DESC:FORM 2

THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENT RULES, 2003

COMPLETE SPECIFICATION
(See Section 10 and Rule 13)

Title of invention:
A FLOWMETER CALIBRATION SYSTEM AND METHOD OF FLOW METER CALIBRATION THEREOF

Applicant:
BEML Limited
A company Incorporated in India under the Companies Act, 1956
Having address:
BEML Soudha, 23/1, 4th Main,
Sampangirama Nagar, Bengaluru - 560 027,
Karnataka, India

The following specification particularly describes the subject matter and the manner in which it is to be performed.

CROSS-REFERENCE TO RELATED APPLICATIONS AND PRIORITY
[001] This patent application claims priority from Indian Provisional Application 202041002472 filed on January 20, 2020.
TECHNICAL FIELD
[002] The present disclosure in general relates to a flowmeter calibration system and more specifically, to a method for calibrating the flowmeter.
BACKGROUND
[003] A flowmeter is a device used to measure volume flow or mass flow of viscous fluids like gas or liquid. The types of flow meters include turbine flow meters, PD meters, ultrasonic flowmeters etc. These flow meters must be calibrated according to international standard viz “Measurement of liquid flow in closed conduits-weighing method”, ISO 4185–1980” which is a general standard covering the calibration of flowmeter in viscous and non-viscous medium. The flow meters are used for measuring a flow rate of viscous fluids like Hydrol 10, Hydrol 30 have to be calibrated on same medium as meter factor is dependent on viscosity of the fluid. Generally, a horizontal type of calibration system is used wherein the flow meter is mounted horizontally. Vertical type of calibration system can also be used for flow meter calibration. Normally, a weighing platform in these types of calibration system have 3 to 4 load cells which contribute more uncertainty due to weight. Hence, there is a need to develop a system with minimum uncertainty of measurement that provide more accurate results.
[004] The information disclosed in this background of the disclosure section is only for enhancement of understanding of the general background of the disclosure and should not be taken as an acknowledgement or any form of suggestion that this information forms prior art already known to a person skilled in the art.
OBJECT OF THE INVENTION
[005] The main object of the invention is to develop a vertically suspended flow meter calibration system.
[006] Another object of the invention is development of a flow meter calibration system for measurement of flow of oils having different viscosity by using static weighing principle.
[007] Yet another object of the invention is to enable use of a single load cell suspended to a weighing tank of a system.
[008] Yet another object of the invention is to provide a flow meter calibration system with minimum uncertainty of measurement.
[009] Yet another object of the invention is to provide a constant flowrate of a fluid throughout a flow meter calibration.
SUMMARY
[010] Before the present subject matter is described, it is to be understood that this application is not limited to a particular flowmeter calibration system as there may be multiple possible embodiments, which are not expressly illustrated in the present disclosures. It is also to be understood that the terminology used in the description is for the purpose of describing the particular implementations, versions, or embodiments only, and is not intended to limit the scope of the present application. This summary is provided to introduce aspects related to a system and a method for a flow meter calibration. This summary is not intended to identify essential features of the claimed subject matter nor is it intended for use in determining or limiting the scope of the claimed subject matter.
[011] The present subject matter relates to a flow meter calibration system. The said calibration system comprises a weighing tank of predefined capacity configured to be suspended vertically with a vertical stand wherein the fluid flow from a direction control valve 2 is diverted to the weighing tank, a sump tank of predefined capacity configured to be mounted below the weighing tank such that the drain from the weighing tank opens above a mouth of the sump tank, at least one load cell of predetermined capacity is configured to be suspended above the weighing tank with a rod end bearing at each end of the load cell, a separate air cooled oil cooler provided with separate pump driven an electric motor is configured to cool the fluid circulating in the system in order to maintain a temperature of fluid within a target temperature value to minimize uncertainty due variation of a density of the fluid and a flow from plurality of gear pumps are configured to be combined at a junction block wherein the flow from the junction block is provided to the direction control valve 2 through a direction control valve 1. Further, the flowrate of the fluid is configured to be maintained to a level of ±0.1% of a flow reading by using the plurality of pumps driven by an electric motor.
[012] Further, a method for calibrating a given flow meter, wherein the flow meter calibration method comprising the steps of: installing the flow meter to be calibrated in the flow meter calibration system wherein the flow meter is oriented vertically or horizontally, adjusting an electrical motor speed on AC variable speed drive panel based on required flowrate to be passed through the flow meter, switching on a direction control valve DCV1 and a power pack to allow a fluid to a sump tank through the flow meter and a direction control valve DCV2, closing a drain valve of a weighing tank, determining the reading at load cell indicator, switching the DCV2 to weighing tank side for a predetermined time, determining a maximum and minimum flow rate of an indicated flow, determining a temperature of fluid, fluid pressure, ambient temperature and barometric pressure, switching off the DCV2, switching off the DCV1 and the power pack after predefined time, allowing the fluid to settle in the weighing tank for a predetermined time, determining a final force value (N) generated due to weight of fluid tank, repeating an above-mentioned procedure for multiple times for each calibration point and calculating the volume flow rate and the mass flow rate.
BRIEF DESCRIPTION OF DRAWINGS
[013] The foregoing detailed description of embodiments is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the present subject matter, an example of construction of the present subject matter is provided as figures; however, the present subject matter is not limited to a specific system or a device disclosed in the document and the figures.
[014] The present subject matter is described in detail with reference to the accompanying figures. The same numbers are used throughout the drawings to refer various features of the present subject matter.
[015] Figure 1 illustrates a hydraulic circuit for flow meter calibration system, in accordance with an embodiment of the present subject matter.
[016] Figure 2 illustrates a schematic for control circuit in a flow meter calibration system, in accordance with an embodiment of the present subject matter.
[017] Figure 3 illustrates a schematic of automation circuit to remotely control a flow meter calibration system, in accordance with an embodiment of the present subject matter.
[018] Figure 4 illustrates a schematic for circuit gate to find out time period in a flow meter calibration system, in accordance with an embodiment of the present subject matter.
[019] Figure 5 illustrates schematic for vertical suspended layout used in flow meter calibration system, in accordance with an embodiment of the present subject matter.
DETAILED DESCRIPTION
[020] Some embodiments of this disclosure, illustrating all its features, will now be discussed in detail. The words "comprising," "having," "containing," and "including," and other forms thereof, are intended to be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items. It must also be noted that as used herein and in the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Although any devices similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present disclosure, the exemplary devices are now described. The disclosed embodiments are merely exemplary of the disclosure, which may be embodied in various forms.
[021] Various modifications to the embodiment will be readily apparent to those skilled in the art and the generic principles herein may be applied to other embodiments. However, one of ordinary skill in the art will readily recognize that the present disclosure is not intended to be limited to the embodiments described but is to be accorded the widest scope consist in this regard, in a generic sense.
[022] Below is the list of various elements of an embodiment used throughout the present disclosure.
Subscript Nomenclature
QM Measured flow in lpm or kg/min
F Corrected Force in N (Corrected difference between beginning and end of collection period in Newton using polynomial equation of Load cell calibration certificate)
glocal Local gravity in m/sec2 = 9.7806594 m/sec2
?air Density of air in kg/m3
?oil Corrected density of oil in kg/m3 (Oil density corrected to meniscus height, cubic expansion of hydrometer glass, compressibility and line pressure)
t Corrected time in seconds
Following is a list of equipment required in the present flow meter calibration system,
Equipment Name
Hydraulic Power pack
Load cell (Type: Z3H2, 0 - 2 ton capacity) with ML30 amplifier
Oil Weighing tank suspended on load cell.
Direction control valve, Solenoid operated (4-port, 2-position Valve)
Oil temperature indicator with PT100 sensor
Ambient temperature indicator with PT100 sensor
Barometer to measure atmospheric pressure
Frequency counter to measure time of collection
Hydrometer to measure oil density
Pressure gauge/Pressure transducer to measure oil pressure
[023] A flow meter may be calibrated by using different methods like weighing method, gravimetric method, volumetric method etc. It is known that the calibration by gravimetric method delivers lowest measurement uncertainty, however a complexity of the method is greater. The known systems for flow meter calibration generally uses 3 to 4 load cells. In the present subject matter, a static weighing principle is used for the flow meter calibration. The flow meter of the present invention uses a vertically suspended tank with a single load cell. In the present disclosure, the flowmeters from nominal bore size 9 mm to 65 mm may be mountable in both horizontal and vertical orientations, with inlet and outlet flow straightening sections. This feature enables simulation of identical conditions for a turbine of the flowmeter and hence realize improved correlation between the calibration conditions and installation conditions. Further, in the present subject matter, the flowrate of the fluid may be maintained within ±0.1% of the reading before start of collection, during collection time and after collection time in order to avoid the uncertainty caused due to instability of a flow source. However, maintaining a constant volume flowrate while using a temperature dependent liquid having velocity in range of 10 cSt to 100 cSt, involves specific design of system and control system. Further, in the present system, the flow source may be a plurality of positive displacement pumps or gear pumps wherein the flow from the pumps may be combined in a diffusion chamber or a junction block that enables to maintain a uniform flowrate and may be independent of pressure variations. In the present invention, a cooling system with thyristor-controlled DC motor driven bypass circulation system may be used to maintain an oil temperature within ±1°C of a targeted temperature. Further, in the present invention, a single load cell is used with vertically suspended arrangement of the weighing tank to minimize the uncertainty in the measurement of a fluid mass.
[024] Referring to figure 1, a hydraulic circuit used in the present subject matter is shown. The hydraulic circuit comprises a plurality of pumps (P1-P5) driven by an electric motor A1 wherein the flow generated by the pumps (P1-P5) may configured to be combined in a junction block with a safety relief valve in parallel. In an embodiment, the pumps may be positive displacement type gear pumps and the electric motor may be an induction motor with AC variable speed drive with a pulse encoder feedback and servo control for maintaining constant flow in a range of 10 to 1500 rpm. In the present invention, speed of the pumps (P1-P5) may be controlled within ±0.01% of a flow reading and a flowrate may be maintained constant at any given temperature and viscosity of a fluid. A change in the viscosity of the fluid due to temperature change may lead to a small variation in the flowrate as volumetric efficiency of the pumps (1-5) may change wherein this variation in the flowrate may be compensated by integration of the flowmeter output signal with the AC variable speed drive panel in a closed loop as shown in a block diagram of an enclosed control system. Further, the flow from the junction block may be routed through a direction control valve (DCV1) (10) which may either drained to a sump tank (S1) or may be directed to a flow manifold where a calibrating flow meter may be connected through a ball valve. The flow manifold may be provided with draining facility for bleeding an air entrapped in a system. Further, the fluid flow passing through the flow meter may be led through the manifold and through a vertical pipe into a second direction control valve (DCV2) (11). The flow from DCV2 (11) may be either drained to the sump tank (S1) or a weighing tank (W1). Furthermore, a separate pump P6 driven by an electric motor A2 may be provided to supply the fluid from the sump tank and passes the flow through an oil cooler and returns the flow back to the sump tank. Further, a plurality of pressure gauges may be mounted before and after the flow manifold to measure positive pressure and to monitor a pressure drop.
[025] Referring to figure 2, a schematic diagram of a flow meter calibration system is shown. A control system of the flow meter calibration system comprises a primarily closed loop control for the motor (2) in the form of an AC variable speed drive (3) wherein the control system may be configured to take a feedback from the motor shaft through a pulse encoder (1) to control a predetermined speed. Further, a flow read out signal (9) may also be connected to the AC variable speed drive (3) for optionally realizing the closed loop control in order to maintain the constant flow rate. The direction control valve (DCV1) (10) may be activated through a signal from SSR board (5) for diverting the flow back to the sump tank (S1) and the direction control valve (DCV2) (11) may also be actuated by the SSR board (5) to divert the flow from the sump tank (S1) to the weighing tank (W1). On actuation of DCV2 (11), a gating signal may be tapped through a proximity switch mounted at an end cover of DCV2 (11) and the gating signal may be processed through a gating signal board (7) to a frequency counter (8) wherein the frequency counter (8) starts a clock. Further, the clock may be stopped on receiving the gating signal from the proximity switch mounted at another end of DCV2 upon switching back the DCV2 (11).
[026] Referring to figure 3, a schematic diagram for an automation used in the flow meter calibration system is shown. The flow meter calibration system may be automatically operated from a personal computer comprising a mother board mounted DAS1702 card through a ribbon cable configured to provide TTL signals to STA 1800 connector box that in turn drives a plurality of solid state relays (SSR1-SSR6). In an embodiment, SSR1 and SSR2 may be used to control the Direction control valve DCV1 (10) and SSR5 and SSR6 may be used to control the direction control valve DCV2 (11). Further, the solid state relays SSR3 and SSR4 may be used to control AC drive control panel (4) for starting and stopping the motor (2).
[027] Referring to figure 4, a circuit diagram for a gating signal in the flow meter calibration system is shown. In the present invention, the gating signal may controls 5 to 800 lpm gating system, which is central and most crucial to a calibration accuracy of the flow meter calibration system. The logic circuit of the gating system may tap the signals from the proximity switches (P1, P2) from both ends of the directional control valve 2 (11). Further, the signal from the proximity switches (P1, P2) may be conditioned through a low power quad operating amplifier (LM324) before being OR gated and may be fed to the frequency counter (8) for time signal integration.
[028] Referring to figure 5, a flow meter calibration system with vertically suspended layout is shown. The flow meter calibration system comprises a weighing tank (W1), a vertical stand (15), a load cell (12) with rod end bearing (13) at both ends and a sump tank (S1). The weighing tank (W1) may be suspended from the vertical stand (15) through the load cell (12) and the sump tank (S1) may be mounted on castor wheels below the weighing tank (W1) such that a drain valve (14) of the weighing tank (W1) may directly open above a mouth of the sump tank (S1). In an embodiment, the weighing tank may configured to be of 1000 liters capacity, the load cell may configured to be of 2-ton capacity and the sump tank may configured to be of 1400 liters capacity.
[029] Further, a method of the flow meter calibration is explained. The said method may uses SAE10 / Hydrol 10 oil as a fluid wherein the density of the oil may be determined at every 0.5°C interval and recorded in the density data sheet. Further, the density may be measured once in every 3 months and may be recorded in the same sheet. The density measurement may be carried out as per the procedure detailed in BS 718. In an embodiment, for using the oil other than SAE10 / Hydrol 10 oil, the density of the oil may be measured immediately before use. The said method may be carried out in environmental conditions with a temperature in a range of 18 to 36°C, a luminosity greater than or equal to 400 lux and an acoustic noise less than 80 dBA. The method of the flow meter calibration comprises steps of: installing the flow meter to be calibrated in the flow meter calibration system either vertically or horizontally, controlling the direction control valves (DCV1, DCV2) to allow the fluid to the weighing tank or to the sump tank, adjusting a motor speed on AC variable speed drive panel based on required flowrate to be passed through the flow meter, switching on DCV1 and a power pack to allow the fluid to the sump tank or through the flow meter and DCV2, closing a drain valve of the weighing tank, determining the reading at load cell indicator, switching the DCV2 to weighing tank side for a predetermined time, determining the maximum and minimum flow rate of the indicated flow, determining the temperature of fluid, fluid pressure, ambient temperature and barometric pressure, switching off DCV2, switching off DCV1 and the power pack after predefined time, allowing the fluid to settle in the weighing tank for a predetermined time, determining a final force value (N) generated due to weight of fluid tank, repeating the procedure from steps of adjusting the motor speed up to determining a final force value (N) for predetermined time for each calibration point, calculating the flow rate as per below equations,

Volume Flow rate:

---- (1)

Mass flow rate:

[030] Exemplary embodiments discussed above may provide certain advantages. Though not required to practice aspects of the disclosure, these advantages may include the following:
[031] The proposed flow meter calibration system provides vertical as well as horizontal orientation of a weighing tank.
[032] The proposed flow meter calibration system enables use of different oils with different viscosities in a given flow meter.
[033] The proposed flow meter calibration system provides stability of flowrate to maintain uncertainty in measurement.
[034] The proposed flow meter calibration system enables use of a separate air-cooled oil cooler to maintain temperature of a fluid within a target value.
,CLAIMS:
1. A flow meter calibration system comprising:
a weighing tank (W1) is suspended vertically configured for a fluid flow from a direction control valve (11), to the weighing tank (W1);
a sump tank (S1) configured to be mounted below the weighing tank (W1) wherein the drain valve (14) from the weighing tank (W1) opens in the sump tank (S1);
at least one load cell (12) is configured to be suspended above the weighing tank (W1) with a rod end bearing (13) at each end of the load cell (12);
a separate cooler configured to cool the fluid circulating in the system to maintain a temperature of fluid within predetermined temperature value to minimize uncertainty due variation of a density of the fluid; and
plurality of pumps (P1-P5) are configured to integrate the flow at a junction block to minimize variation in a flow rate;
a direction control valve 1 (10) configured to receive the fluid flow from the junction block to supply the fluid flow to the direction control valve 2 (11); and
at least one flow meter configured to be mounted for calibration in the said flow meter calibration system.

2. The flow meter calibration system as claimed in claim 1, wherein the weighing tank (W1) with 1000 litres capacity configured to be suspended on a vertical stand (15).

3. The flow meter calibration system as claimed in claim 1, wherein the sump tank (S1) is configured with a capacity of 1400 litres.

4. The flow meter calibration system as claimed in claim 1, wherein the single load cell (12) is configured with a capacity 2-ton.
5. The flow meter calibration system as claimed in claim 1, wherein the cooler is configured to be an air-cooled oil cooler and the said cooler is provided with a separate pump (P6) driven by an electric motor A2.
6. The flow meter calibration system as claimed in claim 1, wherein the flowrate of the fluid is configured to be maintained to a level of ±0.1% of a flow reading by using the plurality of pumps (P1-P5).

7. The flow meter calibration system as claimed in claim 1, wherein the plurality of pumps are configured to be positive displacement type gear pumps driven by an electric motor A1.

8. The flow meter calibration system as claimed in claim 1, wherein the flow meter fluid is configured to be a SAE10 / Hydrol 10 oil.

9. The flow meter calibration system as claimed in claim 1, wherein the flow meter is configured to be mounted vertically or horizontally.

10. The method for calibrating a given flow meter, wherein the flow meter calibration method comprising the steps of:
installing the flow meter to be calibrated in the flow meter calibration system wherein the flow meter is oriented vertically or horizontally;
adjusting an electrical motor speed on AC variable speed drive panel (4) based on required flowrate to be passed through the flow meter;
actuating a direction control valve DCV1 (10) by a power pack configured to flow a fluid to a sump tank (S1) or to the flow meter and a direction control valve DCV2 (11);
closing a drain valve of a weighing tank (W1);
determining the reading at load cell indicator;
operating the DCV2 (11) for fluid flow to the weighing tank (W1) for a predetermined time;
determining a maximum and minimum flow rate of an indicated flow;
determining a temperature of fluid, fluid pressure, ambient temperature and barometric pressure for calculating a volume flow rate and a mass flow rate;
switching off the DCV2 (11) to stop the fluid flow in the DCV2;
switching off the DCV1 (10) and the power pack after predefined time;
allowing the fluid to settle in the weighing tank (W1) for a predetermined time;
determining a final force value (N) generated due to weight of fluid tank;
repeating an above-mentioned procedure for multiple readings for each calibration point; and
calculating the volume flow rate and the mass flow rate.