Automation of Water Resource Recovery Facilities. Water Environment Federation

for a low-bid project are different than those needed for a design–build project. In addition, it is a good idea to include preliminary process control narratives (PCNs) identifying the general concepts without going into the details required for the PCNs needed for final design. Preliminary PCNs could then simply be a broad outline of the utility’s methods of operation.

      During this phase, the design team should begin to address security issues. The team should start by reviewing standards and guidelines for supervisory control and data acquisition (SCADA) system security that have developed since the September 11, 2001, terrorist attacks in New York City and Washington, D.C. Security is of such importance to utility automation systems, including water and wastewater treatment, that a separate chapter (Chapter 12) has been dedicated to this topic.

      At the end of this phase, the design team should write a predesign report that includes project objectives, necessary project steps, required design documents, standards for these documents, and, perhaps, some preliminary design documents (e.g., technical memorandum describing the proposed I&C system) and prepare a budget estimate based on available information and project scope. The owner should approve this report before the design team begins the next phase.

1.3 Detailed Design Phase

      During the detailed design phase, the design team should develop process flow diagrams (PFDs) followed by process and instrument diagrams (P&IDs). Process and instrument diagrams are typically the first design drawings completed and serve as blueprints for the more detailed work in the final design phase. An excellent tool and starting point for any design is the P&ID, a schematic diagram showing significant components of a process or processes, interconnections among them, instruments, measuring points, and control elements. If the designers can reach a consensus on these significant design components, much of the rest of the design is straightforward and simplified.

      At this stage of design, detailed PCN development should proceed. This can be done concurrently with P&IDs because PCNs will themselves affect I&C system design, including panels, instruments, hardware, software, and so on. Owners must be involved in P&ID development because the control strategies shown on these drawings will directly affect WRRF operations. (For more a more detailed presentation of P&IDs, see Chapter 4.)

      Electrical designers are typically also involved in this phase because of the numerous interactions between control and electrical systems. Elementary wiring diagrams (EWDs) are often developed simultaneously with P&IDs (typically, 60% phase). Preliminary EWDs can begin in the early stages of P&ID development; however, they cannot be completed until the P&IDs have progressed to at least a 60% level.

      Other design documents, such as input/output (I/O) and instrument lists, are generated directly from P&IDs. They might be completed now or during the final design phase. The owner should approve these documents before the start of the final design phase.

1.4 Final Design Phase

      If project standards have been established and design activities have been outlined, the final design phase should proceed smoothly. The goal is to produce remaining I&C drawings and specifications needed to complete the final design.

      Control system specifications (i.e., written details on equipment, methods, and functions that contractors must supply or implement) are especially important during this phase. These specifications typically are organized according to the format established by the Construction Specifications Institute (CSI) (http://www.csinet.org). Automation and instrumentation industry standards, which were revised in 2004, organize specifications into sections that correspond to significant construction categories. The CSI format is structured such that there is minimal overlap with other sections. Completed specifications are then submitted to the end user or owner for their comments and approval (see Chapter 6 for more details on this topic).

2.0 DESIGN DOCUMENTS

      The following subsections present brief introductions to significant documents used to design control systems. The type of documents included in a design package depends on the specific contract format used for a project (e.g., fixed fee, design–build) (see Table 3.1 for a list of design documents).

2.1 Bid Documents

      2.1.1 Specifications

      Bid documents include the specifications listed in Table 3.1. At a minimum, these documents are required for a traditional design package with implementation of the design by a contractor or system integrator or a combination of both.

TABLE 3.1 Various design documents and industry standards.

2.1.1.1 General Requirements for Process Automation Systems

      General requirements must include minimum qualification criteria for selection of a system integrator when the contract requires one. The specifications should follow design standards established for the project and include compliance with relevant industry standards. At a minimum, design standards should address

      • Power supply requirements, including uninterruptible power supplies (UPSs) required for an automation system;

      • Response to power failures;

      • Hardware redundancy;

      • Surge and lightning protection for panels and instruments; and

      • Signal requirements for instrumentation and control (e.g., field bus, traditional 4 to 20 m for analog, highway addressable remote transducer [HART] communication, etc.).

2.1.1.2 Factory Testing

      Before delivery of control system equipment to the site, a complete factory test of the entire control system, including hardware, software, and control logic (excluding field instruments), should be performed at the supplier’s factory. The test should be witnessed by representatives from the design engineer and end user. Additional support personnel from the contractor may be present.

      The following sections present a broad outline of hardware and software specification issues that must be considered for a complete design. This list is not meant to be a substitute for complete detailed specifications, which must be prepared for these items. For more comprehensive coverage of these items, see specific hardware and software specification sections of this manual.

2.1.1.3 Panel Enclosure

      The following items should be considered when specifying panel enclosures:

      • Industry standards (i.e., National Electrical Manufacturers Association [NEMA]) rating;

      • Construction (stainless steel or painted, panel gauge, or nonmetallic);

      • Conduit penetration areas;

      • Sealed windows for viewing interior components;

      • Thermal management;

      • Supports (wall-mounted or floor-mounted);

      • Method of compliance with area classification (purging, explosion-proof, etc.); and

      • Agency approval (Underwriters Laboratories’ [2009] 508 listing).

2.1.1.4 Operator