PART 1 GENERAL

1.01 SUMMARY

A. This specification is for a system for measurement and control of dissolved oxygen (D.O.) in an aeration chamber of a package wastewater treatment plant.

1.02 RELATED SECTIONS

1.03 REFERENCES

1.04 SUBMITTALS

1.05 DELIVERY STORAGE AND HANDLING

1.06 SYSTEM DESCRIPTION

A. The system comprises a complete control loop for dissolved oxygen. It includes a dissolved oxygen sensor and transmitter, a process setpoint controller, and an electrically operated control valve serving as a final control element.

PART 2 PRODUCTS

2.01 GENERAL

A. All wiring, hardware, and connection means shall be in compliance with the National Electrical Code and or applicable local codes.

2.02 MOUNTING

A. All components shall be mounted as shown in the construction drawings.

B. Mounting guidelines shall be followed as indicated in the installation instructions as provided by the manufacturer

2.03 EQUIPMENT

2.03.1 Dissolved Oxygen Sensor/Transmitter

A. The transmitter shall be housed in a fiberglass NEMA 4X enclosure with brackets for wall or handrail mounting. It shall have a digital display controlled by microprocessor circuitry. It shall NOT require any charts or manual inputs of any kind to determine the dissolved oxygen or to calibrate the system. All program memory and features of the instrument shall be unaffected by power interruptions and shall not require any type of battery backup. All run, programming, and calibration functions shall be accessible without having to open the enclosure. The transmitter shall have the following general capabilities:

1.) One button air calibration or in-thank calibration to a known value.

2.) Unit will display parts per million D.O.

3.) Programmable to display percent of saturation.

4.) Sensor and transmitter self-diagnostics including sensor output voltage, circuitry stability, unstable sensor output, and low sensor output level.

B. Outputs:

1.Isolated 4-20 mA for D.O.

2.Isolated 4-20 mA for temperature

3.Two programmable relays

C. The sensor shall be the replaceable cartridge type. It shall be a self-generating galvanic cell type. It shall have a zero output, repeatable at zero. D.O. The probe shall be of the membrane type, utilizing a one or two mil Teflon membrane and shall be equipped with a thermistor circuit providing continuous, automatic , active temperature compensation in the range from 0-50 degrees C. The sensor shall be made in two parts: (1) the backshell which contains the thermistor and sensor connection electronics and (2) the cartridge, which is disposable and shall have normal life expectancy of one year. The cartridge shall not have a shelf life prior to being placed in service. The cartridge shall be replaceable into the backshell without the use of any tools. The sensor shall include a jet clean self cleaning system operating from plant water of between 30 psi and 60 psi

D. All components of the mounting hardware shall be either anodized aluminum or 316 stainless steel.

2.03.2 Process Controller

A. Controller shall be a microprocessor based process controller with both continuous loop control and logic and sequence control capability. Auto tuning algorithms shall be available

B. Unit shall have the following available inputs: 1-5 VDC, 4-20mA, RTD, and thermocouple.

C. The following outputs shall be available: 4-20 mA and SPDT relay

D. Unit shall have a NEMA 4 front face.

2.03.3 Control Valve

A. Type- electrically actuated with straight through sliding gate seat design with a linear flow characteristic.

B. Cv shall be ( )

C. Connections shall be ( )” threaded.

D. Materials of construction:

1. Body: ductile iron

2. Seats and trim: 303 stainless steel

3. Packing: Teflon

E. Shut-off rating shall be ANSI Class IV

F. Pressure/Temperature shall be 250 psi at 100 F minimum

G. Command signal shall be 4-20 mA

H. Input power shall be 120 VAC

I. Full stroke operating time shall be 20 seconds maximum

J. Valve shall be direct acting with fail-in-last-position operation.

K. Actuator shall have a NEMA 3 or NEMA 4 rating

2.04 MANUFACTURERS

A.) All components of the system shall be provided by the same supplier so as to provide single source responsibility for the correct operation of the system.

B.) Supplier shall document in writing to the engineer the sizing of the control valve Cv including a list of all operating assumptions made in the calculation.

C.) Supplier shall document in writing the control strategy used to program the process controller including all parameters configured in the controller.

D.) Base specifications are for Mark I D.O. Control System as supplied by Applied Engineering of Midlothian, VA.

PART 3 EXECUTION

3.01 INSTALLATION

A. Installation shall be performed by personnel who are certified in all applicable electrical practices, standards, codes, and wiring techniques as they pertain to installing field instrumentation

B. Location of the control valve and the dissolved oxygen sensor shall be as indicated on the construction drawings.