Technical Information

Stamolys CA71CODcr
COD analyzer
Photometric analytical system for determining the chemical oxygen
demand following the DIN dichromate method

Application• Monitoring sewage treatment plant inlets and outlets• Monitoring of industrial wastewater discharges• Monitoring of industrial wastewaters
Your benefits• Thermal digestion acc. to DIN38409 H41 and GB 11914-89• Measuring ranges 5 to 200 mg/l O2 or 50 to 5000 mg/l O2• Mercury-free chloride elimination• Low reagent requirement• Variable digest times (from 10 to 180 min, in steps of oneminute)• High accuracy

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Function and system design
Measuring principle

After sample preparation, the sample pump of the analyzer pumps some of the filtrate into the combined
reactor. Chloride ions in the sample would distort (increase) the COD measured value since they would beoxidized to chlorine. Sulfuric acid is added to remove interfering chloride ions in the sample and the resultinghydrochloric acid is stripped from the sample.
The dichromate reagent subsequently dosed converts the organic load of the sample. With the aid of a silver
sulfate catalyst, dichromate oxidizes organic substances to carbon dioxide:
The inherent color of the dichromate reagent changes. The change is determined photometrically and reagent
consumption, and thus the COD, is calculated.
The COD dichromate method covers both biodegradable and nonbiodegradable organic substances, but also
some inorganic substances.

Chemical oxygen demand

As a sum parameter, the COD is a measure of the sum of all the substances present in the water which areoxidizable under certain conditions. It indicates the amount of oxygen (in mg/l) that would be needed tooxidize the substances if oxygen were the oxidizing agent.
The chemical oxygen demand can be used to quantify the organic load in wastewater. In addition, the COD
can also be used to describe the concentration of organic carbon compounds at sewage treatment plants (CODbalance).
The organic materials entering the environment cause a change in the oxygen balance of a body of water due
to the oxidation that takes place during their decomposition. In addition, the organic material has an effect on
the nutrition base of the body of water and this can result in a change in the ecological community. For thisreason, the COD is also an indicator of the quality of water and is used as a basis for calculating wastewater
levies.

Photometric determination

With the CA71COD-A, the decrease in the inherent color of the Cr(VI) reagent is determined photometrically.
The reagent consumption, and thus the COD, is calculated from this.
With the CA71COD-B, the increase in the inherent color of the resulting Cr(III) is determined and used foranalysis purposes.

Interferences

Certain inorganic compounds can be oxidized under reaction conditions and cause excess levels of COD:
• Bromide and iodide• Hydrogen peroxide and its adducts• Certain sulfur compounds, e.g. sulfite ions
• Nitrite ions
• Certain metal compounds, e.g. Fe(II) compounds
Volatile hydrophobic substances can escape analysis through vaporization.
Aromatic hydrocarbons and pyridines are not recorded.

Sample conditioning

Backwash filter (Stamoclean CAT221, optional) and agitated collecting vessel with levelmeasurement
A sample flow of 1 to 2.5 m3/h (4.4 to 11 gal/min) is permanently conveyed through the backwash filter bymeans of a sampling pump or compressed air or rinse water. The filtrate passes through the wedge wire sieve
and is then transported to the measuring device.
Clogging is minimized by the flow at the wedge wire sieve. Automatic backwashing results in a filter operatingtime of several weeks.
The automatic backwashing and a small compressor or compressed air resp. rinse water supply guarantee lowmaintenance and low-energy operation.
Sample pump with backwash function and agitated collecting vessel with level measurement
The sample is transported to the agitated collecting vessel. The backwash function avoids the choking of thesuction side.
Customer specific solution
Before analysis, the sample has to be conditioned, homogeneous and to be transported to an external or to thedelivered collecting vessel.

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Measuring system

Backwash filter
A complete measuring system comprises:• a CAT221 filter system• an agitated collecting vessel• a CA71COD analyzer• a sample pump or sample pressure line
• a compressor resp. compressed air supply

81267534a0013925

Complete measuring system

1234

Backwash filterCompressor or compressed air
Sampling pump or sample pressure line
Sample outlet

5678

Collecting vessel (optional)
Overflow
Analyzer
Sample line to the analyzer

Without filter
A complete measuring system comprises:• a sample pump with backwash function• an agitated collecting vessel• a CA71CODcr analyzer

a0016626-1

Complete measuring system

12
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Pump with backwash function
Sample line to the analyzer
Analyzer

456

Overflow
Agitated collecting vessel
Sample3

Stamolys CA71CODcr

Input
Measured variable

COD [mg/l O2]

Measuring rangeCA71COD-A
5 to 200 mg/l O2
CA71COD-B
50 to 5000 mg/l O2

Wavelength

CA71COD-A
465 nm and 625 nm
CA71COD-B
589 nmOutputOutput signal

0/4 to 20 mA
Modbus RS485 (optional)
Signal coding

EIA/TIA-485

Data transmission rate

9600 BaudGalvanic isolation

YesConnectors

Top-hat rail clamp

Bus termination-Signal on alarm

Contacts: 2 limit contacts (per channel), 1 system alarm contact

Loadmax. 300 

Load capacity

230 V AC max. 2 A

Data interface

RS232-C
Modbus RS485 (optional)

Data logger

1024 data pairs with date, time and measured value
100 data pairs with date, time and measured value for calibration factor determination (diagnostic tool)

Protocol specific data

Modbus RS485

4Protocol

RTU

Function codes

03 (Read holding registers)

Broadcast support for function codes-Output data

1 main measured value at address 40008 (2 bytes)

Data format

16 bits

Input data-

Supported features

Slave address, data format, check sum and baudrate can be configured using
Advantech ADAM Utility Software at re-boot with set init switch

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Power supply
Electrical connection!

CAUTION

Shown diagram ( å 1) is an example
The terminal assignment and cable colors can deviate from the actual assignment and colors!
► Only use the terminal assignment of the sticker in the device ( å 2) to connect your analyzer!

a0012456

Fig. 1:

Example of the connection sticker

Fig. 2:Analyzer from top (open version resp. folded out)

a0017149123
4Connection department sticker
Printed circuit board with terminal strip
Backside of the analyzer
Connection department sticker Modbus RS485 (optional)

Supply voltage

230 V AC, 50/60 HzPower consumption

ca. 210 VA

Current consumption

approx. 0.9 A

Fuses

1 x slow-blow 0.5 A for electronics
2 x semi-delay 0.2 A for photometer1 x slow-blow 0.1 A for motors
1 x slow-blow 1 A for heating and coolingEndress+Hauser

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Stamolys CA71CODcr

Performance characteristics
Digestion time

10 to 180 min, selectable

Maximum measured error

CA71COD-A< 110 mg/l O2: ± 11 mg/l O2> 110 mg/l O2: ± 10 %CA71COD-B< 500 mg/l O2: ± 50 mg/l O2> 500 mg/l O2: ± 10 %Measuring intervaltmes = 150 min (factory setting, shorter digestion times can be set)tmes = sample dosage + reagent dosage + chloride stripping + reagent dosage + digestion + measured value
calculation + sample discarding + measuring break + rinse time

Sample requirement

54 ml (1.82 fl.oz.) per measurement

Reagent requirement

250 ml (8.45 fl.oz.) of dichromate solution
4 l (1.06 US gal.) of H2SO4 for 60 days with a digestion time of 2 h

Calibration interval1)

0 to 720 h

Maintenance interval

1 week (typical)

Servicing requirement

15 minutes per week (typical)

Installation
Installation instructions

Installation on a vibration-free wall

Environment
Ambient temperature

10 to 35 ˚C (50 to 95 ˚F), avoid strong fluctuations

Humidity

below the condensation limit, installation in usual, clean rooms
outdoor installation only possible with protective devices (customer supplied)Ingress protection

IP 43

Process
Sample temperature

5 to 40 ˚C (40 to 100 ˚F)

Sample flow ratemin. 5 ml (0.17 fl.oz.) per min

Consistence of the sample

aqueous and homogenizedSample inlet

Unpressurized1)

6Standards have a limited durability due to biological activity

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Mechanical construction
Design, dimensions

a0015014

Dimensions

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Stamolys CA71CODcr

Collecting vessela0016672

Collecting vessel
12
3
4
5
6

Connection for level measurement
Ventilation
Sample supply to analyzer, connection
for hose with ID3.2mm(0.13")
Connecting cable of electric agitator
Sample supply, connection for hose withID3.2mm (0.13")
Sample overflow, connection for hosewith ID10mm (0.39")

a0016671

Dimensions: collecting vessel and base plate

Weightapprox. 32 kg (71 lbs)

Material

Housing:Front windows:
Endless hose:
Pump hose:
Valves:Connecting the sample line

Collecting vessel (at analyzer, with or without level measurement)
Connection
hose ID 3.2 mm (1/8 inch)

Glass-fibre reinforced carbon (GFR)
Polycarbonate
C-FLEX, NORPRENE, PTFE, PFA
TYGON
C-FLEX, PVDF, FFKM

Customer collecting vessel
Connection
Max. distance from collecting vessel to analyzer
Max. height difference from collecting vessel to analyzer
Sample outlet

Connection

Min. volume per measurement

hose ID 1.6 mm (1/16 inch)
1 m (3.3 ft)
0.5 m (1.6 ft)

Hose ID 4 mm (0.16 inch)– Max. length of closed loop: 1 m (3.3 ft)– Open outlet downgrade installed– No combination of several devices to a closed-loop system
68 ml (2.30 fl.oz.)

Separated outlets• Chromate containing waste (12 ml (0.41 fl.oz.) per measurement)• Spill and aqueous waste (56 ml (1.89 fl.oz.) per measurement)

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Operability
Local operation

a0012457

Display and operating elements
12
3
4
5

LED (measured value)
LC display (status)
Serial interface RS 232
Operating keys and control LEDsDisplay of the heating element

Modbus installation

a0017161

Installation of Modbus RS485

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Ordering information
Product pagewww.products.endress.com/ca71cod

Configurator

1.

You can choose from the following options on the product page located on the right:

2.

Click "Configure this product".

3.

The configurator opens in a separate window.
Use the radio buttons to configure the order code from the nameplate of your device.

4.

Afterwards, you can export the order code as a PDF or Excel file.
To do so, click the appropriate button at the top of the page.

Product structure

The following product structure represents the status of printing. You can create a complete and valid
order code on the Internet using the configurator tool.
Measuring range
ABY

5 to 200 mg/l O2
50 to 5000 mg/l O2
Special version acc. to customer’s specification

Sample transfer
1

From one measuring point

Power supply
03

230 V AC / 50 Hz
230 V AC / 60 Hz

Collecting vessel (for up to 3 analyzers)AC

Not selected (without collecting vessel)
Collecting vessel with level measurement

Housing
2

GFR housing

OutputAC

0/4 ... 20 mA, RS 232Modbus RS485

Reagents
12345
CA71COD-

10To order separately
1 set, active, measuring range A
2 sets, active, measuring range A
1 set, active, measuring range B
2 sets, active, measuring range B
complete order code

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Scope of delivery

The scope of delivery comprises:• an analyzer with mains plug
• 4 fastening clips• a cleaning injector• a tube of silicone grease• a NORPREN hose, length 2.5 m (8.2 ft), ID 1.6 mm (1/16 inch)• a C-FLEX hose, length 2.5 m (8.2 ft), ID 3.2 mm (1/8 inch)• a PVC hose, length 2.5 m (8.2 ft), ID 10 mm (0.39 inch)• two hose fittings of each size:– 1.6 mm x 1.6 mm (1/16 inch x 1/16 inch)– 3.2 mm x 1.6 mm (1/8 inch x 1/16 inch)• a hose fitting 3.2 mm x 1.6 mm (1/8 inch x 1/16 inch) for TYGON hose
• two T-hose fittings of each size:– 1.6 mm x 1.6 mm x 1.6 mm (1/16 inch x 1/16 inch x 1/16 inch)– 3.2 mm x 3.2 mm x 3.2 mm (1/8 inch x 1/8 inch x 1/8 inch)• an interference suppressor for the current output• 4 edge covers• protective cloves• protective glasses• a lab coat
• a hose 4/6 mm (0.16/0.24 inch), PTFE, length 4.5 m (14.7 ft)• a 5 l (1,32 US gal.) container for chromate containing waste• a cover for the container, with hose connector• a quality certificate• an Operating Instructions (English).

Certificates and approvals
4 approval

Declaration of conformity
The product meets the requirements of the harmonized European standards. It thus complies with the legalrequirements of the EC directives.
The manufacturer confirms successful testing of the product by affixing the 4 symbol.

Test reports

Quality certificate
Depending on the order code, you receive a quality certificate.
With the certificate the manufacturer confirms compliance with all technical regulations and the successful
individual testing of your product.

Accessories
Reagents andstandard solutions

Reagent set for CA71COD-A• Order no. CAY440-V10AAE– 250 ml (8.45 fl.oz.) dichromate solution– 4 x 1 l (34 fl.oz.) H2SO4– Dichromate decontamination reagent• Order no. CAY440-V20AAE– 250 ml (8.45 fl.oz.) dichromate solution– 2 x 2.5 l (85 fl.oz.) H2SO4– Dichromate decontamination reagent
Reagent set for CA71COD-B• Order no. CAY441-V10AAE– 250 ml (8.45 fl.oz.) dichromate solution– 4 x 1 l (34 fl.oz.) H2SO4– Dichromate decontamination reagent• Order no. CAY441-V20AAE– 250 ml (8.45 fl.oz.) dichromate solution– 2 x 2.5 l (85 fl.oz.) H2SO4– Dichromate decontamination reagent

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Standard solutions, 1 l (34 fl.oz.) each• 0 mg/l O?, Order no. CAY442-V10C00AAE• 30 mg/l O?, Order no. CAY442-V10C03AAE• 100 mg/l O?, Order no. CAY442-V10C01AAE• 2500 mg/l O?, Order no. CAY442-V10C25AAE
Collecting vessel

Agitated collecting vessel with level measurement• Prevents particles from settling in the collecting vessel• Order no. 71154317

Maintenance kit

Kit CA71COD: Wear parts• a set of pump hoses TYGON yellow/blue• a set of pump hoses TYGON orange/white• a C-FLEX hose ID 1.6 mm (1/16")• a NORPRENE hose ID 1.6 mm (1/16")• 3 hose fittings, 1.6 x 1.6 mm (1/16" x 1/16")• 2 reduction fittings, PP• 4 glands with nozzle, PTFE
• 2 hose cases• a hose extension tool
• a tube of silicone grease, 2 g• a cleaning injector, 20 ml• Order no. 71102950

Additional accessories• Interference suppressor for control, power and signal linesorder no. 51512800• Silicon grease, tube, 2 gorder no. 71079930• Kit CA71COD hose set
order no. 71103284• Kit CA71COD hose connectors
order no. 71103286• Kit CA71COD composite container for chromate wasteorder no. 71103287

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