1、Design of Secondary Containment in Petrochemical Faci I ities Prepared by the TASK COMMITTEE SECONDARY CONTAINMENT of the PETROCHEMICAL COMMITTEE of the ENERGY DIVISION of the AMERICAN SOCIETY OF CIVIL ENGINEERS Published by 5c1e American society .ii=il 5 of Civil Engineers 345 East 47th Street New
2、York, New York 10017-2398 Abstract: Current codes and standards do not address many of the structures found in the petrochemical industry. A task committee was established because of a significant interest in the petrochemical industry in dealing with environmental issues and in interpreting and com
3、plying with government environmental standards. The purpose of this task committee report is to help provide some uniformity to the current mix of internal and published criteria, and provide guidance in design of secondary containments. Though the makeup of the committee and the writing of this doc
4、ument are directed at petrochemical facilities, these guidelines are applicable to similar design structures in other industries. Library of Congress Cataloging-in-Publication Data Design of secondary containment in petrochemical facilities I prepared by the Task Committee on Secondary Containment o
5、f the Petrochemical Committee of the Energy Division of the American Society of Civil Engineers. p. cm. ISBN 0-7844-0263-9 1. Petroleum refineries-Design and construction. 2. Petroleum refineries-Safety measures. 3. Petroleum chemicals-Storage. 1. American Society of Civil Engineers. Task Committee
6、on Secondary Containment. TH4571.D474 1997 97-20917 665.5389-dc2 I CIP The material presented in this publication has been prepared in accordance with generally recognized engineering principles and practices, and is for general information only. This information should not be used without first sec
7、uring competent advice with respect to its suitability for any general or specific application. The contents of this publication are not intended to be and should not be construed to be a standard of the American Society of Civil Engineers (ASCE) and are not intended for use as a reference in purcha
8、se specifications, contracts, regulations, statutes, or any other legal document. No reference made in this publication to any specific method, product, process or service constitutes or implies an endorsement, recommendation, or warranty thereof by ASCE. ASCE makes no representation or warranty of
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12、n or bulk copying should be addressed to Permissions and b. Capable of detecting and collecting releases and accumulated liquids until the collected material is removed.“ Per 40 CFR 264.193(c), “Secondary containment systems must be at a minimum: a. Constructed of or lined with materials that are co
13、mpatible with the wastes(s) to be placed in the tank system and must have sufficient strength and thickness to prevent failure owing to pressure gradients (including static head and external hydrological forces), physical contact with the waste to which it is exposed, climate conditions, and the str
14、ess of daily operation (including stresses from nearby vehicular traffic). b. Placed on a foundation or base capable of providing support to the secondary containment system, resistance to pressure gradients above and below the system, and capable of preventing failure due to settlement, compression
15、, or uplift; 2-2 c. Provided with a leak detection system that is designed and operated so that it will detect the failure of either the primary or secondary containment structure or the presence of any release of hazardous waste or accumulated liquid in the secondary containment system within 24 ho
16、urs, . ; d. Sloped or otherwise designed or operated to drain and remove liquids resulting from leaks, spills, or precipitation. Spilled or leaked waste and accumulated precipitation must be removed from the secondary containment system within 24 hours, . “ 40 CFR 264.193(d) goes on to say: “Seconda
17、ry containment for tanks must include one or more of the following devices: a. A liner (external to the tank); b. A vault; c. A double-walled tank; d. An equivalent device as approved by the Regional Administrator.“ This gives the design engineer the opportunity to be creative in developing systems
18、that have not yet been used. Per 40 CFR 193(e) In addition, secondary containment should be: a. Designed to contain the capacity of the largest tank, plus the precipitation from a 25-year, 24-hour rainfall event. Also, firewater accumulation and wave action should be considered in determining the re
19、quired freeboard. b. Free of cracks or gaps. c. Designed with joints that prevent leakage. Also, see sections 2.4. l(e) and 2.4.2(c). d. Designed of a material that is compatible with the material being contained. 2.3.2 Onground and Aboveground Storage Tanks Considering the RCRA regulations, seconda
20、ry containment systems for onground and aboveground storage tanks consist of three parts. a. The secondary containment. b. An interstitial space between the primary containment and the secondary containment where liquid can accumulate or leaks can be detected. 2-3 c. A visual or other leak detection
21、 system to detect the accumulated material. See Chapter 8. The secondary containment is normally provided by a liner or a double-bottom. The liners are normally constructed using various materials including, but not limited to, synthetic membranes, reinforced concrete, and clay or combinations there
22、of. The interstitial space between the primary containment and the secondary containment is normally provided under a tank by one of the following: a. Grooves in the top of the concrete mat foundation. b. Placing grating, structural shapes, welded wire fabric, geosynthetic materials, granular materi
23、al, etc. on top of the concrete mat to separate the tank bottom from the concrete foundation. c. Granular material inside of concrete ringwalls above the membrane liner. d. The space between the bottoms of a double-bottom tank. e. For aboveground storage tanks, the physical separation from the groun
24、d. The leak detection is normally provided by visual inspection. This is accomplished by sloping the interstitial space to observation points where the leak is detected. Leak detection is discussed in Chapter 8. Figures 2.1 through 2.4 are intended to show generally the parts of secondary containmen
25、t systems for onground storage tanks. These figures are not intended to provide detailed designs for the construction of secondary containment systems. 2.3.3 Underground and lnground Storage Tanks The methods of providing secondary containment for underground and inground storage tanks include: 2.3.
26、3.l External Liner Figure 2.5 shows the concept of secondary containment of an underground tank using a synthetic membrane. In using this arrangement, special consideration must be given to the following: a. Backfill must be free draining to allow rainwater or the liquid being contained to flow to t
27、he sump. 2-4 b. A means must be provided to test the liquid within the liner for compliance with discharge permits prior to releasing the contained liquid. c. The valve should normally be kept closed. d. An impermeable soil membrane liner layer or pavement could be placed over the tanks to reduce th
28、e amount of rainwater that enters the secondary containment. 2.3.3.2 Double Wall Tank Figure 2.6 shows a typical inground storage lank installation with the top of the tank above ground. Figure 2.7 shows a horizontal underground storage tank. Also, since the secondary containment completely surround
29、s the primary tank, the interstitial space need only be large enough to accommodate leak detection, sampling and liquid removal. 2-5 OPTIONAL GRANULAR FILL FOR LINER PROTECTION (NOTE: DISPOSAL COST SHOULD BE CONSIDERED) EARTHEN DIKE ANCHOR ,. THESE DRAWINGS ARE TO ILLUSTRATE THE CONCEPT WITHIN, THEY
30、 ARE NOT TO BE USED AS CONSTRUCTION DRAWINGS. 2-8 OPTIONAL GRANULAR FILL FOR LINER PROTECTION (NOTE: DISPOSAL COST SHOULD BE CONSIDERED) EXPOSED LINERS REQUIRE U.V. PROTECTION EARTHEN DIKE ANCHOR _ THESE DRAWINGS ARE TO ILLUSTRATE THE CONCEPT WITHIN. THEY ARE NOT TO BE USED AS CONSTRUCTION DRAWINGS.
31、 2-11 TO PUMP I I I I 11 .,- _ - - - - - - - - _J_L _ - - - _J _J_ - - - - - - - - - - - ,._ 11 / I I 11 I I LIQUID REMOVAL I I 11 ( : LEAK DETECTION PUMP SUCTION -t_ : : I WELL 1 f-.11 I J II I I II I I I II J_ _ J_/ : u y, “v“ lJ/, 1:!.Q!L ELEVATION PRODUCT PIPING CONNECTED TO TANKS MAY ALSO REQUI
32、RE DOUBLE CONTAINMENT. SEE SECTION 3.0 FOR RECOMMENDATIONS. FIGURE 2.7: Double Wall Tank !:!.Q1L THESE DRAWINGS ARE TO ILLUSTRATE THE CONCEPT WITHIN, THEY ARE NOT TO BE USED AS CONSTRUCTION DRAWINGS. 2-12 2.3.3.3 Open Top Vault Figure 2.8 shows an arrangement with two storage tanks within a concrete
33、 vault. The concrete surface may require a coating compatible with the material being stored. Exterior waterproofing may also be required. Figure 2.9 shows a similar installation in which the secondary containment does not extend to the top of the storage tank. This is acceptable so long as the volu
34、me between the tank and the liner is greater than the volume of the largest tank, plus a 25-year, 24-hour rainfall event. 2.3.4 Retrofit of Existing Tanks The design to retrofit existing tanks requires considerations including service, environmental, materials, types of failure, corrosion, roofs, sh
35、ells, bottoms, design methods, design conditions, construction methods, repair methods, details, tolerances, inspection and testing. 2.3.4.1 Design Guide Currently AP/ 653 -APPENDIX I, is a document that can be used a guideline for existing OST, IST and AST tanks. a. Refer to AP/ 653 for repair and
36、alteration details which will assist in the retrofit of existing tanks for secondary containment and leak detection. b. A tank retrofit involves physical changes that can impair the tanks ability to perform safely and reliably if installed improperly. 2.3.4.2 Fabrication New tank construction and fa
37、brication methods will work well for the retrofit of existing tanks. An existing tank will present restrictions and limits to some of the normal construction practices. The retrofit end result should meet the same standards as a newly-constructed tank. a. For the retrofit of tanks, lap-welded patche
38、s or square comer insert plates should not be used on the shell or at comer joints. b. Welds joining new plates to existing bottom plates that pass under the shell will require the shell to be notched with a “rat hole“ as shown in Figure 2.10. A properly sized notch, weld location and minimum weld c
39、learai:ice provides for sound welding practice. 2-13 WATERPROOFING IF REQUIRED PLAN SECTION SECONDARY CONTAINMENT COLLECTION SUMP FIGURE 2.8: Concrete Vault NOTE: THESE DRAWINGS ARE TO ILLUSTRATE THE CONCEPT WITHIN, THEY ARE NOT TO BE USED AS CONSTRUCTION DRAWINGS. 2-14 WATERPROOFING IF REQUIRED SEC
40、TION FIGURE 2.9: Partial Height Concrete Vault NOTE: THESE DRAWINGS ARE TO ILLUSTRATE THE CONCEPT WITHIN, THEY ARE NOT TO BE USED AS CONSTRUCTION DRAWINGS. 2-15 NOTE: SEE API 653 FOR RECOMMENDED DIMENSIONS BOTTOM PLATE FIGURE 2.10: Shell Notch “Rat Hole“ tlll!L THESE DRAWINGS ARE TO ILLUSTRATE THE C
41、ONCEPT WITHIN, THEY ARE NOT TO BE USED AS CONSTRUCTION DRAWINGS. 2-16 2.3.4.3 Corrosion Corrosion under a tank bottom can affect the retrofit and repairs required to develop a secondary containment system in an existing tank. AP! 653 provides guidance and methods for determining the minimum tank bot
42、tom thickness for in service operations. a. Bottom plates can be repaired with a patch plate that is lapped and fillet welded over a section that is cut out as shown in Figure 2.11. b. Tank bottoms that cannot be repaired should be replaced or a new bottom added on top of the existing bottom. 2.3.4.
43、4 Construction Practice Current construction industry practice for installation of a second bottom to create secondary containment or leak detection system requires the use of door sheets, shell jacking or shell slotting construction techniques. a. Small diameter tanks can be physically lifted and r
44、emoved from the foundation with a crane or moved with an air flotation skirt. b. Large diameter tanks have been successfully lifted with jacks or air bag lifting devices. 2.3.4.5 Door Sheet A door sheet is cut in the bottom shell course to provide ventilation and construction access for materials an
45、d equipment, to remove, replace or repair the existing tank bottom. a. Figure 2.12 shows the door sheet detail requires the upper corners to have a radius and bottom corners to be square at the tank bottom to control stresses. b. Exterior bracing or stiffeners around the door sheet opening are norma
46、lly required to reinforce the tank shell and to keep it from becoming out-of round. 2.3.4.6 Shell Jacking Shell jacking is used to replace a tank bottom by cutting loose all sketch or annular plates and lifting the tank shell with lugs attached to the shell as shown in Figure 2.13. The removal and r
47、eplacement of an existing tank bottom and the installation of second bottom can be accomplished with this method. 2-17 ,- I I I I I I I I I I l _ J * SS SS s ( ;sz 22 2 2 22 RADIUS CORNERS FIGURE 2.11: Bottom Repair With Patch Plate .JjQll.i._ THESE DRAWINGS ARE TO ILLUSTRATE THE CONCEPT WITHIN. THE
48、Y ARE NOT TO BE USED AS CONSTRUCTION DRAWINGS. 2-18 EXISTING TANK SHELL NEW BOTTOM PLATE RADIUS CORNERS DOOR SHEET OPENING EXISTING BOTTOt.l PLATE EXTERIOR BRACING OR STIFFENERS FIGURE 2.12: Door Sheet With Shell Reinforcing t!l!L THESE DRAWINGS ARE TO ILLUSTRATE THE CONCEPT WITHIN, THEY ARE NOT TO BE USED AS CONSTRUCTION DRAWINGS. 2-19 LUG TO JACK SHELL EXISTING TANK SHELL /rLAME-CUT / THROUGH SHELL EXISTING BOTTOM PLATE TO BE REMOVED FIGURE 2.13: Shell Jacking Method THESE DRAWINGS ARE TO IUUSTRATE THE CONCEPT WITHIN, THEY ARE NOT TO BE USED AS CONSTRUCTION DRAWINGS. 2-20
