Laserfiche WebLink
0 0 <br /> 2.1.9 Test for Flammable Vapor Concentrations <br /> a) The most important phase of the operation is testing for flammability.Test the excavated <br /> area for flammable vapor concentrations before testing the tank. Conduct tests for <br /> flammable vapor concentrations with a combustible gas indicator,properly calibrated on <br /> hexane-in-air, thoroughly checked and maintained according to manufacturer's <br /> recommendations. <br /> b) If an eductor air mover is being used, perform vapor concentration tests through probe <br /> hole located in the side of the eductor (see Detail 1 A, Figure 1) with the air mover on.To <br /> ensure that vapors are drawn off the bottom of the tank, do not remove the drop tube <br /> when using the probe hole for vapor testing. <br /> Prior to opening the tank,a reading of 10%or less of the LFL (lower flammable level) must <br /> be obtained. <br /> c) If a diffused air blower is being used, perform test by removing the fill (drop) tube and <br /> placing the combustible gas indicator probe into the fill opening.With the blower off,take <br /> vapor readings at the bottom, middle and upper portions of the tank. Do not permit any <br /> liquid product to enter tube. Also test vapor concentration at the vent riser with the air <br /> blower operating.Once vapor readings of 10%or less of the lower flammable limit (LFL) in <br /> the tank and at the vent riser have been reached,the tank may then be opened safely. <br /> 2.1.10 Opening the Tank <br /> a) The tank may be opened after determining that a safe atmosphere has been established. <br /> Maintain continuous monitoring of vapor concentrations during the tank opening process. <br /> If there is no existing man way,a minimum 18"x 18"access opening may be cut in the top <br /> of the tank per API 1631,using air-driven or explosion-proof tools.However,some local and <br /> state regulators may require a minimum 22"x 22"opening.Check with the local regulations <br /> before determining minimum access opening size. Use chalk to outline the section to be <br /> removed, and drill a hole at one corner of the section, using an explosion-proof drill. Use <br /> lubricating oil to reduce friction and prevent sparking.Insert the combustible gas indicator <br /> probe into the hole to test for vapor concentration, and verify that the vapor <br /> concentration does not exceed 10%LFL. <br /> b) Cut out the access opening using an explosion-proof saw or snipper,using lubricating oil to <br /> reduce friction,heat and possible sparking. Before making the final cut,support the entry <br /> section to prevent it from falling into the tank. <br /> c) Pre-Entry Requirements and Precautions <br /> 1) Before entering the tank,follow all procedures described in API publications 2217 and <br /> 2015,ANSI 2117.1, NIOSH 80-106,NFPA 77,and all applicable sections of 29 CFR,Part <br /> 1910. (Also see Section 4). <br /> 2) Maintain controlled ventilation to ensure a safe atmosphere of 10%LFL prior to tank <br /> entry and while personnel are working within the tank.Monitor vapor concentrations <br /> periodically throughout the tank lining process. <br /> 2/99 <br /> Page 5 of 30 <br />