API RP 554 2021 pdf download.Process Control Systems— Functions and Functional Specifcation Development.
1.2 Document Organization This document is organized to follow the sequence of activities associated with the typical life cycle of a PCS as summarized in Table 1. The life cycle phases as they apply to PCSs are listed below. — Appraise. Develop business goals and requirements and identify basic functions required. This step is often also referred to as the concept stage. — Select. Further develop business goals and functions into a PCS’s scope defnition. This step is often part of the early portion of front-end engineering design (FEED). — Defne. Finalize PCS’s scope defnition, select hardware and software, and prepare all applicable design drawings and specifcations, and procure other hardware and equipment. This step often forms the bulk of FEED. — Execute. Develop detailed design and procurement, construction/installation, testing, and commissioning. — Operate. Commission, operate, and maintain. API 554 consists of three parts, each focusing on a major aspect of PCSs. The three parts and the areas that they cover are as follows: — Part 1, Process Control System Functions and Functional Specifcations. Covers the basic functions that a PCS may need to perform, and describes recommended methodologies for determining the functional and integration requirements for a particular application. — Part 2, Process Control System Design. Covers the hardware and software applied to PCSs and provides recommendations for implementation. Design considerations and references to design practices for control centers and other control system buildings and enclosures are also provided. — Part 3, Process Control System Project Execution and Ownership. Covers project organization, skills and work processes required to frst execute a process control project and then to own and operate a PCS. The portions of API 554 that deal with each phase of the life cycle are identifed in Table 1.
2 Normative References The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any addenda) applies. API Recommended Practice 552, Transmission Systems 3 Terms and Defnitions The following terms and defnitions are used in this document. Additional defnitions are provided in Parts 2 and 3 when necessary to support the content of those documents. 3.1 batch control Control functions that occur in a series of complex steps or phases that may combine continuous control, sequence control, and discrete control to execute a processing scheme. 3.2 business network A digital communications network that is used for general purpose business use such as desktop computing, non-process control database applications or other general purpose applications. Can be referred to as Purdue level 4. Typically, business networks use industry standard communications methods such as Ethernet. 3.3 central control room CCR Inhabited facility (typically a building) that houses plant personnel and PCS equipment to permit the operation and coordination of one or more process plants. Control rooms are not always located adjacent to the process equipment being controlled and often centralize operation of multiple process plants or areas. Trends are to locate control centers away from potential blast zones. 3.4 continuous control Control functions that are continuously and repetitively executed to control the values of process variables such as pressure, temperature, fow, etc. that are part of a continuous process such as a refning process, or within a portion of a process associated with a batch control system.
3.5 control loop That part of an instrument control system that includes the input sensor, transmitter, communication path, control algorithm, and fnal control element. Control algorithm may be executed as one of many such algorithms in a PCS or be performed by stand-alone electronic, pneumatic, or mechanical devices. 3.6 control module A processing module that performs various control and data acquisition functions in a PCS. Typically, this module is used to poll data from system I/O modules, perform basic regulatory or other control functions, and communicate I/O and control information to other modules in the PCS. 3.7 demilitarized zone DMZ A physical or logical subnetwork that contains and exposes an organization’s external-facing network services to a larger and untrusted network, i.e. the organization’s business local area network (LAN) or the Internet. The purpose of a DMZ is to add an additional layer of security to an organization’s LAN, by isolating external communications to the process control network.