MAINTENANCE, CALIBRATION OF DRYING OVEN, BOD AND COD

I. MEANS OF CALIBRATION

Multipoint thermometer. Range depending on the calibrated temperature of equipment. Resolution: 0,10C

Mean of time, divided by 0,01 s.

Mean of humidity and ambient temperature

Range of humidity: (0 100) %RH, divided by 2 %RH

Range of temperature: (0 50) oC, divided by 1oC.

II. CALIBRATAL CONDITIONS AND PREPARATION OF CALIBRATION

2.1. Calibratal conditions

The test room must have controlled environmental conditions:

- Temperature: (23 ± 2)0C

- Relative humidity: 40%RH - 70%RH

2.2. Preparation of calibration

Before proceeding with the calibration, make the following preparations:

- Operating equipment according to the instruction manual to stable operation.

- Operating multipoint thermometer to stable operation.

III. CONDUCTIVITY CALIBRATION

3.1. External Test

Visual inspection to determine the suitability of equipment specified in the technical documentation, the shape, size, temperature indicator, power use, the brand, the structure which ensure fitting tightness of equipment, materials and spare parts.

3.2. Technical inspection

Test normal operation of equipment according to the instruction manual.

3.3. Inspection measurement

3.3.1. Determine the temperature deviation

Measuring temperature directly in distilled water, be placed in the equipment, by multipoint thermometer. Measuring according to the diagram.

Calibration conducted by following sequence:

- Set the temperature of the equipment at stable operating temperature.

- Place the probe of multipoint thermometer according to the diagram.

- After 1 hour, record indication value. Record the results.

- The temperature deviation at each calibration point is calculated the difference between two temperatures: value is set the equipment and value of multipoint thermometer.

T = TT – Tm

Including:

T: The temperature deviation at temperature stable operation.

TT: The temperature is set the equipment at temperature stable operation.

Tm: The temperature is measured by multipoint thermometer.

The deviation of calibration point is not greater than the equipment (not greater than 1 oC).

Note: If the equipment is COD Hach, measurement points is where put the COD pipes

3.3.2. Determine the stability over time

Performance clause in 3.3.1 in 8 hours, once per hour. However, depending on the type of equipment to choice the time of next measurement.

Ex: COD equipment, measure once per half - hour, repeated after 1 minute.

The stability of calibration point is not greater than the equipment (not greater than 1 oC).

IV. RESULTS OF CALIBRATION

If the equipment is achieved the inspections, it will be certified and stamped verification and/ or labeled verification stamp as prescribed.

If the equipment is not achieved one of the inspections, it will not be certified and removed the old stamp.

V. CALIBRATION AND CHECK INTERVALS

EquipmentCalibration

period (year)

Check period

(month)

Method and recommendation

DRYING OVEN

Initial

On useMonitor temperature with appropriate sensor

12Check temperature variation within the working zone

BOD

COD1 On use

Check the temperature at the start of the test. The maximum and minimum temperature of the laden chamber must be monitored for the test period.