Archive | Flowmeter information

What’s in a typical flow meter datasheet?

First, let’s have a look at what might land on your desk.  Later, we’ll review it line by line.

A typical datasheet relating to a flowmeter is given as below – this one is based on a NORSOK format:

Flowmeter datasheet – Norsok layout.

This one is for the same meter but based on an ISA format (a version used by Litre Meter which uses S20.25 as it’s base):

Flowmeter datasheet – ISA layout, describing the same flowmeter.


This is an approximate layout, typified by NORSOK.

1 General

1.01 Type – a description of the flowmeter, by trade name and basic principle

1.02 Manufacturer – manufacturer’s name.

1.03 Design Temperature Limits – maximum and minimum design temperatures in suitable temperature units (°C)

1.04 Design Pressure Limits – maximum and minimum design pressures in suitable pressure units (bar gauge)

1.05 Estimated Pressure Loss – pressure drop at a specific flow such as maximum in suitable units (millibar)

1.07 Face to face dimension – complete assembly length in millimetres, with a tolerance

1.08 Mounting – type of mounting, in this case, In-Line but could be insertion, clamp-on etc.

1.09 Weight – dry, without fluids – in kilogrammes

2 Instrument Characteristics

2.01 Calibrated Range – flow rate range that the unit will be calibrated over – and units

2.02 Characteristic – an appreciation that not all meters are necessarily linear – some are non-linear such as orifice plates where the pressure drop is related to the flow rate by a square law, in this case linear – and linearised.

2.03 Meter factor – an estimated value of the number of pulses per litre – or other volume or mass unit

2.04 Accuracy – with percentage bounds and either proportional to the actual reading or FSD (Full Scale Deflection)

2.05 Linearity – with percentage bounds and either proportional to the actual reading or FSD (Full Scale Deflection)

2.06 Repeatability – with percentage bounds and proportional to the actual reading

2.07 Max Range limit – not necessarily the same as the maximum calibrated flow – describes the capabilities of the flowmeter

3 Meter Body

3.01 Nominal Size – normally relating the meter body size to the pipe size

3.02 Manufacturer model number – to precisely define the scope of supply

3.03 Process connection size and type – Size and flange or thread type, for example

3.04 Pressure rating – the rating of the flowmeter body in comparable units to 1.04

3.05 Face to face dimension – will match 1.07 in most cases

3.06 Body inner diameter – where appropriate

3.07 Sour service specification – nominated when appropriate – ISO or NACE in this example

3.08 Material, body – A specification for the material of the flowmeter body i.e. the main part of the meter

3.09 Material, Raised –

3.10 Protective coating/color

3.11 Other


4.01 Type – such as rotor and chamber or another description of the flowmeter internals and principle

4.02 Material, shaft – if any

4.03 Material, support – if any – this might refer to a turbine flowmeter part

4.04 Material, rotor

4.05 Material, bearing – if any, may include material and type

4.06 Material, Seal – not just the materials but may include seal type

4.07 Material, pick-up – i.e. sensor material, wetted, or not

4.08 No of pick-ups

4.09 Other


5.01 Type

5.02 Material

5.03 Connection

5.04 Other


6.01 Material

6.02 Connection up/downstr.

6.03 Up/downstream length

6.04 Tube inner diameter

6.05 Other


7.01 Type

7.02 Body/mesh material

7.03 Connection

7.04 Other

8              TRANSMITTER

8.01        Manufacturer model no

8.02        Mounting

8.03        Max distance meter/trans

8.04        Cable connection

8.05        Cable entry

8.06        Dimension

8.07        Material

8.08        Enclosure protection

8.09        Ex. classification

8.10        Protective coating

8.11        Indicator

8.12        Tamb

8.13        Totalizer

8.14        Output signal (note 9.02)

8.15        Communication

8.16        Recommended loop voltage

8.17        Transmitter loop voltage drop

8.18        Max loop current (fault condition)

8.19        Other – in this case describes more of the hazardous area ratings and standards – CSA, IECEx and ATEX

Measuring Sodium Hypochlorite in Hazardous Areas

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.Sign up for FlowSight, the Litre Meter newsletter.
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. Download brochure.

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.

VFF Flowmeter Sizes and Connections.

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 at the end of this article assists in the selection of the best technology.

Sodium Hypochlorite Flowmeters ‐ Applications and Rates ‐ Pelton Wheel

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.

Pelton Wheel Flowmeter for Sodium Hypochlorite

The Pelton Wheel is an economical device with low pressure ratings and needs to have relatively steady state non‐pulsing flows.
The table at the end of this article 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:

PVC, Hastelloy and titanium
The PVC design can be used up to 15 bar pressure maximum. Hastelloy (UNS N10276) up to 1035 bar. For the ultimate select titanium (UNS R50400) designed for 1380 bar (20,000psi, 20 ksi)

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.

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.
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

What’s the best chemical injection flow meter?

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.

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.

Electronic documentation – leading the way

Litre Meter now provides all documentation electronically for it’s manufactured flowmeters.  That’s not just a manual emailed to the client, either.  Each meter has a product label and includes a QR code and URL. At the website location there’s a minimum of a calibration certificate, quick start instructions and a full Installation and Operation Manual (IOM). Most will also have material certificates, hydrostatic test certificates, wiring diagrams and a function test cert.

The product label is comprehensive, providing all calibration data.  The URL provides everything else the installation engineer might need. Using a smart phone and scanning the QR code is even more convenient.

Charles Wemyss, CEO of Litre Meter, says:”If a client needs any information emailed we just send the link. For larger projects with a number of flowmeters and larger documentation packages we include a single zip file for ease of downloading.  We’ve been providing this as part of our service since 2013 and our customers love it! This is a project dear to our hearts that cuts waste right down and provides our clients with a very quick and easy access point.  As far as we know, there is no other instrumentation company providing this level of data direct to their clients.”.

LM QR code

Litre Meter QR code allows remote access to documentation

KEM Küppers Subsea flowmeter solutions

Litre Meter are now the exclusive distributors for KEM Küppers. In addition to their standard ranges of positive displacement and turbine flowmeters KEM offer a customisation service that encompasses the necessary modifications and approvals for subsea service. Both the ZHM gear meter and HM turbine meter have versions that are designed to rigorous subsea specifications. The subsea versions have encapsulated electronics, a welded stainless steel cover and an FEA designed housing that remains stable at high external pressures. All of these are manufactured by Litre Meter’s sister company KEM Küppers in Germany.

Two Subsea Applications:

Production – Blow Out Preventers (BOPs) are large subsea control valves used to prevent uncontrolled release of pressure or flow of fluid during well drilling operations or production. The hydraulic valve can be remotely controlled to close or open to avoid a “blow out”, and are typically installed multiple times in stacks as a precaution. Maintenance of BOPs and regularly testing is a very high priority for both the oil company and drilling rigs. Subsea turbine flow meters are used on the hydraulic fluid to monitor the valves to ensure that they are functioning correctly when needed.

ZHM: Positive displacement gear meter with wide flow range. Image shows subsea cover and connector.

Subsea chemical injection – As oil is pumped from the subsea well, many chemicals and additives are injected to ensure maximum productivity. In many cases, oil companies install subsea flow meters to measure these chemicals at the point of entry, which is often far below the surface, instead of topside where the liquid has to travel a great distance before entering the flow stream. Often this is more cost effective. Subsea Positive Displacement (PD) flow meters are used to inject additives such as mono ethylene glycol (MEG), methanol, and low-dose inhibitors (LDIs).

HM: Axial turbine flowmeter, redesigned for subsea duty, with subsea electrical connectors.

Call Litre Meter now for further information. 01296 670200.

What is linearisation – what is it and why do I need it?

Linearisation is a process that enhances the accuracy of any repeatable flowmeter. Sign up for FlowSight, the Litre Meter newsletter.

This article will show the amount of accuracy increase that can be expected from optimising linearisation points in terms of number and position.

A standard calibration of a VFF flowmeter will involve 10 calibration points. These are always spread out along the customer’s operating flow range. They will be distributed in favour of lower flow rates – where changes in raw meter accuracy are higher.

Below is an example of a flowmeter calibration curve. The results of a calibration are a table of flow rates and the corresponding pulses per litre.  In an ideal world, there would be a hundred or a thousand such points so that the complete curve could be plotted and for any given flow rate the pulses per litre would be known. In practice, there are usually 10 to 20, distributed as shown.

A plot of flow rate against frequency would be an apparently straight line relationship.  The angle of the straight line would be the ‘meter factor’ or the average number of pulses per litre.

Flowmeter linearisation. Flow rate versus frequency.

Flowmeter linearisation. Flow rate versus frequency.

To make this more visual, it’s common to plot the flow rate against the ‘pulses per litre’. This emphasises the changes as the flow rate increases.

Flowmeter meter factor or 'k' factor plotted against flow rate.

Flowmeter meter factor or ‘k’ factor plotted against flow rate.

Better still is a plot of flow rate against accuracy using the ‘meter factor’ as a zero.  The biggest positive excursion defines the positive error and the biggest negative excursion is the negative error.

Flowmeter linearity expressed as percentage error versus flow rate

Flowmeter linearity expressed as percentage error versus flow rate.

If the flowmeter is repeatable then we can use a technique called linearization.  In other words, if the curve (i.e. the relationship between flow rate and pulses per litre) is the same the next time around, then the flow rate can be calculated from the frequency output using the specific pulses per litre value rather than an average pulses per litre value.  If the flow rate is identical to one of the original calibration points there is no adjustment. At other flow rates a calculation is required.  In between the points most linearization systems use simple linear interpolation. For example, if the flow rate is halfway between two original calibration points then an average of the pulses per litre for those two points is used.

The error is represented here by the length of the red arrow.

Linearisation is normally linear interpolation between two points. The difference between the brown linear interpolation and the blue real value is the subsequent error.

Linearisation is normally linear interpolation between two points. The difference between the (brown) linear interpolation and the (blue) real value is the subsequent error.

Now the measurement error is no longer compared to a single meter factor from min to max but a linearity curve built into the meter.

By carefully selecting the calibration flow rates along the range the remaining error can be minimised.  In the example below, the actual curve (in blue) is shown plus the linear approximation (in brown).

The meter character and the linear interpolation between linearisation points for the whole range of the meter

The meter character and the linear interpolation between linearisation points for the whole range of the meter.

Magnified in scale:Here is how this linearization improves the accuracy, on the same scale:

Results of the linearisation.

Results of the linearisation.

Magnified in scale:

The result of linearisation. Now between +0.19% and -0.28%.

The result of linearisation. Now between +0.19% and -0.28%.

And here is the result, if there are 4 calibration points at the lowest flow rates rather than 2.

Concentrating the calibration and linearisation points at low flows, in this example, has a further impressive improvement to overall linearity.

Concentrating the calibration and linearisation points at low flows, in this example, has a further impressive improvement to overall linearity.

As a result of linearization, the overall error has been reduced from max error: 1.19%, min error: -3.98% to max error: +0.19%, min error: -0.28% representing an 11x improvement.  Selecting the calibration points carefully improves this further.  Every calibration point has a cost so there are diminishing returns. If the repeatability is +/- 0.25% then 10 points overall are normally enough.

If enough calibration time is available and the repeatability of the system is considerable then more points can be selected for the linearisation table.  In this extension of the example above 21 points are used rather than just 10.  Arranged carefully throughout the flow range, the net effect is to reduce the max/min to 0.08%, a 64x improvement over the non-linearised version.  If the repeatability of the system was ±0.1% then no more points are required.The flowmeter response (blue) is almost perfectly matched by 21 carefully selected calibration points (brown).

The flowmeter response (blue) is almost perfectly matched by 21 carefully selected calibration points (brown).

The flowmeter response (blue) is almost perfectly matched by 21 carefully selected calibration points (brown).

The final analysis. Total non-linearity reduced from 5.17% to 0.08%.

The final analysis. Total non-linearity reduced from 5.17% to 0.08%.

This article shows that linearisation with a flowmeter instrument can significantly improve the linearity of the flowmeter system.  In this example, if the meter is repeatable, then 6 to 60 times improvements are possible.

Next article: Is there good and bad linearisation?

Sign up for FlowSight, the Litre Meter newsletter.

VFF FilterPro filter protects VFF meters from contamination

Litre Meter introduces the VFF FilterPro Filter that maximizes the efficiency of its flow meters by eliminating contaminants that cause reduced flow, damage to internal construction as well as a blockage.  As 96% of flow meter failures are associated with contamination issues, the FilterPro protects flow measurement instrumentation, assuring optimal flow in liquid injection, batch processing, and lubrication systems. Sign up for FlowSight, the Litre Meter newsletter.

Featuring a four-layer wire woven mesh filtration design, the FilterPro uses a proven surface filtration principle that filters elements from 10 to 100 microns (depending upon unit option) by trapping particulates between its layers.  Available in three key filter sizes, the FilterPro pairs perfectly with the company’s positive displacement, rotary piston, and turbine flow meters with connection sizes from ¼” up to 9/16” in multiple thread types.   Offered in 316 stainless steel or exotic materials, the FilterPro is available in the same materials as VFF flow measurement instrumentation to avoid compatibility and performance variances.

Units are suitable for use in low and high viscosity liquids at pressures up to 20,000 psi (1,380 bar) and can withstand a pressure drop of 870 psi (60 bar) with a burst pressure drop of 2,175 psi (150 bar).  Simple to install, the FilterPro is easily cleaned by unscrewing 8 bolts and replacing the filter insert.  The company is currently developing larger filters to accommodate larger meters while incorporating a filter maintenance indicator and greater resistance to burst pressure. Sign up for FlowSight, the Litre Meter newsletter.

VFF FilterPro pressure drops for viscosity and flow rate values - 30 micron

VFF FilterPro pressure drops for viscosity and flow rate values – 30 micron

Exploded view of VFF FilterPro with annotation

Exploded view of VFF FilterPro showing simplicity of design and disassembly

VFF FilterPro with filter cartridges

VFF FilterPro with filter cartridges, available in 10, 30 and 100 micron sizes

VFF FilterPro Dimensions - threaded body

VFF FilterPro Dimensions – threaded body – NPT or Autoclave Medium Pressure. Other connections on request.

VFF FilterPro typical materials and pressure ratings

VFF FilterPro typical materials and pressure ratings


VFF FilterPro typical connections and pressure ratings

VFF FilterPro typical connections and pressure ratings

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.

Fuel and fuel additive test system uses Tricor for final testing of Formula 1 gasoline pumps

APPLICATION: Fuel and fuel additives test system for final testing of gasoline pumps at Parker Hannifin Manufacturing Germany GmbH & Co. KG in Mainz-Kastel. The pumps are used by Formula 1 racing teams. Every single gasoline pump is tested and qualified on the test system under completely different operating parameters before they are delivered to the racing customers.

CHALLENGE: A test system of high technical complexity was being designed and modelled for unlimited final testing of gasoline pumps for Formula 1 racing customers. To meet the very high demands for quality, the test must cover the entire performance spectrum and provide the optimum testing conditions for the final test. In the area of flow measurement, the task was to specify a highly accurate sensor for the most varied operating parameters. The flow conditions comprised a large spread in temperature and process pressure. This resulted in a change in the viscosity of the fuel. In the first design, turbine flow meters and TRICOR Coriolis mass flow meters were considered. The solution with turbine flow meters required a cascading of several devices to cover the required flow measurement range. Furthermore, different calibration curves needed to be used in order to meet the accuracy requirements.

TCM 0650-FA-HGSS-CSDS Tricor Coriolis for fuel measurement

TCM 0650-FA-HGSS-CSDS Tricor Coriolis for fuel measurement

SOLUTION: TRICOR Coriolis mass flow meters, by contrast, provide multiple technical advantages for this test bed. Flow meters using the Coriolis principle are significantly more accurate, faster and are almost completely independent from the medium properties like viscosity, temperature and pressure – in contrast to some other flow meters. The TCM 0650 covers the entire testing measurement range. With the TRICOR Coriolis solution, Parker Hannifin can cover the required temperature and process pressure range on the fuel test bed with one device. There are no restrictions in regards to fluid, viscosity or accuracy of measurement. Additional components for a cascading measurement (such as needed with the turbine flow meter option) and the associated added expense are eliminated.

CUSTOMER ADVANTAGE: All requirements are met by the broad measurement range of a single TCM 0650. It reduces not only the purchasing costs but also the costs for having replacement devices. Using analogue output signals and modbus TRU interfaces, mass flow, volume flow, temperature and medium density can be read out at the same time on the local display – remote optional. The TCM 0650 is the optimal solution for Parker Hannifin in order to master this challenging measuring task.

Exclusive distributors of KEM Kuppers flowmeters

Litre Meter are now the exclusive UK distributors of the KEM Küppers range of flowmeters.  These include the ZHM, SRZ positive displacement, HM turbine and the Tricor coriolis series. Sign up for FlowSight, the Litre Meter newsletter.

KEM ZHM01/3 gear meter

KEM ZHM01/3 gear meter

ZHM: Positive displacement gear meter with wide range and in a variety of materials including aluminium and 316 stainless steel.

HM series turbine meters

HM series turbine meters

HM: Axial turbine flowmeter, also in range of materials, from 0.03 to 25,000 litres per minute and up to 350°C.

SRZ helical screw positive displacement flowmeter

SRZ helical screw positive displacement flowmeter

SRZ: Helical screw positive displacement flowmeter combining exceptional accuracy and viscosity rangeability.  Flows from 0.01 to 400 litres per minute. Low pressure drop.

Tricor coriolis mass flowmeters

Tricor coriolis mass flowmeters

Tricor: Coriolis mass flow meter for gases and liquids. Smallest size available in very high pressure rating (1550bar). Range measures from 3 to 230,000 kg per hour, and higher.

All of these units are manufactured in Germany by Litre Meter’s sister company, KEM Kueppers GmbH. Sign up for FlowSight, the Litre Meter newsletter.



Chemical Manufacturing – Chlorine Gas – Coriolis application

APPLICATION: A bayonet-style heat exchanger is used by this customer to heat and vaporise dry liquid Chlorine, to supply multiple reactors at various flow rates with Chlorine gas, at 54°C (130°F) and 180 psig. Pure liquid Chlorine is fed to the vaporizer from a pressurized railcar. The heat source was low pressure steam. The existing system did not control the liquid level in the vaporizer nor the flow of the liquid Cl2, and the vapourizer’s liquid level was limited by equilibrium.

TRICOR PRODUCT SUPPLIED: TCM-28K Hastelloy Coriolis Mass Flow Meter with Integral Transmitter

Using Tricor Coriolis meter for the transfer of chlorine. Hastelloy selected.

Using Tricor Coriolis meter for the transfer of chlorine. Hastelloy selected.

CHALLENGE: Chlorine has a high coefficient of thermal expansion. Process upsets or momentary shutdowns sometimes resulted in excessive liquid levels, which rapidly led to undesired pressure excursions. There were also cases of low liquid levels, which led to super-heating of the gas. This problem was compounded by the over-sized tube bundle in the vaporiser.

SOLUTION: Since a very small amount of liquid CL2 can lead to serious swings in level, and therefore over-pressure excursions, a highly accurate and repeatable flow meter was required. The customer chose the TRICOR TCM-28K Hastelloy C-22 flow meter. The C-22 alloy features excellent corrosion resistance to Chlorine, and has proven to be superior to C276 for these applications.

RESULT: The new system uses re-circulating hot water as a heat source, rather than steam, and the CL2 liquid level is now controlled via a cascade master and a mass flow control loop.

Tricor coriolis meter selected in Hastelloy for Chlorine measurement

Tricor coriolis meter selected in Hastelloy for Chlorine measurement









see the full brochure:


Tricor Coriolis – available from Litre Meter

Petrochemical Processing – Oil Additive Blending – Tricor Coriolis

APPLICATION DESCRIPTION: This lubricant manufacturer now uses two TRICOR Coriolis meters: one measures the individual petrochemical products as they are offloaded into their tank farm, and the second is for batch control as they create products using components from various tanks. The Coriolis meter for batching is used with a Precision Digital Batch Controller and a pneumatic control valve for precise batching.

TRICOR PRODUCT SUPPLIED: TCM-65K Coriolis Mass Flow Meter with Integral Transmitter

CHALLENGE: This customer used multiple hydrocarbon components to create their products, and some components are measured using a manual weight scale. The display was hard to read and the weight scale was unreliable. Additionally, hydrocarbon components were not being measured upon delivery by the customer.


The Tricor Coriolis installed on the hydrocarbon line

SOLUTION: One 2-inch Coriolis flow meter was placed in the receiving pipeline for measurement of the individual components as they are off-loaded from delivery trucks to the individual storage tanks which provided accurate measurement and billing. Also, by using the batch controller, control valve and Coriolis meter for the batching process, the customer can now dial in the desired amount of individual components and then walk away. These flow meters were also integrated into a local display, a Precision Digital Consolidator which displays values of tank levels and flow rate.

Tricor Coriolis used for blending

Tricor Coriolis used for blending

RESULT: The new batching system is set to control the flow rate, totalize the flow, and shut off the flow when the setpoint is reached. The customer is pleased with the accuracy achieved.

Available from Litre Meter.

Dimethylformamide (DMF) measurement with Tricor


DMF (Dimethylformamide, N,N-Dimethylmethanamide, (CH3)2NC(O)H) is a clear liquid organic solvent used in a number of industrial processes, particularly in the manufacture of polyurethane products, pesticides, electrical equipment, pharmaceuticals, and synthetic leathers and fibres. The Tricor coriolis meter proved itself on this technically challenging application using standard equipment.


Tricor coriolis mass flowmeters used in the flow measurement of DMF

Tricor coriolis mass flowmeters used in the flow measurement of DMF


Medium: DMF

Pressure: >4 bar

Density: 995 kg/m3

Viscosity: 2 cSt

Flow range: up to 20,000 kg/h / 50,000 kg/h for loading and unloading

Flow range: up to 12,000 kg/h / 25,000 kg/h for product supply for a PU coating agent into the reactor.



TCM 028K Coriolis Mass Flow Meters (28,000 kg/hr max)

TCM 065K Coriolis Mass Flow Meters (65,000 kg/hr max)

TRICOR_Chemical_Manufact._DMF_EN_spotlight_160705_E002 Brochure


Tricor coriolis mass flowmeters used in the flow measurement of DMF

Expert advice on flowmeters and calibration

Charles Wemyss lists 10 reasons why you should – and should not – calibrate your flowmeter

We use the word flowmeter to describe a device that measures the flow of a fluid. Mostly we’re considering gases or liquids in a closed pipe or conduit and we need either the instantaneous flow rate or the total amount of fluid that has passed. There are many varieties of techniques dependent on the fluid being measured and dependent on the flow rate, pressure, viscosity and more. The flowmeters range from miniature positive displacement devices to large electromagnetic or ultrasonic units used for pipes over 3m diameter. The way we garner confidence in the displayed value is through calibration.

Most flowmeters are supplied by the manufacturer with a ‘laboratory’ calibration. In other words, they have been tested in close to ideal conditions. Depending on the meter type, once installed in your process, that original calibration may be valid – or it may not be.

Litre Meter’s latest rig FlowLabPro is designed for calibrating ultra-low flowmeters

There are a number of key reasons why it should be calibrated:

* To reflect the new, current conditions

* Because some component has a wear factor

* There is an accumulation of dirt or setting product, affecting the sensor

* Because the calibration frequency states it has to be

* Because the results don’t feel right compared to the rest of the process

* The process is producing poor quality product yet the flowmeter seems stable.

The best calibration is that which is performed in situ. Many of the variables are tuned out. The fluid is the same, as is the installation attitude, straight lengths, etc. That’s the precise reason why you should re-calibrate; it gives you that confidence in the device. If in situ is not possible, for example, when the fluid is hazardous or at high pressure then it has to be uninstalled and calibrated elsewhere.

Why shouldn’t it be calibrated?

Clean versus dirty is the first argument for not calibrating your flowmeter. If it comes out of the line dirty and is sent away for calibration then you’d normally expect to ship it clean. The test lab calibrates it in the clean state. However, as soon as you re-install it the process might be depositing dirt back on it. It has been calibrated for a perfect installation and is almost immediately imperfect.  In this scenario, calibration is pointless.

Next, it’s hard to compare installation to installation. All calibration laboratories pride themselves on making adequate provisions for calibration, especially good installation practice. If they’re testing a turbine meter, for example, then they should have a long length of correctly sized piping before the meter – and a length after, too. This eliminates swirl, if it’s long enough, to generate a flat flow profile and present optimum conditions to the meter. Most labs have this setup for horizontal installation – so if you have a vertical install, then watch out. Likewise, if you don’t have a long length of correctly sized pipe, or perhaps a connector that necks the diameter down a few percent, then don’t bother. The results they give you will be meaningless.

The Litre Meter low flow rig FlowLabPro delivers automatic calibration of flowmeters and instrumentation within a flow range of 0.0006 to 200 l/hr to an accuracy of ±0.2%

Next you should ask whether it is the right fluid. Unless your process is running clean water or, maybe a calibration fluid, then your average lab will not be able to calibrate with the same fluid. For some flowmeter types this may not be important. For example, if you fluid is a weak acid with a viscosity of 1.2cP and the meter is an electromag, then the calibration with water will be perfectly valid. Contrarily, if you have 10cP process fluid and it’s a turbine meter then it could be very important that the test fluid is in the 9 to 11cP range to adequately represent the effect of viscosity on meter performance at lower flows.

Traceability is next on the list. If you have been able to clear the hurdles above then it’s important you pick a lab that has the right traceability for you. If your process demands an indication of flow within +/- 4% then there’s little point on getting a UKAS-accredited laboratory with an uncertainty level of 0.22%.

We’re regularly asked ‘how often should it be calibrated?’ Recalibration periods of flowmeters are based on industry standards. In industrial applications, depending on the industry, periods of six to 12 months are recommended. We advise the user to seek out data relating to the process, other components within the process and the usage of the meter. If the measurement is critical then the recalibration should be more frequent than a non-critical, rarely used device. In the absence of any other data we advise an annual check and to vary the future calibration periods depending on results.

If it has remained unused then no recalibration may be necessary, depending on the meter type. It is wise to check that no fluid has settled in the meter that might alter the way the meter works or even cause corrosion. In the event of any doubt then the manufacturer is always your best source of advice.

{originally published in International Process Engineer in May 2016,}

What is a flow meter and how does it work?

Flow gauge, flow indicator, liquid meter, flow meter – they’re all the same thing; depending on the industry they may have different names, but their function remains the same: to measure flow.

In the simplest of terms, a flow meter is a device which is used to measure the quantity and/or flow rate of a gas or liquid as it moves through a pipe. Some flow meters measure the amount of fluid that passes through the pipe in a given time, while others measure the total amount of fluid or gas that has passed through the flow meter. Sign up for FlowSight, the Litre Meter newsletter.


How do flow meters work?

Flow meters consist of three parts: a primary device, a transducer, and a transmitter. As the fluid passes through the primary device, the transducer senses it; the raw signal from the transducer is then sent to the transmitter and turned into a usable flow signal.

Mathematically speaking, a flow meter typically uses the following equations:

  • Q = A · v – Where the volume of fluid passing through a flow meter is equal to the cross-sectional area of the pipe (A) multiplied by the average velocity of the fluid (v).
  • W = r · Q – Where the mass flow of fluid passing through a flow meter (A) is equal to the fluid density (r) multiplied by the volume of the fluid (Q).


Different types of flow meter

There are a number of different types of flow meter available, each one suited to a different purpose, but always with the same goal of measuring the flow of a fluid or gas through a pipe.

  • Positive displacement flow meters: As the only meters to measure the actual volume, positive displacement meters work by repeatedly filling and discharging fluids from a chamber. Also known as volumetric flow meters, or rotary piston meters due to the way in which they operate.

    Rotary Piston flow meter with Hub connectors

    Rotary Piston Positive Displacement flow meter with Hub connectors

  • Inferential flow meters: These types of meters don’t measure volume, mass, or velocity. Instead they measure the flow of a fluid by inferring its value from other measured parameters such as differential pressure.
  • Velocity flow meters: The flow of fluid through the pipe is measured by the velocity of the flowing stream in order to determine the volume of the flow.
  • Mass flow meters: A mass flow meter, also known as an inertial flow meter, measures the flow rate of the mass of fluid as it travels past a fixed point during a specified unit of time.


What type of flow meter do I need?

There is no one-size-fits-all solution when it comes to flow meters. It largely depends on the industry you’re in, and what the flow meter will be used for. Here at Litre Meter we’re the flow meter experts, so we can help you to choose which type will work best for your needs, but here are a few questions to ask yourself before looking into purchasing a flow meter for your company:

  • What gas or liquid do I want to measure?
  • What level of accuracy do I require?
  • What is the temperature and viscosity of the fluid?
  • Does the fluid flow continuously or intermittently?
  • Will the meter be mounted in a safe or hazardous location?
  • What are the minimum and maximum flow rates?
  • What is the maximum pressure at the location?
  • What level of pressure drop is allowable?
  • Is the fluid compatible with the materials used in the flow meter?

Each type of flow meter has a different set of applications and constraints, so the best way to choose the right one is to use the application of the equipment, rather than the technology, to guide you in your choice. Once you know the answers to some or all of these questions speak to us and we can help you to determine which flow meter will best suit your needs.

The versatile VFF

Litre Meter was founded 40 years ago as a manufacturer of industrial flowmeters. Today, the company still manufactures flowmeters, but with a slight shift in focus – more than 80% of its products are designed specifically for the harsh conditions of the offshore oil and gas industry.

The shift towards offshore supplying happened largely due to Litre Meter’s ability to engineer new products, as many offshore oil and gas rigs require custom-built flow measurement solutions for chemical injection; however, the ability to engineer new products has sometimes been a setback for Litre Meter, as the majority of orders would often require custom engineering despite the company’s extensive catalogue of standard products.

Litre Meter defines its company by the strapline, ‘Specialist flow measurement engineering’, representing four of its unique and client-oriented company principles:

  • Specialist: Litre Meter is a specialist manufacturing company, focusing solely on products for measuring flow, rather than level or pressure.
  • Flow: its products drill down into the finer flow details, such as flow rate and flow total.
  • Measurement: its products measure flow accurately – they are not flow switches or flow indicators.
  • Engineering: although it offers a catalogue of standard products, Litre Meter can engineer bespoke solutions for unique challenges.

The VFF series

Litre Meter’s shift in focus began a little over 25 years ago, when it first adapted a standard industrial flowmeter for use on a North Sea oil rig. The popularity and success of this custom device led to the eventual production of their flagship range: the Viscous Fluids Flowmeter (VFF) series.

The VFF series is hugely popular and very adaptable, but its standard range has still been largely overshadowed by a flood of custom orders – until recently. One of the innovations for the 2015 range of VFFs included a new by-product: the FlowPod. The device itself is two-wire and fully HART compatible, with stainless steel housing. It opens up the popular VFF series to an even wider range of low-flow applications, and gives even the most obscure requirements near-instant access to Litre Meter’s innovative engineering without the need for custom designs.

Introducing the FlowPod

Flow Pod direct mount

The FlowPod mounts directly on the VFF flow meter.

Litre Meter decided quite early on that the FlowPod would be its only supporting instrument, and it has completely transformed the way the VFF range can be used.

Designed as Exi and Exd from the outset, the FlowPod was built in an enclosure small enough to be mounted directly onto the meter body, and gives Litre Meter an innovative method of incorporating extra functionality like reverse flow and redundancy measurement.
For Litre Meter, introducing the FlowPod to the VFF range was a great way to combine multiple design elements, gathered over 30 years of experience, to make an impressive and useful meter with a focus on utility plus weight and size reduction.
The 2015 VFF range includes more than 800 end-user drawings, representing more than 115,000 meter combinations and covering almost every conceivable possibility. While previously, around 80% of Litre Meter’s sales were for custom products, the introduction of the FlowPod means that only 5–10% of meters will now need any extra engineering at all. Most customers can simply access instant PDFs of general arrangement drawings, parts-list drawings and lifting diagrams, together with STEP files, as part of their Litre Meter quotation.
For Litre Meter, this means a faster sales cycle and more revenue; for the customer, it means much faster quotation, production and manufacturing times. 2015 has already been a big year for Litre Meter, and by raising its game and producing a range of meters without equals, it has truly cemented itself as a top-tier supplier of flowmeter technology to the chemical injection industry.

First published in Gas Technology Review


New reed sensors now available

IMG_9574 sensor white bgWe have launched new sensor solutions to complement our revamped range of VFF flowmeters.

Our reed sensor package has been improved and now comes in a 316 stainless steel enclosure which is easy to install within the VFF range. The sensor comes complete with two reed switches that can be set for reverse flow detection or redundancy.

The sensor is tested to one billion pulses and environmentally tested in accordance with BS EN 13628-6: 2006. It is temperature rated to -20 to +80°C and it is available with the two or four wire Flowpod – the new explosion proof flow indication display unit for Litre Meter positive displacement flowmeters.

The non-wetted part has an M6 connector and the sensor is compact and designed for use at high pressures.

The new optional field sensor package comes in the same robust 316 stainless steel housing in order to make the sensors interchangeable with one another. The field sensor enables the output resolution of the VFF meter to be increased by a factor of twelve and it can still detect reverse flow.

Next Generation Flowmeters for Fluid Measurement and Control Solutions

Charles Wemyss, Litre Meter Limited

Types of Flowmeters fall into many categories. One could use the involvement of moving parts and electronics to define this. Mechanical meters, used and invented before domestic electricity was prevalent must be Old Generation. These would include what you and I have outside our houses for the measurement of domestic water. They would also include meters in our gas supply for the measurement of our consumption of gas. The very first turbine meters credited to Woltmann in 1790 were considered for calculating the loss of energy in open canals. It would be true to say that these were used for counting or totalising flow rather than providing an instantaneous rate display or output.

From the Old to the New

Those using electricity or electronics with a moving part like a rotor are also Old Generation as turbine meters have been around for several decades, for example. The first of these were axial turbine types developed, in essence from Woltmann, in the Second World War for accurately determining the fuel consumption of military aircraft and torpedoes. The pick-up or sensor with a magnet and rotating conductor enabled the number of rotations to be counted, totalised and used for rate display.
If we define Next Generation meters as having no moving parts so that the definition encompassed Thermal, Coriolis, Ultrasonic and Electromagnetic, then there would be a modern outlook. Apart from the fact that Faraday tried making an electromagnetic meter to measure the River Thames almost 200 years ago! He only failed because his instrumentation wasn’t sophisticated enough.
The obvious question to ask is: What is Next Generation, What is Current Generation and What is Old Generation? We can be certain that Old Generation does not mean unusable. We can also be certain that Old Generation in some people’s eyes is more than adequate for various tasks. This article explores the provenance of some flowmeter technologies, what might be round the corner and how to select the best meter for each project.

Some new and not-so-new flow measurement techniques:

New Technology

Coriolis, inertial force was first formulated by Gustave Coriolis in 1835 but MicroMotion didn’t release a commercial unit until 1977.

Electromagnetic, proven by Faraday but commercially produced from 1952. *Ultrasonic, from 1963.

Vortex, using the van Karmann effect of the generation of alternate vortices past a bluff body commercially from 1969, famously spotted by Leonardo da Vinci in 1504.

Thermal, hot wire anemometers were used from the early 1900s, commercially from the 70s.

Sonar, unconventional and measures turbulence since 2003.

Optical, measuring the speed and direction of individual particles using a laser beam, in research labs in the 70s and 80s but only commercially used in flare gases.

Traditional Technology

Differential Pressure like an orifice plate or Dall tube with a separate differential pressure transmitter. Also nozzles, pitots, Venturis and wedges. Still the most popular non-domestic meter type.

Positive Displacement, commercially pre 1830s for diaphragm gas meters with sheepskin diaphragms and sheet steel enclosures.

Turbine, first drawn up in 1790, commercially available post Second World War.

Variable Area, available for most of the 20th century.

Low Flow technology and the next ten years

There are various technologies that present themselves for low flow shown below. Many of the others mentioned elsewhere do not scale effectively.

Coriolis: Most manufacturers concentrate on ½” (15mm) and above. The issues of balance and producing thin wall tube to the required dimensional tolerances are hard to overcome. Smaller sizes exacerbate this.

Thermal: Microelectromechanical systems (MEMS), generally 0.01 mm to 0.1 mm in size, consist of a CMOS circuit on a thin silicon substrate. For lower flows these will replace a larger heated element and sensor. Liquids have a massively different thermal conductivity so the same device can measure at grams per hour rather than grams per minute.

Positive Displacement: Generally their purpose is to positively measure a trapped volume of fluid ? either gas or liquid. Gas versions tend to be for higher flows with the most popular one being used for domestic gas measurement. At lower flow the leakage between successive volumes is too large for effective measurement. For liquids where there is more viscosity the PD meters work well. Developments focus on some novel types and constant improvements to existing designs. There is a law of diminishing returns as the smaller the mechanical parts are, the harder they are to manufacture accurately. Also, leak paths are proportionally larger. One of the new types is the pendulum. This has one moving part with low mass and minimal friction loss, enabling it to respond to extremely low flow volume rates from 0.3 litres/hour. Unusually, this unit only works with viscosities up to 5 centiStokes. The rotary piston meter also has one moving part. In terms of flow rate, like most PDs, these prosper on viscosity. At 10 cSt a typical meter will start measuring at 0.08 l/h and when water is measured this increases to 0.4 l/hr.

In line ultrasonic: What happens when the pipes reduce in size and the type where a sensor is clamped on the outside of the pipe is no longer applicable? The sensors are mounted inside the pipe usually contrived in the shape of a U so that the ultrasound is passed between sensors at the base of the U. By knowing the diameter of the tube and the velocity between sensors, the volumetric flow can be calculated. Liquid flow rates down to 2 ml/min can be measured.

So if it’s not the methods of measurement we use that define Next Generation what is it? Perhaps: intelligence? The rise of smart meters i.e. those with digital communications and with the ability to self-verify are undoubtedly modern but were defined decades ago and have been in use for many years.

What’s Next?

Wireless communication is similarly up-to the- minute. HART digital communication has been around since the mid-1980s when it was developed by Rosemount Inc. for a range of measuring instruments, not just flowmeters. The HART foundation was formed in 1993 and the wireless version came along in 2007. So quite modern but Next?
So, is it the flowmeters that inhabit university laboratories and the R&D departments of flowmeter manufacturers that constitute Next Generation? Can we speculate what a cutting edge meter might look like in ten years’ time?

No Moving Parts

It would be fair to say that this Future meter would have no moving parts. This improves the chances of long term use as it would not suffer from mechanical degradation either planned or unplanned. It would ideally be non-invasive i.e. it would fit on the outside of a pipe and nothing would actually breakthrough the pipe wall. Currently, just ultrasonic meters match this criterion so let’s say that’s less than likely and the meter will therefore be non-intrusive. The sensor will break through the pipe wall but won’t impede the flow or perhaps just negligibly. What will the sensor measure, what techniques will it employ? That’s the $64,000 question. A single sensor is less likely as there will have to be a reference point for comparison.
Probably two sensors set apart, then, monitoring a property of the fluid. The clever part will be the intelligence of the signal processing; looking for perturbations in the signal amplitude and comparing it to the next sensor. Dumping thousands of comparisons for the sake of a few, locking onto patterns and pumping out high strength signals. In fact, the real hurdles will be firstly customer acceptance and secondly, electronic component obsolescence. Will the customer accept this meter and will it continue to find the small perturbations in property? Can he see it in action? Does he get a sense of goodness in the signal, in the rejection rate? What if the pipe vibrates, if the temperature ramps up, if the ‘property’ disappears? Then we find out that metering and measuring is about confidence, experience rather than Next Generation.

Bringing the Oil and Gas Industry Up-to-Date

The Oil & Gas industry is relatively conservative, relatively slow moving. The prevalence of HART and 4-20 mA signals decades after their introduction speaks volumes. Wireless, Bluetooth and fancy bus protocols are only just now making significant in-roads offshore. The creep of domestic innovation exemplified by the rise of the smart phone encourages instrument designers to bring their act up-to-date. Most instrumentation can only be compared with the most basic mobile phone. There is an inherent expectation that the modern user will have something easy-to-use, colourful and dangerously (?) customisable. The smartphone has many different uses of course beyond that of making calls. Arguably, it’s an instrument display in its own right. The logical conclusion is that the meter ‘display’ will be with the operator the whole time, in his/her hand. The obsolescence of components that bugs the subsea side of the industry is irrelevant in the actual instrument as this is replaced by the mobile phone and it’s ‘app’.
That still leaves the problem of the fast-moving world of miniature components for the clever parts – that will always be a thorn in the side of designers. Just as with most technologies, we’re not trying to design something to last for 30 years; the likelihood is that it will be overtaken by a new Next Generation device in ten years and then again in twenty years. All we can hope for is that the unit is still working in ten and twenty years and only needs replacing in thirty.
To select the best flowmeter for each application it is not just a question of looking up the first flowmeter you thought of on Google. Nor is it asking the engineer on the next desk or even consulting the internal specification guides issued by your employers. And it certainly shouldn’t be by selecting the cutting-edge meter of the day. It should be by consulting a flowmeter specialist – a specialist that has a wide range of solutions, not just one that is shoehorned into every application. Ideally, an independent specialist who can give unbiased advice and who will, if necessary, recommend an external solution.

Looking to the Future

In conclusion, the Next Generation of flowmeters is already operating, they’re already proven and they’re probably on the specification lists. Most applications can be met, more than adequately, by existing techniques. But the manufacturers aren’t standing still. They’re continually leveraging current technology with creeping demands. It’s more evolutionary than revolutionary but we’re all getting there – safely, economically and technically.