Abstrict A method and apparatus for utilizing a controller to monitor a
flow volume in a fluid transportation system is disclosed. The controller
being operably connected to a module. The module being operably
connected to a flow meter. The module senses a series of pulses
that represent a known fluid volume in a proving loop. The module
also measures the fluid density of the fluid in the proving loop.
The controller utilizes a dynamic density of the fluid and the sensed
pulses to determine a correction factor to more accurately calculate
the flow volume through the measuring flow meter. The controller
ensures the accuracy of the flow meter by utilizing the partial
pulses sensed during a meter proving period by using an interpolation
method.
Claims I claim:
1. A method of proving a flow meter, the flow meter being operably
connected to a controller and a proving loop, the proving loop having
a known flow volume, wherein the controller monitors a fluid flow
within the proving loop, the method comprising the steps of: starting
a meter proving period; sensing a pulse signal responsive to a flow
meter being operably connected in the path of the fluid, the flow
meter generating the fluid flow; ending the meter proving period;
calculating the amount of sensed pulse signals occurring during
the meter proving period; determining a flow volume of the proving
loop; and, comparing the known flow volume of the proving loop to
the calculated flow volume of the proving loop, wherein the proving
process of the meter is executed within the controller.
2. The method of proving a flow meter of claim 1 wherein the known
flow volume of the proving loop is substantially equivalent to 10000
pulse signals.
3. The method of proving a flow meter of claim 1 further including
the step of adjusting the flow meter in response to the comparison
of the known flow volume of the proving loop to the calculated flow
volume of the proving loop, wherein the flow meter more accurately
calculates the fluid flow.
4. The method of proving a flow meter of claim 1 further including
the step of adjusting a module operably connected to the controller
in response to the comparison of the known flow volume of the proving
loop to the calculated flow volume of the proving loop, wherein
the module more accurately calculates the fluid flow.
5. The method of claim 1 further including converting the calculated
flow to a measurement unit consistent with an API 2540 standard
measurement unit.
6. The method of claim 1 wherein calculating the amount of sensed
pulse signals occurring during the meter proving period comprises
interpolating a partial pulse signal of the sensed flow meter signal
occurring after sensing has begun and before a first full pulse
signal, and interpolating a partial pulse signal of the sensed flow
meter signal occurring after the last full pulse signal of the flow
meter signal and before sensing has stopped.
7. The method of claim 6 wherein the calculation of the sensed
flow meter pulse signal utilizes a double chronometry method of
interpolation.
8. The method of claim 1 wherein the flow meter is a turbine.
9. A method of measuring a flow volume of a fluid within a conduit,
a controller having a module and being operably connected to a flow
meter and the conduit wherein a standard industrial equation AGA-7
is utilized by the module to determine the flow volume of the fluid
within the conduit, the method comprising the steps of: sensing
a density of the fluid; storing the sensed density value as a dynamic
variable in the controller; and, utilizing equation API 2540 in
cooperation with the sensed dynamic density of the fluid to calculate
a correction factor, M.
10. The method of claim 9 further including utilizing the correction
factor with equation AGA-7 to calculate the flow volume.
11. The method of claim 9 wherein the flow meter is a turbine.
12. A controller for monitoring a fluid transportation system,
the system comprising a flow meter operably connected to a conduit,
the controller monitors a fluid within the system and calculates
a flow volume of the fluid flowing through the conduit, the controller
comprising: a module being operably connected to the controller,
the module for sensing a pulse generated by the flow meter; an input
channel being adaptable to a range of input voltages; a densitometer
being operably connected to the input channel, the densitometer
senses the real time density of the fluid and stores the sensed
value as a dynamic variable in the controller; and, a calculator
comprising standard equation API 2540 the calculator determines
a correction factor for the volumetric flow of the fluid by utilizing
the sensed dynamic density value and the sensed pulse signals.
13. The controller of claim 12 comprising a display for displaying
a system error, the error is identified with the input channel.
14. The controller of claim 12 wherein the range of input voltages
is 25 mV-30V DC.
15. The controller of claim 12 wherein the flow meter is a turbine.
16. A controller for meter proving a fluid transportation system,
the fluid transportation system comprising a conduit being operably
connected to a flow meter, and a proving loop attached to the conduit,
the proving loop having a known flow volume measured in pulse signals
generated by the flow meter during a meter proving period, the controller
comprising: a module being operably connected to the controller;
a plurality of input channels being operably connected to the module;
a pulse monitor having a 5 MHz resolution clock, the pulse monitor
senses a pulse signal generated by the flow meter during the meter
proving period; an interpolator for determining a fractional pulse
signal amount of the sensed partial pulse signal; an accumulator
for summing all the pulse signals sensed during the meter proving
period, the sensed pulse signals include the full and interpolated
partial pulse signals, a calculator for calculating the flow volume
of the proving loop in response to the accumulated pulse signals
during the meter proving process, the calculated flow volume measured
in pulse signals; and, a comparator for comparing the known number
of pulses of the proving loop and the accumulated pulse signals
sensed during the meter proving period.
17. The controller of claim 16 wherein the meter proving period
for sensing the pulse signal generated by the flow meter is approximately
10000 pulse signals.
18. The controller of claim 16 wherein the interpolator utilizes
a double chronometry pulse interpolation.
19. The controller of claim 16 wherein the plurality of input channels
are each adaptable for receiving an input signal having a voltage
range of 25 mV-30V DC.
20. The controller of claim 16 wherein the flow meter is a turbine.
Description DESCRIPTION
[0001] The present invention is generally related to monitoring
and controlling a fluid transportation system. More specifically,
the present invention is directed to a controller having a flow
meter module for monitoring and controlling a fluid flow volume
in a fluid transportation system.
BACKGROUND OF INVENTION
[0002] The production, transportation and sale of energy products
has always required some form of measurement to determine the quantity
produced, bought or sold. The accuracy and reliability of a system
that measures an energy product, i.e., gas and liquid, is extremely
important to the buyers and sellers involved. A seemingly insignificant
error within the measuring system can result in extensive monetary
losses.
[0003] Technological advances in the areas of fluid flow metering
and computation has led to improved accuracy and reliability. Some
of these advances have been made in the area of metering, or measuring,
transported energy products. These advances have also focused on
factors such as safety, reliability and standardization.
[0004] Today=s metering and transfer system involves more than
simply measuring fluid flow; it can also involve extensive electronics,
software, communications interfaces, analysis and control. Measuring
fluid flow includes multiple turbine meters with energy flow computers,
densitometers, gas chromatography, meter proving systems and RTU
or SCADA interfaces. Measurement and control of energy sources is
a valuable process for companies producing and transporting energy
sources. Many governments, organizations and industries have enacted
standards and regulations related to the recovering, refining, distributing
and selling of oil and oil by-products, i.e., gasoline, kerosene,
butane, ethanol, etc. The energy resource industry has various standards
and regulations to ensure the accuracy and safety of transporting
and metering these energy sources.
[0005] The process of transporting fluid, typically oil, through
a pipeline is monitored and controlled with the assistance of a
combination of sensors and process computers. Generally, a computer
processor monitors the several aspects of the oil transportation,
such as fluid flow volume.
[0006] The control of the equipment facilitating the transportation
of oil is generally performed by environmentally robust devices
such as a controller. The controller regulates valves, tanks and
scales without requiring an individual to constantly interact with
the system.
[0007] A very important aspect of a fluid transportation system
involves the fluid flow meters utilized to monitor the amount of
oil delivered to a customer. Because of the vast amounts of fluid
delivered, the accuracy of the fluid flow meter must be ensured
at regular intervals. An inaccurate fluid flow meter can result
is overcharging or undercharging a customer for the delivered product.
[0008] A turbine flow meter is an accurate and reliable flow meter
for both liquids and gas volumetric flow. Some applications utilizing
a turbine flow meter involve water, natural gas, oil, petrochemical,
beverage, aerospace, and medical. The turbine comprises a rotor
having a plurality of blades mounted across the flow direction of
the fluid. The diameter of the rotor is slightly less than the inner
diameter of the conduit, and its speed of rotation is proportional
to the volumetric flow volume. Turbine rotation can be detected
by solid state devices or mechanical sensors.
[0009] In one application incorporating a variable reluctance coil
pick-up, a coil is a permanent magnet and the turbine blades are
made of a material attracted to a magnet. As each blade passes the
coil, a voltage pulse is generated in the coil. Each pulse represents
a discrete volume of liquid. The number of pulses per unit volume
is called the meter's K-factor.
[0010] In another application utilizing inductance pick-up, a permanent
magnet is embedded in the rotor. As each blade passes the coil,
a voltage pulse is generated. Alternatively, only one blade is magnetic
and the pulse represents a complete revolution of the rotor. Depending
upon the design, it may be preferable to amplify the output signal
prior to its transmission.
[0011] Proving the fluid flow meter is a process for ensuring the
accuracy of the flow meter. Typically, a section of the fluid system
called a proving loop is utilized during the meter proving.
[0012] The dimensions of the proving loop are known and the flow
of fluid within the loop can be monitored by sensors wherein a variety
of fluid characteristics can be sensed. The meter proving process
simultaneously monitors a pulse signal generated by a turbine operably
connected within the fluid system. The flow volume of the fluid
is determined by utilizing the sensed values with industrial standard
flow volume equations, e.g., American Gas Association and American
Petroleum Institute standard equations. The calculated flow volume
is then compared to the known flow volume of the proving loop. By
comparing the calculated fluid flow volume to the known fluid flow
volume of the proving loop, the accuracy of the flow meter can be
determined.
[0013] The duration of a meter proving process is generally one
hundred thousand turbine pulses. This amount of time is believed
to be adequate to accurately determine the fluid flow volume. Generally,
the turbine pulse signal is not in synch with the flow meter proving
process, i.e., the meter proving process will generally not start
at the beginning of the turbine pulse signal. When the pulses are
counted at the end of the proving period, the partial pulses occurring
at the beginning and end of the proving period are omitted. Because
of the duration of the proving period, it is generally believed
that these partial pulses are negligible. However, utilizing the
partial pulses and other characteristics of the monitored fluid
can reduce the time required for the meter proving process, thus
reducing the length of the proving loop.
[0014] This invention is directed to solving these and other problems.
SUMMARY OF THE INVENTION
[0015] The present invention is directed to utilizing a controller
to monitor a flow volume in a fluid transportation system. The controller,
preferably a programmable logic controller, cooperates with a flow
meter to sense a fluid and determine a flow volume. The controller
also ensures the accuracy of the flow meter using an interpolation
method. As a result, a less expensive implementation of monitoring
a fluid transportation system with a controller can be realized.
[0016] An embodiment of the present invention is directed to a
method of proving a flow meter. The flow meter is connected to a
controller and a proving loop within a fluid transportation system.
The proving loop has a known flow volume. The controller monitors
a fluid flow within the proving loop. The method comprises the steps
of starting a meter proving period and sensing a pulse signal responsive
to a flow meter. The flow meter generates a fluid flow through the
fluid transportation system. The meter proving process is terminated
and the amount of sensed pulse signals occurring during the meter
proving period is calculated. The fluid flow volume of the proving
loop is determined in response to the pulse signals occurring during
the meter proving process and other sensed characteristics, preferably
density, of the fluid. The calculated flow volume of the proving
loop is compared against the known volume of the proving loop. The
meter proving process is executed within the controller.
[0017] The calculation of the sensed pulse signals is the sum of
the full pulse signals and the partial pulse signals occurring during
the meter proving process. The partial pulse signals are interpolated
to provide an accurate pulse signal measurement.
[0018] A further aspect of the above embodiment of the present
invention is directed to adjusting the flow meter and/or controller
in response to the comparison of the calculated flow volume of the
proving loop and its known flow volume, wherein the fluid flow meter
and/or controller more accurately calculate the flow volume.
[0019] A further embodiment of the present invention is directed
to method of measuring a flow volume of a fluid within a conduit.
A controller is connected to a flow meter and the conduit. The controller
monitors the fluid flow volume through a plurality of input channels
operably connected to the flow meter of a fluid transportation system.
The controller senses a pulse signal generated by the flow meter
over a period of time determined by the size of the meter proving
loop. A densitometer being operably connected to the controller
senses the real time density of the fluid. The density of the fluid
is sensed and stored by the controller as a dynamic variable to
be utilized in the determination of the flow volume. The controller
utilizes the sensed dynamic density in cooperation with an industrial
standard, API 2540 which yields a correction factor, M, to be used
by another standard industrial equation, AGA-7 for calculating
a flow volume through the measuring flow meter.
[0020] Significant cost savings can be attained by implementing
a less expensive controller capable of performing the monitoring
and control functionality required for determining a flow volume.
In addition, more accurate flow volume calculations can be obtained
by utilizing additional characteristics, i.e., real time density
values, in cooperation with the industrial standard equations.
[0021] Other advantages and aspects of the present invention will
become apparent upon reading the following description of the drawings
and detailed description of the invention.
BRIEF DESCRIPTION OF DRAWINGS
[0022] FIG. 1 is diagram depicting one embodiment of a turbine
flow meter;
[0023] FIG. 2 is a diagram depicting another embodiment of a turbine
flow meter;
[0024] FIG. 3 is a block diagram of one embodiment of the present
invention:
[0025] FIG. 3A is a block diagram of an embodiment of a proving
loop used with the present invention;
[0026] FIG. 4 is a block diagram of another embodiment of the present
invention; and,
[0027] FIG. 5 is a timing diagram of the preferred interpolation
method of the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
[0028] While this invention is susceptible of embodiments in many
different forms, there is shown in the drawings and will herein
be described in detail a preferred embodiment of the invention with
the understanding that the present disclosure is to be considered
as an exemplification of the principles of the invention and is
not intended to limit the broad aspect of the invention to the embodiment
illustrated.
[0029] A flow meter 10 preferably a turbine, comprises a rotor
12 having a plurality of blades 14 mounted across the flow direction
of the fluid within a conduit 16. See FIGS. 1 and 2. The diameter
of the rotor 12 is slightly less than the inner diameter of the
conduit 16 or pipe, and its speed of rotation is proportional to
the volumetric flow volume. Turbine rotation can be detected by
solid state devices or mechanical sensors. As each blade 14 revolves,
a voltage pulse is generated. Each pulse represents a discrete volume
of liquid. Alternatively, only one blade 14 can generate a pulse,
thus, each pulse represents one complete revolution of the rotor
12. The number of pulses per unit volume is called the meter's K-factor.
[0030] The volume of rotation and registration of each rotor blade
14 implies the passage of a fixed volume of fluid. Fluid flow in
a pipeline is the actual volume of fluid that passes a given point
during a specified time. Volumetric flow can be calculated by monitoring
various characteristics of the fluid, such as velocity, density,
temperature and pressure. These characteristics are monitored by
a controller 20 for use with industrial standard equations for fluid
flow calculation, preferably in accordance with AGA and API standards.
[0031] A controller 20 having a module 22 operably attached to
the backplate of the controller, is operably connected to the flow
meter 10 via a plurality of input channels. See FIG. 3. The pulse
signal generated by the turbine 10 is received by the module 22.
The input channels of the module 22 are adapted to receive input
signals in the range of 25 mV-30V DC. Thus, the module 22 can be
directly connected to the flow meter 10. The module 22 receives
the flow meter frequency signal and can be programmed with K and
M factors for converting the frequency input to a specified volumetric
flow volume measurement unit. Typical units of volumetric flow include
gallons (or liters) per minute and cubic feet (or meters) per minute.
[0032] A more accurate flow volume can be obtained by utilizing
an additional characteristic, i.e., real time fluid density, of
the monitored fluid in cooperation with the industrial standard
equations.
[0033] See FIG. 4. A densitometer 24 is operably connected to an
input channel of the controller 20.
[0034] The densitometer 24 senses the density of the fluid within
the pipeline. The real-time sensed density value is utilized with
the API 2540 standard to calculate a correction factor, M, for the
AGA-7 flow equation that measures the fluid flow through a flow
meter. Preferably, the real-time sensed density values are stored
as a dynamic variable within the module 22. Utilizing dynamic density
values with an API 2540 dual chronometry pulse interpolation standard
equation takes into account the effects that changing pressure and
temperature of the fluid (and the material of the conduit 16 itself)
will have on the calculated flow volume. The use of the dynamic
density values provides for a more accurate flow volume than a flow
volume calculated with a static density variable for the fluid having
an assumed temperature and pressure value.
[0035] Proving the fluid flow meter 10 is a process for ensuring
the accuracy of the flow meter. See FIGS. 3 and 3A. Typically, a
section of the pipeline 16 called a proving loop 26 is utilized
during the meter proving. The dimensions of the proving loop 26
are known and the flow of fluid through the loop can be monitored
by sensors wherein a variety of fluid characteristics can be sensed.
The flow volume of the fluid is determined by utilizing the sensed
characteristics with industrial standard flow volume equations,
e.g., AGA-7. A comparator 38 compares the calculated flow quantity
to the known flow volume of the proving loop 26.
[0036] During the meter proving process, the controller 20 senses
the amount of pulse signals generated by a turbine 10 that occur.
The controller utilizes a calculator 30 to calculate the a fluid
volume for the proving loop 26 in response to the sensed pulse signals
that occurred during the meter proving process. By comparing the
calculated fluid flow volume to the known fluid flow volume of the
proving loop 26 one can determine the accuracy of the flow meter
10.
[0037] The proving loop 26 is a U-shaped conduit having a known
fluid volume. The proving loop 26 is operably attached to the fluid
transportation system. A pair of valves V1 V2 connect the ends
of the proving loop 26 to the system. At the start of the meter
proving process, the valves are switched to allow fluid into the
proving loop 26. The fluid entering the proving loop 26 pushes a
ball, also known as a Apig,@ through the proving loop. Initially,
the pig passes and activates a first switch, S1. Upon activation
of the first switch, S1 the controller 20 senses the pulses generated
by the flow meter 10 until the meter proving process is terminated
when the pig passes a second switch, S2. The time it takes the pig
to travel from the first switch, S1 to the second switch, S2 is
the duration of the meter proving period.
[0038] During the meter proving process, the module 22 senses the
density of the fluid flowing in the proving loop 26. The sensed
density values are linearized by the controller 20. The controller
utilizes the linearized density value and the amount of pulses sensed
during the meter proving process to calculate a correction factor,
M, to later be used by the controller, for determining the volume
of fluid flowing through the transportation fluid system. The correction
factor is utilized in equation AGA-7 to update the accuracy of the
flow meter 10 in the system. The accuracy of the flow meter 10 can
be improved by adjusting the flow meter or the factors (M or K),
used to determine the flow volume of the flow meter.
[0039] Generally, the turbine pulse signal is not in synch with
the flow meter 10 proving process, i.e., the meter proving process
will generally not start at the beginning of the turbine pulse signal.
See FIG. 5. Thus, partial pulses occur at the beginning and end
of the proving period. An interpolator 32 utilizes a pulse interpolation
method to improve the discrimination of the flow meter=s output,
thus requiring a lesser amount of pulse signals to be collected
during the meter proving process. Because fewer pulse signals are
required, the proving loop 26 can be shortened, thus reducing the
cost of the fluid transportation system.
[0040] While various interpolation methods can be used, the preferable
interpolation method utilized by the controller 20 is double chronometry,
also found in the API 2540 standards. Double chronometry pulse interpolation
requires counting a total integral number of flow meter pulses,
Nm, generated during the proving process and measuring a set of
time intervals, T1 and T2. T1 is the time interval between the first
pulse before or after the first detection signal and the first pulse
before or after the last detection signal. T2 is the time interval
between the first and last detector pulses. See FIG. 5.
[0041] The pulse monitor 34 is started and stopped by a meter prover
detector 28. The time intervals T1 and T2 correspond to Nm pulses
and the interpolated number of pulses, N1 respectively. The interpolated
pulse count, N1 is equal to Nm(T2/T1). An accumulator 36 sums and
stores the total number of pulse signals for use by the controller
10 in determining flow volume. The total number of pulses is the
sum of the integral pulses and the interpolated partial pulses.
At the beginning of another meter proving process, the controller
20 resets the accumulator 36 calculator 30 and the pulse counter
21.
[0042] While the specific embodiment has been illustrated and described,
numerous modifications come to mind without significantly departing
from the spirit of the invention, and the scope of protection is
only limited by the scope of the accompanying claims. |