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API IP 1585:2001 pdf download

6.1.7 If high flow flushing back to a tank is undertaken. it is necessary to ensure that the venting capacity of the tank is not excccdcd. If there is any doubt, a roof manhole, dip hatch or other top opening should be opened during the receipt of the fuel.
6.I. Fuel conductivity should be considered. see Section 13 and Table B I.
6.I.9 If a ‘return to tank’ system is not possible, the flushing should be carried out through the system. preferably into tcmporary fixed tankage. Where temporary fixed tankage cannot be provided, tank vehicles or refuellers can be used, but the limited flushing volume makes the associated operational and safety aspects more difficult to manage. As there may be limited refueller capacity at airports with a hydrant system. the use of outside road tank vehicles should be considered.
The flushing tanks need to be in a clean condition, or be able to be cleaned to this standard, to allow the product to be returned to normal jet fuel storage. If this is not possible, the flushed product may have to be downgraded to non-aviation use unless it is confirmed by laboratory testing against the relative fuel specification that it is fit for use in aircraft.
6.1.10 To achieve the high flow, it may be necessary to install a manifold at the end of the line to be flushed so that the fuel may be pumped into more than one temporary tank, into the compartments of a single vehicle, or into more than one vehicle.
6.1.11 It is recommended that at least two, preferably three, times the capacity of the section being cleaned. be flushed at the fastest flow velocity achievable. tJp to 3 rn/sec is desirable.
6,1.12 Where there is a shortage of access points some types of low point may be converted for flushing by removing the small sampling/flushing line and installing a pit valve on the riser. In this way, a faster flow through the hydrant system is possible. If a low point is used, the dry-break should be removed to avoid damage, jamming with debris etc.
6.1.13 After each flushing sequence. low points should be checked for cleanliness (with ‘sample tubes’ replaced, if removed as in 6.1.12).
6.3.$ Although not yet used in jet fuel on an operational hydrant system, a reverse flow nozzle (nozzle with vents pointing backwards, see Figure I) is very commonly used in drain clearing. This method has been used successfully to remove dirt from a newly constructed hydrant system and from an underground pipework system in a depot. This was done before hydrotesting of the system. water was used to blow back (he dirt.
This device travels forward by the propulsion provided by the reverse flow. The pressure may be adjusted to ensure that the dirt is dislodged. The dirt can be vacuumed out by a suction device (such as the cleaning sledge) or returned to the truck used for the pumping. Precautions should be taken to ensure that the dirt being blown back does not pass the entry point (possibly a cleaned out section of the hydrant). This method does not limit travel to 50 m (theoretically unlimited fora straight section of the hydrant) as it has a built-in propulsion system. As the nozzle is small in size, the volume of water required to propel it forward and blow back the dirt is relatively small but at a high pressure. After the nozzle has travelled the maximum distance that it is intended to travel, it may be retracted slowly while pumping through the nozzle continues,
The dirt and debris continue to be blown back as the nozzle is retracted. A tandem powerful suction device can be used.
6.3.6 (‘(‘TV survey has shown that small ‘cone shaped’ mounds of particulate can build up in the hydrant main below risers. This may be caused by line debris starting to risc in the pipe during high flow only to drop back under gravity when the flow reduces or stops. Such debris may be pumped out by lowering a hose or metal lance down the riser alter removing the pit valve. If a metal lance or equivalent is used, care is necessary to avoid causing damage to the internal lining of the pipe.


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