Spiraflo Steam Flowmeters - Spirax Sarco

Spiraflo
Steam flowmeters

2
The Spiraflo steam meter with density compensation
is designed to give very accurate results,
regardless of variations in steam pressure
How it works
The Spiraflo steam meter operates on the wellestablished
spring loaded variable area principle.
A circular plate positioned in the flow is free to move
against the action of a heavy duty precision made
torsion spring. To determine the plate angle, a rotary
transformer of special design is incorporated into the
unit. This converts the plate angle into an electrical
output which is proportional to the flow. The device
operates within the pressurised body of the transducer,
thus eliminating the need for any rotary seals. The
result is a robust design, well suited to the rigours
of steam service. It offers good turndown, high
accuracy and repeatability.
An in-built temperature probe provides information
which enables the flow computer to compensate for
the pressure variations which are commonplace in
steam systems. This density compensation is
essential in achieving accurate measurement
of steam flow.
The addition of a pressure transmitter enables the
Spiraflo to be used for superheated steam as well as
saturated steam systems.
Density compensation
It is rare for the pressure in a steam system to
remain absolutely constant. Unless this variation is
taken into account, flow measurement errors will
occur. The automatic
density compensation
offered by the Spiraflo
system completely
eliminates these errors
1 000
900
800
Flowrate
and allows accurate
700
metering whatever the
600
steam pressure. This is 500
shown in the diagram.
400
300
200
Flowrate, kg / h
PTX
RVDT - Rotary variable differential
transformer
RTD - Resistance temperature
detector
PTX - Pressure transmitter
Signal conditioning unit
(the signal conditioning unit converts
the signal into a form suitable for
use in the flow computer)
Flow computer
Spring loaded plate
RVDT
The Spiraflo system components
100
0
0 1 2 3
Cumulative error
4
Hours elapsed
5 6 7
0
8
In this example a simple non-compensated meter is set for 6 bar g. The actual pressure in the system varies
through the day and unless this is allowed for, by the end of the day, very significant errors can arise. This is
typical of many steam systems.
RTD
Actual
system
pressure
10
8
Pressure bar g
6
4
2
2 500
2 000
1 500
1 000
500
0
Cumulative error, kg

Flowrate, kg / h
Good turndown - essential for steam systems
The turndown of a flowmeter is the ratio of the maximum to minimum flowrate over which it will meet its specified
performance. In steam systems, varying load can give rise to wide flow variations and it is essential that a
steam flowmeter can cope with these. It is also very important that it is designed for typical flow velocities that
are encountered in steam systems.
Some flowmeter types require very high velocities (up to 75 m / s) to achieve their claimed performance. In
practice, to reduce noise, erosion and waterhammer, steam flow velocities should be limited to 30 - 35 m / s.
Consider a typical flow pattern for a distributed steam system shown below.
1 000 2 000
Actual flowrate
Cumulative flow error
1 700
750
1 500
500
250
40
25
0
Spiraflo
1 2 3 4
Hours elapsed
5 6 7 8
Flowrate below minimum of 250 kg / h (i.e. 1 000 kg / h ÷ 4)
10 20 25 30 40 50
Turndown ratios with steam velocities limited to 35 m / s
Cumulative error, kg
Threshold at
4:1 turndown
This graph shows a typical demand curve for a distributed steam system with a high start-up load and variable
demand through the day. An orifice plate meter, with a 4:1 turndown is sized on the peak load of 1 000 kg/h. Any
flowrates below 250 kg/h are ‘lost’ or, at best, recorded with a significant error.
The Spiraflo steam meter, with its 25:1 turndown (40:1 intermittent) completely eliminates this type of error.
Comparison of turndown ratios
Good steam practice dictates that flow velocities should be kept below 35 m / s as far as practical to avoid
erosion and possible waterhammer problems. The table below shows the realistic turndown ratios for various
types of steam flowmeter when the steam velocity is limited to 35 m / s.
Spiraflo
Orifice
Shunt
Vortex
Orifice plate
25:1 continuous
40:1 intermittent
Depends on system pressure.
Typically up to 10:1 with flow velocity of 35 m / s
Typically 7:1
Typically 4:1
1 000
500
3

4
Using a Spiraflo steam meter from Spirax Sarco will enable you
to measure steam use accurately under all load conditions.
It will provide vital information on usage and associated
costs which can improve efficiency in four key areas:-
Plant efficiency
Is idle machinery switched off ?
Is plant loaded to optimum efficiency ?
Identify cleaning and / or maintenance needs.
Identify major steam users.
Highlight peak steam usage times.
Indicate whether working practices are
satisfactory.
Energy efficiency
Monitor the results of energy saving
schemes.
Compare the efficiency of various
pieces of plant.
Process control
Confirm if the correct quantity of steam
at the right pressure and temperature
is being supplied.
Spiraflo 6 diameters
Vortex meters - up to 30 diameters
Orifice plates - up to 30 diameters
Weatherproof cable gland
allows outside installation.
Stainless steel cover.
Asbestos free gasket.
Carbon graphite bushes for
zero maintenance.
High accuracy temperature
sensor in stainless steel pocket.
Installation
All flow meters must be correctly installed. For steam systems in particular, care must be taken to ensure correct line drainage and that
adequate lengths of upstream and downstream straight pipe runs are provided. With only six upstream pipe diameters and three
downstream pipe diameters required, Spiraflo installations are extremely compact.
10 20 30
Number of upstream diameters of straight pipe
Costing
Cost steam as a raw material.
True cost of individual product lines can be
established.
Relate steam energy costs to total plant
efficiency.
Check individual plant performance.
Charge for steam usage.
6 pipe diameters
(minimum)
3 pipe
diameters
(minimum)

Heavy duty, precision made
nickel cobalt spring for long
term stability.
Stainless steel plate.
Cast steel or SG iron body in
sizes DN40 to DN100.
Flanged construction for quick
and easy installation.
M210G flow computer gives
automatic density compensation
plus analogue, pulse and
RS232C outputs as standard.
Local signal conditioning
allows M210G flow computer
to be installed over 300 m
from metering location.
Available displays
Flowrate
Totalised flow
Time and date
Temperature and pressure
Peak rate and time
Four batching timers
Eight day repeating batch
timer
High / low flowrate alarm
High / low pressure /
temperature alarm
User benefits
● Purpose designed for steam with density
compensation and dryness fraction correction.
● Flow computer can be sited up to 300 m away
from the pipeline unit.
● Easy to install and use, with accurate password
protected 16 digit alpha numeric display.
● Built-in choice of imperial or metric units with
flow expressed in terms of energy or mass.
● Battery back-up to protect setting information.
● RS232C interface port - compatible with energy
management systems.
5

6
M111 series transducer
This is fitted in the steam line and provides analogue
flow and temperature signals to the M322 signal
conditioning unit. These units must be fitted
within two meters of each other.
EL2600 pressure transmitter
Only required for superheat conditions.
Provides 4 - 20 mA pressure signal to the M322
signal conditioning unit.
M322 signal conditioning unit
Converts flow, pressure and temperature signals into
digital form for transmission to M210G flow computer
which can be located up to 300 metres away.
EL2600
pressure
transmitter
Separator
➤
Isolating valve
M322 signal
conditioning unit
The ability of any flowmeter to perform to specification
and give years of trouble-free service is, to a large
degree, governed by the way it is installed. This is
especially true for steam systems where there are
always potential difficulties from surges and
waterhammer arising from poor line drainage.
Whatever kind of flowmeter is used, it is essential to
install it properly:-
System details
Y-type
strainer
Installation
Air vent
➤
D
➤
➤
Trapping set
M210G series flow computer
Executes all the necessary calculations to provide
density compensation. Gives local display of rate,
total, pressure and temperature. Provides timer
functions, programmable outputs and alarms.
➤
6 D
Minimum
M111
series transducer
➤
Spiraflo meter
M210G series flow computer
Ensure adequate lengths of upstream and
downstream straight pipe (only six pipe diameters
upstream and three downstream are required for
the Spiraflo).
Install a steam separator and strainer
upstream of the flowmeter to give good steam
quality and help avoid waterhammer.
Provide adequate steam trapping.
Avoid installing the flowmeter immediately
downstream of a pressure reducing valve.
Avoid rapid actuation valves.
Avoid reverse flow by fitting a check valve.
➤
3 D ➤
Minimum
➤
Check valve
➤
➤
➤

Flow capacities for saturated steam
Steam pressure (bar g)
Size Flowrate kg / h 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
a) Maximum 610 740 845 940 1 020 1 100 1 175 1 240 1 300 1 365 1 425 1 480 1 530 1 585 1 635 1 685 1 730
DN40 b) At 35 m / s velocity 180 260 350 420 500 580 660 740 820 900 970 1 050 1 120 1 200 1 275 1 350 1 440
c) Minimum 15 18 21 23 25 27 29 31 33 34 36 37 38 40 41 42 43
a) Maximum 955 1 155 1 320 1 470 1 600 1 720 1 830 1 940 2 035 2 130 2 225 2 310 2 395 2 475 2 555 2 630 2 705
DN50 b) At 35 m / s velocity 280 410 540 660 790 910 1 030 1 150 1 275 1 400 1 520 1 640 1 760 1 870 1 990 2 100 2 250
c) Minimum 25 28 33 37 40 43 46 48 51 53 56 58 60 62 64 66 68
a) Maximum 2 445 2 955 3 380 3 755 4 095 4 400 4 690 4 960 5 215 5 460 5 690 5 915 6 130 6 335 6 540 6 730 6 920
DN80 b) At 35 m / s velocity 720 1 050 1 375 1 695 2 010 2 330 2 640 2 945 3 265 3 580 3 885 4 195 4 490 4 800 5 105 5 415 5 755
c) Minimum 60 74 84 94 102 110 117 124 130 136 142 148 153 158 163 168 172
a) Maximum 3 820 4 615 5 285 5 870 6 395 6 880 7 330 7 750 8 150 8 530 8 895 9 240 9 575 9 900 10 215 10 515 10 815
DN100 b) At 35 m / s velocity 1 125 1 640 2 145 2 645 3 140 3 640 4 125 4 600 5 100 5 590 6 070 6 555 7 020 7 495 7 980 8 460 9 000
c) Minimum 95 115 132 147 160 172 183 194 204 213 222 231 239 247 255 263 270
Notes on the above table
The steam meter will continue to give a reading up to the maximum value in the
above table. However, the steam flow velocities at these maximum flowrates could be
extremely high (up to 120 m /s at the low pressures and up to 42 m /s at the high
pressures) and could lead to serious erosion damage both to the transducer and to
the associated pipework and fittings. It is not recommended that a flowmeter is selected
to operate at flowrates continuously resulting from a velocity above 35 m /s.
Flow capacities for superheated steam
In general terms, the flow capacity for the transducer is calculated using the
following equation:-
Q =
AV
Sv
x 3600
Where :- Q = Capacity in kg / h
A = Pipe cross sectional area in m²
V = Flow velocity in m / s
Sv = Specific volume in m³ /kg
Approximate dimensions and weights (mm, kg).
M111 series transducer
PN BS10 ANSI ANSI JIS
25 H 150 300 20
Size A A A A A C D E F Weight
DN40 176 175 175 181 176 180 100 76 28 9.5
DN50 180 178 178 184 176 180 100 76 28 10.5
DN80 240 236 240 249 236 220 152 76 76 25.0
DN100 260 263 260 276 260 220 152 76 76 34.5
E
EL2600 pressure transmitter
EL2600
A B C D E Weight
73 50 36 13 30 0.1
U - syphon and isolating valve
F G H J K L M Weight
297 160 70 170 145 69 25 0.5
C
D
C D A
A
E
B
K
M
F
G
L
H
J
F
Turndown of the transducer is defined as the maximum flow divided by the
minimum flow: using the maximum figures from the above table, the turndown is
40:1 throughout the size and pressure range. However, based on the
recommended maximum velocity of 35 m/s, the turndown available will vary
from 12:1 at 1 bar g up to 33:1 at 17 bar g. The average continuous turndown of
the flowmeter is therefore 25:1.
The saturated steam flow capacities in the above table are calculated using this
equation. Superheated steam flow capacities can be calculated in the same way.
Example: What is the capacity of a DN80 transducer on superheated steam at
5 bar g and 200°C.
Assume maximum velocity = 35 m / s Sv = 0.4252 m³ / kg.
Q = 3.14 x 0.08 x 0.08 x 35 x 3600 = 1 489 kg / h
4 x 0.4252
M322 signal conditioning unit
A B C D E F G H I Weight
250 175 75 198 232 27 40 85 130 0.8
G
H I
B
A
F
M210G series flow computer
Wall mounting
A B C D E F G H J K Weight
185 138 170 50 130 170 100 20 92 52 1.9
Panel mounting
A B C D E F Weight
192 144 156 140 186 40 1.7
E
B
B
A
A
F
C
C
H
C
D
E
J
K
K J
D
F
E
D
E
7

M111 series transducer
Sizes available: DN40, 50, 80, 100
Flanges M111 BS 4504 PN25
BS 10, Table H
JIS 10, JIS 20
ANSI B16.5 Class 150 & 300
M115 BS 4504 PN25
BS 10 Table H
JIS 10, JIS 20
ANSI B16.5 Class 150 & 300
Body materials M111-SG Iron DIN 1693 GGG40
M115-Steel DIN 17245 GSC2
Internal materials - mostly stainless steel
Torsion spring material - nickel cobalt alloy
Gaskets - exfoliated graphite (EFG)
Principle of operation - spring loaded variable area
Flow medium - saturated or superheated steam
Flow capacities - see tables
Maximum operating temperature - 230°C
Maximum operating pressure - 17 bar g
Minimum operating pressure - 1 bar g
Dimensions and weights - see table on page 7
Turndown - 40:1 intermittent, 25:1 continuous
Accuracy a) ± 1 % FSD at 50 % of flow, b) ± 2 % of actual flow
Installation - straight pipe lengths: 6 D upstream, 3 D downstream
(D = normal pipe diameter)
Mounting - horizontal, vertical (flow down) acceptable
M322 signal conditioning unit
The M322 signal conditioning unit accepts temperature and flow signals
from the M111 transducer as well as a 4 - 20 mA analogue pressure
signal from an EL2600 pressure transmitter. These signals are
converted into digital form for onward transmission to the M210G flow
computer which can be located up to 300 m away.
Materials of construction of enclosure - polycarbonate
Dimensions and weights - see table on page 7
Enclosure rating: IP65 (when fitted with suitable cable glands)
Type of mounting: Wall mounting using brackets supplied
Maximum operating temperature: 65°C
Supply voltage - 24 Vdc (from M210G computer)
Channel Input Output
Port 1 Analogue input from Frequency signal
M111 transducer (150 - 1500 Hz) which
proportional to plate is proportional to flow
deflection angle through the M111
(using RVDT) i.e.: flow transducer.
Port 2 Analogue input from Frequency signal
(temperature) Pt100 temperature (150 - 1500 Hz) which
sensor incorporated is proportional to
into M111 transducer measured temperature
Port 3 4 - 20 mA from EL2600 Frequency signal
(pressure) series pressure (150 - 1500 Hz) which
transmitter Max. loop is proportional to
impedance = 150 ohms
Open circuit
voltage = 15 volts
measured pressure
EL2600 pressure transmitter
NB. This is only required for superheated steam applications
Options available for use 0 - 1.6 bar g
with Spiraflo 0 - 2.5 bar g
0 - 4.0 bar g
0 - 6.0 bar g
0 - 10.0 bar g
0 - 16.0 bar g
0 - 25.0 bar g
'U' Syphon assembly
Process connection
Mount the EL2600 via a ¼" BSPP connection into the 'U' syphon
assembly and mount the 'U' syphon assembly via a ¼" BSPP connection
directly into the pipework.
Full installation details are supplied with the EL2600.
Maximum pressure
EL2600 - The rated pressures can be exceeded to the following limits
without degrading performance: 3 bar for 1.6 bar g range.
3 times FS (Full Scale) for ranges 2.5 to 25 bar g.
'U' syphon - the 'U' syphon is pressure rated for use with the pressure
transmitters listed above.
Burst pressure
EL2600 only - 50 bar for ranges 0 to 25 bar g.
Maximum temperature
With 'U' syphon - up to 450°C maximum.
Enclosure rating
IP65 to BS 5490 (IEC 529).
Accuracy
0.5 % FSD (including hysteresis, repeatability and thermal error).
Output
2 wire 4 - 20 mA current loop.
Supply - 24 Vdc standard (11 to 33 Vdc operable).
Maximum loop resistance 650 W at 24 Vdc.
Connection via 4 pole plastic connector.
Materials of construction
EL2600 - wetted parts stainless steel plus stainless steel body with
moulded plastic head and connector assembly. 'U' syphon assembly
zinc plated carbon steel tube (BS 1706) with plated carbon steel valve
colour passivated to DEF 130.
Dimensions and weights
See table on page 7.
M210G series flow computer
Function - carry out all signal processing and provide local display of
flow, total, pressure, time and date.
Units of display - metric or imperial. Flow parameters can be
displayed in mass or energy units.
Full density compensation inbuilt.
Customer programmable for steam quality correction.
4 batching timers with peak flow capture.
1 x 8 day repeating timer.
High / low flowrate alarm.
High / low pressure alarm.
High / low temperature alarm.
Battery back-up for clock and flow data.
Access security code protected.
Programmable 4 - 20 mA analogue output for flowrate (kg / h).
Programmable pulse output for total flow kg.
RS232C interface.
Can be located up to 300 m from point of flow measurement.
Supply voltage 110, 220 or 24 Vac (50 / 60 Hz).
Power consumption - less than 15 W.
Enclosure - light / dark grey polycarbonate.
Mounting - wall or panel mount.
Rating IP65 (with suitable cable glands) - NOT panel mount
Maximum ambient temperature: 50°C.
Some of the products shown may not be available in certain markets.
Spirax-Sarco Limited, Charlton House,
Cheltenham, Gloucestershire, GL53 8ER UK.
Tel: +44 (0)1242 521361 Fax: +44 (0)1242 573342
E-mail: enq@spiraxuk.attmail.com
Internet: www.spirax-sarco.com
© Copyright 1996 Spirax Sarco is a registered trademark of Spirax-Sarco Limited
SB-P330-01 MI Issue 4
SFLO