Rosemount 498CL pH-Independent Free Chlorine Sensor Quick Start Guide

Rosemount™ 498CL

pH-Independent Free Chlorine Sensor

Quick Start Guide

LIQ-QSG-498CL, Rev M

July 2017

Contents

Contents

Chapter 1 Plan ..................................................................................................................................1

1.1 Unpacking and inspection .............................................................................................................. 1

1.2 Specifications .................................................................................................................................1

Chapter 2 Install ...............................................................................................................................3

Chapter 3 Wire .................................................................................................................................5

Chapter 4 Maintenance .................................................................................................................... 7

4.1 Cleaning the membrane .................................................................................................................7

4.2 Replacing the electrolyte slurry and membrane ............................................................................. 7

4.3 Storage .......................................................................................................................................... 9

4.4 Rejuvenating a sensor following improper storage ......................................................................... 9

Chapter 5 Accessories .................................................................................................................... 11

Quick Start Guide i

Contents

ii Rosemount 498CL

1 Plan

1.1 Unpacking and inspection

1. Inspect the shipping container. If it is damaged, contact the shipper immediately for
instructions.

2. Save the box.

3. If there is no apparent damage, unpack the container. Be sure all items shown on the
packing list are present. If items are missing, notify Rosemount immediately.

1.2 Specifications

Sensor specificationsTable 1-1:

Physical characteristics Specifications

Linear range 0 to 20 ppm (mg/L) as Cl2. For higher ranges, consult the fac-

tory.

Pressure Sample must drain to open atmosphere. No back pressure

allowed.

Temperature (operating) 0 to 50 °C (32 to 122 °F)

Wetted materials PVC, polyethersulfone, polyester, Viton

stainless steel.

Cathode Gold mesh

Accuracy Accuracy depends on the accuracy of the chemical test used

to calibrate the sensor.

Linearity between 0 and 20 ppm 1% (per IEC 60746)

Linearity between 0 and 2 ppm ±0.05 ppm following calibration at about 2 ppm

Sensitivity to pH Between 6.5 and 10 sensor signal changes <4% per unit

change in pH. Below pH 6.5, the change is < 1% per unit
change in pH.

Sample conductivity > 10 µS/cm

Interferences Monochloramine, dichloramine, and permanganate

Response time < 2 minutes to 90% of final value following step change at

1.2 gal/hr (75 mL/min) and 25 °C (77 °F)

Electrolyte life 3 months (approx.)

Cable length (standard integral cable) 25 ft (7.6 m)

Cable length (maximum) 300 ft (91 m)

Sample flow 1.2 gal/hr (75 mL/min). Changing flow from 0.5 to 2.5 gph

(30 to 160 mL/min) increases the sensor signal by about
30%. Increasing flow increases pH dependence.

(1)

, silicone, and 316

Plan

Quick Start Guide 1

Plan

Sensor specifications (continued)Table 1-1:

Physical characteristics Specifications

Process connections Sensor must be used in flow cell PN 24091-01

Weight/shipping weight

(2)

Sensor with integral cable: 2 lb/3 lb (1.0 kg/1.5 kg)

Sensor with VP connector: 1 lb/2 lb (0.5 kg/1.0 kg)

(1) Viton is a registered trademark of EI duPont de Nemours.
(2) Weights and shipping weights are rounded up to the nearest whole pound or 0.5 kg.

Flow cell specificationsTable 1-2:

Part number

Wetted materials Polycarbonate, polyester, 316 stainless steel, and silicone

Maximm inlet pressure 65 psig (549 kPa abs)

Process connections 1/4 in. OD tubing compression fitting or 1/4 in. FNPT

(1) Sold separately

(1)

24091-01 (low flow cell with bubble sweeping nozzle)

CAUTION!

SENSOR/PROCESS APPLICATION COMPATIBILITY

The wetted sensor materials may not be compatible with process composition and operating
conditions. Application compatibility is entirely the responsiblity of the user.

2 Rosemount 498CL

2 Install

Complete the following steps to install the sensor in the low flow cell.
The sensor leaves the factory with a shipping membrane in place.

CAUTION!

EQUIPMENT DAMAGE

Do not remove the shipping membrane until you are ready to put the sensor in service.

Procedure

1. Remove the red protective cap from the sensor.

2. Holding the membrane end pointing up (cable end pointing down), unscrew the
retainer cap and remove the shipping membrane.

See Figure 2-1. It is not necessary to remove the O-ring. Save the shipping
membrane. It should be reinstalled when the sensor is not in use.

Install

Rosemount 498CL SensorFigure 2-1:

3. Still holding the membrane end pointing up, install the chlorine membrane.

The chlorine membrane is in the plastic bag attached to the sensor.

4. Screw the retainer back in place.

5.

Place the sensor in the flow cell and start the flow.

CAUTION!

EQUIPMENT DAMAGE

Do not store or operate the sensor for more than about 45 minutes in a non-flowing
sample.

The sensor must drain to open atmosphere without back pressure. Do not leave the
sensor in the air.

Quick Start Guide 3

Install

InstallationFigure 2-2:

The plastic adapter shipped with the flow cell is not used.

Keep sample flow constant and between 1 and 2 gph (60 to 120 mL/min).

4 Rosemount 498CL

3 Wire

NOTICE

For additional wiring information on this product, including sensor combinations not shown
here, please refer to the Liquid Transmitter Wiring Diagrams.

Wire

Figure 3-1:

Rosemount 498CL Sensor Wiring to Rosemount 1056 and 56
Transmitters

Quick Start Guide 5

Wire

Figure 3-2:

Pin out Diagram for Rosemout 498CL-01-VP Sensor (Top View of
Connector End of Sensor)

6 Rosemount 498CL

4 Maintenance

The sensor requires routine maintenance which includes cleaning the membrane as well as
periodically replacing the membrane and fill slurry. The fill slurry and membrane should be
replaced at approximately three-month intervals. The frequency of cleaning can be
determined only by experience.

4.1 Cleaning the membrane

Keep the membrane clean and free from dirt and algae. Clean the membrane with water
sprayed from a wash bottle.

CAUTION!

EQUIPMENT DAMAGE

Maintenance

Do not use tissues to clean the membrane. Touching the membrane may bend the cathode and
permanently damage the sensor.

4.2 Replacing the electrolyte slurry and membrane

Complete the following steps to replace the electrolyte slurry and membrane in the
sensor.

WARNING!

HARMFUL SUBSTANCE
Fill solution and solid may cause irritation. Avoid contact with skin and eyes. May be harmful if
swallowed. Read and follow manual.

Procedure

1. Unscrew the membrane retainer and remove the membrane assembly and O-ring.

See Figure 2-1.

2. Remove the fill plug.

3. Empty all remaining fill slurry from the sensor. Rinse with deionized water until there
is no significant amount of solid left in the sensor.

4. Place a few drops of water in the replacement membrane assembly and place it on
the mesh cathode.

Quick Start Guide 7

Maintenance

CAUTION!

EQUIPMENT DAMAGE

Do not touch the mesh cathode. Doing so may bend the mesh and permanently damage
the sensor.

5. Screw the membrane retainer into place.

6. Obtain one bottle of saturated succinic acid (PN 9210381, 40 mL) and one bottle of
succinic acid crystals (PN 9210379, 40 g) from the electrolyte kit. Remove the red
cap from the fill spout on each bottle.

7. Using a razor blade or scissors, cut the fill spout on the bottle of dry succinic acid just
below the line on the spout.

8. Hold the sensor with the membrane end pointed slightly upward. Insert the spout of
the bottle of succinic acid solution into the fill port. Squeeze the bottle until half of
the solution has been transferred to the electrolyte chamber.

9. Pour the solid succinic acid crystals into the fill port.

If the crystals accumulate in the fill hole, shake or tap the sensor to gently unblock
the port.

10. Use the remainder of the succinic acid solution to rinse crystals adhering to the
threads in the sensor. Keep adding solution until it overflows the fill port. Tap the
sensor a few times to be sure no air bubbles are trapped in the sensor.

11. Screw the fill plug back into place until it is flush with the body.

12. Hold the sensor with the membrane end pointing down and give it a few shakes as
though shaking down a fever thermometer.

Shaking helps clear bubbles that might have become trapped behind the mesh
cathode.

The sensor may require several hours operating at the polarizing voltage to equilibrate
after the electrolyte had been replaced.

NOTICE

Be sure to place the sensor in flowing, chlorinated water for equilibration.

8 Rosemount 498CL

4.3 Storage

The sensor must be stored in a flowing sample. Minimum sample flow is 0.5 gph
(30 mL/min). Do not let the membrane dry out. If the sensor cannot be stored in a flowing
sample:

1. Turn off power to the transmitter.

2. Remove the sensor from the flow cell.

3. Replace the membrane with the shipping membrane provided with the sensor.

For a replacement shipping membrane, order PN 23501-00.

4. To protect the sensor from physical damage, store it in the dry flow cell.

4.4 Rejuvenating a sensor following improper storage

If the sensor is stored in a stagnant sample for more than a day or two, it can become
contaminated with copper. Corrosion of the external copper electrode produces copper
ions, which diffuse through the membrane into the sensor. If the sensor was powered up
during storage, copper will plate out on the cathode. If the sensor was not powered up, the
copper will start plating out as soon as the polarizing voltage is applied. Once copper has
coated the cathode, the sensor zero current will become very high, and the sensor will be
unusable until the cathode has been cleaned.

1. If the sensor was not powered up during storage, do not apply power. Complete the

following steps:

Maintenance

a. Empty the fill slurry and thoroughly rinse the sensor with deionized water.

b. Refill the sensor with fresh fill slurry.

c. Let the sensor run in flowing chlorinated water overnight.

d. Zero and calibrate the sensor.

See the transmitter instruction manual for details. The zero current should be
less than about 100 nA.

2. If the sensor was powered up during storage, the cathode is probably coated with

metallic copper. Complete the following steps:

a. Disconnect the sensor from the transmitter.

b. Remove the membrane and clean out the fill slurry.

c. Immerse the mesh cathode in 10% nitric acid solution (10 mL of concentrated

nitric acid in 90 mL of water) for about 5 minutes.

d. Rinse thoroughly with deionized water.

e. Refill the sensor with fresh slurry and install a new membrane.

f. Let the sensor run overnight in flowing chlorinated water.

g. Zero and calibrate the sensor.

Quick Start Guide 9

Maintenance

The zero current should be less than about 100 nA.

10 Rosemount 498CL

5 Accessories

Rosemount 498CL pH-Independent Free Chlorine Sensor accessoriesTable 5-1:

Part number Description

24150-01 Variopol, 6.0 interconnecting cable, 10 ft (3 m)

24150-02 Variopol 6.0 interconnecting cable, 50 ft (15 m)

24091-01 Cell, low flow, 1/4 in. inlet and outlet, with bubble shedding nozzle

33970-00 Fill plug

33521-03 Membrane retainer cap

23501-10 pH-independent free chlorine membrane assembly, includes one

23502-10 pH-independent free chlorine membrane assembly, includes three

24146-00 pH-independent free chlorine sensor electrolyte kit, includes three

Accessories

membrane assembly and one O-ring

membrane assemblies and three O-rings

bottles of saturated succinic acid solution and three bottles of suc­cinic acid crystals

Quick Start Guide 11

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LIQ-QSG-498CL

Rev M

2017

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