WATER JET CONFERENCE - Waterjet Technology Association

or the abrasive must be manually topped up on a regular basis. System capacity is usually of the
order of 50 kg. per gun, depending on the design of the machine and the amount 'lost' by resting
on flat areas within the machine.
Aglomeration of Abrasive.
If the recirculation machine is used as part of a degreasing process, or where an aqueous
rust inhibitor is added to the water, care must be taken to prevent the abrasive gelling into large
amorphous masses. Similarly no additives which have a tendancy to foam must be used,
otherwise the machine may dissappear under a cloud of foam. The design of each individual
machine must be very carefully made to eliminate flat areas where abrasive can sit, and the
conical section of tanks are sloped greater than the natural piping angle of the specific abrasive
chosen (Figure 13).
SPECIAL ENTRAINING DEVICES:
Tube Cleaning Heads for Rotating Tube Systems.
Normal cleaning heads have the abrasive inlet, spool and discharge tube along a single
axis However, they may be angled [see Fig. 14]
This head is mounted on a rigid lance, which can slowly be inserted into the tube, while
the latter is rotated. If the speed of entry and rotation are correctly coupled together the internal
pipe surface will be cleaned by a screw cutting action.
360° Tube Cleaning Devices.
There has been a need for an abrasive internal pipe cleaning device, which can give
complete coverage without the need for the pipe to be rotated. Such a device for the cleaning of
50ft. 7" diameter drill pipe,is shown in Fig. 15.
This unit has many special features. The unit has two jetting heads combined on the
carrier, the rear one being for abrasive jetting while the front one is for washing and the removal
of debris. The rear abrasive jets are angled backward, so the unit is self propelled up the pipe.
The speed of advance is controlled by the speed at which the high pressure hose is fed off a
hydraulic hose reel. Abrasive is fed into the unit via the two inlets at the rear, while high pressure
water is fed via a single central entry at the rear. The unit progresses up the pipe at a
predetermined rate, until on reaching the far end, the front valve spindle is moved by contact
with a blanking plug. This has the effect of opening a second circular jetting orifice at the front
of the unit. Because the pump is new feeding two sets of jets; the pressure falls. This fall in
pressure is detected at the hose reel, which reverses, thus pulling the cleaning head debris and
abrasive back to the entry end. At the same time the abrasive feed is turned off and on return all
debris is flushed out of the pipe. This unit is designed to run at a pressure of 10,000 psi with a
flow rate of 40 gallons U.S. per minute. Figure 16 shows the relationship between cleaning head
advance rate and abrasive feed for varying pump horsepowers at a constant pressure of 7000 psi.
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