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reading. Inspect for leaks by monitoring both gauges for any Vacuum Testing of Jacketed, fluctuations in pressure. If no leaks are detected, release Secondarily Contained Tanks pressure on tanks by First releasing the air on the interstice. Once air has completely exhausted from the interstice, then Jacketed, secondarily contained underground tanks are shipped release pressure in the primary tank. with a vacuum between the interstice and primary tank. When a tank is shipped in this manner it is not subject to the air/soap Refer to the PEURP-100 for additional comments. testing method as described earlier. This is provided the tank arrives at the installation site within the following vacuum limits. Tanks shipped from Modern Welding Company facilities shall Air source Quick coupler have a minimum vacuum reading of at least 8" Hg. NFPA-30 states that a vacuum of at least 5.3" Hg must be maintained for one hour to confirm tank's tightness. If this minimum vacuum is maintained for one hour, both the inner and outer tank are considered properly tested. Small fluctuations in interstice vacuum are caused by temperature, elevation and barometric pressure changes. It is required that the customer or customer's representative confirm and sign off on Modern Welding Company's "Bill of Lading" in the presence of delivering driver, that the tank was received at jobsite with the noted vacuum reading. Vacuum Primary (inner)tank readings at time of delivery and just before the tank is covered up must be noted on the installation checklist to implement the Interstice warranty of the tank. Secondary(outer) tank BACKFILL AND BEDDING REQUIREMENTS Acceptable materials of backfill and bedding are: a. Clean sand which is graded, well granulated, free flowing, non corrosive and inert. Sand must be able to be compacted to 85%compaction density for proper structural support of tank. Vacuum Testing of Double Wall Tanks b. Crushed rock which is well graded,granulated,free flowing, (Type I Construction Only) non corrosive and inert. Angular particle size must be no smaller than 1/8" and no larger than 1/2". Some Modern Welding Company Double Wall tanks are c. Pea Gravel must be clean, naturally rounded, free flowing, shipped with a vacuum between the interstice and primary tank. non corrosive and inert. Angular particle size must be no When a tank is shipped in this manner it is not subject to the smaller than 1/8"and no larger than 3/4". air/soap testing method as described earlier. This is provided _ the tank arrives at the installation site within the following i<::�:?.:};;L.;¢..::.,:�\o: ;`.iF 7':<< <:1.;::::';;:i.6vi.:..ia: ;r� �ic:•..<YR vacuum limits. pea ;;;;•Crushed :.; :>:�;; :::> :.g9Sa.i: � �;:3a:i::t �. ..;... gravel` "�" .,,� rock l Tanks shippedg Company under vacuum from Modern Welding facilities shall have a vacuum readingof at least 8"Hg. '' •��'� NFPA-30 states that a vacuum of at least 5.3" Hg must be 2 ' ' ' ''' ' '''' ' maintained for one hour to confirm tank's tightness. If this 1 minimum vacuum is maintained for one hour, both the inner •• • 4 ... M. ., •. , :;Y;k:K• 7:�k : and outer tank are considered properly tested. Small <>:;<:�.•: s µfi'/.:•a:Y:.>.. fluctuations in interstice vacuum are caused by temperature, elevation and barometric pressure changes. All materials must be free of ice and snow when used as backfill It is required that the customer or customer's representative material. confirm and sign off on Modern Welding Company's "Bill of Lading" in the presence of delivering driver, that the tank was Crushed rock and pea gravel shall have no more than 3% (by received at jobsite with the noted vacuum reading. Vacuum weight)of the material pass through a#8 sieve. readings at time of delivery and just before the tank is covered up must be noted on the Installation Checklist to implement the Whichever of the three materials used for your excavation, a warranty of the tank. 85%compaction rate must be achieved.