|All secondary containment piping
systems shall be an engineered and totally prefabricated DOUBLE-PIPE type
containment system. Carrier pipe shall be protected from the exterior
environment by the secondary containment. The system supplier shall have
at least 5 years of experience in the manufacture of secondary contained
pipe systems having an integrated sensor cable leak detection/location
alarm system. All straight sections, fittings and other accessories shall
be factory prefabricated to job dimensions. Secondary containment joints
completed at the factory shall be 100 percent air-tested. The system shall
be manufactured to allow the placement of the leak detection cable in the
secondary containment. The containment shall be drainable, dryable and air
pressure testable. Contractor fabricated systems, whether built on site or
off site, shall not be acceptable.
The secondary containment shall not be exposed to pressures which exceed the maximum for the selected containment material. When product pipe design pressures exceed the maximum allowable pressure for the secondary containment, then either a control system activated by the leak location alarm station relay or a pressure relief valve shall be utilized. When the leak detection/location system is used, the normally energized alarm station relay shall de-energize and break the control circuit, which will deactivate the control relays for valves and/or pumps which supply pressure in the carrier pipe.
All secondary containment systems shall be equipped with a PAL-AT leak detection/location system supplied by the manufacturer of the double containment system.
Trained factory representatives of the piping supplier shall provide technical field support during critical periods of installation, including final check out of the PAL-AT leak detection/location system.
The system shall be designed in accordance with the following conditions:
The secondary containment manufacturer shall supply a complete design submittal, including layout drawings, leak detection routing, catalog sheets, material data and pipe stress and end load calculations in accordance with ANSI B31.3 latest edition. The calculations shall be stamped by a Registered Professional Engineer.
|Carrier pipe shall be standard weight carbon steel, ASTM A-53, Grade B, ERW or seamless. All joints shall be butt welded for sizes 21/2 inches and greater and socket or butt welded for 2 inches and below. Where possible, straight sections shall be supplied in 40 foot random lengths with 4 inches of piping exposed at each end for field joint fabrication.|
|The secondary containment shall be
a fabricated out of carbon steel, in accordance with ASTM A-135 Grade B or
ASTM A-53 Grade B, to the thickness specified below:
The carbon steel containment pipe shall have a fiberglass reinforced polyester (FRP) external cladding, at least .100 inch thick. The cladding shall be applied to a shot blasted steel surface that meets SSPC SP-7 surface finish.
The cladding on straight sections shall consist of multiple layers of helical windings of continuous glass reinforcements applied at a winding angle of 58o to 62o. The cladding on fittings shall consist of either a chopped spray-up polyester resin/fiberglass reinforcement composite, or wrapping of glass cloth fully saturated with a two part catalyst adhesive.
All field joints shall be covered with a wrapping of glass cloth, fully saturated with a two part catalyst adhesive, identical in properties to the factory applied cladding system. The minimum thickness of the field hand lay-up shall be .100 inches.
|Supports shall be carbon steel.250" thick plate and shall be designed and factory installed by the secondary containment manufacturer. Support spacing shall be determined by the manufacturer based on pipe diameter, pipe material and operating temperature of the product pipes. In all cases, pipes within the secondary containment shall be supported at not more than 10 foot intervals. These supports shall be designed to allow for continuous air-flow and drainage of the secondary containment in place. When used with a leak detection/location cable, the supports shall have a 3/4" ID Type 304 flared end stainless steel guide tubes that facilitate cable pulling and prevent cable damage during pulling operations. No plastic supports will be allowed.|
|End seals and other subassemblies shall be designed and factory prefabricated to prevent the ingress of moisture into the system. All subassemblies shall be designed to allow for complete draining of the secondary containment.|
|LEAK DETECTION/LOCATION SYSTEM|
|The secondary containment system
manufacturer shall furnish a PAL-AT cable type leak detection/location
system. The piping shall be designed to allow pulling of the leak
detection cable into the containment pipe, both during and after piping
installation. Containment pull ports shall be located a maximum of 500
feet apart for straight runs and reduced by 150 feet for every 90o change
in direction.The leak detection/location system shall consist of a
microprocessor based panel capable of continuous monitoring of a sensor
string for leaks/faults. The unit shall have a sensing range of 
 feet per cable [with up to eight cables per panel]. The alarm
unit(s) shall operate on the principle of pulsed energy reflection and be
capable of mapping the entire length of the sensor cable and storing the
digitized system map in nonvolatile memory. The alarm units shall provide
continuous indication that the sensor cable is being monitored.
After proper acknowledgment of a minor leak, the leak detection/location system shall be capable of monitoring the entire sensing string for additional leaks, even if they are smaller than the leak previously acknowledged. The system shall be capable of accounting for minor installation irregularities, static moisture and puddles (such as condensation) with no loss in accuracy or sensitivity. The system shall locate the point of origin of the first leak or fault within + 1% of the distance from the last calibration point to the leak or + 5 feet, whichever is greater. The monitoring unit shall report and record, to nonvolatile memory, the type of fault, distance, date and time of an alarm.
The system manufacturer shall have at least ten years of experience with leak detection/location sensor cable technology and provide a factory trained representative at two on-site meetings for pre-construction and sensor/electronics installation.
The systems shall have multi-level security passwords for access to operating functions, with recording of all password entries to nonvolatile memory.
The alarm unit(s) shall be enclosed in a modified NEMA 12 enclosure and have a two line by forty character display providing status and alarm data. The monitoring unit(s) [shall be field connected to an] [shall have a factory mounted] alarm horn. The monitoring unit shall be U.L. Listed and FM approved to provide connections for intrinsically safe sensor circuits for use in a Class I, Division I, Groups C and D hazardous locations.
The system shall be tested and found to comply with the limits for a Class A Digital device, pursuant to part 15 of the FCC rules and so labeled.
The systems shall be evaluated by an independent third party, according to the Third Party Procedures developed according to the U.E. EPA;s "Standard Test Procedure for Evaluating Leak Detection Methods: Liquid-Phase Out-of-Tank Product Detectors".
Ability to locate a leak shall not depend on battery backed-up functions. In the event of power failure, system conditions and parameters shall be stored in nonvolatile memory allowing the units to automatically resume monitoring without resetting, upon restoration of power.
The monitoring unit(s) power requirements shall be 120/240 VAC, 100 VA, 50/60 Hz, single phase. Monitoring units shall be equipped with an RS-232 communication port and a common alarm relay for the panel and one relay per cable. SPDT relays are rated for 250 VAC, 10A.
The sensor cable, connectors (probes) and jumpers shall be supplied by the manufacturer of the monitoring unit(s). The cable sensing principal shall provide for continuous monitoring while short lengths of the cable are in contact with liquids, without altering the systems sensitivity and/or accuracy. The sensor cable shall be designed as follows [select one]:
|The installing contractor shall install the system in accordance with the directions furnished by the manufacturer and as approved by the architect and engineer. The secondary containment shall be air tested at 10 psig and the product piping shall be hydrostatically tested to 50 psig or 1½ times the operating pressure, whichever is greater. The test pressures shall be held for not less than one hour. The contractor shall strictly adhere to the installation guidelines supplied by the system manufacturer and shall keep the secondary containment system clean and dry at all times during the installation process.|
|A 4-inch layer of sand or fine gravel shall be placed and tamped in the trench to provide a uniform bedding for the containment pipe. The entire trench shall be evenly backfilled with a similar material as the bedding in 6 inch compacted layers to a minimum height of 6 inches above the top of the piping system. The remaining trench shall be evenly and continuously backfilled in uniform layers with suitable excavated soil. Bedding and backfill materials shall be as recommended by the manufacturer.|
A Subsidiary of MFRI, Inc.
7720 North Lehigh Avenue
Niles, Illinois 60714
Phone: (847) 966-2235 ext. 2850 or 2859
Fax: (847) 470-1204