ISA RP77 60 02-2014 Fossil Fuel Power Plant Human-Machine Interface Hard Panel Alarms.pdf

1、ISA-RP77.60.02- - 1 - RECOMMENDED PRACTICE ISA-RP77.60.02-2014 Fossil Fuel Power Plant Human-Machine Interface: Hard Panel Alarms Approved 10 November 2014 Copyright 2014 ISA. All rights reserved. ISA-RP77.60.02-2014, Fossil Fuel Power Plant Human-Machine Interface: Hard Panel Alarms ISBN: 978-1-941

2、546-29-1 Copyright 2014 by ISA. All rights reserved. Not for resale. Printed in the United Sates 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), witho

3、ut the prior written permission of the Publisher. ISA 67 Alexander Drive P.O. Box 12277 Research Triangle Park, North Carolina 27709 - 3 - ISA-RP77.60.02-2014 Copyright 2014 ISA. All rights reserved. Preface This preface, as well as all footnotes and annexes, is included for informational purposes a

4、nd is not part of ISA-RP77.60.02-2014. This document has been prepared as part of the service of ISA 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. Toward this end, the Society welcomes al

5、l 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 Standards and Practices Department is

6、 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 standards of incorporating suitable refere

7、nces 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 reports to the greatest extent possib

8、le. Standards for Use of the International System of Units (SI): The Modern Metric System, published by the American Society for Testing however, these guidelines are generic in nature and suitable for use in other process industries. 3 Definitions 3.1 alarm: An audible and/or visual means of indica

9、ting to the operator an equipment malfunction, process deviation, or abnormal condition requiring a response. 3.2 annunciator: An electro-mechanical or electronic packaged alarm system, usually consisting of one or more light boxes, associated logic, and power supply. 3.3 first-out: In a multiple-al

10、arm scenario, a method of determining which alarm occurred first. 3.4 light box: Plug-in alarm module used with hard-wired, panel-mounted alarm systems. ISA-RP77.60.02-2014 - 10 - Copyright 2014 ISA. All rights reserved. 3.5 sequence of events: A system that records the time status changes of equipm

11、ent or process variables occurred, usually to a one-millisecond resolution, for use in post-event analysis. 4 Functional grouping of alarms 4.1 Alarm grouping In a fossil-fueled power plant, as in any process plant, the ideal way to group control and alarm functions is by process area or system. For

12、 a fossil-fueled power plant, this grouping might consist of the following major areas: a) Fuel handling and preparation b) Combustion air c) Feedwater and steam drum d) Main steam e) Turbine f) Generator g) Turbine extraction and condenser h) Condensate and feedwater heaters i) Exit gas cleanup j)

13、Electrical auxiliaries k) Mechanical auxiliaries l) Steam auxiliaries When a process problem or equipment failure occurs, the instrument and control functions for that process or equipment area are most likely to experience abnormal conditions that caused the problem to occur. For example, if a feed

14、water pump trips, the feedwater and steam drum area will most likely be first to sense an abnormal process condition or equipment failure. In this case, the operator is notified that an equipment failure has occurred. The operator then takes the appropriate corrective action. An example of alarm fun

15、ctional grouping is shown in Annex B. 4.2 First-out groups The use of first-out groups when developing alarm-system requirements should be considered as a means of helping operations personnel determine which alarm, in a multiple-alarm situation, occurred first. This approach is helpful in pinpointi

16、ng the originating condition, for example, in an equipment trip or process shutdown. The use of first-out grouping also allows the design engineer to subdivide an alarm system into logical groups consistent with the functional groups, such as those identified in 4.1. First-out groups are used to ide

17、ntify the initiating event, not to provide sequence of events. Whenever suitable, this function is fulfilled by a sequence-of-events recorder (SER) or DCS. 4.3 Spare alarms It is important when adding alarm systems, both in new construction and in retrofit work, to ensure that each alarm group conta

18、ins some spare spaces or channels, or both, to allow for future additions. By the time a project nears the end of its construction phase, “spares” included in the design phase often have been used to cover items overlooked in the original project definition or items added by plant operational requir

19、ements after construction began. Thus, no real “spares” are left for future requirements. - 11 - ISA-RP77.60.02-2014 Copyright 2014 ISA. All rights reserved. 5 Prioritization of alarms To obtain maximum benefit from alarms, the arrangement should consider the needs of operators in responding to a pr

20、ocess upset or equipment failure. By grouping alarms in conjunction with a process area, operators are able to identify the problem areas soon after alarms occur. The system designer has at his/her disposition the following means to implement the prioritization of alarms: the relative location withi

21、n the light box lamp flashing speed window color associated sound Clear conventions of using these tools should be adopted. 5.1 Alarm priority selection For alarms to be useful to the operator during times of equipment failure or process upset, each alarm must be displayed in accordance with a prior

22、ity determined from the process requirements. In any plant, the highest priority must be placed on personnel safety. Subsequent priorities should be based on the likelihood of catastrophic equipment damage or damage to the surrounding community due to fire, explosion, toxic release, or equipment fai

23、lure. In light of these requirements, the following priorities are suggested for fossil-fueled power plants: a) Personnel safety b) Equipment safety/protection 1) Catastrophic equipment failure 2) Flame safety 3) Boiler protection 4) Turbine-generator protection c) Process safety/protection 1) Combu

24、stion air system 2) Fuel system 3) Main steam and water system 4) Emissions monitoring d) Miscellaneous 1) Balance of plant-electrical 2) Balance of plant-mechanical 5.2 Alarm categorization Each of the categories, such as shown in 5.1, may be divided as appropriate to meet the specific requirements

25、 (including the equipment types) of the plant site. Subgroups of these categories should be developed wherever necessary to avoid an accumulation of alarms that are of little value to the operator in an upset situation. Most importantly, proper prioritizing alarms will help the operator respond corr

26、ectly and quickly to any upset condition. NOTE The items and the order of such in 5.1 are suggestions only and should be modified as necessary to reflect the type of equipment and operating mode(s) involved. Examples of alarm prioritizing are shown in Annex C. ISA-RP77.60.02-2014 - 12 - Copyright 20

27、14 ISA. All rights reserved. 6 Order and consistency of alarms The order in which alarms are displayed should take into account the prioritization of alarms. One way to accomplish prioritization in a conventional annunciator arrangement is to use a “decision tree” in developing the annunciator logic

28、. This “decision tree” should be based on the type of unit and the operating mode(s) involved. For example, a “once-through” boiler would have different equipment priorities than a conventional drum-type boiler. Similarly, a small gas- or oil-fired peaking unit would have different operational requi

29、rements than a base-loaded, coal-fired unit. 6.1 Alarm consistency Consistency in alarm presentation, order, and prioritization is necessary so the operator understands and reacts the same way for each type of alarm. Each plant site should have a standardized approach for alarm(s) presentation, orde

30、r and prioritization. ISA-18.1-1979 (R2004), Annunciator Sequences and Specifications, provides guidance in selecting the alarm functions required or desired for each application. 6.2 Alarm sequence Particular attention should be given to specifying the alarm sequence in a plant modernization or exp

31、ansion. The alarm sequence specified should be consistent with the sequences already in use wherever practical. Likewise, alarm descriptions and functions should be consistent with those already in use. The wording (and particularly the abbreviations) used in identifying alarms should be the same as

32、 those used on panel labels and engineering drawings. Alarm lettering, coloring, and response required should be consistent with that already in use wherever possible. Attention to alarm sequence, wording, lettering, coloring, and required operator response will lessen the possibility of confusion a

33、nd error in response by the plant operating staff. Selection of alarm functions should be consistent with the approach already in use at the plant. Review of alarm functions and sequencing should be included as part of the P&ID review or control logic review. The review process should include both O

34、perations and Engineering personnel to ensure suitability of alarm function as well as consistency with plant operating practices. 6.3 Reorganization of alarms When a major modernization or expansion of a plant is planned that will result in the addition of substantial numbers of alarms, considerati

35、on should be given to reorganizing alarm groups. This reorganization, if required, will ensure that the overall alarm functionality is maintained while eliminating the need for the operator to differentiate between “old equipment” alarms and “new equipment” alarms. 7 Alarm colors Color is used in al

36、arm systems to denote the alarm condition of the process variable or equipment in an alarm state. With conventional light-box electro-mechanical annunciators, a process variable or equipment entering an alarm condition usually is indicated by the appropriate annunciator window changing to a flashing

37、 light that is accompanied by an audible warning. The flashing annunciator window is usually red or white, but may be some other color, depending on plant standards. When the operator acknowledges the alarm, the annunciator window stops flashing but remains in its “alarm” color state until the annun

38、ciator is reset or the process variable or equipment returns to a normal state. The use of different colors may also be effective in prioritizing critical alarms. Caution should be exercised, however, - 13 - ISA-RP77.60.02-2014 Copyright 2014 ISA. All rights reserved. when using colors, as some oper

39、ators may be color blind to certain colors or combinations of colors, especially red combined with green. NOTE Many plants have a combination of non-programmable and programmable alarms. The color scheme of these two alarm types should be compatible to facilitate operator-alarm recognition from othe

40、r sources. 8 Alarm display format The display format used to arrange alarm groupings should consider the locations of the alarm lights with respect to the operator, ambient lighting conditions, and also the control center, panelboard, or field cabinet arrangement. For example, in a central control r

41、oom where multiple process units are operated, the alarms should be grouped by unit(s) and by major equipment to minimize confusion. 8.1 Physical arrangement of alarm equipment When commercial light-box-style annunciators are used for alarm displays, the number of points to be alarmed will dictate h

42、ow many windows are required. Most systems will support up to four points per light-box. Newer, miniature alarm units, which use LED indicators rather than backlit windows, are generally designed for mounting in the control panel. These miniature alarm units typically require about as much panel spa

43、ce as a conventional 1/8 DIN “single-loop” controller (144 mm 5-21/32 in. high by 72 mm 2-27/32 in. wide). Pilot-light-styled alarms may be employed in control-room settings but are more common in field-mounted applications, where their design provides effective environmental protection. 8.2 Alarm e

44、quipment selection The type of alarm unit employed should be based on the total number of points to be alarmed, the number of points in each alarm group, the panel space available, and the distance of the operator from the alarm display. For example, in a conventional board-style, control-room situa

45、tion, the light-box-style annunciator units would be suitable for mounting in a vertical boiler or turbine panel while still providing good visibility for operating personnel. Miniature LED-style annunciators, on the other hand, would be suitable for mounting in the benchboard beside the unit contro

46、ls. Pilot-light-style alarms require a suitable labeled (engraved or stamped) name plate indicating the process condition being alarmed. When pilot-light-style alarms are to be employed, care must be taken to ensure that enough panel space is allowed for each name plate. Most annunciator systems pro

47、vide means for an “OR” or “AND” logic between (field) alarms, and the resulting value commands the lamp (LED). Careful attention must be paid not to “mask” in this way alarms, which are important by their own value. 8.3 Alarm lettering When light-box annunciators are used, care must be taken to ensu

48、re that lettering on window faces is large enough to permit easy reading by the operator from the control benchboard. For this reason, the use of quad-input annunciator windows should be restricted to those applications where the operator can stand directly in front of the annunciator. Quad-input wi

49、ndow annunciators are usually suitable for field-mounted panels, where operator access is usually required for equipment or process monitoring. In control-room settings, the use of single- or dual-input annunciator window(s) is recommended for those applications where the light boxes are to be mounted in a vertical board behind the benchboard. For further information on the size and height of annunciator labels, nameplate labeling examples from ISA-RP60.6-1984 are shown in Annex D. While ISA-RP60.6-1984 addresses nameplate labeling versus ISA-RP77.60.02-2014 - 14 - Copyright