PROGRAMMABLE LOGIC CONTROLLER 16942.01 GENERAL

A. Description

This section includes requirements for materials, testing, and installation of programmable logic controllers (PLCs).

B. Related Work Specified Elsewhere

General Instrumentation Requirements: 16900.

C. Submittals

Refer to Section 16900.

16942.02 MATERIALS A. Materials

1. Manufacturers

The PLC's shall be Siemens S7-200 or equivalent Allen Bradley 1400 series Micro Logix.

However, contractor shall note that county standard PLC drawings are designed around the Siemens product addressing and I/0. If Allen Bradley Micro Logix is submitted, the contractor's Control System Integrator shall be responsible for submitting revised drawings/schematics and component list to the Engineer and county for review and approval. Contract drawings and As-builts shall be updated accordingly.

2. Programmable Logic Controllers

a. The PLC's shall be a 16-bit PLC microprocessor-based stand-alone device. It shall be a process and logic controller designed for industrial environments. It shall be capable of a mix of logic, timing, counting, computation, library of preprogrammed subroutines, and PID loop control capabilities necessary for the unit process application.

b. The PLC shall come complete with central processor, memory, power supply, interconnecting cables, and discrete and analog I/O interfaces.

c. The PLC and associated hardware shall have the following ratings:

d. Operating Temperature: 0°C to 60°C.

e. Humidity: 5% to 95% relative (non-condensing).

f. The PLC shall meet the following specifications:

i. Operating Voltage: 24VDC

ii. Maximum Scan Time: 4.4 ms per 1 K of ladder logic.

g. PLC System Alarm: The PLC shall monitor the internal operation of the PLC system for failures. If a failure is detected, the system shall shut down and freeze all inputs and outputs in their last states until the error is cleared. As a minimum, the following failures shall cause the PLC to shut down:

i. Memory failure.

ii. Memory parity error.

iii. I/O cycle failure.

iv. Operating system failure.

3. Memory

a. Memory shall be read/write RAM, with an EEPROM module provided.

b. During each scan cycle, the PLC shall update the input and output table, execute the entire ladder logic program, and communicate with special functions modules installed in the rack or attached to the network. The PLC shall scan only the portion of memory utilized by the ladder logic program. Unprogrammed portions shall be skipped.

4. Math, Data and Control Functions

a. The PLC hardware and software shall perform the following functions:

i. Logic Control: The PLC shall be capable of performing the same functions as conventional logic systems including on delay timers, off delay timers, counters, and drum sequencers.

ii. Compare Function: The PLC shall perform the compare function that compares two integers or floating point numbers for less than, equal to, greater than, and not equal to.

iii. Move Function: The PLC function shall move an integer or floating point value from one memory location to another memory location when an internal permissive is enabled.

iv. Math Function: The PLC shall be capable of performing addition, subtraction, multiplication, and division on integer or floating point numbers.

v. Square Root Function: The PLC shall be capable of taking the square root of a positive integer or floating point number.

vi. Binary to BCD Function: The PLC processor shall be capable of converting a positive binary number to a positive four-digit BCD coded number.

vii. BCD to Binary Function: The PLC processor shall be capable of converting a positive four-digit BCD coded number to a positive binary number.

viii. Integration: The PLC shall integrate an input as a function of time. The integrated value shall be stored by the PLC until the PLC initiates a reset command.

ix. Averaging: The PLC processor shall provide a resettable averager that integrates the input in time increments, divided by the number of times it integrates. The PLC shall reset the averager at the end of each time cycle.

x. Elapsed Time Meter (ETM): Motors specified for scheduled servicing shall be accomplished by monitoring the accumulative run time using a resettable ETM at the PLC with a range in hours in one-minute increments, divided by the number of times it integrates. The PLC shall reset the averager at the end of each time cycle.

xi. PID Loop Function: The PLC shall perform all the functions of the conventional three-mode (PID) analog controller. The controller shall perform proportional only control, proportional plus reset, and proportional plus reset plus derivative and integral only control.

b. The PLC shall be able to generate a minimum 16 PID loops with a minimum sample time for 1.0 seconds. PID tuning constants shall have the following adjustable range:

i. Proportional Gail 0.0% to 99.99%

ii. Reset Time 0.01 to 999.99 minutes

iii. Derivative Time 0.0% to 99.99%

B. Input/Output

1. The following specifications for input/output modules is for general definition of the connections to the 1/0 modules. The module part numbers are identified in Item F. Provide the latest module available should the part numbers in Item F be obsolete or unobtainable from the manufacturer.

2. Analog transmitters and receivers have 4- to 20-ma signals. Discrete (on/off) inputs originate from dry relay contacts. For discrete control output, provide relays with dry contacts.

3. The discrete input modules shall be 24-volt d-c and have noise filters or use other techniques to reject short-time constant noise and 60-Hz pickup.

4. The discrete output modules shall be 24-volt DC solid-state drivers suitable for operating control relays. Each discrete output module shall include fuses and fuse blown indicators.

5. The analog input modules shall be suitable for accepting 4 to 20 ma from either 2 or 4 wire transmitters. The input power shall be from an external 24-volt d-c power supply.

6. The analog output modules shall be 4 to 20-ma signals suitable for driving into a 0- to 600- ohm load without load adjustments. The output power shall be from an external, 24-volt d- c power supply provided by the Contractor.

7. Discrete PLC I/O modules shall have individual LED status lights for each I/O point. All discrete and analog modules shall be wired to terminal blocks for termination of the I/O wires.

Individual I/O points shall be capable of withstanding low energy common mode transients to 1,500-volts.

8. Refer to drawings for I/O module types, chassis, and layout. Provide a minimum of 25% spare I/O, or spares noted on the drawings, whichever is greater.

C. Programming Software: The PLC programming software shall be supplied by the Contractor, and be of the same manufacturer as PLC. The programming software shall run on a laptop or personal computer, and provide the means for directly entering, debugging, and documenting the Ladder Logic or special function program, both on-line and off-line. Provide all cabling and accessories for direct connection to the PLC. The software shall be the latest version, with provisions, modules, and software for all communications. The software shall be licensed to Anne Arundel County, Maryland, Department of Public Works, Utilities Electrical Coordinator, Central Maintenance.

D. Manufacturers

1. Siemens PLC components shall be S7-200:

2. Processor: Model CPU 224 XP.

3. Digital Input Module: 24VDC, 16pt. Model EM 221-16DI.

4. Digital Output Module: 24-volt, relay Model EM 222-4DO-Relay.

E. Spare Parts

The Contractor shall furnish to the Engineer all necessary spare parts of components required to maintain the system. Prior to final acceptance of work, the Contractor shall provide a spare parts listing of all necessary spare parts and quantities for review by the Engineer. The spare parts shall include the following minimum requirements.

F. Minimum Spare Parts Lists

Part Description Quantity

Power Supply 1 each

CPU and Memory Module 1 each

Analog Input Module 1 of each type

Discrete Input Module 1 of each type

Discrete Output Module 1 of each type

16942.03 EXECUTION

A. Refer to Section 16900 for instrument mounting system calibration, configuration and programming testing and training requirements.

B. Refer to Section 16920 for general instrumentation requirements for interfacing to the PLC’s.

END OF SECTION

SECTION 16946