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,.. .f 11.1.2.Diameter measurements of the tank must be taken at 11.3.6.Record the measurement at the appropriate place(as one or more locations on each tank or tank compartment.It is Measurement#1,#2,#3 or#4)on the Tank Installation Checklist. preferable to take the deflection measurement near the center 11.4. CALCULATION AND COMPARISON of a tank or compartment if possible. 11.4.1.To get the deflection measurement at any time during 11.1.3.An initial measurement must be taken before installa- installation,take a diameter measurement and subtract it from tion of the tank begins.This first measurement is used as a Measurement#1. comparison reference for subsequent measurements in order to check proper backfill placement. 11.4.2.Compare this measurement to the applicable allowable deflection shown in TABLE 17-1. 11.1.4.Additional measurements must be taken:a)after apply- ing anchor straps(if used),b)after backfilling is brought to the top of the tank,c)after backfilling is brought to subgrade and Tank Diameter Allowable Deflection before placement of reinforced concrete or asphalt(if used). 4' 1/2• 11.1.5.Measure the distance from the bottom edge of a tank 6' 34• fitting to the bottom of the tank immediately below that fitting. 8' 1 1/8• 11.1.6.Described here are two methods using a dipstick to 10' 1 1n• measure the internal diameter of the tank—one not using a 12' 1 1 314• standpipe and one using a standpipe. 11.1.6.1.Similar methods can be used,such as using a tape TABLE 11-1 measure,for example. 11.4.3.Vertical deflection in excess of this measurement indi- cates improper installation. 11.1.7.The deflection measurement can be obtained by using the same method twice or by using each method once. 12. BALLASTING TANKS (ADDING LIQUID) 11.1.8.For both methods,drive a small-headed,nonsparking 0 WARNING nail(for example,brass)halfway into a wooden dipstick 1 inch above its base. Inert the tank and use inert gases(not air)to pressure test a tank that contains or has contained flammable or com- 11.2. DIAMETER MEASUREMENT WITHOUT bustible liquids or vapors.Failure to follow this warning A STANDPIPE could result in an explosion,and could result in death or 11.2.1.Place the dipstick into a service fitting. serious injury. 11.2.2.Measure the distance from the tank bottom to the top 0 WARNING of the fitting and record this measurement. If flammable or combustible product is used as ballast,exer- 11.2.3.Pull the dipstick up until the exposed nail catches on cise special care in handling.Safeguard against sparks,fire the inside top of the tank. or product spills.Failure to follow this warning could result in a fire or an explosion,and could result in death or serious 11.2.4.Measure the distance from the tank top(inside)to the injury. top of the fitting.Subtract the distance from the nail to the base of the dipstick(1 inch)and record this measurement. F 0 WARNING 11.2.5.Subtract the second measurement(inside tank top to top The tank must be adequately vented to prevent the develop- of fitting)from the first measurement(tank bottom to top of fitting). ment of vacuum or pressure when filling or emptying the tank.Failure to properly vent the tank could cause tank fail- 11.2.6.Record the measurement at the appropriate place(as ure,and could result in death or serious injury. Measurement#1,#2,#3 or#4)on the Tank Installation Checklist. 12.1. GENERAL 11.3. DIAMETER MEASUREMENT WITH 12.1.1.In most anchoring systems,a tank is not adequately A STANDPIPE protected against flotation until the tank is fully backfilled and 11.3.1.Place the dipstick into a service fitting with a standpipe. the top slab is in place.Therefore,during the installation 11.3.2.Measure the distance from the tank bottom to the top process,the tank should be ballasted completely after the of the standpipe and record this measurement. backfill is at least 75 percent of the way up the tank and after postinstallation testing has been successfully completed. 11.3.3.Pull the dipstick up until the nail catches on the inside 12.1.2.Only under wet-hole conditions should ballast be top of the tank. added before the backfill is 75 percent of the way up the tank. 11.3.4.Measure the distance from the tank top(inside)to the See SECTION 5.3. top of the standpipe.Subtract the distance from the nail to the 12.1.3.Care must be taken so that the use of ballast does not base of the dipstick(1 inch)and record this measurement. contaminate the product being stored.This is especially im- 11.3.5.Subtract the second measurement(inside tank top to portant for potable water,chemical and diesel exhaust fluid top of standpipe)from the first measurement(tank bottom to (DEF)tanks. top of standpipe). 19