Table of Contents
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INSTALLATION, OPERATING
AND MAINTENANCE INSTRUCTIONS
DESIGN & PRINCIPLE OF OPERATION:
These VFF series flowmeters are defined as rotary piston meters of a type as detailed in British Standard
BS.7405:1991 which is a guide to flowmeters. They offer a wide metering range and can measure low and
high viscosity fluids. For most of the flow range the viscosity may be varied with minor effect on the output
characteristic.
Litre Meter provides a standard factory calibration representative of the application in terms of viscosity
and flow rate range. A calibration certificate is provided which details the calibration fluid and viscosity,
together with pulses per litre at a range of flow rates specifically for the application or the total meter
range.
The only moving part of the flowmeter is the rotor which is equipped with a top mounted central magnet.
The rotor oscillation is detected by a sensor or pair of sensors. The interaction between the magnet and
a sensor does not impose drag on the rotor which could otherwise affect the low flow rate measurement
capability. The certificate shows the number of active sensors. The reed-switch sensors are inherently
intrinsically safe.
THE METER MAY NOT BE DESIGNED FOR USE ON WATER – PLEASE CONSULT THE
FAT Issues
FACTORY. See
Document No LM0670 Issue A Rev 2 November 2017
VFF SERIES ROTARY FLOWMETERS
Typical VFF Flowmeter parts
on page 12.
Page 1 of 15
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Table of Contents
Summary of Contents for Litre Meter VFF Series
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Page 1: Design & Principle Of Operation
DESIGN & PRINCIPLE OF OPERATION: These VFF series flowmeters are defined as rotary piston meters of a type as detailed in British Standard BS.7405:1991 which is a guide to flowmeters. They offer a wide metering range and can measure low and high viscosity fluids. -
Page 2: Table Of Contents
Contents DESIGN & PRINCIPLE OF OPERATION: ....................1 SPECIFICATION: ..........................3 METER CONTENTS DESCRIPTION all as stated on the calibration certificate ......3 MATERIALS: ............................3 FILTRATION: ............................3 Meter Size ............................3 FLOW PULSATION: ..........................4 COMMISSIONING and START-UP: ....................4 MECHANICAL INSTALLATION: ...................... -
Page 3: Specification
The ambient temperature can range from -40°C/-40°F to +75°C/+167°F (dependent on instrumentation). LIFE RATING – Sensor: Litre Meter have carried out life testing on the latest reed sensor. At the current and voltage of a Fluidwell display they have successfully lasted over 15 billion operations representing 30 years continuous running at over maximum flow rate. -
Page 4: Flow Pulsation
FLOW PULSATION: The VFF series meters can be affected by pulsing flow rate particularly if there are severe flow rate variations in terms of the nominal flow. Sometimes a damping value can be utilized in the electronics to provide a smoother displayed value of flow rate. -
Page 5: Mechanical Installation
Decomposition of unstable fluids. unstable fluids. Means of Examination. Litre Meter VFF Flowmeters are designed so that all critical Pressure equipment must be designed and parts are contained within the meter body and cannot be constructed so that all necessary examined while in service. -
Page 6: Application Warnings
Vertical access should be provided for the field cabling connection and for maintenance purposes. Litre Meter do not recommend the meter is installed for vertically downward flow. The calibration certificate will confirm calibration orientation, if non-standard. -
Page 7: Intrinsic Safety Exi - Installation Notes
In the absence of any other data Litre Meter advise an annual check and to vary the future calibration periods depending on results. -
Page 8: Handling And Shipping Procedures
HANDLING AND SHIPPING PROCEDURES The systems are packed entirely within wooden or cardboard boxes suitable for protecting the units during normal handling. We would recommend that they are kept in these boxes for as long as is practicable until they are finally required. One note of caution: please do not lift or handle the meters by solely lifting the display, glands or cables. -
Page 9: Meter Maintenance - General
METER MAINTENANCE – GENERAL This unit should not require regular maintenance providing the installation precautions above are taken into consideration. The warranty will not be invalidated if the cap is removed to inspect the rotor and its chamber. Document LM0638 lists all the possible failure scenarios and resolutions and to some extent, probabilities –... -
Page 10: Weee - Waste Electrical And Electronic Equipment
If appropriate see the separate instruction for the display unit. WEEE - Waste Electrical and Electronic Equipment Litre Meter Ltd has a formal product disposal Take-Back and Recycle Program in Europe that complies with the European Union Directive 2012/19/EU on waste electrical and electronic equipment, also known as the "WEEE Directive". -
Page 11: Measurement Principle
What’s a pressure balanced chamber? Extensive testing by Litre Meter in 2005 proved that leaks occur over the top of the rotor at higher pressures. This is due to minute distortions of the cap. For example, at 700bar the cap moves by just 0.02mm in the centre. -
Page 12: Fat Issues
FAT Issues The Factory Acceptance Test can be the first time the meter is run after being despatched from the factory. Here are some common problems encountered and their resolution: The most frequently used FAT fluid is water. This won’t damage the meters at all, but it does have a very low viscosity. There are two significant effects. Firstly, the meter will probably not measure as low as the flow rates achieved at time of factory calibration. The calibration viscosity is taken to be the viscosity of normal operation. Secondly, if it does operate at the lowest flows, then the accuracy may be greatly reduced. It is likely to under‐read by up to 30%. The solution is to change the FAT fluid. The addition of glycol or replacement by glycol for the FAT is quite common. Dirt in the system is hard to avoid. Even with filtration at 40 or 100 microns it is still quite easy for potentially blocking particles to be held in the piping, even after flushing. We would recommend the meter is taken out of line before pipe flushing. Items like PTFE tape and the remnants of thread locking compounds will prevent the rotor from turning. However, the rotor and chamber can be simply cleaned by disassembly and washing. Installation attitude can be different from original calibration. The meters are normally calibrated in a horizontal line with the meter installed upright. If a different orientation is advised or used it will be noted on the calibration certificate. There will be some small functional differences if the meter is installed on vertically upward flow or upside down. Litre Meter do not recommend the meter is installed for vertically downward flow. Performance at the very lowest flows may be compromised unless calibrated in the correct orientation. An error analysis system is described in document LM0638, VFF Fault Finding. On-Site Flowmeter Calibration This procedure must be integrated with the approved Health and Safety policy at site. The purpose of this section is to outline a general calibration procedure for various flowmeters. It will make specific reference to volumetric flowmeters but most of the principles are equally applicable to other flow measurement technologies. The important consideration is that there is access to the reading of the Meter Under Test (MUT) and a sufficiently accurate understanding of the actual flow rate. On-Site calibration This is how Litre Meter calibrate flowmeters in ... -
Page 13: Flying Start And Finish
Avoid pulsating flow and cavitation to have meaningful results Prepare a weigh tank The tank should of sufficient size to contain a volume of fluid running at the required range of flows for a minute or so. For example, if the meter has a flow range from 1 to 30 litres per minute then a 30 litre tank would be appropriate. As the tank may be difficult to empty completely having it a little larger is advisable; care should be taken that it is deep enough or so shaped that splashing outside of the tank doesn’t occur. The tank needs to be weighed before and after the test to sufficient accuracy. For lower flow rates there is not necessarily a requirement to measure 30 litres each time. This will depend on other factors such as weighscale resolution, accuracy of weighscale, accuracy of flowmeter and accuracy of density determination. This method is normally used for water where the density is well known as it measures mass but will be applied to volumetric flow meters. As guidance Litre Meter recommends a weighscale with a resolution 10,000 times smaller than the maximum weight and a densitometer accurate to the ±0.001 g/cm³ (if water isn’t used). In some instances, a volumetric tank could be used where the volume is accurately known. Prepare start and end of test. There are two options: Flying start and finish This method is very widely used when flow rate meters must be calibrated with water. It is perhaps less appropriate for the calibration of volumetric meters, or for meters which are being calibrated with oils or fuels. The mass flow rate is calculated by dividing the mass collected in the tank by the diversion time, and this can be converted to a volumetric flow rate by dividing it by the density at the appropriate temperature. A diversion is caused by switching the stream of fluid into a weigh tank at the start of the test and reversing the switch at the end of the test. Accuracy of calibration is obtained by ensuring the timing error at the start and end is minimised by both good technique and by relatively long test periods (at least 60 seconds, for example) and repeatable, quick diversion. ... - Page 14 Data Collection Approx Weight Time for Calculated Displayed Actual flow Test # Density flow rate collected test Volume Flow rate rate Litres/hour Seconds gm/cm³ Litres Litres/hour Col C Col F*3600 Col E Col D 1500 25.106 60.015 1.0015 25.068 1500 1503.73 1500 24.976...
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Page 15: Appendix
Appendix Fluidwell wiring – please also see separate wiring diagram Refer to drawing depending on what has been supplied. The correct drawing is supplied with each order and can be accessed via the website url. The url is given on the quick start instructions and the outside of the flowmeter and instrument.
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