1、 AMERICAN NATIONAL STANDARD ANSI/ISA-77.70.02-2014 Fossil Fuel Power Plant Instrument Piping Installation Approved 15 December 2014 Copyright 2014 ISA. All rights reserved. ISA-77.70.02-2014 Fossil Fuel Power Plant Instrument Piping Installation ISBN: 978-1-941546-34-5 Copyright 2014 by the Internat
2、ional Society of Automation. All rights reserved. Printed in the United States of America. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means (electronic, mechanical, photocopying, recording, or otherwise), without the prior writte
3、n permission of the publisher. ISA 67 Alexander Drive P.O. Box 12277 Research Triangle Park, North Carolina 27709 Email: standards isa.org 3 ANSI/ISA-77.70.02-2014 Copyright 2014 ISA. All rights reserved. Preface This preface, as well as all footnotes and annexes, is included for information purpose
4、s and is not part of ANSI/ ISA-77.70.02-2014. The standards referenced within this document may contain provisions which, through reference in this text, constitute requirements of this document. At the time of publication, the editions indicated were valid. All standards are subject to revision, an
5、d parties to agreements based on this document are encouraged to investigate the possibility of applying the most recent editions of the standards indicated within this document. Members of IEC and ISO maintain registers of currently valid International Standards. ANSI maintains registers of current
6、ly valid U.S. National Standards. This document has been prepared as part of the service of ISA, the International Society of Automation, toward a goal of uniformity in the field of instrumentation. To be of real value, this document should not be static but should be subject to periodic review. Tow
7、ard this end, the Society welcomes all comments and criticisms and asks that they be addressed to the Secretary, Standards and Practices Board; ISA; 67 Alexander Drive; P. O. Box 12277; Research Triangle Park, NC 27709; Telephone (919) 549-8411; Fax (919) 549-8288; E-mail: standardsisa.org. The ISA
8、Standards and Practices Department is aware of the growing need for attention to the metric system of units in general, and the International System of Units (SI) in particular, in the preparation of instrumentation standards. The Department is further aware of the benefits to USA users of ISA stand
9、ards of incorporating suitable references to the SI (and the metric system) in their business and professional dealings with other countries. Toward this end, this Department will endeavor to introduce SI-acceptable metric units in all new and revised standards, recommended practices, and technical
10、reports to the greatest extent possible. Standard for Use of the International System of Units (SI): The Modern Metric System, published by the American Society for Testing for all other services, the line shall be designed for process piping design pressure and temperature. Line size should prevent
11、 plugging and have sufficient mechanical strength for the service conditions. Blowdown valves 4.1.3Blowdown valves shall be the gradual-opening type. For steam service, these valves shall be suitable for the maximum design pressure of the process line and its corresponding satur ated steam temperatu
12、re. For all other services, the blowdown valve shall be designed for the process piping design pressure and temperature. Where the process fluid temperature and/or pressure are sufficient to create a safety hazard to personnel, consideration shall be given to routing the blowdown discharge to a safe
13、 point or means of discharge. 4.2 Tubing wall thickness ANSI B31.1 provides the formula for calculating minimum wall thickness required for a given pressure and temperature. The minimum wall thickness calculation is based on a bending allowance of three (3) diameters and includes no mechanical stren
14、gth or corrosion allowance. Refer to ANSI B31.1 for detailed information. 4.3 Tubing material Tubing material shall be compatible with the process and meet the requirements of ANSI B31.1. Either tubing or piping may be used for the instrument sensing lines. The following are materials commonly used
15、for instrument sensing lines. Stainless-steel tubing, ASTM A213, Grade TP304 4.3.1This material should be limited to non-corrosive applications not exceeding 1000F (537.78C). Stainless-steel tubing, ASTM A213, Grade TP316 4.3.2This material should be limited to non-corrosive applications not exceedi
16、ng 1200F (648.89C). Stainless-steel tubing, ASTM A213, Grade TP316L 4.3.3This material is not as readily available as TP304 and TP316. Its use should be limited to corrosive conditions. The design temperature shall not exceed 850F (454.44C). ANSI/ISA-77.70.02-2014 12 Copyright 2014 ISA. All rights r
17、eserved. Copper ASTM B88 or B75 drawn or annealed soft temper 4.3.4Copper may be used in dead-end water, air, or gas service. However, for continuous service, these lines shall not be used above 406F (207.78C). Copper or copper alloy pipe is not recommended for steam or ammonia service. Carbon steel
18、 ASTM A210, Grade A1 4.3.5This material should be limited to non-corrosive applications with temperatures not exceeding 775F (412.78C) and annealed to Rc 72 max* or manufacturers recommendation for fittings. *NOTE: Rc = Rockwell hardness (C-scale); a unit of metal hardness according to the Rockwell
19、hardness test. 4.4 Fittings Fitting material 4.4.1The fittings shall be manufactured from material that is suitable for the application and is compatible with the tubing or pipe used. Compatibility criteria should be based on the requirements of ANSI B31.1, as well as the process requirements. When
20、“O“ ring seals are required, they shall be suitable for the application. Prohibited material 4.4.2Fittings and fitting components shall contain no metallic mercury or mercury compounds and shall be free from mercury contamination, except as alloying elements of the required base or bonding corrosion
21、-resistant plating. Fittings and fitting components shall not contain low melting-point metals (such as lead, antimony, arsenic, bismuth, cadmium, magnesium, tin, or zinc) in concentrations greater than 250 ppm, except as alloying elements of the required base materials. Design 4.4.3The design dimen
22、sions of the fittings shall be in accordance with the manufacturers standard design. Flow area reduction 4.4.4Installation of a fitting shall be in accordance with the vendors standard makeup procedures with no special tools or mandrels and should not significantly reduce flow area. Reuse 4.4.5Makeu
23、p of a fitting should not damage or modify the fitting in any manner that would prevent or hinder its reuse. Welded or brazed fittings shall not be reused. Finish 4.4.6The use of anti-galling coatings, as provided by the manufacturers for stainless-steel fittings, is recommended in accordance with t
24、he manufacturers published procedures. 4.5 Instrument valves and manifolds Design pressure and temperature 4.5.1When blowdown valves are not used, the instrument valves and manifolds shall have the same design rating as stated in 4.1.2. The valves shall be of the gradual-opening type and shall be ca
25、pable of operation during maximum design differential pressure and temperature. Materials of construction 4.5.2Materials for pressure-retaining parts such as the body, bonnet, disc, pipe plugs, fittings, tube stubs, or bolting shall be as required by ANSI B31.1. Packing materials shall be rated for
26、the pressure and temperature service intended. Asbestos shall not be used. 13 ANSI/ISA-77.70.02-2014 Copyright 2014 ISA. All rights reserved. 4.6 Condensate pots Condensate pots, also referred to as reservoirs, shall be designed in accordance with ANSI B31.1. 5 Installation 5.1 Tubing preparation To
27、 straighten coiled tubing, it shall be laid on a flat, smooth surface to prevent scratches. The tubing should be straightened by hand without pulling or hitting the material, which can change the inside diameter (I.D.) and cause deformation of the tubing. Only the necessary amount of tubing shall be
28、 uncoiled since repeated uncoiling will cause distortion, hardening, and stiffening. Coiled tubing can also be straightened using multiple rollersfour or five sets on both sides of the tubing. 5.2 Tube cutting Copper, carbon steel, and stainless-steel tubing shall be cut with a fine-toothed hacksaw
29、when tubing is to be flared. If tubing is connected using compression-type fittings, then the tubing shall be cut with either a fine-toothed hacksaw or the appropriately sized tube cutter. When cutting tubing with a hacksaw, use a fine-toothed hacksaw with a tubing sawing vise or guide blocks. All t
30、ubing cuts shall be squared off with a fine file, and all internal and external burrs shall be removed without causing damage to the tubing. Tubing cut with a tubing cutter shall be reamed with an appropriate reaming tool to remove burrs and restore the ID of the tubing. The cutting wheel of the tub
31、e cutter shall be sharp and in good condition to prevent damage to the tubing. The tubing surface shall not be scratched when removing burrs. After cutting and squaring, all areas of the tubing on inside and outside areas shall be free of all foreign material. 5.3 Tube bending Where directional chan
32、ges for tubing lines are made by bends, the bends shall be performed at ambient temperature using the appropriate bending tool, not by free hand. All tube bends shall be free of deformation, kinks, wrinkles, flat spots, or scoring. The minimum bending radius shall be 2 times the tubing outside diame
33、ter (O.D.) for tubing less than inch (12.70 mm) O.D. and 3 times the tubing O.D. for tubing inch (12.70 mm) and larger. Fittings shall be at least three tubing diameters away from a bend. 5.4 Joining tubing and tube fittings Tube-fitting installation shall be in accordance with both ANSI B31.1 and t
34、he manufacturers recommendations. Breakable tube fittings should be used for process and control signal connections to the instrument to allow for instrument removal. 5.5 Welding Welding procedures and welding performance qualifications shall be in accordance with the latest edition and addenda of A
35、NSI B31.1, Section IX, at the time of qualification. Filler material used for qualification and installations shall meet the requirements of ANSI B31.1, Section II, Part C, and IX, as applicable. ANSI/ISA-77.70.02-2014 14 Copyright 2014 ISA. All rights reserved. 5.6 Threaded connections Tape-type se
36、alants may generally be used up to a temperature of 450F (232.22C) on clean air, water, and steam service. Manufacturers recommendations shall be followed for the actual limitations on the installation of the tape. If tape-type sealants are used, the tape shall not extend beyond the smallest taper t
37、hread. Non-tape-type, thread-sealant compounds applied in accordance with the manufacturers recommendations shall be used on all other pipe connections. Sealant compounds shall not be used on the tubing side of breakable tube fittings. To prevent seizing and galling, the fitting manufacturers recomm
38、endations should be followed. Thread damage or galling can occur on stainless steel or other special alloy fittings. Galling can be prevented on the tube end of the fitting by special treatment of the nuts during manufacture. 5.7 Tubing slope instrument installation Routing of sensing lines shall en
39、sure that the function of these lines is not affected by the entrapment of gas (fluid-sensing line) or liquid (gas-sensing line). One of the following methods shall be used to ensure that the sensing line is not affected method (a) is preferred: a) For liquid measurement, it is preferred that the se
40、nsing line have a continuous downward slope of 1 inch or more per foot (80 mm or more per meter) of run maintained from the tap to the instrument.; for gas measurement, it is preferred that the sensing line have a continuous upward slope of 1 inch or more per foot (80 mm or more per meter) of run ma
41、intained from the tap to the instrument.; where the minimum slope cannot be obtained in the two cases above, the lines shall be installed to the maximum slope available, and in no case shall the slope be less than inch per foot (20 mm per meter). b) High-point vents or low-point drains, or both, sha
42、ll be provided to ensure that all entrapped gas or liquid can be purged from the sensing line. c) No more than two tubes shall be stacked on top of one another. Tubing runs shall contain as few fittings as necessary. Bending tubing instead of using tubing fittings to change direction or angle of the
43、 tubing run shall be incorporated whenever possible. Where tubing lengths are long enough to require tubing unions, the unions shall be installed in 45 degree offsets when the tubing is installed in a tray or when more than one tube is ran side by side. Except where required to be sloped, instrument
44、 tubing runs shall be installed in a plumb and level manner. Steam and water service 5.7.1Instruments shall be located below the root valve whenever possible. The purpose of running the sensing line downward from the root valve is to limit the penetration of gas bubbles into the system and to limit
45、the temperature at the instrument. This location also facilitates the downward slope of the sensing line, minimizing the need for high-point vents. Vacuum service 5.7.2For applications in which the line pressure is below atmospheric pressure during operation (e.g., a vacuum), the instrument shall be
46、 located above the process connection, with the sensing lin e sloped downward to the process connection. The purpose of this location is to eliminate the condensed liquid in the sensing line, which could cause an error in the measurement. If a diaphragm seal and filled capillary are used, the proces
47、s connection nee ds to be located on the top or side of the process line or vessel to avoid accumulation of liquid or deposits in the connection. Air and gas service 5.7.3Instruments measuring air or gas in process piping should be located above the process connection, with the sensing line sloped d
48、ownward to the process connection. This arrangement will allow any condensed moisture to drain back into the process rather than into the instrument, 15 ANSI/ISA-77.70.02-2014 Copyright 2014 ISA. All rights reserved. which could cause error in measurement. Otherwise, condensate pots shall be requir
49、ed. If a diaphragm seal and filled capillary are used, the process connection needs to be located on the top or side of the process line or vessel to avoid accumulation of liquid or deposits in the connection. 5.8 Condensate pots Condensate pots are used in the measurement of steam or other vapors for condensing the vapor to a liquid state to minimize errors due to gas trapped in the instrument piping. Condensate pots installed in a horizontal position should be installed level and be protected from excessive vibration. Those installed in
