Rotary Piston versus Turbine Flow Meters – Application strengths

We’re often asked why we recommend our VFF Rotary Piston device for chemical injection and, in particular, against the traditional turbine flowmeter.  Here are 8 specific advantages of the VFF over turbine flowmeters:

  1. Low Flow The lowest flow measurable by a VFF rotary piston positive displacement flowmeter is two orders lower, especially if the viscosity is greater than water. For example, the LF03 at just 10cP will measure down to 0.025 l/hr – that’s a teaspoon every 12 minutes. A small turbine, even at 1cP, it’s optimum viscosity, peters out at 0.03 l/min – over 70 times higher.
  2. Pulsing Flow Customers tend to use pulsing pumps for chemical injection and even with pulsation dampers turbine meter blades will tend to over spin and cause the flow meters to read high if you are measuring total flow. Pulsation dampers are set at a pressure higher than the line pressure and are only guaranteed to reduce the pulsation to within ±10% at best of line pressure. If the line pressure changes at all during operation, then pulsation dampers are useless as they can only be set for one pressure. In our experience PD meters are ideal as they track the pulse and will read accurately for total flow even if no dampers are fitted.
  3. Display stabilisation The second problem with pulsing flow on a turbine meter is that the flow rate indication or 4-20mA output will range up and down at a frequency slightly out of synchronisation with the actual flow. To stabilise this reading rolling average electronics are often used. However, this can have two negative effects: firstly, the rolling average function, which is software based, will increase the response time on a control loop, the effect being that any changes in flow will take longer to be corrected. Secondly, you can easily get the control loop constantly ranging up and down chasing the flow meter reading but never quite catch up. These could be expensive for the client with wasted chemical. PD meters do not require the rolling average function as their reading while moving with the pulsing flow will be accurate.
  4. Viscosity effects Turbine meters are inferential devices: even small changes in viscosity due to ambient air temperature changes will be sufficient to affect the accuracy. In addition, if the viscosity is above 1 cSt then the lower end of the flow range will be less accurate and some of the measurement range will be lost. With chemical injection applications offshore it is inevitable that through the year there will be a wide range of ambient air temperatures and viscosity changes are very likely. PD meters are not affected by viscosity changes; in fact, if the viscosity increases their accuracy gets even better as the slippage past the gears or piston reduces. In our experience the only application where a turbine meter may be used for chemical injection is Methanol as it has a very low viscosity of 0.6cSt at 25°C and much higher injection rates.
  5. Maintenance If something fails in service in a turbine meter the whole unit must be removed from the line. With a PD meter the meter body can be left in the line and the top cover removed to replace the internals.
  6. No straight lengths Turbine meters typically require a minimum of 10 diameters upstream and 5 diameters downstream of the flow meter, increasing installation space requirements.  In most configurations of piping prior to the meter much more is needed. Positive displacement flow meters do not require straight lengths.
  7. Non-standard connections There is a design issue if the turbine assembly cannot slide through the connector inside diameter. If it can’t physically pass through then there has to be at least one if not usually two adaptors. For example, Autoclave Engineers fittings can have 5mm id tubes. It is not possible for most turbine assemblies to be made this small.
  8. Range ability Most turbine flowmeters have flow ranges limited by bearing friction, hydrodynamic influences like viscosity and sensor drag. A ratio of maximum to minimum flow is typically 10:1, maybe higher of the viscosity is low. In the LF03 example given in point 1, the turndown ratio is 720:1. Furthermore, in the LF series the rotors and chambers are interchangeable. The LF15 and LF05 will drop into the body of an LF body previously holding an LF03 chamber. If the flow rate is set to decrease over the years of installation, then a new chamber can extend the life of the unit. Any future iterations of the VFF will use the same size ensuring the LF02 or LF01 will extend the range even further down.

If there are any doubts then please consult the specialists.

Six Degrees of customisation

Litre Meter supply a range of flow meters for Oil & Gas applications. They specialise in customising a range of flowmeters to meet specific customer requirements. A good example of this is flow meters for subsea use i.e. with the ability to work subsea and transmit a flow signal signal to the surface. The image (from 2011) shows another which uses many of the custom attributes of the VFF series of rotary piston positive displacement meter.

A 2011 VFF showing 5 degrees of customisation

There are six degrees of customisation:

  • Connections – in this meter Grayloc hubs were utilised
  • Materials – normally 316 but Duplex S32760 was specified
  • Flow Range – This series included 139 meters all with PVD coating, removable PBCs and special calibration ranges.
  • High Pressure – most were 1035 bar/15,000 psi/15ksi
  • Communication – these had HART 5. The current FlowPod versions offer HART 7
  • Subsea – The only missing degree…
A 2018 VFF Flowmeter showing the compactness of the FlowPod display. Same 5 degrees of customisation: High pressure, special connections, communication, low flow, flow range

PBC

The Pressure Balanced Chamber (PBC) is used to isolate the measuring element from the pressure vessel purpose of the VFF. This allowed optimised materials for the rotor and chamber – to give better flow range, for example, and simultaneously enabled the use of more exotic materials for the pressure vessel. Many more units have been constructed in duplex and super duplex which would have proved almost impossible to use for measurement surfaces (due to the tolerances of manufacture).

PVD

When Litre Meter separated the meter into two functions of measurement and pressure containment the use of coatings could be exploited. After careful selection and testing all of the VFF range are now supplied with PVD coating. This remarkable addition enables both higher and lower flow rates. For example, and it is the best example, the HF66 size was rated to 66 l/min maximum. Typically, without coating, the stainless steel rotor could measure down to 5 l/min on water. With the PVD coating the coefficient of friction is reduced and the minimum reduces to 12 l/hr, yes 12 litres per hour, and the added hardness enables over-range up to 130 l/min – subject to factory approval.

Why should I measure Corrosion Inhibitor (and how)? – our experts explain:

It is essential to measure Corrosion Inhibitor, accurately and continually.  With the correct system, pipeline life can be extended for many years.

Corrosion Inhibitor, sometime abbreviated to CI, is manufactured by various chemical companies to inhibit (to stop or slow) the rate of corrosion inside a pipeline as it carries a flowing product. In the normal Litre Meter context, a company that is heavily involved in Oil & Gas flow measurement, the flowing product is crude oil, straight out of the well.

Depending on the chemistry of the well, a specific inhibitor will be recommended or will be formulated to treat the oil in an optimum manner. As each well is different a large variety of solutions can now be chosen.  For flow measurement, the two main variables are flow rate and viscosity. Usually the fluids are compatible with stainless steel but sometimes higher specification steels or more exotic materials like titanium are required.

If not enough CI is present in the oil then the pipe walls will be corroded and will eventually lose their integrity and then fail. If too much is injected then costs can quickly mount up. Not only is the raw inhibitor expensive but also the tanks will need replenishing more often. Worse still, the refineries will charge dollars per barrel to remove the excess before the crude oil can be processed.

Corrosion Inhibitors prevent corroded pipes

Relying on pump speed, combined with calculation of volume per stroke, is insufficient for full flow assurance. The pump motor can be going but that’s no guarantee the fluid is flowing or that the amount is correct. Full flow measurement is necessary. Optimal meter selection, by experts, ensures good measurement over the full range of flows that the process can experience. It’s not unusual for the flow rate to vary by a factor of a 100 during the life of a well so a wide ranging flowmeter system is a good choice.

The VFF positive displacement flowmeter has been developed over the years to meet all the requirements of chemical injection and more.  They all offer:

  • Excellent materials, for long life, compact and lowest weight.
  • Repeatability – what happens now is the same as a year ahead
  • State of the Art instrumentation – mostly in SS with 4-20 and HART and linearisation.
  • Flexibility, changeable internals for gross range changes, high pressure ratings as standard, etc

Corrosion Inhibitor measurement = VFF

Low Flow Calibration – limits

The accuracy of the flowmeter can be determined by the change in the pulses per litre value over a flow rate range selected from the calibration certificate.  (This source document is also available for download from litremeter.com.)

  • Repeatability is better than ±0.1% of reading over the top 99% of range.
  • Accuracy with linearisation is better than ±0.5% of reading.

The minimum flow rate achievable depends on many variables but can be reduced to two factors:

  • the viscosity of the fluid. The higher the viscosity, the lower the low flow rate ability.
  • the perfection of the meter dimensions and components.
  1. Standard (STD) calibration rates can be achieved 99 times out of a 100. No special selection required
  2. Low Flow (LF) calibration requires matched parts and more calibration time
  3. Ultra Low Flow (ULF) calibration requires the best parts and the most patience by our calibration engineers. It is highly unlikely we can provide a batch of ULF meters due to their scarcity.

In particular, for LF03, LF05 and LF15, we can compare the low flow limits both on a linear scale and, secondly, on a logarithmic scale, as well as in a traditional table. The respective maxima are 18, 30 and 90 litres per hour:

Describes the low flow performance of the LF15
VFF flowmeter LF15 – flow range on various viscosities STD vs. LF vs. ULF
Describes the low flow performance of the LF05
VFF flowmeter LF05 – flow range on various viscosities STD vs. LF vs. ULF
Describes the low flow performance of the LF03
VFF flowmeter LF03 – flow range on various viscosities STD vs. LF vs. ULF

These tables were all updated in August 2019; rounding of some of the flow rate values understated the flowmeters’ abilities.

Additionally, work is underway to improve availability of the LF and ULF calibration bands.  Each rotor and chamber is now pre-calibrated on a nominal viscosity when first received. In actual fact, they are not calibrated as such but the low flow is determined using a custom flow programme on our automatic calibration lab.  This low flow value then enables the chamber and rotor to be categorised into one of the three bands. When an order is received with flow range and viscosity parameters the best chamber and rotor can then be selected with a high confidence level.

A history of subsea flowmetering – Litre Meter experts

Here is a short history of deploying flowmeters, of various technologies, subsea
France, 1985:
The first custom design involved the LM pelton wheel. A compact product was required for installation on a submarine.  The pelton wheel is a radial turbine meter type suitable for low viscosity liquids and, in this incarnation, with a stainless steel body rated to 20 bar internal pressure and capable of 0.1 to 28 l/min. Sign up for FlowSight, the Litre Meter newsletter.
Challenger Oceanic, 1992:
Litre Meter contributed a plastic bodied LM pelton wheel.  The internal and external pressures were identical so the plastic housing was quite strong enough with simple hose connections. The electronics, however, was inside a submersible pod where the pressure was 1 bar. To withstand the pressure differential (300bar, 3000m) the sensor wall, thin for good signal acceptance, was constructed in a titanium alloy, previously purposed for the nose cone of a Harrier Jump Jet. The meter was installed on Alvin and used as part of a sampling system in subsea fumaroles, in places such as the Marianas Trench. Particles were collected and the volume of water measurement helped determine the percentage of solids.
North Sea, 1993:
For a simple solution to the flotation and righting of an offshore vessel two VFF 4 flowmeters were designed with subsea totaliser displays.  The VFF4 was the original VFF flowmeter size capable of measurement, at that time, of 4 l/minute as they were fitted with carbon graphite rotors.  A simple reed switch sensor was used.  With a battery powered LCD display mounted behind a clear acrylic window the diver were able to assess the amount of hydraulic fluid being used and thereby the angle of the platform as it slowly rotated from it’s horizontal transport position.  The challenge was to design a compact subsea display against a tight cost restraint.
Heron and Egret, 1996:
As Litre Meter extended it’s capability with increased design freedom internal pressures increased to 690 bar. The application required a very low flow of chemical to be measured and the smallest meter at the time, the MF15, was selected, again with a carbon graphite rotor.  The next problem was designing for 300 bar external pressure and provide a loop powered 4-20mA output with a customer specified Tronic connector.  Two sensors were utilised with a well designed electronic board that provided redundancy by continuous monitoring each sensor.  Typically, scale inhibitor was measured at 0.5 to 2.5 litres per hour. A stainless steel housing was constructed incorporating the connector and fully O-ring sealed.  The housing was tested by Sira at 300bar.
VFF MF15 for subsea duty with 4-20mA loop powered output
Subsea visual rate display, 2005 onwards
By upgrading an existing turbine design Litre Meter engineers were able to add a submersible battery powered display for use by an ROV mounted camera.  Starting with a standard ‘topsides’ meter a subsea collar was welded on. Then a stainless steel canister was constructed with a heavy duty acrylic window to withstand the pressure at 800m external depth. A large height LCD rate and total instrument was incorporated.  As the turbine used a magnetic sensor requiring no power, a simple battery powered solution was provided to the client. Flow rates were typically 5 to 90 l/min of water but the design has been incorporated in to different size turbines since.
Turbine flow meter for subsea duty with battery powered LCD totaliser
Galley Tieback, 2006:
Hydraulics measurement was needed, in a very specific envelope. The fluid was Castrol Brayco running at a wide ranging 1 to 50 litres per hour. Internal pressure was up to 414bar and the external pressure was 20bar.  A 4-20mA loop powered electronics was integrated within a cylindrical housing and utilised a Tronic connector.
MF30 VFF flowmeter developed for subsea use, mounted
Thunderhorse, 2006
When hydraulic fluid is measured valve position can be interpreted.  When subsea this is considerably more difficult as the measurement has to be compact and resist high pressures inside and out.  With an innovative manifold base little of the VFF MF30 meter remained. The sensor was standard but all other aspects of the design were optimised to use least space, maintain a pressure rating in and out and incorporate a custom electronics interface. Forward and return lines were monitored with pressures at 760bar and 345bar respectively. External pressures could be up to 300bar. Glass to metal seals for the sensor outputs were utilised together with the redundant sensor design used before.
MF30 VFF flowmeter developed for subsea use, with manifold mounting
Subsea valve, 2006 onwards:
The VFF meter in it’s various sizes were becoming more and more popular for chemical injection particularly at high pressures and low flows.  The MF15 was redesigned as the LF15. This enabled a higher accuracy, lower flow ability and crucially a smaller chamber diameter.  This, in turn, allowed a more compact meter design at the same pressure or, usefully, a higher pressure rating for a specific cap diameter.  The design brief was simple: Could we design a 1,035 bar meter for 90 litres per hour and 345 bar external rating in the same envelope as a can of Guinness? – we’re still working on this! What we did end up with is a fairly compact device (100mm diameter and 125mm long) where we  supply just the chamber and cap and the customer integrates these parts into a subsea module.  The unique chamber design allows pressure independent measurement whether at 1 bar or 1,000 bar.
With an expected lifetime of 30 years all efforts were made to increase the ability of the rotor and chamber.  Extensive testing on various bearings and coatings refined the design, retaining it’s simplicity but greatly improving resistance to high flow shocks and significantly improving low flow performance.  A full 2.5 years continuous running at twice the previous maximum flow demonstrated it’s durability. Careful calibration showed that low flow measurement at the start and the end of the 30 months were identical thereby proving that 90 litres per hour was the new maximum with that design and coating.
Hundreds are in service subsea around the world. The meter is used to provide feedback on the flow rate of chemical.  The pulse output (with a redundant sensor) requires no power and the meter has excellent particle size acceptance.
North Sea, 2012
The VFF4, when specified with a PVD coated Nitronic rotor and chamber, can measure up to 8 litres per minute. With a pressure rating of 300 bar (external and internal) a compact 3 wire 4-20mA meter was designed with 1/2″NPT connections. Hydraulics footprinting was then possible subsea. A Seacon Micro Wet-Con 4 pin connector was utilised with dual reed switches for redundancy. Field not known.
VFF4 VFF flowmeter developed for high pressure subsea use on hydraulics
North Sea, 2013
Apart from the Pelton Wheel, turbine and VFF rotary piston flowmeter designs there are other meter types that an provide a significant design benefit to subsea modification.  The ZHM gear meter offers a wide range and high pulse output rate. A SubConn subsea connector was incorporated and a high pressure 690bar design modified for 0.3 to 6 litres per minute.  The application was again chemical injection and 409 bar was the external rating.
ZHM positive displacement gear meter for subsea use
North Sea, 2015 onwards
When a clean sheet of paper is used then a streamlined solution can result.  The subsea turbine flow meter developed for hydraulics measurement from 3 to 33 l/min (HM009) is typical of this approach.  The turbine blades are standard whilst the sensor and Canbus electronics board are encapsulated by welding into the integral stainless steel housing. The customer specified subsea connector provides easy integration electronically. Internally, the meter can withstand 1,035 bar (tested to 1550 bar, 22,500 psi) and externally the specification allows for 300 bar.
HM turbine flowmeter for subsea use in two common configurations

Why should I measure Scale Inhibitor (and how)?

Money, money, money – or, as we now call it, Flow Assurance, coupled with a low flow meter

Allowing scale to build up on the inside of the pipeline may seem fairly inconsequential. However, when the amount of scale is considered, (and referencing the image) it is immediately obvious that the expensive crude will slow down and pumping costs will soar. Sign up for FlowSight, the Litre Meter newsletter.
Scaling reduces the area of a pipe if scale inhibitor is not used
Scaling reduces the area of a pipe if scale inhibitor is not used – Stock image
Chemists will analyse the crude oil as it comes out of the well, sometimes years before production starts. From geotechnical surveys other technicians will determine the rate of oil output through the anticipated life of the field.  With this data the chemist will recommend what the concentration of the scale inhibitor should be.  The pressure of the well will determine at which pressure the inhibitor needs to be injected at. Day to day the temperature will vary according to the seasons, the weather and location of the measurement.
The analysis of the crude, unrefined oil will tell the chemist whether the pipe will start to scale up as a result of pumping the oil through a pipe to the ship or refinery.  Certain chemicals are then formulated to optimise and negate the scale.  There will be compromises between concentration of the fluid, application flow rates and storage availability.  If the concentration can be increased so that the tanks only need filling up once per month then that is preferred to once per fortnight. Inevitably this means that the flow rate is lower, and probably, the viscosity increases. Measurement range will also vary through the life of the field. It may start slow, then plateau a few years later and then tail off as the field winds down.  Additionally to this, the consistency of the unrefined oil will probably change from start to finish.  All of these variables can lead to a range of viscosities and a range of flow rates.
In summary, selection of the meter philosophy and specification is critical to successful measurement of scale inhibitor and future condition of the oil pipeline.

The VFF rotary piston flowmeter has been used for many years to measure scale inhibitor at a variety of flow rates, pressures and viscosities.

VFF flowmeter for chemical injection service, with FlowPod display

Flowmeters for Sodium Hypochlorite – Hazardous Area, too

Sodium hypochlorite

Sodium hypochlorite is a green/yellow liquid with the characteristic smell of chlorine. It was first used as a bleaching agent and was then discovered to be effective in controlling wound infections. Subsequently, it is most commonly known as household bleach. The solution exhibits broad spectrum anti‐microbial activity and is widely used in healthcare facilities in a variety of settings. It is usually diluted in water depending on its intended use.
In the chemical injection arena, it is common to inject sodium hypochlorite into sea water. Sea water can contain dissolved oxygen, bacteria and solids. These can affect an oil reservoirs life. Hypo is used as a bactericide whilst filters take care of the solids. Hypo is aggressive before it is diluted in the sea water and therefore requires some specialized devices in terms of wetted materials.
Litre Meter have been manufacturing flowmeters since 1975.
We’ve always concentrated on the harder margins of metering typically at low flows and/or at high pressure. For this application note Litre Meter illustrate two solutions to this application based on <20 % solution.

Sodium Hypochlorite Flowmeters ‐ Applications and Rates ‐ VFF

The VFF has successfully metered fluids such as oils, hydraulic fluids, corrosion / wax / demulsifier / pour point dispenser /scale / hydrate inhibitors, biocides, oxygen scavengers, etc. for over 30 years. Meter bodies are produced in a variety of high grade materials which offer good chemical and environmental resistance. For sodium hypochlorite, Litre Meter recommend Titanium for the body and chamber with carbon graphite for the actual rotary piston. This ensures maximum compatibility, life and accurate response. The magnet is either encapsulated in titanium or PTFE.
Applications for flow‐rates as low as 0.5 litres per hour have been supplied. Normal minimum flow rates depend on operating viscosity. In this case, viscosity is assumed to be between 1 and 2.5cP. Using the smallest VFF with carbon graphite rotor (LF15) and calibrating on water, which has a lower viscosity than NaOCl, a range of 0.5 to 40 L/hr is achieved.
The meters range in size from the smallest titanium body, LF15 – 40 L/hr, to the largest V270 ‐ 270 L/min max. Higher flow‐rate meters are available to special order. The table on the last page assists in the selection of the best technology.

Sodium Hypochlorite Flowmeters ‐ Applications and Rates ‐ Pelton Wheel

Pelton Wheel Flowmeter for Sodium Hypochlorite

Litre Meter started manufacturing the Pelton Wheel turbine in 1975. These usually had some stainless steel components together with a plastic rotor, elastomer seals and sapphire bearings. All plastic versions soon followed, including all Polypropylene, all PFA, all PVC and all PVDF. The other wetted parts are still sapphire with a suitable elastomer such as FKM or FFKM for the single O ring seal.
The normal specification for Sodium Hypochlorite compatible Pelton Wheel flow meters is now PVC for the main body and cap with PVC or titanium internals, sapphire bearings, an FKM O‐ring and PFA rotor.
The Pelton Wheel is an economical device with low pressure ratings and needs to have relatively steady state non‐pulsing flows.
The table on the last page assists in the selection of the best technology.

Compatible Materials

Due to the nature of Sodium Hypochlorite only a select group of tested materials is recommended by Litre Meter. We tailor our meters using three key materials, developed over 30 years of measuring Sodium Hypochlorite:

These material make up the body and the cap of the meter. The seals between the meter body and cap are normally FKM. Other seal materials include FFKM and PTFE. All Seals within the meter are fully compatible with Sodium Hypochlorite.

Flow ranges and references

All Litre Meter manufactured flowmeters are custom calibrated across the customer specified minimum to maximum flow conditions and working viscosity. The minimum flow rates achievable are dependent on fluid viscosity. With sodium hypochlorite, in most normal concentrations, water is used as the calibration medium as this proves to be the best for accurate calibration representation. The table below assists in selecting which technology is preferred.
Normal engineering materials like 304 and 316 stainless steel, aluminium, brass and steel are unsuitable due to the aggressive nature of the free chlorine in the Sodium Hypochlorite. Plastics such as PVC and PTFE are suitable together with Hastelloy C and purer grades of Titanium.

Comparison Table:

Table showing selection criteria for Sodium Hypochlorite meters in two different flow technologies.

Litre Meter can provide optimum solutions for a wide range of flow rates of Sodium Hypochlorite. Using a variety of materials, a flowmeter can be constructed that handles any specific concentration of NaOCl and provide a display and/or output for measurement and control. For references etc please download our brochure.

What’s the best chemical injection flow meter? An expert explains:

Litre Meter VFF rotary piston positive displacement flowmeters have proven to be the foremost solution for chemical injection flow metering applications. They are able to handle the wide range of flows at pressures from a few bar up to 10,000 and 20,000 psi (690, 1,380 bar) and higher. The FlowPod instrument has been developed after feedback from many clients in the chemical injection arena, focussing on ease-of-use, compactness and functionality. Sign up for FlowSight, the Litre Meter newsletter.

In many chemical injection applications the VFF is the sole answer because of it’s unique capabilities at the ‘margins of measurement’. This might include super low flow rates and low viscosity or awkward chemical compatibility and material requirements. The standard range of VFF meters, available from 2015, was also designed in response to user feedback. It provides a number of bespoke chemical injection features that are no longer specials.  Since then, 80% of meters supplied have been from stock designs as opposed to 20% before.  This also means that drawings are immediately available including STEP files, lifting diagrams and parts lists.

Since 2013, as standard, all VFF meters have a URL given on the name plate and a QR code that links to a website with specific calibration certificates, manuals, hydrostatic test certificates and material certificates.

  • VFF positive displacement meters can measure accurately at any pressure and with a pulsing pump.  The measurement accuracy is unaffected by working pressure or change due to the unique construction.
  • VFF positive displacement meters can measure a range of chemicals at extreme low flows such as less than 100 ml per hour and at low or high viscosity.  Particle size limits are a generous 40 or 100 microns.
  • VFF positive displacement meters can measure a variety of chemicals requiring alternatives to 316L.  Titanium rotors are standard with titanium, super duplex and Hastelloy options for body and cap.
  • VFF positive displacement meters can be constructed using exotic materials and/or exotic material specifications. Litre Meter have developed their own material specification for 316L, duplex and super duplex. We have built meters from highly specified materials with extensive testing regimes to tight delivery times.

Call us now with your chemical injection metering requirements for probably the best flowmeter.  (it’s why LITRE METER RECEIVES A QUEEN’S AWARD FOR ENTERPRISE)

VFF Flowmeter Sizes and Connections.

20k meters – brochure available

Litre Meter have been making meters for higher pressures for over 3 decades. Our first 1,380bar unit was shipped in 1997.  We’ve now produced a brochure to cover these ratings.

Download the 20k VFF datasheet
20,000 psi rated VFF flowmeters – brochure

Litre Meter have been manufacturing flowmeters since 1975. We’ve always concentrated on the harder margins of metering typically at low flows and/or at high pressure. The VFF range has many uses in the oil and gas industry and meets the high specifications required. Outside of oil and gas we have manufactured these to 2,500 bar. We have recently noticed a trend towards 20,000 psi ratings and this brochure is in response to that.

Since 1997 Litre Meter has made numerous VFF meters for 1,380 bar in Oil and Gas applications and a reference list is provided at the end of this article.
The same design can be used on 22.5ksi (1,550 bar) with little modification.
The breakthrough in our design philosophy came in 2005 when we separated the measurement of the fluid from the pressure containment. We designed a measurement chamber that floats in the pressure vessel. This ensures accurate, pressure independent flow metering from 10 psi to 20,000 psi. The Pressure Balance Chamber is explained below.

Key Features

  • Rotary Piston/ Oscillating Piston type flow meter with a single moving part provides robust and low maintenance technology.
  • Suitable for low & high viscosity liquids at pressure ratings up to 4,000 bar (60,000 psi). 20,000 psi designs as standard.
  • Available materials of construction: 316L (UNS S31603), Duplex F51(UNS S31803), Super Duplex F53(UNS S32750)/F55(UNS S32760), 6Mo F44(UNS S31254), Hastelloy (UNS N10276) & Titanium (UNS R56400).
  • Connections: Autoclave, Grayloc Hubs, Galperti Hubs, Techlok hubs. More on request.
  • Communications: 4‐20mA HART, Pulse, MODBUS, Foundation Fieldbus, dependent on electronics and certification requirements.
  • Compact
  • Very Low Flow Measurement
  • Tolerant of particulate up to 100+ microns
  • Low pressure drop (<0.1 bar typical)

20K Flowmeters ‐ Applications and Rates

The VFF has successfully metered fluids such as oils, hydraulic fluids, corrosion / wax / asphaltene / demulsifier / pour point depressant (PPDs) /scale / hydrate inhibitors, biocides, oxygen scavengers, etc. for over 30 years. Meter bodies are produced in a variety of high grade materials which offer good chemical and environmental resistance.
Applications for flow‐rates as low 0.00013 litres/min (0.19 litres/day) have been metered within the offshore oil industry. The VFF flow meter provides exceptional rangeability with potential turndowns of up to 3000:1, dependent on operating viscosity.
The meters range in size from the smallest standard stock size, LF03 ‐ 18 L/Hr max, to the largest V270 ‐ 270 L/min max. Higher flow‐rate meters are available to special order.
An extensive range of meter designs and materials offers pressure ratings to 20,000 psi (1,380 bar). Higher pressure rating designs are manufactured up to 4,000 bar (60,000 psi). 20,000 psi designs available, as standard, up to HF60 and special designs can measure higher flow rates.

20K Flowmeters ‐ Meter Sizes

The VFF meter is not just one size, one specification. It’s a comprehensive range of carefully engineered devices to meet today’s standards in the most demanding oil & gas arenas. It’s truly a Versatile Fluids Flowmeter.

In the illustration below the smallest meter is typically housing an LF05 or LF15 rotor and chamber with FlowPod instrument and Autoclave Engineers MP connections.

The middle unit is a medium size meter, say, VFF4 with hub connections and FlowPod display.

The right‐hand meter also has hubbed connection sizes, FlowPod display but is larger to accommodates the HF60 rotor and chamber.

VFF Flowmeter Sizes and Connections.
VFF Flowmeter Sizes and Connections.

Pressure Balance Chamber

What Is a Pressure Balance 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 700 bar the cap moves by just 0.02mm in the centre. Increasing the bulk of the cap still produces this movement. The effect on meter performance was the creation of a leak path for fluid that avoided the positive displacement of the rotor. This was equivalent to about a 3% inaccuracy at 700 bar. As a result, of this Litre Meter designed a pressure balance chamber for its VFF flowmeters so it could operate at extreme pressure and at low flow rates. The pressure balance chamber acts as a barrier, protecting the internal measurement components of the instrument from the high pressure conditions, preventing them from expanding and contracting under the immense pressure. NO DISTORTION MEANS ACCURATE MEASUREMENT AT ANY PRESSURE. All VFFs over 414 bar are fitted with this technology. It is identified by the letters PBC in the calibration certificate.
Key Benefits:

  • No distortion of the chamber at higher pressures.
  • Enables selection of optimal materials for the chamber to match the rotor i.e. PVD coated stainless steel or titanium.
  • Enables selection of optimal materials for the pressure vessel.
  • Enables construction of a duplex bodied flowmeter.
  • Swappable PBC for simplified sparing.

Flow ranges and references

All VFF flowmeters are custom calibrated across the customer specified min – max flow conditions and working viscosity. The minimum flow rates achievable are dependent on fluid viscosity. To see the achievable calibration ranges for each meter size please consult the table below. We can offer meters that range from 0.005 L/hr to 3,600 L/hr at 20K pressures to best suit your applications and with exceptional turndowns.

20K flow ranges

Areas of key significance:

  • Extended experience in measuring 20,000 psi in Oil & Gas applications.
  • World leaders in low flow and high pressure measurement.
  • High or low viscosity fluids flow measurement.
  • The Chemical Injection Specialists.
20,000 psi reference list
20,000 psi reference list VFF meters

Future developments

Litre Meter have already provided meters for 2,500bar. Offshore models at 22.5k & 25k are designed and 30k, 40k and 50k will be produced.
Litre Meter continues to innovate in the field of flow measurement. Recent successes include the LF05 and LF03 size meters, a new sensor, the FlowPod instrument and the FlowLabPro calibrator series. In the near term, expect to see lower flow capabilities, more calibrators and a low flow meter for any liquid type.

Offshore Corrosion Inhibitor Measurement at 20,000psi

APPLICATION: Various chemicals are injected into a deep water well to prevent corrosion, paraffins, hydrates, and scale. The flow rates for the injection are generally very low and need to be metered precisely to prevent under or over-dosing a well.

PRODUCTS SUPPLIED: • VFF series LF03, LF05, and LF15 • HM turbines HM-007 and HM-009/TC-AC/S-EX

CHALLENGE: As oil exploration goes into deeper and deeper water and deeper reservoirs, new challenges arise that put current technology to the test. The newest development is reservoirs that are reaching pressures of up to 20,000 psi. The chemicals need to be injected at a pressure that will overcome the force of the oil flowing up the umbilical.

SOLUTION: By utilizing different technologies available through the TASI Flow portfolio, we were able to offer a solution for this unique chemical injection challenge.
Positive displacement meters from Litre Meter were used for their ability to measure ultra-low flows and their flexible materials of construction that allows for high tensile strength steels exceeding the 20,000 psi pressure requirement. For the higher flow methanol and LDHI applications, the high pressure HM turbine line from AW was used for their ability to measure very non-lubricating fluids while also achieving the desired pressures.
The hazardous area location of these meters also require that all electrical components be hazardous area certified. Because of the close cooperation in development between AW and Litre Meter, as well as all other TASI Flow brands, we were able to offer a single type of user interface for all the meters. Using Litre Meter’s FlowPod transmitter in conjunction with the AW HUB-40EX pickup added a uniformity to the installation of all the meters on the chemical skid.

Corrosion Inhibitor measured at 20,000 psi 1380bar
Corrosion Inhibitor measured at 20,000 psi 1380bar

RESULTS: This is simply one of the first projects heading to locations with reservoirs up to 20,000 psi. In the near future equipment manufacturers in this segment of the market are going to need to produce technology that can keep up with industry needs. TASI Flow’s continuing innovations and ability to customize will allow them to keep pace with the constant change in the O&G production environment. Sign up for FlowSight, the Litre Meter newsletter.

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