UL 120404-2012 UL Standard for Safety Pressurized Enclosures (First Edition Reprint with revisions through and including November 13 2015).pdf

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1、 UL 120404 STANDARD FOR SAFETY Pressurized Enclosures UL COPYRIGHTED MATERIAL NOT AUTHORIZED FOR FURTHER REPRODUCTION OR DISTRIBUTION WITHOUT PERMISSION FROM UL UL COPYRIGHTED MATERIAL NOT AUTHORIZED FOR FURTHER REPRODUCTION OR DISTRIBUTION WITHOUT PERMISSION FROM UL UL Standard for Safety for Press

2、urized Enclosures, UL 120404 First Edition, Dated July 25, 2012 Summary of Topics Adoption of ANSI/ISA 12.04.04, Standard for Pressurized Enclosures as ANSI/UL 120404. This Standard is being issued to update the title page to reflect the reaffirmation of its ANSI approval. No changes in requirements

3、 have been made. As noted in the Commitment of Amendments statement located on the back side of the title page, UL and ISA are committed to updating this co-designated standard jointly after processing according to the standards development procedures by UL. These requirements are substantially in a

4、ccordance with Proposal(s) on this subject dated September 4, 2015. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form by any means, electronic, mechanical photocopying, recording, or otherwise without prior permission of UL.

5、UL provides this Standard “as is“ without warranty of any kind, either expressed or implied, including but not limited to, the implied warranties of merchantability or fitness for any purpose. In no event will UL be liable for any special, incidental, consequential, indirect or similar damages, incl

6、uding loss of profits, lost savings, loss of data, or any other damages arising out of the use of or the inability to use this Standard, even if UL or an authorized UL representative has been advised of the possibility of such damage. In no event shall ULs liability for any damage ever exceed the pr

7、ice paid for this Standard, regardless of the form of the claim. Users of the electronic versions of ULs Standards for Safety agree to defend, indemnify, and hold UL harmless from and against any loss, expense, liability, damage, claim, or judgment (including reasonable attorneys fees) resulting fro

8、m any error or deviation introduced while purchaser is storing an electronic Standard on the purchasers computer system. UL COPYRIGHTED MATERIAL NOT AUTHORIZED FOR FURTHER REPRODUCTION OR DISTRIBUTION WITHOUT PERMISSION FROM UL ISA - International Society of Automation ANSI/ISA 12.04.04-2012 (R2015)

9、 First Edition Underwriters Laboratories Inc. ANSI/UL 120404 First Edition Pressurized Enclosures July 25, 2012 (Title Page Reprinted: November 13, 2015) ANSI/ISA/UL 120404-2012 (R2015) UL COPYRIGHTED MATERIAL NOT AUTHORIZED FOR FURTHER REPRODUCTION OR DISTRIBUTION WITHOUT PERMISSION FROM UL Commitm

10、ent for Amendments This standard is issued jointly by ISA and Underwriters Laboratories Incorporated (UL). Comments or proposals for revisions on any part of the standard may be submitted to UL at any time. ISBN 978-1-941546-74-1 Copyright 2015 ISA All rights reserved. Not for resale. Printed in the

11、 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 written permission of the Publisher. The most recent designation of ANS

12、I/ISA-12.04.04 as a Reaffirmed American National Standard (ANSI) occurred on November 13, 2015. Copyright 2015 Underwriters Laboratories Inc. ULs Standards for Safety are copyrighted by UL. Neither a printed nor electronic copy of a Standard should be altered in any way. All of ULs Standards and all

13、 copyrights, ownerships, and rights regarding those Standards shall remain the sole and exclusive property of UL. This ANSI/UL Standard for Safety consists of the First Edition including revisions through November 13, 2015. The most recent designation of ANSI/UL 120404 as a Reaffirmed American Natio

14、nal Standard (ANS) occurred on November 13, 2015. ANSI approval for a standard does not include the Cover Page, Transmittal Pages, Title Page, (front and back), or the Preface. Comments or proposals for revisions on any part of the Standard may be submitted to UL at any time. Proposals should be sub

15、mitted via a Proposal Request in ULs On-Line Collaborative Standards Development System (CSDS) at http:/. ULs Standards for Safety are copyrighted by UL. Neither a printed nor electronic copy of a Standard should be altered in any way. All of ULs Standards and all copyrights, ownerships, and rights

16、regarding those Standards shall remain the sole and exclusive property of UL. To purchase UL Standards, visit Comm 2000 at http:/m- or call toll-free 1-888-853-3503. UL COPYRIGHTED MATERIAL NOT AUTHORIZED FOR FURTHER REPRODUCTION OR DISTRIBUTION WITHOUT PERMISSION FROM UL UL COPYRIGHTED MATERIAL NOT

17、 AUTHORIZED FOR FURTHER REPRODUCTION OR DISTRIBUTION WITHOUT PERMISSION FROM UL 1 ANSI/ISA-12.04.04-2012 (R2015) ANSI/UL 120404 November 13, 2015 General Notes This is the common ISA and UL, Standard for Pressurized Enclosures. It is the first edition of ANSI/ISA-12.04.04 and the first edition of AN

18、SI/UL 120404. The document is a modification of the ISA document to create the equivalent UL version and maintain the ANSI approval of this standard. ANSI/ISA-12.04.04 and ANSI/UL 120404 contain identical requirements, and identical publication dates. This common standard was prepared by the (ISA) -

19、 The International Society of Automation on July 20, 2012 but is now being maintained by Underwriters Laboratories Inc. (UL). Note: Although the intended primary application of this standard is stated in its scope, it is important to note that it remains the responsibility of the users of the standa

20、rd to judge its suitability for their particular purpose. UL COPYRIGHTED MATERIAL NOT AUTHORIZED FOR FURTHER REPRODUCTION OR DISTRIBUTION WITHOUT PERMISSION FROM UL November 13, 2015 ANSI/ISA-12.04.04-2012 (R2015) ANSI/UL 120404 2 Preface (ISA) This preface is included for information purposes and i

21、s not part of ANSI/ISA-12.04.04-2012 (R2015). 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. The ISA Standards and Practices D

22、epartment 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 standards of incorporating sui

23、table references to the SI (and the metric system) in their business and professional dealings with other countries. Toward this end, this Department will endeavour to introduce SI-acceptable metric units in all new and revised standards, recommended practices, and technical reports to the greatest

24、extent possible. Standard for Use of the International System of Units (SI): The Modern Metric System, published by the American Society for Testing b) Provide an operating shaft with a bushing that is 0.5 in. (12.7 mm) or longer and the opening between the bushing and the operating shaft is less th

25、an 0.005 in. (0.13 mm); or c) Provide a bezel around a through-the-enclosure component to reduce the opening to less than 0.005 in. (0.13 mm). 6.2.2 Vents should be protected to reduce the risk of the release of ignition-capable particles by one of the following methods: a) Provide the vent with a h

26、ub (so that it may be used with pipes or ducts that exhaust into a unclassified location); b) Provide suitable baffles to deflect any particles away from the vent; or c) Provide the vent with a substantially noncombustible screen or filter. NOTE Materials rated as 94 V-0 or 94 5V (as described in AN

27、SI/UL 94 and CSA C22.2 No. 0.17) are considered as substantially noncombustible. CAUTION PROVIDING A SCREEN OR FILTER MAY REDUCE VENTING CAPACITY AND MAY REQUIRE A DESIGN WITH A LARGER VENT. 7 Non-metallic enclosures, non-metallic parts of enclosures and components that protrude through the enclosur

28、e One or more of the following methods is permitted where there is the possibility that damage to the protected enclosure or to a component that completes the enclosure may result in exposing a potential ignition source, but not result in reducing the pressure, within the enclosure below the minimum

29、 value. Use a component that is certified for the hazardous location external to the protected enclosure. Verify that the part of the enclosure that may be damaged is capable of passing the impact test described in 8.2. UL COPYRIGHTED MATERIAL NOT AUTHORIZED FOR FURTHER REPRODUCTION OR DISTRIBUTION

30、WITHOUT PERMISSION FROM UL 13 ANSI/ISA-12.04.04-2012 (R2015) ANSI/UL 120404 July 25, 2012 Recess the potential ignition source at least 2.5 mm behind the enclosure wall to insure outward flow of protective gas through any damage in the enclosure will prevent ingress of the explosive atmosphere. Prov

31、ide an additional cover over the potential ignition source (such as a keypad), see 7.1. Limit the energy to the component, see 7.2. 7.1 The volume within the additional cover should also be maintained at a positive pressure of at least 25 Pa when the cover is closed. The cover or enclosure adjacent

32、to the cover should be marked not to open if the equipment within the enclosure is energized when an explosive atmosphere is present. The cover should require a key to open for Type X and Type Y pressurized equipment. 7.2 The component is protected by a type of protection suitable for Division 1 or

33、Zone 1 for a Type X or Type Y pressurized enclosure or protected by a type of protection suitable for Division 2 or Zone 2 for a Type Z pressurized enclosure. 8 Protecting hot surfaces and ignition-capable components 8.1 Electrical components mounted internally and electrical components mounted thro

34、ugh the enclosure shall be protected so that likely failure or abuse will not expose a hot surface or an ignition-capable arc to the external flammable atmosphere. (Additional information is located in Annex A.) NOTE 1 Ignition-capable arcs can occur either during normal operation or as a temporary

35、arc occurring as a result of the likely failure or abuse. NOTE 2 Ignition by a hot surface is discussed in NFPA 496. EXCEPTION: Equipment that (1) does not normally create ignition-capable particles, (2) is for use in Class I, Division 2 HAZARDOUS LOCATIONS, and (3) has an ALARM to notify the user w

36、hen PRESSURIZATION fails does not require further protection. 8.2 The enclosure, external components, and nonmetallic parts of the enclosure that protect internal components should not be damaged when exposed to the impact levels in Table 2. Parts that can be removed without the use of a tool are to

37、 be removed before testing. Table 2 Impact levels for enclosure parts Type of part Impact energy (joules) Drop height factor (meters-kg) Light-transmitting parts with guard (tested without guard) 2 0.204 Light-transmitting parts not guarded 4 0.408 Other parts of enclosure 7 0.714 Compliance is veri

38、fied by subjecting the electrical apparatus to the effect of a test mass falling vertically from a drop height (h). The drop height (h), in meters, is determined by dividing the value shown in the drop height factor column by the mass of the test mass in kilograms. The impact head of the test mass s

39、hould be a 25 mm (1 in.) diameter hardened steel hemisphere. Components fail the test if hot surfaces or arcing contacts are exposed or if an ignition-capable arc occurs. Enclosures fail if hot surfaces or arcing contacts are exposed. 9 Protecting against enclosure rupture 9.1 Failure of the PROTECT

40、IVE GAS SUPPLY pressure regulator could result in flying fragments from the enclosure. Personnel should be protected from injury by either of the following methods: UL COPYRIGHTED MATERIAL NOT AUTHORIZED FOR FURTHER REPRODUCTION OR DISTRIBUTION WITHOUT PERMISSION FROM UL July 25, 2012 ANSI/ISA-12.04

41、.04-2012 (R2015) ANSI/UL 120404 14 a) The inlet should be restricted by either the supply connector size or by an additional orifice such that the leakage openings in the enclosure and any pressure relief devices will be able to prevent the internal pressure from exceeding the rated MAXIMUM OPERATIN

42、G PRESSURE, verified by the test in 11.1 and 11.2; or EXCEPTION: The test in 11.1 may be replaced by a calculation of the relief valve size for the enclosure based upon the MAXIMUM OPERATING PRESSURE, the inlet size, the pressure relief outlet size and pressure relief operating point. b) Instruction

43、s should require the user to limit the pressure as specified in 9.3. 9.2 High internal pressures can cause doors or covers to open violently. Personnel should be protected from injury by methods such as the following: c) Use of multiple fasteners so that the enclosure will safely vent before all fas

44、teners are released; d) Use of a two-position fastener to allow safe venting of the pressure when opening the enclosure; or e) Limiting the maximum internal pressure to not greater than 10 in. H2O (2.5 kPa). 9.3 When instructions require the user to limit the pressure, the MAXIMUM OPERATING PRESSURE

45、 should be marked on the enclosure, and the instructions should contain either of the following: f) Requirements for the user to install a PROTECTIVE GAS SUPPLY that will not exceed the MAXIMUM OPERATING PRESSURE of the enclosure under single-fault conditions. The fault should be self-revealing. Pro

46、tection can be either with a redundant regulator or with an external pressure relief valve that is capable of handling the maximum flow rate; or g) Requirements for the user to use only a blower system and not compressed air for the PROTECTIVE GAS SUPPLY. Compliance is checked by inspection of the i

47、nstructions and markings. 10 PURGING requirements Airflow through the enclosure during PURGING should be designed to avoid air pockets. Air pockets can be avoided by properly locating the PROTECTIVE GAS SUPPLY inlet and outlet and by minimizing the effect of partitions as follows: 10.1 For gases or

48、vapors that are heavier-than-air (i.e., with a specific density greater than 1.0), the inlet for the PROTECTIVE GAS should be near the top of the enclosure, and the outlet near the bottom of the enclosure. 10.2 For gases or vapors that are lighter-than-air (i.e., with a specific density less than 1.

49、0), the inlet for the PROTECTIVE GAS should be near the bottom of the enclosure, and the outlet near the top of the enclosure. NOTE 1 The specific densities of many gases and vapors are specified in NFPA “Fire Protection Guide to Hazardous Materials”. NOTE 2 Locating inlets and outlets at opposite sides of the enclosure promotes cross ventilation. 10.3 Internal partitions (e.g., circuit boards) should not obstruct the flow of PROTECTIVE GAS. Where the flow is significantly obstructed, e