* Clean-up costs can easily exceed $1,000,000.

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1 DOUBLE CONTAINMENT PIPING SYSTEMS Richard W. Birch Chemtrol, a Div. of NIBCO 5250 W. 76th St. Indianapolis, IN Introduction As a result of increasing concern over groundwater contamination, and ever tightening pollution regulations, "double containment" has become the latest pair of buzzwords making the rounds of the metal finishing industry. Double containment is quite simply a secondary containment device, such as a pipe, tank or trough, which is designed to capture a liquid from a primary pipe or tank and prevent it's entry to the ground water supply. The EPA has identified underground storage tanks (UST's) and piping as a key area requiring correction. Their findings clearly point out the reasons for their concerns: There are about 3,000,000 UST's in the U.S. * About 100,000 UST's are leaking and another 250,000 soon will be. * Two-thirds of the leaks are from the piping supplying the UST's. Leaks are not detected-until the damage is done. * Clean-up costs can easily exceed $1,000,000. Requlat ions Not surprisingly, a number of laws and regulations have been enacted which govern the use of double containment. These are predominantly found under the auspices of the Resource Conservation and Recovery Act (RCRA) and regulate the containment of three major classes or substances * Petroleum and Petroleum Products such as fuels. * Hazardous substances, a list of about 800 chemicals identified in the regulations. * Hazardous waste. Among the metal finishing chemicals on the list of hazardous substances are: Antimony Compounds Cadmium Compounds Chromium Compounds Copper Compounds * Cyanides 1

2 1 The Proceedings o# the 79th AESF Annual lechnical Conference "s~rt - Juri- SEZ=ZSw '19)SBZ Atlanta, Georgia The American Electroplaters and Surface Finishers Society, Inc. (AESF) is an international, individualmembership, professional, technical and educational society for the advancement of electroplating and surface finishing. AESF fosters this advancement through a broad research program and comprehensive educational programs, which benefit its members and all persons involved in this widely diversified industry, as well as govemment agencies and the general public. AESF disseminates technical and practical information through its monthly joumal, Plating and Surface Finishing, and through reports and other publications, meetings, symposia and conferences. Membership in AESF is open to all surface finishing professionals as well as to those who provide services, supplies, equipment, and support to the industry. According to the guidelines established by AESF's Meetings and Symposia Committee, all authors of papers to be presented at SUWFIN@have been requested to avoid commercialism of any kind, which includes references to company names (except in the title page of the paper), proprietary processes or equipment, Statements of fact or opinion in these papers are those of the contributors, and the AESF assumes no responsibility for them. All acknowledgments and references in the papers are the responsibility of the authors. Published by the American Electroplaters and Surface Finishers Society, Inc Research Parkway Orlando, FL Telephone: 407/ Fax: Copyright 1992 by American Electroplaters and Surface Finishers Society, Inc. All rights reserved. Printed in the United States of h~rica. This publication may not. m ) or transmitted in whole or part, in any form or by any means, e l e c t r o w or 0th erwise without the prior written permission of AESF, Reseash >arkway, Orlando, FL Printed by AESF Press SURFIN@ is a registered tradema& of the American Electroplaters and Surface Finishers Sodew, h.

3 * Lead Compounds * Nickel Compounds Mineral Acids Caustic Soda Silver Compounds * Zinc Compounds In addition, there are many state and local regulations, and many more to come, which regulate below ground, and in some cases above ground, tanks and piping. UST's governed by RCRA include: Those that contain the substances noted above. * Systems where 10% or more of their total volume is below the ground surface. * Any piping system having 10% of it's volume below the ground surface is considered a UST. In addition, the EPA requires in varying degrees depending on the substance: * Leak Detection * Corrosion Protection * Proper Design and Installation * Frequent Inspection * Spill/Overfill Prevention By law,every tank and piping system installed in 1974 or earlier must now have leak detection. Every installation made in the years must have leak detection by December Installations from 1980 until 1988 have until December 1993 to comply. All systems from 1989 and newer should have been installed with leak detection. System Selection The lack of detailed specifications by regulatory agencies is both a plus and minus. It allows unscrupulous and/or unknowledgeable vendors to supply systems with poor design, trapping unsuspecting customers with a system doomed to failure. On the other hand, it allows the user to design a system ideally suited to his needs. Therefore, a cautious approach with a reputable vendor can result in a system that is economically and environmentally sound. In the search for a double containment system, there are a number of basic design criteria that must be considered. They are: * Material Selection * Pressure Requirements * Installation Requirements I

4 * Thermal Expansion * Leak Detection Some detail on each of these is now presented. Material Selection There is considerable confusion in the area of material selection. There are no regulations that call for certain materials, nor are there any universal materials suitable for all applications. All of the materials commonly (or uncommonly) used as piping materials can be used with double containment, provided they are used properly. The best way to start is with your existing piping. If you are presently using a metallic pipe to transfer a fluid, it can probably be designed as a double containment system as well. The same is true of most plastics. An important point to consider here is that the inner and outer pipe do not have to be the same material. The confusion has arisen from the fact that a fair amount of Polypropylene has been sold in the country for double containment. Many of these systems are imported from Europe, or are of European design. The reason is that Polypropylene is a staple piping product in Europe, much like PVC is here. It has a fairly broad chemical resistance range and is fairly easy to manufacture. However, polypropylene piping is fairly expensive and more difficult to field fabricate. It is a fine material to use where service conditions warrant, but many other materials may work equally well for a given application, at far lower cost. Virtually any combination of piping materials may be used, even combinations of metal and plastic. It is not unusual, for example, to have a copper inner pipe for handling fuel oil, and a fiberglass outer containment pipe. There are no wrong material combinations, only wrong applications. Pressure Reauirements Pressure requirements for double containment are fairly straightforward. The inner pipe must be able to handle the normal Pressures required in the process. The outer pipe should be designed to relieve the entire inner pipe, should a failure occur. If the outer pipe is a sealed system, then it must be rated to the Same pressure as the inner pipe. If the outer pipe is vented to a storage tank, it's pressure rating may be considerably lower. If the inner pipe is only a gravity feed line, the outer pipe need not have any significant pressure rating. 3

5 The most important consideration is that both the inner and outer pipe mus, be rated to the highest pressure that could occur in an upset condition, such as from a closed valve, pump surge or head pressure. Installation Requirements There are a variety of installation requirements to consider when choosing a double containment system. Weight - An all metal system could be very difficult to install suspended from high above. The weight of a double metal pipe can be significant and pipe supports must be designed to handle the weight of the pipe plus the flooded weight from an upset condition. Joining Method - A fusion weld or metal weld can be difficult in tight quarters or where no power is available. A solvent cement joint may be difficult to make in very hot or cold weather. And threaded joints should never be used for either the inner or outer pipe. Burial - If the system is to be buried, care must be taken to properly bed the pipe, allow for expansion or contraction, and protect against corrosion. W Protection - Certain plastics such as Polypropylene and ABS are W sensitive. If W inhibitors are not a part of the material, shielding or painting is required if the piping system is exposed to direct sunlight. Thermal Expansion Thermal expansion is an often overlooked phenomenon which can cause considerable damage when ignored. A general rule of thumb is that most plastics will expand about 10 times more than steel and will be less forgiving of a lack of expansion space. This is particularly critical for systems that incorporate different inner and outer pipe materials. The problem is most critical at 90' bends. The expansion of the inner pipe is limited by the wall of the outer pipe. If the inner pipe is subject to high temperatures, severe damage can occur if thermal expansion has not been considered in the design. There are a variety of design techniques and expansion joints available, depending on the materials being used. Be sure to 4

6 8. :onsult with a reputable supplier for the proper design.ecommendations.,eak Detection 'he heart and soul of a double containment system is the leak letection system. Without it, the system is rendered useless.?here are a wide variety of detection systems, each with it's idvantages and disadvantages. Here is a summary of the most :ommon: Continuous Cable - This system can be either resistance or impedance based. This is probably the most common type of leak detection. The advantage is that it can rather accurately pinpoint the location of a leak. However, it may not work equally well with all fluids, is difficult and costly to install in a large system, makes pipe repair difficult, and may be damaged by the leaking fluid. Density Sensing - This is a detector mounted outside the outer pipe. It is easy to install, inexpensive, allows for easy pipe repair and has no direct contact with fluid. However, the outer pipe must be zoned in order to identify the area of the leak. Liquid Level Sensor - This is the simplest of systems and is very reliable. However, it will not distinguishbetweenprimary fluid and condensation or ground water influx, and must also be zoned for leak site determination. ph Detection - This is normally used as a secondary means in conjunction with another system such as liquid level. It can help distinguish between a primary fluid and groundwater or condensation, but cannot be used with all fluids. Pressure System - This is also a good back-up system, but must generally consist of two parallel systems in order to determine whether a failure is in the inner pipe or the outer pipe. 5

7 There are a number of other systems available such as moisture/vapor detection, manual valve on a drip-leg, visual sight glass detection or periodic pressure testing. All systems are appropriate for certain applications. It is often recommended that two systems be incorporated, with one serving to back up the other. Double containment systems are without doubt a significant financial burden to anyone handling the fluids which are required by law to be contained. However, they are cheap alternatives to cost of cleaning up ground water supplies or other environmental damage. And they can actually have a positive economic effect when used in areas such as filtration loops for precious meta solutions, or piping from bulk storage tanks. At any rate, a thorough understanding of the systems available wil be a valued asset in meeting the federal and local regulations tha will continue to be enacted and enforced. 6