WTW FCML 412 N / FCML 412 M12 Operating Manual

1 Overview

The FCML 412 chlorine sensors are membrane-covered, amperometric sensors for the determination of free chlorine.

1.1 Structure

Figure 1-1: Structure of FCML 412 M12. The sensor consists of: 1. Connection (PG7 gland for FCML 412 N, Flange plug for adapter ADA CL/IDS for FCML 412 M12); 2. Shaft; 3. Auxiliary electrode; 4. Electrode finger; 5. O-ring 14 x 1.8; 6. Reference electrode; 7. Measuring electrode; 8. Valve opening (behind hose ring); 9. Membrane cap; 10. Membrane holder; 11. Membrane disk.

With its special design (potentiostatic three electrode system), the sensor measures all the free chlorine present (sum of gaseous dissolved chlorine, hypochloric acid and hypochlorite) and the chlorine that is bonded to isocyanuric acid. The sensor has a strongly reduced pH dependence. The sensor has integrated measuring electronics and delivers a measuring signal that is already temperature compensated. It does not require a zero point adjustment. The routine calibration is carried out through comparison with the photometric DPD method according to DIN 38408.

1.2 Electrical connection

FCML 412 N: The FCML 412 N sensor is connected with the measuring transmitter (e.g. MULTILINE 1000) via a two-wire connection. The wires are used for the power supply of the measuring transmitter and for the transmission of measurement signals (4 - 20 mA current signal).

FCML 412 M12: The FCML 412 M12 sensor has an M12 flange plug for connection to the adapter ADA CL/IDS (see section 5.4 MAINTENANCE EQUIPMENT AND REPLACEMENT PARTS). The adapter ADA CL/IDS connects the sensor to the MIQ/IDS module of the IQ Sensor Net. Power supply and transmission of the measuring signal are carried out via the adapter ADA CL/IDS.

[info-symbol] Except for the different electrical connection, all FCML 412 sensors are identical.

2 Safety

2.1 Safety information

2.1.1 Safety information in the operating manual

This operating manual provides important information on the safe operation of the product. Read this operating manual thoroughly and make yourself familiar with the product before putting it into operation or working with it. The operating manual must be kept in the vicinity of the meter so you can always find the information you need.

Important safety instructions are highlighted in this operating manual. They are indicated by the warning symbol [warning-triangle] in the left column. The signal word (e.g. "CAUTION") indicates the level of danger:

WARNING: Indicates a possibly dangerous situation that can lead to serious (irreversible) injury or death if the safety instruction is not followed.
CAUTION: Indicates a possibly dangerous situation that can lead to slight (reversible) injury if the safety instruction is not followed.
NOTE: Indicates a situation where goods might be damaged if the actions mentioned are not taken.

2.1.2 Safety signs on the product

Note all labels, information signs and safety symbols on the product. A warning symbol [warning-triangle] without text refers to safety information in this operating manual.

2.1.3 Further documents providing safety information

The following documents provide additional information, which you should observe for your safety when working with the measuring system:

Operating manuals of other components of the FCML 412 N, FCML 412 system (power packs, controller, accessories)
Safety datasheets of calibration and maintenance equipment (e.g. cleaning solutions).

2.2 Safe operation

2.2.1 Authorized use

The authorized use of the FCML 412 N, FCML 412 M12 is the stationary measurement of chlorine in drinking water, swimming pool water and process water. Only the operation and running of the product according to the instructions and technical specifications given in this operating manual is authorized (see chapter 6 TECHNICAL DATA). Any other use is considered unauthorized.

2.2.2 Requirements for safe operation

Note the following points for safe operation:

The product may only be operated according to the authorized use specified above.
The product may only be supplied with power by the energy sources mentioned in this operating manual.
The product may only be operated under the environmental conditions mentioned in this operating manual.
The product may not be opened.

2.2.3 Unauthorized use

The product must not be put into operation if:

it is visibly damaged (e.g. after being transported)
it was stored under adverse conditions for a lengthy period of time (storing conditions, see chapter 6 TECHNICAL DATA).

3 Commissioning

3.1 Scope of delivery

Sensor FCML 412 with membrane cap M48 or Sensor FCML 412 N or Sensor FCML 412 M12
Dropping bottle with 100 ml electrolyte solution ELY-FCML 412 N
Polishing strip
Operating manual

3.2 Filling the membrane cap with electrolyte solution

NOTE: Risk of damage for the sensor in the case of improper handling. Do not touch the electrode finger with your fingers. Do not apply pressure to the membrane disk. Do not unscrew the membrane holder.

When it is delivered, the membrane cap is not filled with electrolyte and is loosely screwed onto the shaft. In order to put the sensor into operation, fill the membrane head as follows:

Step 1: Unscrew the membrane cap from the electrode shaft. Place the membrane cap on a clean (non-absorbent) surface.

Step 2: Cut off the tip of the dropping bottle until the opening in the tip is visible, then fill the membrane cap completely with electrolyte solution making sure it is bubble free.

Step 3: Lift off the hose ring of the membrane cap, which closes the valve opening, from the side so that the valve opening is exposed. Hold the sensor shaft in an upright position and place it on the filled membrane cap. Some of the electrolyte solution will leak over the upper edge of the membrane cap while doing this. Then screw the electrode shaft into the membrane cap. For this, first turn the electrode shaft anti-clockwise until the thread catches; then slowly screw in the electrode shaft as far as it will go until no gap can be seen between the sensor shaft and membrane cap.

NOTE: Overpressure in the membrane cap can destroy the membrane disk. Therefore, make sure the valve opening is not inadvertently closed by your fingers. Excess electrolyte solution must be able to escape freely at any time. Screw slowly so that no back pressure can develop.

Step 4: Using a blunt object, slide the hose ring over the valve opening and insert it evenly in the groove.

Step 5: Rinse off any electrolyte solution adhering on the outside.

3.3 Electrical connection

How to connect the FCML 412 N sensor to the measuring transmitter or the MIQ/IDS module is described in the operating manual of the measuring transmitter. How to connect the sensor FCML 412 M12 to the MIQ/IDS module is explained in the operating manual of the module MIQ/IDS.

3.4 Installation in the flow through vessel D-CL

The flow-through vessel D-CL is optimized for the FCML 412 N chlorine sensors.

[info-symbol] The position in the flow through vessel has a considerable effect on the approach flow and, hence, the measuring function of the sensor. Therefore carefully position the sensor as described below.

Proceed as follows to install the sensor:

Slide the black O-ring and then the PVC sliding ring over the sensor.
Unscrew the screw connection of the flow-through vessel.
Insert the sensor into the flow-through vessel without the cable connected.
Slide the screw connection of the flow-through vessel over the sensor.
Screw the screw connection of the flow-through vessel onto the flow-through vessel.
Reconnect the sensor connection cable to the sensor.

NOTE: When commissioning, always open the feed slowly. A strong shock pressure can destroy the membrane.

3.5 Installation in the flow through vessel D 19

The flow-through vessel D 19 is optimized for the FCML 412 M12 chlorine sensor.

The FCML 412 M12 has a marking on its shaft for optimum installation in the flow-through vessel D 19.

Proceed as follows to install the sensor:

Connect the ADA CL/IDS adapter to the M12 flange plug and screw it tight.
Push the coupling ring of the flow-through vessel loosely onto the sensor.
Insert the sensor with the coupling ring in the flow-through vessel.
Align the marking (1) on the sensor with the top edge (2) of the coupling ring.
Tighten the coupling ring by hand.
Tighten the coupling ring approx. a quarter turn further with the M32 assembly wrench. Make sure the sensor is firmly attached. Otherwise, it can be pressed out of the flow through vessel by pressure.

NOTE: When commissioning, always open the feed slowly. A strong shock pressure can destroy the membrane.

The assembly wrench, size M32, is available as an accessory (see section 5.4 MAINTENANCE EQUIPMENT AND REPLACEMENT PARTS).

4 Measurement / Operation

4.1 Run-in period

Polarization: Each time the sensor has been refilled it must be polarized. To do this, immerse the connected and voltage-supplied sensor in a well-stirred chlorine solution with at least 5 mg/l chlorine for an hour. Then put the sensor into use (measuring position). The sensor can be calibrated after a stabilizing time of approx. 20 minutes. After approx. one day, a post-calibration should be performed.

[info-symbol] The sensor filled with electrolyte must not become dry and has to be permanently supplied with electrical voltage. Otherwise the characteristics of the membrane cap, electrode finger and electrolyte will be changed (sometimes irreparably). The sensor may only be stored in an unfilled condition (see also section 5.3 STORAGE).

4.2 Check of the sensor / analysis

Calibration with the DPD-1 method: The chlorine sensor has a linear characteristic curve. Calibration of the chlorine sensor is carried out as a single-point calibration. The calibration value (nominal value) is usually determined photometrically. A common procedure for this is the DPD method for free chlorine. The photometer and test sets for this are described in the WTW catalog or on the Internet.

How to carry out the calibration is described in detail in the operating manual of the measuring transmitter.

4.3 Chlorine measurement with the FCML 412

The FCML 412 chlorine sensor measures inorganic chlorine compounds dissolved in water. The measured values determined with the photometer according to the DPD-1 method (free chlorine) are directly comparable to the values determined by the sensor.

5 Maintenance, cleaning, storage

5.1 Cleaning the measurement electrode / exchanging the membrane cap and electrolyte

We recommend to disconnect the sensor from the measuring transmitter before starting any maintenance work. If calibration is not possible due to readings that are too low, the measurement electrode has to be cleaned with the enclosed polishing strip. Proceed as follows:

Step 1: Using a blunt object, lift the hose ring out of the guiding groove and push it to the side so that the valve opening is uncovered.

NOTE: Negative pressure in the membrane cap can destroy the membrane disk. Therefore, make sure the valve opening is not inadvertently closed by your fingers while unscrewing the membrane cap.

Step 2: Unscrew the membrane cap from the sensor shaft and pour away the electrolyte solution.

Step 3: Rinse the electrode finger and membrane cap with clean water and dab them dry with a clean paper towel.

Step 4: Clean the measurement electrode with the polishing strip. To do so, place the polishing strip on a paper towel and hold it by a corner. Then hold the electrode finger vertically with the tip down and run the tip over the polishing strip two or three times.

NOTE: The brown coating on the shell (reference electrode) of the electrode finger must not be polished off. This would destroy the sensor!

Step 5: Fill the membrane cap with fresh electrolyte solution as described in section 3.2, screw it on the sensor shaft and make the sensor ready for measurement.

[info-symbol] After exchanging the electrolyte solution and/or membrane cap the sensor has to be repolarized (see section 4.1 RUN-IN PERIOD). If calibration is still not possible after cleaning the measurement electrode, change the membrane cap.

5.2 Cleaning

Removing lime deposits on the membrane cap

Remove lime deposits on the membrane cap as follows:

Unscrew the membrane cap from the sensor shaft and pour away the electrolyte solution (see section 5.1).
Put the membrane cap into 10 % acetic acid for several hours.
Then thoroughly rinse the membrane cap with clean water.
Fill the membrane cap with fresh electrolyte solution as described in section 3.2, screw it on the sensor shaft and make the sensor ready for measurement.

5.3 Storage

NOTE: The sensor may only be stored in an unfilled condition.

Proceed as follows to store the sensor:

Unscrew the membrane cap from the sensor shaft and pour away the electrolyte solution (see section 5.1).
Thoroughly rinse the membrane cap and electrode finger with clean water and dry them dust free.
Loosely screw the dry membrane cap on the sensor shaft. The membrane disk must not touch the electrode finger.

Recommissioning: For recommissioning, clean the electrode tip with the polishing strip and use a new membrane cap (see section 5.1). The membrane cap can be put into 10 % acetic acid for some hours to remove any lime deposits (see section 5.2).

5.4 Maintenance equipment and replacement parts

Description	Model	Order no.
Accessory kit for chlorine sensor FCML 412, including: 1x membrane cap M48 100 ml electrolyte solution ELY-FCML 412 N Polishing strip	ZBK-FCML 412 N	205246
Adapter for connecting the sensor FCML 412 M12 to an IDS interface	ADA CL/IDS	108155
Flow-through vessel D 19 for chlorine sensor FCML 412 M12	D 19	401991
Flow-through vessel D-CL for chlorine sensor FCML 412 N	D-CL	201150Y
Accessory for the flow-through vessel D 19 1x assembly wrench M32	R-SET P	904030

6 Technical data

6.1 Measuring characteristics

Measuring principle: Membrane-covered, amperometric sensor with potentiostatic three-electrode system and integrated measuring electronics


Measuring range	FCML 412 M12-20: 0.01 ... 20.00 mg/l Cl₂ FCML 412 M12-2: 0.01 ... 2.00 mg/l Cl₂ FCML 412 N: 0.01 ... 2.00 mg/l Cl₂
Response time	t90 (90% of the final value display after) approx. 120 s
pH dependency	Approx. 10 % slope loss per increasing pH unit
Temperature compensation-	Automatic, by means of integrated temperature sensor
Polarization time	Approx. 2 hours on commissioning or after exchanging the electrolyte
Calibration procedure	Single-point calibration, e.g. with photometric measurement according to the DPD-1 method as a reference

6.2 Application characteristics


Temperature range	0 ... 45 °C (32 ... 113 °F) The measurement medium must be free of ice crystals.
pH application range	pH 4... 9
Max. admissible overpressure	D-CL: 3×10⁵ Pa (3.0 bar), D 19: 3×10⁵ Pa (3.0 bar), Pressureless operation in the flow through vessel is recommended.
Working life of the membrane cap	Typically 1 year (depending on measuring medium)
Approach flow	Recommended minimum flow rate in the flow through vessel: D-CL: > 30 l/h D 19: > 15 l/h
Typical application range	Drinking water, swimming pool water and mains water in the flow through vessel

6.3 General data

Dimensions:

FCML 412 N: 200 mm height, 25 mm diameter.

FCML 412 M12: 175 mm height, 37 mm diameter at connector, 25 mm diameter at sensor tip.


Membrane cap	M48
Membrane type	Microporous, hydrophilic membrane
Electrolyte	ELY-FCML 412 N (from ZBK-FCML 412 N)
Material	Shaft: PVC Membrane cap: PVC Membrane holder, auxiliary electrode: Stainless steel Working electrode: Gold Reference electrode: Ag/AgCl Hose ring: Silicone Cable screw joint: Polyamide

6.4 Electrical data

FCML 412 N:

2-wire connection via permanently mounted cable AK-CL 298
12 ... 30 V DC power supply by the measuring transmitter
Output signal 4 ... 20 mA

FCML 412 M12:

5-pin M12 flange connector: for the ADA CL/IDS adapter by means of screw/plug connection
Power supply: +/- 5 ... 15 V DC through the MIQ/IDS module
Nominal slope: -1000 mV/ppm

7 Disposal

Handle and dispose of all waste in compliance with local laws and regulations.

EU only: Correct disposal of this product — WEEE Directive on waste electrical and electronic equipment

This marking [wEEE-symbol] on the product, accessories or literature indicates that the product should not be disposed of with other waste at the end of its working life.

To prevent possible harm to the environment or human health from uncontrolled waste disposal, please separate these items from other types of waste and recycle them responsibly to promote the sustainable reuse of material resources.

Waste from electrical and electronic equipment can be returned to the producer or distributor.

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