Flow Meters

What is a PV Meter?
A 'PV Meter' is a flow meter that will HANDLE PROBLEM FLUIDS that damage other meters. The Oilgear PV Meter (Proportional Velocity) will pass sand, grit, stones (up to 0.25" diameter in our smallest meter), bits of wood or rubber, and suspensions that could stop and damage other meters. There are no close clearances, no rotating seals, and no stuffing boxes. This simple design provides little that can go wrong. If something should malfunction, there is a simple field fix without having to remove the meter from the line.

Here's how it works:
The Oilgear PV Meter looks like a short section of pipe, with a rotor and rotor chamber offset and perpendicular to the flow axis. The flow stream, combining the effects of a Pelton wheel and a centrifugal flow turbine drives the rotor. This combination gives a rotor speed PROPORTIONAL to the flow VELOCITY passing through the rotor chamber, over a wide range of flow rates. The combination gives the same performance and small size of a typical axial flow turbine meter, but with the lower speed and higher torque of a typical positive displacement meter.

Advantages of the PV Meter

• Large Particle Clearance
  Due to the rotor-cage construction, coupled with the offset chamber, large particles (up to 0.5" diameter in the 2" size 20 meters) can pass through the meter body without causing damage.
• Long Life in Contaminated Liquid
  Low rotor speeds and a high torque values allowed the PV Meter to be designed with large journal bearings (both graphite and tungsten carbide), that provide long life, even in the presence of entrained particles. Additionally, the absence of rotating seals and close tolerances minimizes the potential effects of seal failure.
  NOTE: Ball Bearing rotor meters are available and have lower end operating ranges but they are not recommended for particle entrained or dirty fluids. They should be used only for fluids that have lubricity such as lubricating oils or gasoline etc.
• High Tolerance to Overranging
  The low rotor speed and high torque output also allow a strong, heavy-duty rotor and shaft to be used. Thus, the Oilgear PV Meter is more tolerant of excessive over speed conditions than the small bearings and low-weight shafts of other meters. This design difference means a sudden flow rate surge, such as occurs when a gas slug is pumped along with a liquid, is less likely to cause damage.
• Readout Flexablilty
  Mechanical Readouts
  These devices are used where no electrical power is available and battery power is not desirable. A mechanical readout though, may incorporate passive or active electronic or electrical devices to provide the best of both worlds. This system allows mechanical recording of meter output as backup, in the event of the loss of power.
• Electrical / Electronic Readouts
  The Oilgear Company has produced electronic products for over thirty years and has the capability of equipping the meters with up-to-date readout devices to mate with almost any telemetry equipment. These readouts range from a simple switch closure type, to a square wave encoder.
• Calibration
  Rotor turns are proportional to the fluid flow velocity through the meter. In most meters there is a shelf type septum. By diverting flow under or over the septum by a calibration plug, more or less fluid is diverted to the rotor thereby increasing or decreasing the number of turns the rotor makes. Calibration in our shop requires no compensation factors to compensate for machining errors as in other meters. Field calibration allows +/-3% of nominal values.

• Accuracy
  The PV Meter typically exhibits 0.5% of reading accuracy throughout its specified flow range.
• Repeatability
  The PV Meter exhibits 0.25% of reading repeatability throughout its entire operating range.

Meter Sizes

Pressure Ranges:
Meter pressure ranges vary with the end connection types. Consult the factory for specifics or send for our Bulletin 90901-C

Modifications:
Most meters are made to standard lengths but we can manufacture to meet your specific requirements such as providing oversize flange connections or fitting to precise lengths for your location.

Oilgear Meter Readouts
All Oilgear mechanical readouts are designed around a field proven simple counter mechanism. They are encased in a body of high impact polymer or aluminum with blue anodizing, nickel plating or epoxy paint available as appropriate. The instrument bearings are stainless steel. The nine digit readout characters are 3/16” high and are white on black.
All mechanical readouts use a universal polymeric mounting hub. The polymeric material eliminates galvanic corrosion between the cast register body and the carbon steel or stainless steel meter body. The universal hub allows any register to mount on any Oilgear meter, old or new; only the meter size and units of measurement need be considered
There are four basic types of data acquisition available with the Oilgear PV Meter:

• Mechanical totalizers, Local
• Switch pulsers (Reed switches)
• Magnetic Pick-ups, Standard or Explosion Proof or Intrinsically Safe.(Passive or Active)
• Battery or Loop Powered LCD with variations.

Type "T"
Mechanical Totalizers:
Type "T" Mechanical totalizers use worm driven counters with nine digits. Options include single or dual counters, reset or non-reset, and horizontal or vertical readings. The type "T" readout is used where local totalization is required.


Type "Y" & "Z"
Combination Pulser-Mechanical Totalizer:
Y and Z switch closure types combine the pulser (reed switch) function with the totalizer function, giving both local totalization and pulse transmission. Type Y provides one pulse output, and type Z provides dual simultaneous pulse outputs.


Type "M" & "P"
Magnetic Sensor:
A direct hub mount magnetic sensor, type M, can be added to size 06, 10, 15, 20 and 30 Oilgear meters. Separate housings, type ‘P’, are required for size 40, 60 and 80 Oilgear meters.

These Sensors will provide:

• Square wave DC output using an active transducer.
• Sine wave AC output using a passive transducer.
• Non-contact, non-wetted, externally mounted sensor is not subject to corrosion, contamination or fluid pressure.
• Explosion-proof sensors as well as a full line of active and passive transducers are available.
• Intrinsically safe devices are available.

Type "N"
Mechanical Totalizer:
Type "N" Mechanical totalizer with analog rate of flow scale indicator (no power supply required). Options include single counters, reset or non-reset, and horizontal or vertical reading.


Type "V" & "W"
Switch Pulsers:
Type "V" and "W" switch closures (reed switches) have a solid cover without a window for viewing the single counter.
Type "V" provides one pulse output and type "W" provides dual simultaneous outputs.


Type "F"
LCD Displays:
Type "F" readouts are Liquid Crystal Diode displays that may be locally powered by batteries or by loop power. Their signal is a locally mounted pick-up coil that senses the rotor turns. They can be mounted locally or remotely. They can display locally and provide remote signal to a central location. They can be constructed in Explosion Proof versions or Intrinsically Safe versions. They come in many configurations for Batch Control, Flow Computer, Etc.

Oilgear Quality Control
The Oilgear designed meter prover is typical of the quality assurance steps Oilgear's quality control engineers have provided for manufacturing and testing its flow meters. The prover uses calibrated tanks traceable to the U.S. Bureau of Standards to check the accuracy and repeatability of the PV meter. The 4,000 U.S. gallon capacity meter tester is used to check and calibrate each meter manufactured.
Each meter has a serial number established for it. A calibration curve is run from the prover and maintained on file for each serialized meter.
Material Certifications are maintained on file for most pressure bearing raw materials used in the meter manufacture.

Application and Selection Criteria

• Viscosity:
  The Oilgear PV Meter may be used with fluids having 130 Centistokes viscosity or less without significant change in accuracy. As with all velocity inference meters, the PV Meter accuracy will change with high viscosity fluids; however, the change will be less than typical turbine meters. Since the PV Meter's unique cage chamber construction requires less cutting of the flow stream, viscosity has less effect. Regardless of viscosity, the PV Meter will be repeatable within 0.25%. Consult the factory for application guidelines with higher viscosity fluids.
• Aeration and Flashing:
  PV Meters are volumetric measuring devices and, as such, will measure the volume of any and all materials passed through the meter. This includes entrained air, liquid vapors, and entrapped gases. This should be remembered in designing systems since vapor elimination may be required.
  Volatile fluids, such as LPG and liquid anhydrous ammonia, must be pressurized by pump or sufficient gravity head to prevent vaporizing or "flashing" within the meter. Pressure of the liquid should be increased above that of the supply tank (or wherever vapor and liquid are in equilibrium) so there is a definite excess over tank pressure at the meter outlet. A flow control valve downstream from the meter is recommended.
• Underranging:
  Using the meter below minimum specified flow rate will result in erroneous readings.
• Overranging:
  Consistently using the meter to 130% of maximum flow rate will not cause erroneous readings but may result in lowering the potential wear life of the meter and readout.
• Intermittent Overranging:
  Up to 130% of maximum flow rate at less than 20% of the duty cycle will provide satisfactory results with minimal effect on life.
• Gross Overranging:
  200% to 300% and more may not cause damage depending on how often and how much.

Certifications Available

• Welding procedures certified to A.S.M.E. and others
• Quality assureance programs certified to A.S.M.E. and others
• May be manufactured to NACE specifications
• Hydrostatic testing to 150% of rating
• Certified material tracing
• Radiographic X-ray testing
• Low or high temperature
• Charpy testing
• Magnet particle testing
• Dye penetrant testing
• Ultrasonic testing

Where the PV Flow Meter Excels

Selection of a PV Meter
Flow meter selection requires consideration of many factors including the anticipated flow range, pressure, corrosion resistance, entrained particles, fluid characteristics, etc.
Please contact us and ask for our Bulletin 90901-C for more definitive technical information on selecting the meter for your particular application. We would be pleased to help you make your selection.