Emerson Rosemount 226 User manual

Reference Manual
00809-0100-3226, Rev AA
August 2018
Rosemount™ 226
Toroidal Conductivity Sensors

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Safety Information
WARNING
HIGH PRESSURE AND TEMPERATURE HAZARD
Before removing the senosr, reduce the process pressure to 0 psig and cool down the process temperature.
Failure to reduce the pressure and temperature may cause serious injury to personnel.
CAUTION
EQUIPMENT DAMAGE
The wetted sensor materials may not be compatible with process composition and operating conditions. Application
compatibility is entirely your responsibility.
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Contents
Chapter 1 Description and specifications ...................................................................................... 7
1.1 Overview ......................................................................................................................................... 7
1.2 Specifications .................................................................................................................................. 7
1.3 Unpacking and inspection ............................................................................................................... 7
1.4 Ordering information ...................................................................................................................... 8
Chapter 2 Install ........................................................................................................................... 9
2.1 Installing the Sensor ........................................................................................................................ 9
2.2 Wiring the Sensor .......................................................................................................................... 12
Chapter 3 Calibration .................................................................................................................. 17
3.1 Sensor Calibration ......................................................................................................................... 17
3.2 Calibrating against a Standard Solution ......................................................................................... 17
3.3 Calibrating against a Referee – In Process ...................................................................................... 19
3.4 Calibrating against a Referee - Grab Sample .................................................................................. 21
Chapter 4 Troubleshooting ......................................................................................................... 23
4.1 Maintaining the sensor .................................................................................................................. 23
4.2 Troubleshooting ........................................................................................................................... 23
Chapter 5 Accessories ................................................................................................................. 27
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Contents Reference Manual
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1 Description and specifications
1.1 Overview
The Rosemount 226 sensor is a toroidal (inductive) conductivity sensor. These sensors
work well for measuring in highly conductive liquids up to 2 S/cm (2,000,000 μS/cm).
Unlike metal electrode based conductivity sensors, toroidal conductivity sensors, like the
Rosemount 226, are resistant to fouling, coating, and chemical attack.
Sensors are molded with highly corrosion-resistant glass-filled PEEK
(polyetheretherketone). The sensors include an integral Pt-100 RTD for temperature
compensation. With a large bore hole opening, the Rosemount 226 greatly resists
plugging when used in liquids containing high amounts of suspended solids. PEEK is not
recommended for greater than 50% concentrations (at 77 °F (25 °C) ) of H2SO4, HNO3,
and H3PO4. PEEK is not recommended for use with HF at all.
1.2 Specifications
Table 1-1: Rosemount 226 Toroidal Conductivity Sensor Specifications
Description Material and Units
Conductivity Range Refer to transmitter product data sheet
Wetted Materials Glass-filled PEEK, EPDM Gasket
Operating Temperature 32 to 248 °F (0 to 120 °C)
Maximum Pressure 295 psig (2135 kPa [abs])
Cable Length 20 ft. (6.1 m)
Maximum Cable Length Up to 200 ft. maximum
Process Connections 7/8 in. 9 UNC threads for flange mounting and 1
in. MNPT (with -80 option); see dimensional
drawings for more details.
Weight/Shipping Weight 2 lbs/3 lbs (1.0 kg/1.5 kg)
1.3 Unpacking and inspection
Complete the following steps when you unpack your instrument.
Procedure
1. Inspect the shipping container. If there is damage, contact the shipper immediately
for instructions.
2. If there is no apparent damage, unpack the container and remove the sensor.
3. Ensure that all items shown on the packing list are present. If items are missing, If
items are missing, contact your local Customer Care representative
4. Save the shipping container and packaging.
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They can be used to return the sensor to the factory in case of damage.
1.4 Ordering information
Table 1-2: Rosemount 226 Toroidal Conductivity Sensor ordering information
Model Sensor type
226 Toroidal Conductivity Sensor
Materials of Construction
02 Glass-filled PEEK (1)
Transmitter Compatibility (2)
54 Standard Cable (3)
56 EMI/RFI Shielded Cable (4)
Mounting Kit
80 Submersion (5)
81 Insertion Through User-Supplied Flange (6)
82 No Kit Required (7)
Typical Model Number: 226-02-56-80
(1) The sensor is supplied with an EPDM gasket (a Viton gasket PN 33151-01 is also available; see
accessories).
(2) Cables may be extended using the remote junction box PN 23550-00 (sold separately) and
extension cables (see accessories).
(3) Recommended for use with Rosemount legacy transmitter models 1054 and 2054.
(4) Recommended for use with Rosemount transmitter models 54C, 54eC, 81T, 2081T, 3081T,
4081T, XMT, 56, 1056, 1066, 5081, and 56.
(5) Includes a 1-in. MNPT PEEK adapter
(6) Includes spacer and nut
(7) This option does not include any mounting kit and is for replacement sensors only.
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2 Install
2.1 Installing the Sensor
To ensure accurate readings, it is recommended the sensor be installed so that there is at
least 2.4 inches of clearance between the sensor and tank or pipe walls. If installed too
closely to the walls, an error in readings will be induced by wall effects. Wall effects arise
from the interaction between the current induced in the sample by the sensor and nearby
pipe or vessel walls.
As Figure 2-1 shows, the measured conductivity can either increase or decrease depending
on the wall material. This effect can be seen by watching the conductivity readings change
as the sensor is moved closer to the sides of the pipe, tank, or beaker.
Ensure that the sensor is completely submerged in the process liquid. Mounting the sensor
in a vertical pipe run with flow running from bottom to top is recommended. If the sensor
must be installed in a horizontal pipe run, mount the sensor in the 3 o’clock or 9 o’clock
position.
Figure 2-1: Measured conductivity as a function of clearance between sensor and
walls
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Figure 2-2: Rosemount 226 with 1 in. MNPT process connection mounting adapter
(-80 option) dimensional drawing
Figure 2-3: Rosemount 226 with 7/8 in. 9 UNC thread and insertion through flange
mounting adapter (-81 option) dimensional drawing
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2.1.1 Submersion Mounting
The sensor must be mounted in conduit or stand pipe to protect the back end from
process leakage. Use Teflon tape for a good seal.
2.1.2 Insertion Mounting
The sensor is designed to be mounted through any user-supplied flange. The user is
responsible for cutting a hole through the flange to fit the sensor. The flange may be
drilled and tapped for the sensor’s 7/8 in. 9 UNC thread. Alternatively, a simple 15/16 in.
(2.4 cm) drilled hole will accommodate the 7/8-in. 9 UNC thread.
2.1.3 Sensor Cable
CAUTION
ELECTRICAL HAZARD
Do not run sensor cable in same conduit as the AC power wiring or near heavy electrical
equipment.
Cables run in the same conduit with power wiring or near heavy electrical equipment may
cause measurement errors and damage the sensor.
CAUTION
MOISTURE DAMAGE
Sensor cables routed in conduit must be sealed or plugged with sealing compound.
Failure to properly seal the conduit may allow accumulated moisture in the transmitter
housing and damage the sensor and the transmitter.
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2.2 Wiring the Sensor
For additional wiring information on this product, including sensor combinations not
shown here, please refer to the Transmitter Wiring Diagrams.
Figure 2-4: Wire functions
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Figure 2-5: Wiring for Rosemount 226-54 and Rosemount 226-56 sensors to 1056 and
56 transmitters
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Figure 2-6: Wiring for Rosemount 226-54 and Rosemount 226-56 sensors to 1066
transmitter
Figure 2-7: Wiring for Rosemount 226-54 and Rosemount 226-56 sensors to 5081-T
transmitter
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Figure 2-8: Wiring sensors through a remote junction box
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3 Calibration
3.1 Sensor Calibration
The nominal cell constant of the Rosemount 226 sensor is 1.2/cm. The error in cell
constant is about ± 10%, so conductivity readings made using the nominal cell constant
will have an error of at least ± 10%.
Wall effects as shown in Figure 2-1 will likely make the error greater.
There are two basic ways to calibrate a toroidal sensor: against a standard solution or
against a referee meter and sensor. A referee meter and sensor is an instrument that has
been previously calibrated and is known to be accurate and reliable.
The referee instrument can be used to perform either an in-process or a grab sample
calibration. Regardless of the calibration method used, the connected transmitter
automatically calculates the cell constant once the known conductivity is entered.
For more detailed information on calibration methods, please refer to Application Data
Sheet (ADS 43-025).
3.2 Calibrating against a Standard Solution
Calibration against a standard solution requires removing the sensor from process piping.
This calibration method is practical only if wall effects are absent or if the sensor can be
calibrated in a container identical to the process piping. Ideally, the conductivity of the
standard used should be close to the middle of the range that the sensor will be used in.
Generally, toroidal conductivity sensors have good linearity and so standards greater than
5000 μS/cm at 25°C may also be used.
Prerequisites
CAUTION
Before removing the sensor, be absolutely certain that the process pressure is reduced to
0 psig and the process temperature is lowered to a safe level!
Immerse the rinsed sensor in the standard solution and adjust the transmitter reading to
match the conductivity of the standard. For an accurate calibration several precautions are
necessary:
Procedure
1. If wall effects are absent in the process installation, use a sufficiently large container
for calibration to ensure that wall effects are absent.
2. To check for wall effects, fill the container with solution and place the sensor in the
center submerged at least ¾ of the way up the stem.
3. Note the reading. Then move the sensor small distances from the center and note
the reading in each position.
The readings should not change.
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4. If wall effects are present, be sure the vessel used for calibration has exactly the
same dimensions as the process piping.
5. Also, ensure that the orientation of the sensor with respect to the piping is exactly
the same in the process and calibration vessels.
Figure 3-1: Calibration installation orientation
6. Turn off automatic temperature compensation in the transmitter. This eliminates
error in the cell constant.
7. Use a good quality calibrated thermometer to measure the temperature of the
standard solution.
The thermometer error should be less than ±0.1°C.
8. Allow adequate time for the solution and sensor to reach thermal equilibrium.
If the sensor is being calibrated in an open beaker, keep the thermometer far
enough away from the sensor so it does not introduce wall effects.
9. If the sensor is being calibrated in a pipe tee or similar vessel, it will probably be
impractical to place the thermometer in the standard solution.
10. Instead, put the thermometer in a beaker of water placed next to the calibration
vessel.
11. Let both come to thermal equilibrium with the ambient air before continuing
calibration.
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Figure 3-2: Measuring standard temperature
12. Make sure that the air bubbles are not adhering to the sensor.
An air bubble trapped in the toroid opening has a particularly severe effect on the
reading.
3.3 Calibrating against a Referee – In Process
This method involves connecting the process and referee sensors in series and allowing
the process liquid to flow through both sensors. The process sensor is calibrated by
adjusting the process analyzer reading to match the conductivity measured by the referee
instrument.
Prerequisites
For a successful calibration, several precautions are necessary:
Procedure
1. If possible, adjust the conductivity of the process liquid so that it is near the
midpoint of the operating range.
If this is not possible, adjust the conductivity so that it is at least 5000 μS/cm.
2. Orient the referee sensor so that air bubbles always have an easy escape path and
cannot get trapped.
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Figure 3-3: Calibration with a referee instrument example
3. Tap and hold the flow cell in different positions to allow bubbles to escape.
4. Turn off automatic temperature compensation in the transmitter.
This eliminates error in the cell constant.
5. Keep tubing runs between the sensors short and adjust the sample flow to as high a
rate as possible.
Short tubing runs and high flow ensure that the temperature of the liquid does not
change as it flows from one sensor to another.
6. Wait for readings to stabilize before starting the calibration.
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