June 2000 Understanding Line Leak Detection …

1 June 2000 Understanding line Leak Detection SystemsThis booklet contains information about line leak detectors (LLDs).Although the booklet is intended primarily to assist local agency in-spectors, tank owners and operators, consultants, and contractorsmay also find this information useful. It will discuss the technologicalprinciples of LLDs and provide an overview of installation, inspection,maintenance, and special features of these devices. In addition totechnical information, this booklet will also provide regulatory regulatory requirements referred to in this booklet are in the Cali-fornia Code of Regulations Title 23, Division 3, Chapter 16. To obtain acopy of these regulations or additional copies of this booklet, pleasefax your request to the State Water Resources Control Board, Under-ground Storage Tank Program, at (916) 227- 4349, call (916) 227- 4303,or visit our website at reference to or depiction of commercial products is solely forexplanatory purposes and is not intended as an line Leak Detection SystemsJune 2000 This document was prepared by the following SWRCB staff:Shahla Dargahi Farahnak, , Senior Water Resources Control EngineerMary Drewry, Water Resources Control EngineerScott Bacon, Engineering Student AssistantWe would like to thank the following for their contributions in reviewing this Berrey, SWRCBGreg Breshears, County of Santa Clara Environmental Resources AgencyLaura Chaddock, SWRCBR obert Hart, Veeder-RootDavid Holtry, SWRCBCurt D.

2 Johnson, Alabama Department of Environmental ManagementJohn Kneece, S. Carolina Department of Health & Environmental ControlMarcel Moreau, Marcel Moreau AssociatesCharles Northrop, Charles Northrop and AssociatesEdward Olson, Minnesota Pollution Control AgencyJeff Tobin, State of Montana Department of Environmental QualityJohn Welch, SWRCBJohn White, City of Anaheim Environmental Protection SectionBarbara Wightman, SWRCBJune 2000 Understanding line Leak Detection SystemsTABLE OF CONTENTSINTRODUCTION 1 PART I - OVERVIEW OF PIPING SYSTEMS Overview of Piping Systems .. Delivery Methods .. Construction Material .. Single-Walled and Double-Walled Piping .. 7 PART II - MECHANICAL line LEAK DETECTORS Introduction to Mechanical line Leak Detector.

3 Equipment Components .. Leak Detection Mechanism .. Interference to the Leak Detection Mechanism .. Installation Overview .. Maintenance of the MLLD .. Inspection of the MLLD .. 22 PART III - ELECTRONIC line LEAK DETECTORS Introduction to Electronic line Leak Detector .. Equipment Components .. ELLDs and Automatic Tank Gauging system .. Leak Detection Mechanism .. Pressure Decay ELLDs .. Volume Displacement ELLDs .. Constant Pressure ELLDs .. Wireless ELLD Systems .. Interference to the Leak Detection Mechanism .. Installation Overview .. Maintenance of the ELLD .. Inspection of the ELLD .. 36 APPENDIX A - INSPECTION AND MAINTENANCE CHECKLISTS A-1 Mechanical line Leak Detector Inspection Checklist .. A-2 Electronic line Leak Detector Inspection Checklist.

4 A-3 line Leak Detector (LLD) system Certification .. A-4 APPENDIX B - REGULATORY REQUIREMENTS B-1 Monitoring Requirements for Single-Walled Piping Systems .. B-2 Monitoring Requirements for Double-Walled Piping Systems .. B-3 APPENDIX C - THIRD PARTY CERTIFICATION OF line LEAK DETECTORS C-1 Third-Party Certification .. C-2 Conducting the Evaluation .. C-3 Leak Detection Equipment List .. C-4 APPENDIX D - REFERENCES D-1 References.. D-2 Understanding line Leak Detection SystemsJune 2000 June 2000 Understanding line Leak Detection SystemsINTRODUCTIONU nderground storage tank (UST) systems are composed of tanks, associated pip-ing, and pumps that deliver product to dispensers (see Figure 1). Monitoring thesesystems for leaks is required by state and federal laws and is intended to helpdetect a release before groundwater is contaminated.

5 line leak detectors (LLDs)are devices that alert the tank operator to the presence of a leak in undergroundpiping by restricting or shutting off the flow of product through the piping, or bytriggering an audible or visual alarm. They are installed in the product line , usuallyin or near the pump are divided into two categories: Mechanical line Leak Detectors (MLLD) andElectronic line Leak Detectors (ELLD). Mechanical line leak detectors are designedto perform frequent testing of the piping to detect catastrophic leaks (3 gph or higher).Electronic line leak detectors also test for catastrophic leaks, but they can performmore sensitive leak tests ( gph and gph) as well. These more sensitive testsare designed to detect small leaks, which become a major problem if not detectedand repaired. Both MLLDs and ELLDs are available in a wide assortment of mod-els, representing a variety of leak Detection mechanisms and 1 - A Typical Retail Service Station with Pressurized Piping System1 VentPipesLine LeakDetectorsSubmergedPump AssembliesProductDeliveryLinesProductDis pensersFill PipeTank TruckDelivery HoseUnderstanding line Leak Detection SystemsJune 2000 June 2000 Understanding line Leak Detection SystemsPART IOverview of Piping Systems3 Understanding line Leak Detection SystemsJune 2000 June 2000 Understanding line Leak Detection Overview of Piping SystemsIn order to understand the operation of LLDs, it is necessary to have a basic knowledge ofdifferent types of piping systems.

6 There are various piping systems commonly in usetoday and each is subject to specific monitoring requirements (see Appendix B). Pipingsystems can be categorized by three main properties: delivery method, construction mate-rial, and levels of containment. Suction piping systems use a pump located abovegrade, which pulls product to the dispenser. At gasstations, the pumping unit is located in the systems in which there is no pump or valveinstalled below grade and where the piping slopes backinto the storage tank are known as safe suction sys-tems. If these conditions are not met, it is known as aconventional suction system . Pressurized piping systems use a submersible pumpto deliver product from the tank to the dispenser. Gravity piping systems have no pump, and rely on thedownward slope of the piping to transport PipingPressurized pipelines transport product by pushing it through piping using a submersiblepump.

7 The pump head is located above the tank (see Figure 2), in a sump that is typicallyaccessible by a manhole. The pump turbine is located directly below the pump head in thebottom of the tank. Pressure in the line is typically 28 - 30 psi, depending upon the horse-power of the pump. A single pump can supply product to several dispensers Delivery MethodsDelivery method is the way in which product is moved through the piping. There are threecommon delivery methods in use: suction, pressurized, and gravity. Each method hasspecific characteristics and leak Detection considerations. line leak detectors are onlydesigned for use with pressurized delivery lines, so this text will be limited to discussion ofpressurized line Leak Detection SystemsJune 2000neously. Factors such as the volume of product dispensed, desired delivery time, and thelayout of the UST facility will determine the configuration of system .

8 Pressurized systemsare generally chosen for high-volume facilities with multiple dispensers because the prod-uct can be delivered to several dispensers efficiently and releases ofproduct can occurquickly in leakingpressurized pump will con-tinue to push productthrough a leaking lineif it is not shut 2 - Submersible Pump Construction MaterialUST system piping comes in three main varieties of material: steel, fiberglass-reinforcedplastic (FRP), and flexible. When properly installed and maintained, each material canwork reliably. The choice of material will depend on specific UST facility factors such asstored product, installation cost, long-term reliability, and contractor make surethe piping material,piping connections,and any sealants oradhesives used arecompatible with thesubstance is the least common material in newer UST piping. It isstrong and durable but expensive to install.

9 Steel piping isgenerally found in specialty systems where the chemicalsstored would be incompatible with other piping materials, orin older upgraded facilities where corrosion protection hasbeen added to meet California s is the most common piping material in use today. It hasbeen the industry standard for many years. FRP is strong,durable, and corrosion resistant. Since FRP piping is bondedin the field and constructed such that there are many connections in the piping, leaks willmost likely occur at connections where two or more sections of piping are bonded HeadProduct Lineto Dispenser(s)Submerged PumpTurbine AssemblyUndergroundTankJune 2000 Understanding line Leak Detection SystemsFlexible piping is a technology developed in the early 1990 s. It is often less expensivethan FRP or steel piping since it is less labor intensive to install. Flexible piping uses fewerleak-prone connections than the other materials since it can be rolled off a spool to therequired length and swept around corners rather than using piping unions and angledfittings.

10 The long-term durability of flexible piping is less proven than that of the othermaterials, as its use has only recently become Single-Walled and Double-Walled PipingPiping can be constructed in single-walled or double-walled form. Older UST systems will typi-cally have single-walled piping, as this was the industry standard for many years. Any leaks fromsingle-walled piping will release product directly into the surrounding Leak Detectors must be certified for use withthe piping material of the line they are 3 - Example of FlexibleDouble-Walled PipingFigure 4 - Example of FRPD ouble-Walled PipingSee Appendix B fordetails on regulatoryrequirements formonitoring of single-walled and double-walled piping is a pipe within a larger pipe (see Fig-ures 3 and 4). This configuration provides an extra barrierbetween the product flowing through the inner pipe and theenvironment surrounding the outer pipe.