Bearings feature strongly in revolutionary new pump
Visitors to the Hanover Fair earlier this year had an opportunity to
see the working parts of an innovative new mud pump developed by National
Oil Well in association with its bearing supplier, INA FAG
Oilfield mud pumps are used to circulate drilling fluids down through the
drill string and up through the well bore. Conventional three-cylinder
pumps, called triplex pumps, are large and heavy, and there is little
scope left to enhance their performance, which was why National Oil Well
embarked on a project to develop an all-new pump capable of higher
performance without weight or space gain. Its partner in this project was
bearing manufacturer, INA FAG.
At the heart of the new 'Hex' pump is a precision machined, cast cam
plate that rotates at 212rpm. The motion of the cam plate places
considerable demands on the bearing arrangement and guidance system. And
since it has to cope with variable pressure and flow volume, it must be
able to readjust quickly to conditions - a requirement that has been met
by the cam plate's special stroke contour.
The forces that occur are primarily axial and are supported on the
locating-bearing side by a thrust tapered roller bearing. A cylindrical
roller bearing is responsible for radial guidance, while the mating
bearing is an angular contact thrust ball bearing, pre-loaded via a
pressure ring with springs to prevent slip. In order to make the handling
and mounting easier, all large bearings are equipped with self-retaining
cages and have threads for eyebolts.
The cam rollers are mounted in a fork and these transform the motion of
the rotating cam plate stroke contour into a linear movement of the
stroke cylinder. This task is performed by robust roller type profiled
rail units, RUE 55D and RUE 65D-H, supplied by INA. Two cylindrical
roller bearings, in combination with a four point contact ball bearing,
form the pinion shaft bearing supports of the mud pump drive. The
cylindrical roller bearings support the radial forces while the four
point contact ball bearing supports the axial forces. All of these
bearing arrangements were designed using INA's 'Bearinx' bearing
calculation software.
Because of the critical nature of mud pump applications, the new Hex pump
is equipped with FAG industrial Services' condition monitoring tools.
Using the Dtect X1 online system, vibration signatures are constantly
monitored and any out-of-spec condition is transmitted via satellite for
evaluation by FAG experts. This ensures that any defect is detected at
the earliest possible stage, allowing maintenance to be carried out
before the onset of a serious malfunction.
Compared with a conventional triplex pump, the new Hex pump offers a 33%
reduction in size, a 30% reduction in weight and an improved pumping
performance of up to 3,900 litre/min.