2018 Flow Measurement - Control Global

2018 Flow

Measurement

Part II

eHANDBOOK

TABLE OF CONTENTSThe art of flowmeter selection 4

Here’s what’s good, what’s bad, and what’s ugly about the most common technologies.

Wireless flow measurement 8

Power remains the essential challenge; here are ways to meet it.

Custody transfer flow measurement 11

Why can a DP flowmeter be used for gas but not liquid?

Vortex flowmeter calibration and rangeability 15

How can we determine the best size to balance accuracy against pressure drop?

AD INDEXEndress+Hauser • www.us.endress.com 3

Krohne • www.us.krohne.com 5, 18

ACROMAG • www.acromag.com/XT 11

Kobold • www.koboldusa.com 16

eHANDBOOK: 2018 Flow Measurement, Part II 2

www.ControlGlobal.com

http://www.us.endress.com

http://www.us.krohne.com

http://www.acromag.com/XT

https://koboldusa.com/products/flow/flow-measurement-without-moving-parts/mim-all-metal-electromagnetic-flowmeter

http://www.us.endress.com

Stan: Measurements are our window into

the process. We don’t know what we don’t

measure, and nearly all the process or utility

inputs are flows.

Greg: Co-founder of the ISA Mentor Pro-

gram, Hunter Vegas, gives us considerable

insight as to what flow measurements can

and can’t do. Since this is such a vast topic,

we focus on liquid flow.

Stan: How did you gain your knowledge?

Hunter: Sizing and selection of instrumenta-

tion is becoming a dying art. The subject is

almost never taught in schools, and suppli-

ers may not know or appreciate all of your

plant operating conditions and require-

ments that determine the lowest lifecycle

cost. Like most veterans in the automation

industry, I learned at the knee of several

very patient mentors. One thing to realize

right off the bat is that the pipe must be full

of liquid for all of the meters discussed.

Greg: How do you choose the right flowme-

ter for a process liquid flow application?

Hunter: It is important to realize that

virtually every flow instrument has its

strengths and issues, and there is no

“one size fits all” solution. Therefore, it is

important to understand the limitations of

each flow technology and choose the one

best suited for your budget and process.

Since space is limited in this format, we will

quickly hit the good, bad, and ugly for each

of the most common flow technologies

(ugly being show stoppers that will usually

eliminate that technology as a viable

The art of flowmeter selectionHere’s what’s good, what’s bad, and what’s ugly about the most common technologies.

By Greg Mcmillan and Stan Weiner, PE



option). So cue the cowboy music, throw on

your poncho, pull down your hat, and let’s

look at our options.

Stan: How about vortex meters?

Hunter: The vortex meter measures

volumetric flow. Liquid moves past a

bluff body in the middle of the flow

stream and generates vortices. A sensor

counts the vortices as they are shed to

determine liquid velocity. Good: The

meter is inexpensive to buy and install. It

requires no special freeze protection (just

insulated pipe). It works regardless of the

fluid conductivity and has no moving parts,

though polymerization can plug ports

and/or affect the sensors on some vortex

designs. Bad: The requirements for straight

meter runs upstream and downstream are

particularly long for accurate readings. The

bluff body post makes a wonderful startup

strainer. If a mass flow is desired, the flow

must be temperature-compensated. It

generally needs fairly clean fluids. The

flow coefficient is affected by kinematic

viscosity. The meter differential pressure

(DP) drop is less than an orifice plate, but

more than a magmeter. Ugly: Vortex can’t

handle slurries or viscous or slow-flowing

fluids. It can’t handle high vibration, pulsing

flow, cavitation or entrained air. Probably

the biggest issue is low-flow cutoff: a vortex

meter can’t read low flows, so if the flow

drops below a certain value the meter will

read zero.




Greg: What about magnetic flowmeters

(magmeters)?

Hunter: The magmeter measures volumet-

ric flow. Conductive liquid moves through

a magnetic field and generates a voltage

sensed by two small electrodes. The voltage

indicates liquid velocity, which is converted

to flow. Good: These meters are fairly inex-

pensive to buy and easy to install, requiring

no special freeze protection (just insulated

pipe). They have virtually no obstruction to

flow and can handle slurries, thick/viscous

fluids and corrosive materials since only

small electrodes are exposed to the pro-

cess. Only a short meter run is needed. The

electrodes can tolerate some coating, but

not extensive amounts. Magmeters have no

moving parts, can read down to very low

flow rates, and will remain accurate despite

changes in density, temperature, etc. Bad:

Heavy coatings can keep a meter from

working. Some magmeters can’t handle a

steam-out and vacuum condition because

it collapses the liner. If a catalyst is injected

upstream of a magmeter, the electrochemi-

cal reaction can cause erratic flow readings.

If the pipe is nonconductive, grounding

rings must be used. Ugly: The process liquid

must have a minimum conductivity under

all conditions. The meter will read nothing if

conductivity is too low.

Greg: My favorite flowmeter, if the materials

of construction are available and lifecycle

cost is justifiable, is the Coriolis flowmeter.

It’s a true mass flow measurement regard-

less of composition. No other flowmeter can

get close to its accuracy and rangeability.

What is your take?

Hunter: The Coriolis meter measures mass

flow. Flow moves through vibrating tubes

(or a single tube). Vibration frequency

determines density; vibration phase deter-

mines mass flow rate due to Coriolis effect.

Good: The meter requires no special freeze

protection (just insulated pipe). The meter

works well regardless of fluid properties

(e.g., conductivity, density, pressure, tem-

perature, viscosity). There are no moving

parts and it requires no special meter run.

Coriolis flowmeters can read very low flows,

and the flow and density readings are very

accurate. They can measure liquids with

some entrained air. Bad: The meter is very

expensive but installation is generally not

difficult. Pressure drops are higher for dual

tubes than for single tubes, and will always

be higher than a magmeter. Single-tube

meters pose minimum flow obstruction, but

they’re usually much longer than a bent,

dual-tube meter. Ugly: Coriolis meters are

not an option if you are on a low budget.

Stan: What about differential pressure (DP)

orifice flowmeters?

Hunter: The DP orifice meter measures

volumetric flow. Liquid moves through a

restriction orifice in a pipe and creates a dif-

ferential pressure (DP) due to the Bernoulli



Effect. Good: The meter and orifice are

inexpensive to buy. It works regardless of

the fluid conductivity, and has no moving

parts and no low-flow cut-out. However,

rangeability of a DP meter, even with dual

transmitters, is significantly less than a

magmeter, and extraordinarily less than

a Coriolis meter. Bad: Installation is more

expensive than vortex due to the costs of

impulse lines, freeze protection, etc. A long

meter run is needed to read accurately. The

permanent pressure drop is significant. If a

mass flow is desired, the flow must be tem-

perature-compensated, and composition

must be constant for the temperature effect

on density to be accurate. DP orifice gener-

ally needs fairly clean fluids, and the meter

reading is based on a specified fluid density,

viscosity, temperature, etc. Ugly: DP orifice

meters can’t handle slurries or processes

that tend to plug the impulse tubing.

Greg: How about wedge DP flowmeters?

Hunter: The wedge DP flowmeter measures

volumetric flow. Liquid moves through

a wedge-type restriction in a pipe, caus-

ing a DP due to the Bernoulli Effect. The

meter usually uses capillary seals to mea-

sure DP. Good: A wedge meter can handle

sticky, viscous fluids that might plug an

orifice plate. Bad: A wedge meter is more

expensive than an orifice meter because

the transmitter usually includes two seals

as well as the wedge assembly. The meter

needs a fairly long meter run. The perma-

nent pressure drop is significant. Ugly: Very

high temperatures may exceed the limits of

the diaphragm seals.

Stan: What about other meters?

Hunter: Other, less common meters used to

measure liquid flows include turbine meters,

positive displacement (PD) meters, and

ultrasonic flowmeters, among many others.

Turbine and PD meters are not used as

often due to wear issues with moving parts,

susceptibility to damage from solids, and/

or limited conditions in which they function.

For custody transfer of pure, clean liquids,

they can be the right choice. Nearly every

pump at a gas station has a PD meter.

Greg: Stay tuned—in a future column, we’ll

discuss gas flowmeters.



Flow measurement techniques

continue to grow and evolve with

new methods such as multipath

ultrasonic, magnetic and Coriolis increasing

at the expense of more traditional

technologies such as orifice, weir and

other differential pressure (DP)-based

techniques. The increased use of these

new technologies is partly a result of the

increased capability of microprocessors

and sensors to enable measurements not

possible without enhancements in these

areas. Another reason for their adoption

is that, in most cases, they also provide

higher accuracy and rangeability than

DP technologies. But most of these flow

measurement techniques tend to require

more energy than DP flowmeters, and

hence aren’t well suited for deployment as

wireless devices.

A colleague on one of the international

standards teams I belong to indicated at a

recent meeting, during a conversation on

wireless and batteries, that their company

has only been able to find one source for

a battery suitable for their wireless trans-

mitters to meet a 10-year service life. This

is, of course, with periodic recharging.

Other rechargeable batteries tend to have

‘memory’ and other problems resulting in

operating life of closer to five years.

A bigger concern with using wireless for flow

measurement is the dynamics of the process

itself. The majority of flow loops, especially

for liquids (incompressible fluids) have very

short process response times, often in the

order of seconds, unlike temperature and

level, which tend to be much longer (argu-

ably measureable in minutes). Therefore,

Wireless flow measurementPower remains the essential challenge; here are ways to meet it.

By Ian Verhappen, Senior Project Manager, Automation, CIMA+



if using a wireless sensor for flow control,

you’ll need a rapid update rate for the trans-

mitter at a minimum, which of course leads

to short battery life, and consequently make

the economics for cable look better.

Of course, it would help if it were possible

to develop the perpetual motion machine

and scavenge some energy from differ-

ent flowmeters to maintain or charge the

batteries. For example, if the frequen-

cy-shedding bar of a vortex meter, or

paddle/turbine in those forms of meters,

or pulsations in a positive-displacement

meter could drive some form of coil while

not affecting the measurement proper, this

would eliminate the energy concern for

each of these forms of meter.

One way to address the response time issue

is to increase the capability of the flow

device by adding the ability to perform as

a single-loop or self-contained flow con-

troller. Then the control loop only requires

transmission of the output to the final con-

trol element and remote HMI when such

a change is required, which isn’t likely to

be every sensing or update cycle (assum-

ing the control system can accept some

degree of dead band on the signal). If the

dead band isn’t acceptable, then having the

transmitter update the control system for

historian and measurement purposes every

cycle and the output directly to the device

“as needed” is a much more complex sit-

uation of managing different update rates

from one device depending on data type.

An alternative to every-cycle updates that

may be acceptable is using a totalization

option for the update rate to the con-

trol system, which risks losing raw data

granularity. With all these features, the

transmitter is getting closer to the Open

Process Automation (OPA) forum’s vision

of a device control node (DCN), and closer

to a SCADA RTU field controller being

monitored and controlled (i.e., changing

setpoint) remotely from the central control

station. SCADA typically includes wireless

but again, with longer update cycles and

the need for intelligence at the field end.

As the above discourse indicates, moni-

toring versus controlling has a significant

impact on system design. The apparently

simple choice of monitor versus control

or custody transfer affects not only the

type of sensor required, but as we can see,

how that device interacts with the control

system and other devices within the con-

trol system. Though true for more than

flow measurement, the impact is more

pronounced with fast control loops such

as flow, regardless of how innovative we

try to be to overcome the basic principles

and reason for which the system is being

installed.



http://www.acromag.com/XT

Q: I’m interested to know why

orifice differential pres-

sure (DP) flowmeters aren’t

used in liquid metering systems (for cus-

tody transfer purposes), whereas they’re

widely used in gas metering systems?

What makes an orifice flowmeter a viable,

cost-effective choice for gas metering sys-

tems only?

A. Rashimi

[email protected]

A: The short answer is that orifices are

used for both, but because custody trans-

fer (fiscal metering) is such an important

topic (see Chapter 2.20 in volume one

of my handbook), I will give a more

detailed answer.

Flowmeter selection can be based on gov-

ernment regulations, industry or national

standards, and contractual agreements, and

can also be subject to the approval of such

organizations as API, AGA and ISO.

The acceptable uncertainty in the quan-

tity of transferred liquid or gas determines

meter selection. The uncertainty is the

sum of the errors of all components of the

metering system. In case of volumetric

flowmeters, this includes errors by flow,

pressure, temperature, density, composition

sensors, their A/D converters, and in cal-

culating the amount of energy (not mass,

but energy) transferred. The hydrocarbon

industry claims that custody transfer oper-

ates at an uncertainty of ±0.25% on liquid

and ±1.0% or better on gas service, but I

consider these numbers overly optimistic.

Custody transfer flow measurementWhy can a DP flowmeter be used for gas but not liquid?

By Béla Lipták



Table I lists flowmeters that can be used

to measure hydrocarbon liquids and gases.

The table also gives the chapter numbers

where each is described in my handbook,

their accuracies (if they’re correctly sized,

installed and maintained), and other main

features. Table I doesn’t list their first

costs because, in larger transactions, the

cost differences between meters are small

in comparison to the cost of measure-

ment errors.

For example, when oil costs $60/barrel and

we’re unloading a 500,000-barrel tanker,

each 0.1% uncertainity corresponds to

$50,000. In cases of smaller quantities, meter

cost differences can be considered, and if

accuracy is not critical, one can determine the

transferred quantity without flowmeters, just

by measuring the level change of liquids or

pressure change of gases.

A typical liquid custody transfer skid

includes multiple flowmeters (master

and operating meters), flow computers

and meter provers. For pipe sizes below

42-in. diameter (1.07 m), onsite provers

can be used and API requires prover

accuracy to be 0.02%. The meter prover

volume is calibrated against Seraphin

cans, whose precise volume is traceable to

NIST. Recalibrations should be performed

frequently, typically before, during and after

the batch transfer.

Béla Lipták

[email protected]

A: Orifice meters are still widely used for

liquid measurements and have been for

many years. The orifice meter accuracy is

much affected by the details of installation,

Features Orifice and (Venturi) Coriolis Rotary PD liquid (gas) Turbine dual helical Ultrasonic, multipath

Chapter(s) 2.21-2.34 2.16 2.24, 2.25 2.31 2.32

Accuracy at max. flow 1% (0.25%) 0.15% 0.2% (1%-2%) Liq: 0.25%, Gas: 0.5% Liq: 0.25%, Gas: 0.5%

Accuracy at min. flow 2% (0.5%) 1% 0.1% (2%) Liq: 0.5%, Gas: 1.0% Liq: 0.5%, Gas: 1.0%

Rangeability 3:1-4:1 Up to 100:1 ~ 15:1 Liq: 10:1, Gas: >20:1 >20:1

Reynolds (RE) limitations >10,000 (>100,000) Debated Insensitive Insensitive < 2,000 and >8,000

Size range 0.5-24 in. (1-120 in.) 1.0 mm to 16 in. 1-18 Liq: 1-20, Gas: 2-12 in. Liq: 2- >12, Gas: 2- >42 in.

Straight run up/downstream 20/5 (5/0-3) None None 15-20/5 20/5

Pressure Drop High (low) ~ 10 psid High ~ 5 psid Low

Installation Critical Not critical Not critical Important Important

Maintenance High (high) Low High because moving parts

High becausemoving parts Low

Mass flow or multphase No Yes No No No

Moving parts No Vibration Yes Yes No

Bidirectional Some w/2DP Yes No Some Yes

TABLE I: FLOWMETERS USED IN CUSTODY TRANSFER



and comments about poor accuracy can

usually be explained by poor installation.

The advantages and disadvantages of

the various meter technologies are well

known, and the available technologies

have changed. One example is how Coriolis

meters have become more popular as the

technology has matured and competition

has driven prices down. It’s clear that meter

selection is heavily affected by pipe size. I

find it hard to imagine a Coriolis meter in a

one-meter-diameter pipeline. And the cost?

National and international standards can

affect decisions. Custody contracts may

well have statements limiting options. It

can happen that non-technical people write

those contracts.

I’m prejudiced, but I have the impression

that salespeople tend to suggest the more

expensive choices in their catalogs.

In the decision process, it’s common to

underestimate the costs and details of

installation for the various flowmeters.

Accuracy is expensive.

I once developed a program to aid in

flowmeter selection. The user entered

information about the fluid and flows. The

program then displayed a list of possi-

ble meter types with costs, accuracy and

permanent pressure loss. This brought inter-

esting comments challenging estimated

costs and accuracy. Support for this

program went away as the costs of mainte-

nance would be high as the data changed.

Good question, and we need to discuss

these things.

Cullen Langford

[email protected]

A: Orifice flow measurement is at best

±4% accurate. In spite of this, it was used

for custody transfer of liquids for many

years until better and more accurate

instruments became available. Today,

the Coriolis flowmeter is the standard for

liquid flow custody transfer due to its high

accuracy and often because it directly

measures mass flow instead of volumetric

flow. It’s expensive, so sometimes if

liquid is transferred from tank to tank, the

before and after tank level measurements

are used for custody transfer of liquids.

However, that requires very accurate tank

level measurement.

Measuring the flow of gases with an

orifice flowmeter with compensation for

temperature and pressure is typical for

natural gas transmission, but that still

doesn’t make it accurate. In most cases,

the low value of natural gas makes it

uneconomical to spend extra money on

more accurate gas flow measurement. For

high-value gases, it’s possible to use Coriolis



flowmeters or a high-accuracy, positive-

displacement meter. Sometimes, custody

transfer of gases is calculated from a

change in pressure of the source of the gas,

such as a cylinder.

Orifice flow measurement depends on

Bernoulli’s law that relates pressure drop

thorough a sharp-edge orifice to volumetric

flow rate. The pressure drop is between the

upstream pressure (before the orifice) and

the pressure at the vena contracta formed

by the increased velocity of the liquid or

gas as it passes through the orifice. Unfor-

tunately, the location of the vena contracta

varies with the flow rate, so there’s no prac-

tical way to measure this pressure drop.

We do the best we can, and usually just

measure the pressure drop at the flanges

that hold the orifice plate in place, and

depend on a correlation (approximation)

to estimate the pressure drop at the vena

contracta, or just assume that the pressure

drop at the orifice is the same as that of the

vena contracta.

Richard H. Caro, CEO, CMC Associates

[email protected]

A: One of the biggest reasons why ori-

fice plates are not used for liquid custody

metering has to do with the following:

1. During startup, while the flow stabilizes,

the error in measurment is generally

unacceptable. The same happens when

the system is shut down.

2. Sizing an orifice plate to guarantee cus-

tody transfer precision requirements

generally requires the orifice plate to be

designed and fabricated to extreme tol-

erances that not every company can do.

3. The turndown ratio for liquid orifice

plates would require users to have too

many orifice plates available for when

flow conditions change.

To summarize, though custody transfer can

be performed with orifice plates, it’s not

recommended due to the fact that signal

instability can cause accounting errors; design

and fabrication of orifice plates is very expen-

sive; and finally, if the custody transfer is

based on varying flowrates, then the need for

additional orifice plates is increased.

Alex (Alejandro) Varga

[email protected]



https://koboldusa.com/products/flow/flow-measurement-without-moving-parts/mim-all-metal-electromagnetic-flowmeter

Q: I have a question regarding

vortex flowmeters and hope that

you can clear it up. The line size is

3 in.; the flow is minimum 6 m3/hr, normal

20 m3/hr, maximum 22 m3/hr. The vendor

suggested using a 3-in. Endress+Hauser

(E+H) Prowirl vortex flowmeter with min-

imum flow 4.03 m3/hr, maximum flow

138.22 m3/hr. That unit has a three-point

calibration (30%, 45% and 65%). My client

has the following questions:

1. Why has the vortex flowmeter not been

calibrated for a lesser span range of

0-25 m3/hr?

2. What happens if the flow drops below

4 m3/hr?

Can you let me know if my selected size

is acceptable or I should use a smaller

meter? If I keep the 3-in. meter, is it possi-

ble to use it over this range of 4 m3/hr to

25 m3/hr?

Also, as the flowmeter has a Foundation

Fieldbus transmitter, is it possible to con-

figure the span in the transmitter?

W.Watson.

[email protected]

A: You did not name the process fluid, or

even indicate if it is a gas, liquid or steam,

therefore the correctness of selecting a

vortex meter for the application can’t be

checked (for selection guidance see Table

2.1a in Volume 1 in my handbook).

Meter sizing: I usually select a maximum

meter flow of 1.5 times the maximum

Vortex flowmeter calibration and rangeabilityHow can we determine the best size to balance accuracy against pressure drop?

By Béla Lipták



process flow. Therefore, if your flow range

is 6-22 (rangeability of 3.7), I would look

for a maximum meter reading of 33 or so.

The available ranges of this vendor’s meter

are 1-34 for 1.5 in., 1.5-53 for 2 in., and 4-138

for 3 in., and therefore, I’d consider a 1.5 in.

meter, but there are other considerations.

Reynolds number (Re): Assuming that the

selection of a vortex meter is correct and

it’s on liquid service, the inaccuracy will be

around 0.75% actual reading (AR) if the Re,

even at minimum flow, is above 20,000. If

it’s below that, you can expect an error of

about 1.0% full scale (FS). So the smaller the

meter, the less the error. For liquids, Re can

be calculated using:

Re = 3,160 Gf Qf / Dμ

where:

Gf: process fluid specific gravity at 60 °F

(15.5 °C)

Qf: liquid flow in gpm (1 m3/hr = 4.4 gpm)

D: pipe inside diameter (in inches)

μ: viscosity of the process fluid

(in centipoises)

Pressure drop and operating cost: Obvi-

ously, the smaller the meter, the higher the

pressure drop. Therefore, you must check

if cavitation or flashing will occur, and even

if they do not, you should also consider the

energy cost of operation, which also rises as

the size is reduced. (For the velocity heads

of some flowmeters, see Table I).

The operating costs can be calculated as:

$/yr = C($/kWh)(∆P)(F)(SpG)/(%)

where:

C: Correction factor for the units used (C is

0.65 if the flow is in gpm and the pres-

sure loss is in psid)

%: efficiency of the pump or compressor

So, if the cost of electricity is $0.1/kWh

and the pumping efficiency is 60%, the

operating cost in a water measurement

application is:

$/yr = 0.635 (gpm) (psid)

Straight pipe run requirements: The

meter should be installed at self-draining

low points or in vertical upward flows to

Flowmeter type(in velocity heads)

Permanent pressure loss

Orifice plates Over 4

Vortex shedding About 2

Positive displacement 1 to 1.5

Turbine 0.5 to 1.5

Flow tubes Under 0.5

Table I: Velocity head requirements of different flowmeter designs



keep it flooded, and five or more straight

pipe diameters (D) upstream from all

disturbance sources (regulators, valves,

thermowells, pressure taps, etc.) in areas

where there is no excessive pipe vibration.

The upstream (inlet side) straight pipe

diameter requirements are: 15D from a

reducer, 20D after a single elbow, 25D after

two elbows in the same plane, 40D after

two elbows in different planes, and 50D

after regulators or control valves.

Historical note: The vortex phenomenon

was discovered by Tódor von Kármán while

he was fishing in a fast spring in Hunga-

ry’s Transylvania region. He noted that the

swirls that are formed after the rocks were

the same distance from each other, no

matter how fast the water was flowing. That

observation became the basis not only of

this flowmeter, but also of much of the sci-

ence of space exploration.

Béla Lipták

[email protected]

A: The 3 in. vortex is way oversized for

your application. Normal rule of thumb for

vortex flowmeter sizing is at least one line

size smaller than the pipe size for most

applications. Looking at your requirements,

a 1.5 in. vortex would actually give the best

results because it has an approximately

0.95 to 34 m3/hr range. A 2 in. meter would

also do, as it has a range of approximately

1.5 to 53 m3/hr.




Vortex units are velocity meters. They rely

on vortex shedding and require a certain

minimum flow velocity to generate the vor-

tices (the frequency is linearly related to

the fluid velocity). However, below a certain

velocity, you do not get vortices (and can’t

measure flow).

Each of the sizes measure the same veloc-

ity range (if they are the same style). The

area then gives you the equivalent volume

flow. All the vendor websites have technical

details on how vortex meters work, includ-

ing the basic equation. I suggest that you

review the material.

Simon Lucchini, CFSE, MIEAust CPEng

(Australia), Chief Controls Specialist, Fluor

Fellow in Safety Systems

[email protected]

A: To answer your first question, the vortex

meter can be spanned to something less

than the maximum calibrated range. If you

don’t specifically give them a different

range, they will, by default, span the meter

to the full range.

On your second question, if the flow drops

below 4 m3/hr, the reading will drop to

zero. This is called “low-flow cutoff.” A

vortex meter requires the flow to be in the

turbulent flow regime to function correctly.

As the flow drops to the transitional (or

laminar) flow regimes, it will stop shedding

vortices and the meter reading will become

erratic and then drop out. Note that the

exact point where this occurs depends on

the Reynolds number of the fluid, so if the

density and/or viscosity are different than

water, the actual low-flow cutoff point

will vary from the published value. (The

published value is based on water.) Most

vortex manufacturers have programs that

calculate the exact low-flow cutoff point for

your application. (E+H has their Applicator

program, which you can access online).

Finally, based on the little process informa-

tion you provided, I would agree that 3 in.

probably is oversized. A 2 in. meter has a

minimum linear flow of 2.7 and a max range

of 61.6 m3/hr, which is well within your

specs. In fact, you could even drop to a 1.5 in.

meter size. However, do note that that pres-

sure drop will rise with each drop in meter

size. In addition, you’ll need to reduce the

pipe size far enough upstream and down-

stream of the meter to make sure you have a

good straight run to obtain good accuracy.

Note that your 3 in. meter will work, but

you’ll be unable to read much below 4 m3/

hr. If low flows are expected, you’ll either

need to downsize the meter or consider a

different technology.

P. Hunter Vegas, Wunderlich Malec

[email protected]

A: To the question on configuration, the

answer is yes. Some handheld configurators



are also capable of configuring Foundation

Fieldbus instruments. You may use your

Foundation Fieldbus configurator, which is

often the DCS itself, or software for strat-

egy building running on a PC attached to

your Foundation Fieldbus network. This is

the same software you would use to field

test your device connection and set its tag

name, limits, etc.

The device has an upper range limit and has

a zero default for the lower range limit. You

specify these values when you configure the

AI function block for this flowmeter. E+H

user manuals are available on the Internet

at the E+H website. If you are using Foun-

dation Fieldbus instruments, your DCS must

supply software to configure all field instru-

ments using the parameters of their DCS or

Device Descriptions. Refer to the documen-

tation from your DCS supplier.

You received a standard 3 in. vortex meter

from E+H. Your meter was flow calibrated

for the stated range. As delivered, the

span of this meter is set for 0–138.22 m3/

hr. If you had ordered this meter to be cali-

brated for your desired span of 0–25 m3/hr,

they would have charged you more for the

custom calibration, but you did not order

that way. As delivered, the 20 mA output

will have a span of 138.22 m3/hr.

This is a HART instrument and the span

can be easily changed to 0-25 m3/hr using

a HART handheld (275/375) device. It is

most likely to be even more linear over your

reduced range than the original range.

Dick Caro

[email protected]



Documents

2018 Flow Measurement - Control Global