1、THE ENGINEERING EQUIPMENT AND MATERIALS USERS ASSOCIATION Frangible Roof Joints for Fixed Roof Storage Tanks: Guide for designers and users PUBLICATION 180 Edition 2 Released by IHS. Not for resale. THE ENGINEERING EQUIPMENT AND MATERIALS USERS ASSOCIATION Frangible Roof Joints for Fixed Roof Storag
2、e Tanks: Guide for designers and users PUBLICATION 180 Edition 2 Copyright 2007 The Engineering Equipment and Materials Users Association A company limited by guarantee. Registered in England. Company number 477838. ISBN 0 85931 161 9 Imprint reference 12-2007 Registered and Trading Address 10-12 Lo
3、vat Lane London EC3R 8DN Telephone: +44 (0)20 7621 0011 Fax: +44 (0)20 7621 0022 E-mail: saleseemua.org Website: www.eemua.org EEMUA Publication 180 - Frangible Roof Joints for Fixed Roof Storage Tanks EEMUA ii ENGINEERING EQUIPMENT AND MATERIALS USERS ASSOCIATION The Engineering Equipment and Mater
4、ials Users Association, more commonly known as EEMUA, is a European based, non-profit distributing, industry Association run for the benefit of companies that own or operate industrial facilities. EEMUA aims to improve the safety, environmental and operating performance of industrial facilities in t
5、he most cost-effective way. EEMUA Members pursue these aims by sharing engineering experiences and expertise, and by the promotion of their distinct interests as the users of engineering products. More specifically, the aims of EEMUA Member companies are achieved by: providing the organisation withi
6、n which networking, information sharing and collaboration on non-competitive technical matters can take place; influencing the way written regulations are interpreted and applied in practice; presenting and promoting Members views, and encouraging the application of good, sound engineering practices
7、; developing and publishing user guides, specifications and training materials; facilitating Members participation in national and international standards making; influencing relevant national and European legislation and regulations. Formed in 1949 as the Engineering Equipment Users Association, an
8、d re-named in 1983 (as a result of taking over the materials association, OCMA), EEMUA has for more than fifty years given companies that own and operate process plants, power stations and other significant industrial facilities, a collaborative voice in addressing technical and engineering related
9、issues that impact on good integrity management and asset management practices. The Association is open to companies of all sizes that meet the engineering user criteria. A list of current Members of EEMUA is maintained on the Associations website at www.eemua.org/about.htm. EEMUA activities often l
10、ead to the production of publications. These are prepared primarily for Members use, but may be offered for sale as well. A list of EEMUA publications for sale is given at the end of this Publication. The full list is also on the Associations website at www.eemua.org/acatalog/shop.html, together wit
11、h on-line shopping facilities. To enquire about corporate Membership, write to infoeemua.org or call +44 (0)20 7621 0011. EEMUA Publication 180 - Frangible Roof Joints for Fixed Roof Storage Tanks EEMUA iii About This Publication Legal Aspects All rights, title and interest in this Publication shall
12、 belong to EEMUA. All rights are reserved. 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 other, without the express prior written agreement of the EEMUA Executive Director. I
13、nfringement of copyright is not only illegal, but also reduces the Associations income thereby jeopardising its ability to fund the production of future publications. It has been assumed in the preparation of this Publication that: the user will ensure selection of those parts of its contents approp
14、riate to the intended application; and that such selection and application will be correctly carried out by appropriately qualified and competent persons for whose guidance this Publication has been prepared. EEMUA does not, and indeed cannot, make any representation or give any warranty or guarante
15、e in connection with material contained in its publications, and expressly disclaims any liability or responsibility for damage or loss resulting from their use. Any recommendations contained herein are based on the most authoritative information available at the time of writing and on current good
16、engineering practice, but it is essential for the user to take account of pertinent subsequent developments and/or legislation. Any person who encounters an inaccuracy or ambiguity when making use of this Publication is asked to notify EEMUA without delay so that the matter may be investigated and a
17、ppropriate action taken. Consultation and Feedback EEMUA encourages constructive comments on this Publication from both Members of the Association and others. Comments should be sent on the standard feedback form, a copy of which is provided towards the end of this Publication. An electronic version
18、 of the form is available from EEMUA - e-mail your request for a copy to infoeemua.org, telephone your request to +44 (0)20 7621 0011, or download the form from the EEMUA website at www.eemua.org. Submit comments by e-mail (preferred) or post. Comments will be considered by the relevant EEMUA Techni
19、cal Committees and may be incorporated in future editions of this Publication. New editions will be publicised on the EEMUA website. EEMUA Publication 180 - Frangible Roof Joints for Fixed Roof Storage Tanks EEMUA iv EEMUA Publication 180 - Frangible Roof Joints for Fixed Roof Storage Tanks EEMUA v
20、Foreword This Publication has been developed by the EEMUA Storage Tanks Technical Committee to give guidance to designers and users of fixed roof vertical cylindrical storage tanks on methods of ensuring that, in the event of vapour over-pressure, tank failure occurs preferentially at the roof-to-sh
21、ell joint. This Publication covers the essential features both for new structures and for the modification of existing structures and includes illustrated examples of good design practice and photographs of tank failures. The readers attention is also drawn to the companion EEMUA publications: Users
22、 Guide to the Maintenance and Inspection of Above-ground Vertical Cylindrical Steel Storage Tanks, EEMUA Publication 159 and Guide for the Prevention of Bottom Leakage from Vertical Cylindrical Steel Storage Tanks, EEMUA Publication 183. Acknowledgements EEMUA gratefully thanks the American Petroleu
23、m Institute and the British Standards Institution for granting permission to reproduce selected diagrams from their respective publications. API 650 Welded steel tanks for oil storage. BS 2654 Specification for manufacture of vertical steel welded non-refrigerated storage tanks with butt-welded shel
24、ls for the petroleum industry. Note on the Use of Units This Publication uses SI units throughout, except for the use of bar and mbar signifying gauge pressure, and in extracts from American API documents (US customary units). EEMUA Publication 180 - Frangible Roof Joints for Fixed Roof Storage Tank
25、s EEMUA vi EEMUA Publication 180 - Frangible Roof Joints for Fixed Roof Storage Tanks EEMUA vii Contents Forewordv Acknowledgementsv 1. Introduction and Scope.1 1.1 Introduction1 1.2 Scope 2 2. Types of Fixed Roof Storage Tanks .3 3. Venting Capacities.5 3.1 Normal Venting .5 3.2 Emergency Venting5
26、3.3 Roof Joints and Frangibility .5 3.3.1 According to BS 2654 and API 6505 3.3.2 According to EN 140156 3.4 Older Tanks 6 4. Explosions inside Tanks 7 5. A Review of Reported Incidents 9 6. The Limited Value of a Theoretical Approach to Tank Failure11 7. Ensuring Effective Frangible Roof Joints .13
27、 7.1 A Practical Approach 13 7.2 Conditions and Factors Influencing the Effectiveness of Frangible Roof Joints .13 7.2.1 General.13 7.2.2 Influence of Shape of Roof.13 7.2.3 Roof-to-Shell Welds 14 7.2.4 Annular Bottom Plates.15 7.2.5 Foundations.16 7.2.6 Compression Rings .17 7.2.7 Fixed Roofs with
28、External Support Structure.19 7.2.8 Corrosion 19 7.3 Modifications of Existing Roof-to-Shell Connections.20 7.3.1 Weakening the Fillet Joint20 7.3.2 Frangible Shell Joint20 7.4 Method to Assess Available Frangibility for Existing Tanks21 7.5 Low Cycle Fatigue and Shell-to-Bottom Connection.24 7.6 Ca
29、pacity and Diameter of Emergency Vents.25 7.7 Insulation and Frangibility.26 8. Conclusions and Recommendations 27 Photographs.29 References .35 Other related EEMUA Publications35 Appendix 1 Assessment of presence of frangible roof-to-shell joint in a tank structure .36 EEMUA Publication: Feedback F
30、orm .37 EEMUA Publication 180 - Frangible Roof Joints for Fixed Roof Storage Tanks EEMUA viii Figures Figure 1 Fixed roof storage tank.1 Figure 2 Evaporative losses from a fixed roof tank 1 Figure 3 Typical frangible roof joint.2 Figure 4 Force distribution in roof-to-shell joint induced by an inter
31、nal pressure in a storage tank 5 Figure 5 Ballooning effect11 Figure 6 Dome roof tank with curved rafters 14 Figure 7 Double fillet welds at roof-to-shell connections.14 Figure 8 Seal weld for frangible roof joint 15 Figure 9 Full fillet weld at roof-to-shell connection (too strong).15 Figure 10 Lap
32、-welded annular bottom plates (non-preferred) .15 Figure 11 Butt-welded annular bottom plates (preferred).16 Figure 12 Uplift acting at the shell-to-bottom connection .16 Figure 13 Top curb angle for high pressure tank (diameter 8 metres).17 Figure 14 Details of compression rings 18 Figure 15 Fixed
33、roof with external support structure19 Figure 16 Corrosion at the shell-to-bottom connection.19 Figure 17 Modification of an existing roof-to-shell connection .20 Figure 18 Frangible joint at tank shell .21 Figure 19 Flow chart to determine frangibility of roof-to-shell joint 23 Figure 20 Deflection
34、 of tank bottom on a concrete ring beam foundation24 Figure 21 Deflection of tank bottom on a sand pad foundation25 Figure 22 Detail from EN 14015 and BS 2654.26 Photographs Photo 1 Fixed roof tank with frangible roof joint where the roof-to-shell connection failed under excessive vapour pressure 29
35、 Photo 2 Fixed dome roof tank where the shell-to-bottom connection failed under excessive vapour pressure 30 Photo 3 Roof plating blown off a 24 metre diameter hot oil tank due to excessive over-pressure. 31 EEMUA Publication 180 - Frangible Roof Joints for Fixed Roof Storage Tanks EEMUA 1 1. Introd
36、uction and Scope 1.1 Introduction Vertical, cylindrical storage tanks with fixed roofs have a vapour space between the roof and the stored liquid. This vapour space contains a mixture of product vapour and air; for certain products this mixture may be in the flammable range. Fixed roofs are provided
37、 with open vents or pressure-vacuum valves for venting (see Figure 1). Figure 1 Fixed roof storage tank Under normal operating conditions these vents ensure that the pressure in the vapour space remains close to atmospheric pressure by relieving when over-pressure or vacuum exceeds certain specified
38、 values. Over-pressure can occur when a tank is being filled, or when the temperature and hence pressure in the vapour space is increased by the suns heat on the roof (see Figure 2). The reverse occurs when a tank is being emptied or when the ambient temperature falls. Figure 2 Evaporative losses fr
39、om a fixed roof tank Under conditions of differing degrees of abnormality, caused for example by mal-operation, external fire or internal explosion, the resulting increase in vapour pressure may be so rapid that the venting devices are unable to handle the demand. This may be so even when additional
40、 emergency venting capacity is EEMUA Publication 180 - Frangible Roof Joints for Fixed Roof Storage Tanks EEMUA 2 provided. As a consequence the tank may be damaged. In such cases the design should ensure, as far as possible, that the failure occurs at the roof-to-shell connection and not at the she
41、ll-to-bottom connection. Failure of the roof-to-shell connection will normally create sufficient extra venting capacity so that no further damage to the tank shell occurs and the stored liquid is safely retained inside the shell of the tank (see Photo 1). To increase the likelihood of a preferential
42、 roof-to-shell failure, fixed roof tanks are generally provided with a weak roof-to-shell connection known as a frangible roof joint. A sectional view of a typical frangible roof joint is shown in Figure 3. Figure 3 Typical frangible roof joint 1.2 Scope This Guide covers the factors and conditions
43、that influence, favourably or unfavourably, the effectiveness of a frangible roof joint. These factors and conditions and their effects on roof frangibility are considered from both theoretical and practical standpoints. The Guide is intended to assist designers and users of such tanks to carry out
44、detailed evaluation, of both new designs and existing tanks, as to whether there is: a reasonable chance that the tank will fail preferentially at the roof-to-shell connection; a significant risk that the tank will fail at the shell-to-bottom connection; and in the event of the latter, to assist in
45、identifying the design, constructional or operational parameters which may need to be changed in order to increase the probability of a roof-to-shell failure occurring before a shell-to-bottom failure. EEMUA Publication 180 - Frangible Roof Joints for Fixed Roof Storage Tanks EEMUA 3 2. Types of Fix
46、ed Roof Storage Tanks In Europe, fixed roof storage tanks are now generally designed and constructed in accordance with EN 14015. EN 14015 classifies tanks as follows: non pressure tanks, rating from -5 to +10 mbar; low pressure tanks, rating from -8.5 to +25 mbar; high pressure tanks, rating from -
47、8.5 to +60 mbar; very high pressure tanks, rating from -20 to +500 mbar. Older tanks, constructed before 2004, were mostly designed and constructed in accordance with other codes. Note that these existing tank classifications do not change over time and tanks should be checked against the design cod
48、es used in their construction. These codes were: BS 2654 for tanks with internal pressures up to and including 56 mbar. In this code, tanks are subdivided in three classes: non pressure tanks, rating from -2.5*to +7.5 mbar; low pressure tanks, rating from -6*to +20 mbar; high pressure tanks, rating
49、from -6*to +56 mbar; API 650 for tanks with internal pressures up to an including 180 mbar; API 620 for tanks with internal pressures exceeding 180 mbar up to and including 1025 mbar. Tanks designed and constructed for design conditions equal to or exceeding 20 mbar will have roof-to-shell joints designed for service conditions and these may not be frangible. In such cases the designer should check whether the frangibility characteristics could be met. *For stability calculations thes
