2.1.2.4 Elementary Wiring Diagrams
Elementary wiring diagrams illustrate how a specific piece of equipment will be controlled electrically. The design team should create a separate wiring diagram for each piece of control system equipment. If there are several identical pieces of equipment, one typical drawing can be created with an accompanying chart to identify the respective applicable equipment numbers and any unique characteristics. The diagrams should include selector switches, pushbuttons, lamps, relays, fuses, and field devices (e.g., solenoids and sensors/transmitters for flow, temperature, pressure, level, or other devices with switch outputs that are wired into the circuit) and indicate if contacts are momentary or maintained. Inputs to the control system should be shown for clarity and complete identification of required interfaces with other systems (i.e., motor control centers, motor-operated valves, variable-frequency drives [VFDs], digital inputs to PLCs and DCS, etc.). Outputs from the remote control system must be shown in all instances.
2.1.2.5 Instrumentation and Panel Location Drawings
Instrumentation and panel location drawings should show the physical location of all I&C equipment. They can also be included with electrical-conduit layout drawings or mechanical-equipment layout drawings (in the latter instance, separate electrical drawings should be made based on the mechanical-drawings’ background).
2.1.2.6 Instrumentation Installation Details
Whether or not instruments will operate properly at a WRRF often depends on how they are installed. Installation drawings show how instruments should be mounted and installed. When creating these drawings, designers should make sure that each instrument will be accessible for maintenance. Designers also should review specific manufacturer installation details for any special requirements that should be included with the drawings. Guides from other industries can also be useful. For example, the American Petroleum Institute provides procedures for installing the more generally used measuring and control instruments and related accessories. Finally, as part of the design process, a schedule of deliverables to the client is required (see Table 3.4 for a typical deliverable schedule for a project design by a consulting engineering firm).
TABLE 3.4 An example of a milestone schedule for a typical control system design for a WRRF.
2.2 Automation Design Implementation Documents
In addition to the documents listed in Section 2.1, the drawings described in this section are typically part of the implementation of a complete automation design package. Implementation is typically carried out by a contractor, system integrator, end user, packaged equipment supplier by water process original equipment manufacturer, or a combination of these.
2.2.1 Loop Diagrams
ISA Standard S5.4 details the content and format standards for loop diagrams. Each diagram traces the complete route of a control loop’s wiring. They are useful during installation and critical for system maintenance. Loop diagrams cannot be prepared during the design phase because they involve actual vendor shop drawings and documentation. Instead, they are created during the shop-drawing phase by the design engineer or the contractor’s system integrator.
In general, it is better to have the design engineer prepare loop diagrams, although it depends on whether the owner is willing to pay for this service as part of the design fee or as part of construction costs. Some owners may not require these drawings and simply rely on other documents already produced instead. Whether a loop diagram is used or not depends on maintenance practices at specific facilities.
2.2.2 Interconnecting Wiring Diagrams
Interconnecting wiring diagrams are also known as point-to-point wiring diagrams and, as the name implies, provide wiring connections for the complete control system in addition to wiring connections for equipment power and all other wiring needed for a complete facility design. Interconnecting wiring diagrams include all external wiring for each piece of equipment, control panel, instrument field devices, local control station, motor control centers, VSDs, automated control valves, lighting, and power panels. These diagrams are typically prepared by installing contractors, although, in some instances, design engineers can prepare them if they are included in the electrical design contract. Items to be included are
• Numbered terminal block identification for each wire termination;
• Identification of the assigned wire numbers and color coding for all interconnections;
• Identification of all wiring by the conduit, cable tray, wireway, and tag with, which the cable is installed;
• Terminal, junction boxes, and pull boxes in which the wire or cable is installed;
• Identification of equipment with functional name and contract tag number to which wiring is to be connected; all numbering must match the other contract documents including P&IDs; and
• Fiber optic patch panels with all fibers labeled and terminated, including spares.
2.2.3 Control Panel Design Drawings
Control panel design drawings are a basic component of control system engineering implementation. The design engineer should develop panel sizes conservatively as part of his or her design to allocate enough space in the facility for the panels. In addition, design guidelines should be included in the panel specifications to allow the system integrator to create detailed panel layout and construction drawings for the panel shop. Every effort should be made to solicit facility maintenance personnel input on panel sizing if possible. The panel supplier should provide the following:
• Panel detailed layout drawings with exterior views of the panels that illustrate doors and hinges, lock mechanism, disconnects, and lifting lugs;
• Interior panel layouts of all components, along with naming and numbering standards;
• Panel electrical schematic diagrams;
• Panel bill of material keyed to panel components; and
• Manufacturer data sheets for all panel components.
2.2.4 Programmable Logic Controller Program
Complete program logic documentation should be provided by the system integrator or engineer performing this function. Chapter 14 contains information on different formats of program documentation.
2.2.5 Distributed Control System Configuration
Distributed control system configuration should include logic diagrams in the vendor’s specific format, including controller configuration with all parameters defined.
2.2.6 Instrument Data Sheets
To present information in a uniform standardized format, data sheets should comply with ISA requirements ISA-TR20.00.01 and ISA-20. The ISA data sheets should not replace the vendor catalog and annotated manufacturer technical data sheets that have all
