API IP 1585:2001 pdf download
API IP 1585:2001 pdf download.GUIDANCE IN THE CLEANING OF AIRPORTHYDRANT SYSTEMS.
Note: Air should not be used unless the line being pigged is empty of fuel. Only low air pressure. sufficient to propel the pig. should be used.
6.2.6 Examination of the pig after traversing the line will indicate the internal condition. If (he pig is clean. no further action may be required but if it is dirty. the process should be repeated. Multiple passes may be required and should be carried out until a clean condition is obtained.
6.3 OTHER MECHANICAL CLEANING
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6.3.1 At one airport. a patented ‘Ulcaning Sledge’ has been designed. It has been successfully used to clean out extensive sections of the hydrant in pipes down to 40cm (16 inch). The sledge was fed along the line with a CCTV camera following it to observe and record the results on videotape.
63.2 After depressurising the section. removing the hydrant pit valves and lowering the level of fuel if necessary. the sledge was entered into the main hydrant line through a 15cm (6 inch) diameter riser. The sledge can be fed along to the next riser with an efiective range at present of approximately 50 m. which is considered to be sufficient to work from stand to stand.
63.3 The sledge was fitted with magnets to pick up any ferrous material and a suction hose to pick up nonferrous material and water, where present. The hose was connected to a pump with good suction characteristics, in this case the pit servicing vehicle. with a coarse strainer fitted in the suction line to catch any large debris and to protect the pump.
63.4 It was seen that time should be allowed for adequate seuling of any fine ‘mist’ of particulate that may be disturbed by the movement of the sledge. which may not be pumped out, before reinstating the line to service. It is usual to flush at least twice, or preferably three times, the capacity of the section cleaned into a tank vehicle lo ensure that quality control requirements
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 the 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 for a 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 CCTV survey has shown that small ‘cone shaped’ mounds of particulate can build up in the hydrant main below risers. This may be caused by fine debris starting to rise in the pipc 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 after 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.
