Laserfiche WebLink
Performancegmparison • <br /> of Alternate Monitoring <br /> Systems For Double-Wall <br /> Tanks <br /> Liquid Vacuum <br /> O/C TANKS Sensors In Or Air Gasoline <br /> Hydrostatic Dry Annular Pressure Vapor <br /> Tank Monitor Space Monitors Sensors <br /> Leak Detection Performance <br /> • Meets NFPA 329 criteria as a precision tank test Yes No No No <br /> • Monitors inner wall totally Yes No(()(9) Large Yes <br /> Leaks <br /> Only(s) <br /> • Monitors outer wall totally Yes No(2)(3)(9) Large No(7)(3) <br /> Leaks <br /> Only(s)(3) <br /> • Prevents product from escaping into the annular Yes No(3) No(3) No(3) <br /> space with an inner tank leak <br /> • Few false alarms Few(s)(10) Few(4) Few(s) Few(B) <br /> Proven In Use <br /> • Leak detection performance independently Yes Unknown Unknown Unknown <br /> tested and statistically validated <br /> • Optional electronic equipment tested and Yes Unknown Unknown Unknown <br /> labeled by Underwriters Laboratories <br /> • Long-term proven performance of tank monitor Yes(n) Unknown Unknown Unknown <br /> Design Awards <br /> •Winner of 1985 National Safety Council Yes No No No <br /> Award for achievements in product safety <br /> Footnotes: <br /> (1) Only monitors the portion (5) The vacuum or pressure (8) If the annular space <br /> of the inner wall which is pump can mask small is contaminated with <br /> in contact with liquid leaks in the inner and/or product, residual fumes <br /> product. outer tank wall.This pump are difficult to remove. <br /> is normally required to <br /> (2) Only monitors the portion compensate for pressure (9) If the outer wall has a <br /> of the outer wall which is and vacuum loses caused larger leak than the inner <br /> submerged in groundwater. by line losses or changes wall, product may spill <br /> in product temperatures. without accumulating in <br /> (3)With an inner wall leak, the annular space. <br /> product can leak to the (6) Delivered product tem- <br /> outerwall.Then if the outer peratures will vary from (10) Trapped air in the annular <br /> tank has an unknown summer to winter. Exces- space may "bubble out' <br /> leak, product will spill. sive temperature fluctua- during the first year of <br /> tions of the delivered operation. <br /> (4) Condensation in the product may cause <br /> annular space may cause false alarms. (11) Has been used in Europe <br /> false alarms.Condensation for over 20 years. <br /> cannot be distinguished (7) Does not monitor any <br /> from an outer tank leak. portion of the outer wall. <br /> 13 <br />