Automation of Water Resource Recovery Facilities. Water Environment Federation

following items should be considered when specifying operator interface terminals:

      • Panel-mounted, pedestal, or desktop;

      • Personal computer tablets and smartphones;

      • Operating system if using a personal computer; and

      • Area classification, where located.

2.1.1.5 Panel-Mounted Devices

      The following items should be considered when specifying panel-mounted devices:

      • Pilot lights, including colors and types (light-emitting diode, incandescent, neon, push-to-test functions, physical size, NEMA rating, voltages, etc.);

      • Pushbuttons (sizes, colors, NEMA rating, voltage rating, maintained or momentary contacts, and operator type);

      • Selector switches and potentiometers (sizes, NEMA rating, voltages, maintained or momentary contacts, and maximum resistance value for potentiometer);

      • Strobes (lens colors, NEMA rating, voltages, and mounting);

      • Horns (decibel rating, voltages, and NEMA rating);

      • Terminals (fused, nonfused types, density, voltage rating, etc.);

      • Surge protection devices (types per Underwriters Laboratories [2009] UL 1449, 3rd edition); and

      • Panel wiring (wire markers and wire terminations) such as

       Relays (control, isolation, time delay, industrial type, voltages, and contact rating);

       Timers (elapsed time, electromechanical, electronic battery backed, and other types);

       Wireways;

       Panel markings and labeling;

       Power supplies (redundancy requirements, voltage I/O, regulation, etc.);

       Power conditioners;

       Breakers, fuses, and disconnect switches;

       Process display meters;

       Single-loop controllers (see Chapter 14 for more details);

       Wireless devices; and

       Signal conditioners.

2.1.1.6 Networking Equipment

      The following items should be considered when specifying network equipment:

      • Ethernet switches (managed vs unmanaged, industrial vs office grade, number and type of ports, etc.);

      • Routers (rack-mount vs shelf-mount, built-in firewalls, number and types of ports, management software, etc.);

      • Network racks (standard rack size based on the number of rack units required by components within the rack); and

      • Network security (hardware and software).

2.1.1.7 Input/Output List

      In addition to the I/O list, a monitored variables list should be compiled in a table (see Table 3.2 for an example). The table should note each variable’s anticipated range, whether a setpoint is required, and whether it is fixed or adjustable (all setpoints should be made adjustable unless otherwise specified by the equipment manufacturer, warranty, or other applicable authority). The table should note the initial setting of each setpoint, if available, who can change it (e.g., operator, supervisor, process engineer, maintenance technician, facility superintendent, system administrator, etc.), and whether it should be password protected.

2.1.1.8 Instrument List or Index

      Complete instrument lists help a contractor to accurately bid and procure instruments. Instrument lists can take the form of a spreadsheet or database for easy sorting by various criteria (e.g., flow meters, pressure transmitters, etc.). An instrument list can also be used as a checklist by the design team to ensure that all devices have been accounted for. At a minimum, an instrument list should include the following:

      • Tag number as listed in the P&ID,

      • Description of instrument,

      • Technical specification section,

      • Calibrated-range setting,

TABLE 3.2 A sample list of monitored variables.

      • Setpoints for discrete devices,

      • Location of the P&ID,

      • Physical location drawing number, and

      • Remarks section for any additional information.

2.1.1.9 Network Cabling

      The following items should be considered when specifying network cabling (see Chapter 11 for additional information):

      • Fiber optics (fiber terminations including patch panels and patch cables; use of patch panels is a highly recommended method of fiber cable management for termination of fibers including spares at control panels when such fibers terminate at a control panel);

      • Whether it should be copper-based; and

      • Wireless communications.

2.1.1.10 Uninterruptible Power Supplies

      Uninterruptible power supply requirements should be clearly defined in the specifications. The design engineer should prepare initial sizing calculations for all control equipment to provide this information to the electrical design engineer for correct sizing of breakers and cabling. Final UPS sizing should be left up to the system integrator based on specified design criteria, such as a percentage of connected load 125 to 150% for a defined time (e.g., for half an hour, 1 hour, or other desired period of time). For facilities with on-site generators, a half-hour UPS battery on time is typically sufficient to allow on-site power generators to be fully online in case of utility power failure.

2.1.1.11 Process Control Narratives

      Before preparing detailed PCNs, also called control strategies, the design team should put together a process-function description that notes the owner’s goals for the control system, explains the team’s intentions, and promotes discussion with I&C designers. As stated previously, it is essential that these PCNs be fully developed before development of electrical wiring diagrams (also known as electrical elementaries and