Wetstock Reconciliation at fuel storage facilities - Carrickfergus ...

5d. Tank stock readingsProblem Definition Effect on data SolutionShort dipstick Dipstick is not the correct Large wetstock variances recorded. Replace any short dipsticks.length for the tank.See 5d.i.Vapour recovery Vapour recovery creates Changes in tank pressure affect Fit a pressure relief valvewith dipsticks pressure differences in the tank. tank stock readings. (dump valve) where possible.or unbalanced This has an adverse effect on See 5d.ii.hydrostatic gauges tank stock readings.Tank gauge Gauge is inaccurately Inaccurate gauge readings. Arrange for gauge recalibration and, incalibration calibrated for the tank. the meantime, account for stock level intank when interrogating wetstock data.5d.i – Short Dipstick300l200lEach dipstick is specific to thedimensions of an individual tank soit is important to check that it is thecorrect one for the tank and that thereare no signs of wear on the dipstick.Each division on a dipstick representsa volume of fuel, so the divisions atthe middle of the tank are smallerthan those at the top and bottom ofthe tank. All tanks monitored with adipstick must have a protective plateabove the base of the tank to preventdamage to the tank.Figure 4Dipstick inmiddle of tank8400l8300l8200l8100l8000l7900l7800l100lDipstick at bottomof tankA worked exampleIf the bottom 5cm is missing from a dipstick the stick will sit 5cm lower in the tank.At the bottom of the tank 5cm is equivalent to 1 division on the dipstick, which represents 1unit of volume (in this example 1 division = 100 litres). Therefore this short dipstickwould measure 600 litres of fuel when there are only 500 litres in the tank.At the middle of the dipstick 5cm is equivalent to 5 divisions because the tank is wider,and this means that in the middle of the tank the dipstick will measure 5 units more fuelthan are present. In this example this means that the dipstick measures 500 litres more fuelin the tank than is actually present.Clearly this creates a problem for wetstock records, as the amount of fuel in the tank willbe overestimated by varying amounts depending on the volume in the tank. In turn thiswill make it harder to identify any problems.7700l7600l7500l7400l7300l7200l7100l7000l6900l© Environment Agency10