This volume is part of the Practical Guide Series developed and published by the ISA, the International Society for Measurement and Control. The Practical Guides were conceived because of a shortage of published material in the field of measurement and control that bridges the gap between theory and actual industrial practice. Many books in the field have catered to the needs of technical students, who need to be oriented to basic control theory and concepts, or college-level readers, who are interested in engineering mainly from a classroom perspective. There are handbooks for practicing engineers that cover measurement and control, but these handbooks often devote only a chapter or two to topics that merit more attention. Within the Practical Guides Series, separate volumes address each of the important topics and give them comprehensive, book-length treatments. Each book in the series can be understood and used by technical students, sales engineers, sales personnel, and managers, and relied upon by those who have "real-live" industrial concerns such as correct application, safety, installation, and maintenance. Another unique feature of the Practical Guides is the stress placed on the actual experience of measurement and control practitioners. The Practical Guides are overseen by various Volume Editors and a Series Technical Editor, who have extensive experience in measurement and control. The Volume Editors have been selected for their specific expertise in the volume topics, and bring together numerous Contributing Writers with even more specialized knowledge. The Series Technical Editor, who is responsible for general technical consistency within each volume and across all volumes, helps guide the Volume Editors. The Practical Guides capture the hard-earned experience of the writers and, by employing examples and recording anecdotal observations, make that experience as applicable for the reader as possible. Case studies, either hypothetical or based on real case histories, are used to illustrate typical situations and show how good planning and practical applications made the difference between success and failure. Some of this information has never been documented before. This volume is designed to be at home in a library, in a classroom, or on the plant floor. The comfortable reading style, large pages, and frequent illustrations will contribute to ease of use. The page design uses graphics to "call out" some of the major points of the text, such as crucial safety checks and important examples. Each Practical Guide gathers widely scattered information in a single text, with bibliographies directing the reader to other sources. |
TABLE OF CONTENTS Chapter 16 - Installation
The purpose of this chapter is to describe the following topics for the benefit of the professionals assigned the responsibility of installing a control valve: planning the installation, the receipt-inspection of the valve at the job site, the installation of the valve in the piping, preoperational tests, and specifics involving popular valve types. In 1993 a recommendation was made to the ISA Standards and Practices Board to form a committee to prepare a standard that would address specifications for the receipt, storage, installation, and calibration of instruments and control systems, including control valves. Such a standard had not been issued as of the time of this writing. The Manufacturers Standardization Society has issued a Valve User Guide that addresses some of the shipping, storage, and installation concerns discussed in this chapter [Ref. 1], Most manufacturers will supply instructions for receipt, inspection, storage, and installation as well as start-up, servicing, testing, and the like. Planning DRAWINGS An instrument installation specification can be prepared by plant personnel or by an engineering contractor. It will be useful whether the installation is to be done by plant personnel or by an outside contractor (see Reference 2). The reader is referred to Reference 3 for a detailed discussion of the project documentation that is usually needed. All documents in their latest revisions should be available at the job site. Often, up-to-date documents are available from a master computer that can be accessed at job site terminals. Flow loops needing control valves are typically delineated on process flow diagrams, which show fluid flow rates along with piping, pumps, heat exchangers, vessels, and other related mechanical and electrical equipment. These diagrams may also show temperatures, pressures, and compositions in start-up, normal, minimum, maximum, emergency, and shutdown conditions. Another related drawing is a piping (or process) and instrumentation drawing (P&ID), which will show all pieces of major equipment, including control valves and the instruments in the control loops. Tag numbers of all devices appear on the P&ID, with the possible exception of some accessories. If positioners, limit switches, and the like do not show on the P&ID they should be shown on the instrument installation drawings. If the P&ID shows process conditions, a process flow diagram may not be needed nor have been generated. Instrument installation drawings, location drawings, and piping isometrics, if available, give detailed information. If these drawings cannot be adhered to, typically for reasons of mechanical interference, the site engineer should consult with the design engineer for a resolution and then get the drawings revised. The drawings should have notes for any special spacing requirements. The process engineers may not be aware of spacing requirements; the control valve specifier should take any such requirements into consideration and see that the information is passed on to the other disciplines. Typical notes advise on straight pipe lengths upstream and downstream, which may be needed to assure the proper flow pattern of the fluid entering and leaving the control valve as well as minimum clearances for such servicing as removing topworks and other maintenance procedures. Such spacing is often shown in vendors' catalogs. Also, piping isometrics show reducing fittings (eccentric reducers, straight-side down, may be necessary for draining through the valve) and isolation, bypass, bleed, and drain valves. If the piping downstream of a control valve can be shut off, a pressure relief valve is usually installed to protect against overpressure, which can be caused by a rise in temperature of a trapped liquid or by leakage through the "closed" control valve. |
