the pump seals,
gauges, pressure switches, valve packings, flow switches, etc., may
also be damaged by the pressure and temperature rise at no-flow
situations.
[0005] Regulation of the pump is usually done by monitoring the
pressure of the pump, the temperature of the fluid within the pump,
or the electrical current feeding the pump motor. Normally, a
separate fluid path is provided through the pump to assure a
minimal flow of fluid to prevent overheating of the trapped fluids.
Such a device to control the fluid flow is generally referred to as
a casing relief valve.
[0006] The amount of time between the cessation of fluid flow
through the pump and the onset of damages depends on many factors,
such as liquid temperatures, the design and speed of the impellers
located in the pump, fluid vapor pressure, and fluid volume in the
volutes. Time before the onset of damages can range from over ten
minutes to less than ten seconds, depending on the pump
configuration. As the flow slows and stops within an operating
pump, the pump parameters may change. For instance, the discharge
pressure will rise, the motor current will decrease, the fluid
temperature rises, and the speed of the motor shaft increases.
[0007] The discharge pressure of a centrifugal pump is a function
of two sources: the inlet fluid pressure and any additional
pressure added to the inlet pressure by the pump, with the
additional pressure being dependent on fluid flow through the pump.
Generally, centrifugal pumps produce the highest pressure rises or
changes from the inlet pressure to the discharge pressure at a zero
flow rate ("no-flow"), or churn condition. The amount of additional
pressure the pump contributes decreases as flow increases through
the pump.
[0008] If the inlet pressure changes, the discharge pressure will
change by the same amount. Several factors can lead to these
fluctuations in pressure, including seasonal factors, number of
pumps being employed, demand, and pipe size, to name a few. As an
indicator for no-flow situations, one should monitor the difference
between inlet and discharge pressure.
[0009] As noted above, the motor current also varies, with the
current being approximately fifty percent of the full load at
churn, to nearly one hundred percent of current load at full flow.
Motor currents below a certain level can indicate little or no
fluid flow through the pump. Motor currents of a running motor will
fall below churn levels only if the fluid in the volutes flashes to
vapor. Current levels are not affected by either the inlet pressure
or the fluid temperature, but can be altered by variations in the
voltage of the power source, with lower voltages resulting in
higher current levels.
[0010] Generally, it has been preferred to determine the
temperature of the fluid with the use of a sensor device, such as a
transducer or a switch, by placing the sensor directly into the
fluids located in the centrifugal pump. The fluid temperature is
measured directly, and the sensor device can immediately and
automatically adjust to temperature changes. Pressure or voltage
changes do not alter the sensors. However, such sensors may have
problems of reacting quickly enough for a rapidly rising or falling
temperature.
[0011] The most common packaging configuration for a centrifugal
pump is to mount a "horizontal split case" pump and an electric
motor on a common steel base plate. The drive shafts of the two
devices are connected using a coupling that will allow for some
mis-alignment between the pump and the motor.
[0012] If the coupling is removed and the motor is then started,
the motor will draw approximately twenty percent of the maximum
continuous current, commonly referred to a full load current. If
the coupling is then reinstalled and the pump restarted with the
discharge valve closed, the motor will then draw approximately
fifty-five percent of the full load current. The value of the
current rises as flow is added to the pump by opening the discharge
valve.
[0013] Centrifugal pumps are preferably driven by three-phase
induction motors, commonly referred to as "squirrel cage" motors.
Squirrel cage motors use a differential slip to allow for changes
between the "synchronous" speed (usually 1800 RPM and 3600 RPM) and
an operating speed that is typically 25 to 100 RPM lower than the
synchronous speed. As the mechanical load changes, the speed will
change; a greater load equals a greater slip. A greater slip means
a higher rotor current for the pump, producing higher torques to
drive the load, which translates into a higher flow through the
pump. Devices that monitor the pump load are not generally commonly
used.
[0014] The present state of the art to prevent overheating in a
pump uses a casing relief valve located on the discharge side of
the pump. Fluid pumped through this valve may be discharged to a
drain or recycled into a fluid storage. Some relief valves may pump
the fluid back into the inlet of the pump, which increases the
potential for the pump to overheat. Such devices use a mechanical
pressure detector and an internal valve to release fluids at churn
conditions. The simplest design uses a plunger and a compressed
helical spring to seal the valve. As pressure rises, the plunger is
pushed backward, allowing fluid to flow through into the by-pass
line of the valve. As pressure falls back to normal levels, the
plunger will reseal the valve.
[0015] The described relief valve has some drawbacks. Since the
valve is operated by discharge pressure (as opposed to pressure
differential) it may not open at proper times. For instance, if the
inlet pressure is rather low, the spring and plunger may not
activate, even if there is a significant change in the pressure,
since the outlet pressure may still be lower than the pressure
necessary to activate the plunger. Likewise, the flow amount is a
variable dependent on the differential between the pump discharge
and the valve trip pressure. A lower discharge pressure relates to
a lower flow rate, which increases the possibility of pump damage.
Also, the spacing between the valve and the plunger is based upon
the pressure differential. If the differential is low, the space
will be small, which potentially may lead to small particles
becoming entrapped between the plunger and the valve, which could
prevent the valve from being resealed. The result is a constant
fluid leak, which, eventually, can lead to general failure of the
valve,
[0016] While it has been known to monitor such variables to prevent
pump damage or fatigue, to date there has been no simple
arrangement to monitor up to all three of these variables within a
single system. Thus, it would be advantageous to develop a system
that would monitor centrifugal pumps while minimizing problems that
could lead to failure of the monitoring system and the pump.
SUMMARY OF THE INVENTION
[0017] Within a fluid flow network including a centrifugal pump,
the present invention comprises a system and kit for monitoring the
centrifugal pump and relieving the pump of potentially damaging
fluid when the pump is operating at no-flow conditions. The system
comprises a fluid conduit connected to the pump, at least one
sensor for indicating when the pump is operating at no-flow
conditions. The sensor is selected from the group consisting of:
temperature sensors, pressure sensors, and motor current sensors.
The system has a fluid control means located in the fluid conduit.
An electric snap-action valve, preferably a solenoid operated
valve, is included that has an inlet connected to the fluid conduit
and an outlet and a diaphragm. The diaphragm is movable between a
first position and a second position. A power supply is included.
The method of installing the system and/or kit is also included in
the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a perspective view of a centrifugal pump
arrangement according to the present invention installed in a
piping system.
[0019] FIG. 2 is a perspective view of a possible fluid control
valve according to the present invention.
[0020] FIG. 3 is a perspective view of an alternative fluid control
device according to the present invention.
[0021] FIG. 4 is a perspective view of a temperature sensor used
according to the present invention.
[0022] FIG. 5 is an exploded view of a solenoid valve used
according to the present invention.
[0023] FIG. 6 is a perspective, partially exploded, view of a
possible power supply configuration used with the present
invention.
[0024] FIG. 7 is a perspective view showing an initial step of
installing the pump regulator system of the present invention.
[0025] FIG. 8 is a perspective view showing a further step of
installing the pump regulator system of the present invention.
[0026] FIG. 9 is another further step of installing the pump
regulator system of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0027] Although the disclosure hereof is detailed and exact to
enable those skilled in the art to practice the invention, the
physical embodiments herein disclosed merely exemplify the
invention which may be embodied in other specific structures. While
the preferred embodiment has been described, the details may be
changed without departing from the invention, which is defined by
the claims.
[0028] The present invention provides a pre-engineered set of
components that addresses the shortcomings of the prior art
discussed above with respect to centrifugal pumps. The components
are included as kit that will allow the end user to easily install
the components and efficiently monitor the specific pump. The kit
provides the basis for a method of monitoring the centrifugal pump
and providing relief for the pump when the internal temperature
and/or pressure of the pump reaches critical conditions, or the
sensor indicates that the temperature and/or pressure may reach
critical conditions. The components include 1) a valve, orifice, or
other similar device to determine the volume of fluid flow that
will flow through the pump; 2) a valve to regulate the fluid flow;
3) a sensor to detect a specific variable when the pump is
churning, with the variables being either pressure, temperature, or
motor current; and 4) a means to allow the sensor to operate the
fluid regulation valve. The kit may also include various pipes,
connectors, and other hardware to assist in installing the valves
and sensors. Likewise, instructions may be included with the
kit.
[0029] The present invention provides an easy to use, reliable,
predictable system that will reduce problems associated with
"no-flow" situations through the centrifugal pumps. Whereas
previous designs and arrangements required the placing of
components and piping in specific, fixed locations due to
mechanical constraints of the pump itself, the separate detection
and operation valves of the present invention allows the user to
place the valves in locations where they would be most
advantageous. The flexibility of installation maximizes the ability
to monitor the operation of the pump. Furthermore, the system does
not need to interact with other systems or components to operate,
and may include a back-up power source, if necessary. The
components included in the kit do not require any special tooling
or skilled labor to install.
[0030] FIG. 1 is a perspective view of a pump relief system 10. The
system 10 is showed installed in connection with a fluid flow
network 12 (shown generally in phantom), which employs a
centrifugal pump. As is known in the art, the system 10 is
connected to a fluid conduit or flow path that operates
independently from the normal fluid flow in the network 12. This
allows the system 10 to provide fluid flow when problems arise with
the centrifugal pump, such as "no-flow" conditions, thereby
preventing or minimizing potential damage to the centrifugal pump.
The system generally comprises a fluid flow device, which may be in
the form of a conventional, manually operable gate valve 14; a
solenoid operated fluid regulator valve 15, and a sensor 25,
depicted as a temperature sensor 25 in FIG. 1. As fluid passes
through a fluid conduit or pipe 22 in communication with the pump
12, the sensor 25 can individually monitor fluid flow conditions of
the pump 12 as shown in FIG. 1, or it is possible to include other
sensors such as pressure or motor sensors that can work in tandem
to provide more checks for the pump. It is understood that the
fluid conduit 22 refers to the entire length of pipe used in
connection with the system 10, and should not be limited to a
specific shape or arrangement. The present invention allows for
several various arrangements of the individual sensors.
Fluid Flow Control
[0031] FIG. 2 provides a perspective view of the fluid flow device
14, which, as shown, is generally referred to as a manually
operable gate valve. The gate valve 14 is a simple mechanical
device used for regulating the volume of fluid flow through the
system 10. A handle 24 is turned to either increase or decrease
fluid flow through an internal conduit 26, thereby regulating the
amount of fluid passing through a centrifugal pump during churn
conditions. The design of the gate valve 14 allows for wide
adjustments of fluid flow.
[0032] FIG. 3 provides an alternative fluid flow device, commonly
referred to as a pipe union 114. The pipe union 114 has an internal
restrictor plate 116 with a predetermined orifice 118 that
regulates the amount of fluid passing through the conduit 26. The
pipe union 114 is preferably constructed of a first half 120 and a
second half 122. The restrictor plate 116 is located between the
first half 120 and the second half 122. The three pieces 116, 120,
and 122 are held together with a threaded union section 124. If
necessary, the restrictor plate 116 can be replaced with another
plate having a differently sized orifice if the flow is determined
to be lower or higher than necessary.
[0033] As FIGS. 2 and 3 show, various flow control devices may be
used for the present invention and the present invention should not
be limited to a specific part or device.
Sensors
[0034] FIG. 4 shows a perspective view of the conventional,
commonly available, temperature sensor 25. The sensor 25 comprises
a probe 40 that will be directly inserted into the piping system,
as will hereinafter be described. An electrical connector 42 is
attached to the top of the probe 40, preferably permanently affixed
to the probe 40. A threaded area 44 area on the probe 40 allows the
sensor 25 to be secured to the pipe 22, again as will be later
described, and in connection with the views of FIGS. 1, 7, and 8.
The probe 40 must be in contact with fluid within the pipe 22 at or
near the area very close to the area where actual heat may be
generated in the system. The sensor 25 should be installed
relatively near the impeller of the pump, or the sensor 25 will not
accurately portray the temperature. The temperature sensor
preferably includes a switch that is fixed to operate at
140.degree. F. (60.degree. C.), which is a temperature similar to
the discharge temperature of a residential fluid heater, with a
temperature differential for the sensor being fixed at
approximately 15.degree. F. (or an approximate range of
12.degree.-18.degree. F.). The sensor 25 preferably operates a
pilot duty metallic switch (not shown).
[0035] While a temperature sensor 25 was generally discussed above,
pressure sensors and motor current sensors could be used in place
of the temperature sensor, or may be used concurrently in a single
system. Whichever type of sensor is used, it will operate on
similar principles. The sensors are designed to complete an
electrical circuit, allowing a current to flow from the power
source to a solenoid valve coil, with the circuit being activated
when the sensor registers a predetermined value for the related
variable.
[0036] As with the temperature sensor 25 described above, a
conventional pressure sensor (not shown) used in the system would
preferably include a pilot duty metallic switch. The pressure
sensor can be located and installed at any point in the piping 22
that is connected directly to the pump's discharge. That is, there
should be no check valves or other devices located directly between
the sensor and the pump's discharge. The pressure sensor will also
be adjusted for a particular installation. Preferably, the inlet
pressure for the pressure sensor is constant, which will result in
a constant discharge pressure from the system. If the inlet
pressure is variable, a pressure sensor must be adjusted
accordingly, to insure that the solenoid 18 operating the valve 15
properly opens, even at relatively low pressures.
[0037] A motor current sensor as may be used in the present system,
as will later be described, is preferably a solid state electronics
module, and usually installed within the motor control center.
Solenoid Operated Valves
[0038] FIG. 5 provides a partially exploded view of the solenoid
operated valve 15 used in the present invention. The solenoid 18
has a coil 19 for operating the solenoid armature 21 that is
arranged for separable electrical connection with an electrical
connector 20 to be mounted onto the valve 15. The connector 20 is
secured to an electrical cord 54, which is routed to a power supply
50 (see FIGS. 1 and 6).
[0039] The solenoid operated valve 15 is preferably a piloted
diaphragm operated device. The valve 15 controls the pressure as it
passes a diaphragm 32. A carburetor 35 may be included with the
valve 15 as a pressure release. As the coil 19 is energized by
means of the solenoid armature 21, a diaphragm 74 is pulled towards
the coil 30, which provides complete opening or closing of the
valve 15. The valve 15 is preferably a "snap action" valve.
[0040] Referring further to FIG. 5, the solenoid operated valve 15
can be either a normally open or a normally closed valve. The valve
15 comprises a top section 70 and a bottom section 72. A spring 76
provides resistance and is seated upon the diaphragm 74 to provide
pressure for securing the diaphragm 74 in place. A normally open
version of a valve 15 allows fluid flow when the coil 19 is
de-energized, whereas a selection of a normally closed valve 15
allows fluid flow when the coil is energized. Determination of
which valve type to use generally is based upon whether or not
fluid should be flowing should there be a power outage.
Power Supply
[0041] FIG. 6 illustrates a power supply 50 used in the present
invention. The power supply 50 houses a transformer 52. The power
source 50 is electrically connected to the solenoid 19 of the valve
15 and the sensor 25 with standard electrical cords 54 (see FIG.
1). A motor current sensor 56 (see FIG. 6) for monitoring the motor
used with the pump 12 may also be connected to the motor 55. The
sensor 56 is preferably self-powered by the flow of current
(preferably a 2.5 amp minimum flow) through the sensor 56 to the
motor (not shown). The sensor 56 is connected to the output of the
motor, preferably with a two-conductor cable, commonly known and
used with electrical connections. The motor current flow through
the sensor 56 is preferably detected using a conventional current
transformer 52, which is used to detect the magnetic field of the
motor current. The sensor 56 will test for two conditions: 1)
whether or not the motor current is high enough to assure that the
motor is running, and 2) whether or not motor current is low,
thereby indicating no fluid movement in the system. When the sensor
56 indicates that the current is high enough to indicate that the
motor is running and low enough to indicate that there is no fluid
flow, the electrical output of the sensor 56 is activated, thereby
energizing the solenoid valve 15.
Installation
[0042] FIGS. 7-9 show various stages of installing the system 10.
In FIG. 7, a first section of pipe 60, having a threaded conduit
62, is connected to the pump 12. The threaded conduit 62 will
receive the sensor 25, as shown in FIG. 1. A second section or
sections 64 of pipe 22 connect the pipe section 60 to the gate
valve 14, and a third pipe section 66 connects the gate valve 14 to
the solenoid valve 15. To insure proper fluid flow, the gate valve
14 and the solenoid operated valve 15 are preferably installed
within 2 to 4 inches from one another. FIG. 8 shows the connector
20 being secured to the coil 19 of the solenoid valve 15. In FIG. 9
there is shown a discharge section 68 of the pipe 22 connected to
the solenoid valve 15, and the sensor 25 being finally connected to
the system 10, as further shown in FIG. 1. The pipe section 68 may
lead to a drain or connected to recirculate the fluid into the
general piping system.
[0043] FIGS. 7-9 show one possible way of installing the kit
components and should not be considered as limiting. For example,
one possible preferable alternative way is to install the power
supply, next the sensor or sensors and thereafter the valves. When
starting the installation process, the system installer must be
sure to verify that all of the electrical connections are secure.
After energizing the electrical supply, the operator must slowly
open the fluid supply to the system, which will properly pressurize
the gate valve 14 and/or the solenoid operated valve 15. The
centrifugal pump should then be started and allowed to run. When it
has been determined the pump is running properly, the operator may
adjust the individual sensor to the specific operating
conditions.
[0044] When installing the power supply 50, it is preferable to
mount the supply 50 on a freestanding vertical structure 59, with
the orientation being as shown in FIG. 6. The supply 50 should be
mounted at least 12 inches off of the floor. Power should be turned
off to the supply until it has been established that the sensors
and valves are properly installed.
[0045] When installing the temperature sensor 25, any fluid
pressure on the pump itself should be released before installation
of the sensor 25. The sensor 25 is then threaded into the pipe
section. The sensor 25 should be installed in an upright, vertical
position. An electric connector 54 is attached to the sensor 25
(see FIG. 4) and then routed to the power pack 50 (see FIG. 1).
[0046] As previously stated, the system is tailored for an
individual pump's needs. For example, the size of the fluid control
valve 14 is determined by the amount of fluid that is flowing
through the system. It should also be determined what variable the
system will be monitoring so that the proper sensor will be
included with the kit for the system. This will be taken into
account when deciding how no-flow conditions will be detected in
the system. An extra, back-up battery may be included in the system
in case of power failure. Another factor to consider is whether the
solenoid operated valve 15 will be open or closed if power fails
for the system.
[0047] The present invention provides a simple and easy to use
method for providing a fluid flow detector system for protection of
a centrifugal pump. Essentially, the present invention allows for a
custom made sensor system. It has not been previously contemplated
to provide the end user with such a system selected from a
component kit. The invention allows for the end user to receive an
easy to install system that is tailored for an individual's needs.
Likewise, the end user can obtain a kit including selected
temperature, pressure, or motor sensors, or a combination of all
three. By providing an individual sensor together with an
individual solenoid valve, the present system will provide a
resultant product that can monitor fluid flow through a centrifugal
pump in an optimal fashion.
[0048] The foregoing is considered as illustrative only of the
principles of the invention. Furthermore, since numerous
modifications and changes will readily occur to those skilled in
the art, it is not desired to limit the invention to the exact
construction and operation shown and described. While the preferred
embodiment has been described, the details may be changed without
departing from the invention, which is defined by the claims.
* * * * *