The “snow plough”

This is a robust mechanical cleaning system (photograph above, right) with the primary task of scraping solidified paraffin (also scaling or incrustations) from the pipe wall. It is a segmented tool with universal joints consisting of three modules: the pull module, the plough module and the transmitter module.

It is intended for use within the well proven cleaning concept of running a series of different pigs with gradually increasing toughness or aggressivity. The snow plough tool must be run in a late position. Its steel ploughs, positioned on the middle module and manufactured to the exact wall curvature, take care to remove hard deposits that the previously run cleaning devices have not scraped off. The loading of the individual ploughs is adjustable over a wide range. It is recommended to apply a low load at first and increase it gradually from run to run as the cleaning progresses.

The “snow plough” may remove large volumes of paraffin, which will be left in the line behind the tool. In subsequent runs, it will push these more or less solid particles in front and accumulate an increasing volume of paraffin. In long distance pipelines this process may lead to a critical situation which may ultimately create a plug at a certain location. To avoid this, the snow plough’s pull module (front) is equipped with a large diameter pressure relief valve that opens as soon as a certain pre-set pressure differential is exceeded. This feature allows to set the snow plough to accumulate a certain volume of paraffin, which (together with the tool’s delta p) causes the valve opening pressure. Once the valve inside the pull module is open, crude oil from behind the tool will substantially flush through it, deviated towards the pipe wall in the front of the plough, diluting the paraffin plug. During this flushing phase the tool will decelerate or, if excessive volumes were collected, even stop. As the paraffin plug is dissolved, the pressure relief valve will close again and the tool recovers its normal (non bypass) speed.

This pull module can be used to pull all sorts of pig trains, be it various cleaning devices or any kind of inspection system. Also the GEO+ system shown above is equipped with an identical pull module.

The transmitter module carries a long range/long life pig transmitter that enables pig tracking or locating of a standing pig. The 18” tool (photograph above) can be received with depth of soil coverage up to 5m and has a battery lifetime of 6 weeks.