There are two reasons for the low linefill and low throughput. The
first is the use of blowers (fans) which block the passage of the
capsules. Capsules must stop before they reach any blower, and then
must be routed through a bypass line in order to proceed down the
pipeline without going through the blower. This greatly impedes the
capsule traffic, and limits the linefill rate. Another reason for the low
linefill is in-line loading/unloading. Instead of taking the capsules out
of the pipe for loading/unloading, the current system has the capsules
loaded and unloaded while they are inside the pipe. Flow is stopped
while loading/unloading is taking place. This again greatly impedes
the traffic and reduces the linefill rate.
Therefore, in order to improve the current PCP system and increase
its linefill, two things must be done. First, a non-intrusive type
of pump must be used in lieu of blowers which impede capsule
motion. Secondly, loading and unloading of capsules must be done
outside the pipeline—ie., off-line loading/unloading. With such improvements,
it is believed that a fivefold increase in the linefill of
PCP from the current 3%, to 15%, is possible.
The most promising non-intrusive pump for PCP is electromagnetic
capsule pump such as linear induction motor (LIM), the same
technology used for advanced roller coaster systems and magnetic
propulsion and levitation of high-speed train (5). As capsules of
metallic wall enter the LIM, an electromagnetic thrust is generated on
the capsules to accelerate and to push the fluid forward. The capsule
wall will be made of steel with an outer layer of aluminum. An “eddy
current” is induced in the aluminum wall which generates the electromagnetic
force (thrust) needed to push the capsules forward. By
having the inner diameter of the LIM made slightly smaller than the
inner diameter of the pipe, the capsules going through the LIM behave
like a piston pump, causing the fluid in the pipe to be pushed
forward (6). See Figure 3 for such a pump.
Note that LIMs can be used not only for pumping capsules, but
also for capsule injection/ejection, climbing steeps slopes, capsule
speed control, and capsule breaking. They need not be placed along