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The air box and tube clamp are now set up to blow air through the tube. Connect the
air as for normal blowing. Make sure there are personnel at the other end of the tube
run, and that they are aware that the air is to be turned on. Make sure that a suitable
device is fitted (a catcher is available from CBS Products Ltd; speak to our sales
department for details) to obviate injury should any object be expelled from the far end
of the tube.
The far end of the tube run should be monitored, air should be leaving the tube under
reasonable pressure. The minimum pressure required will vary with the length of tube
in the run, the friction characteristics of the tube and the cable and the lubrication being
used. However, as a starting point the air leaving the far end of the tube should be (at
least) similar to a light breeze. Bear in mind that if the tube run is of considerable
distance, it may take a few minutes for the air to reach the far end of the tube.
If after waiting a suitable time there is no air leaving the far end of the tube, this would
indicate that there is a blockage or similar obstruction in the tube run, or, that the tube
is fractured. In either case the fault should be corrected before any attempt is made to
blow cable down the tube.
Once the tube integrity has been confirmed by the method outlined above. The tube
may be lubricated.
Open the air box and tube clamp assembly, as shown in the sketch above, withdraw
the tube and raise it so that the lubricant will pour into it easily and not overflow from
the top. Pour lubricant of recommended quality and quantity down the tube (A
recommended quantity is 100ml per 1km of tube length). Insert a suitable foam plug
into the tube and put the tube back into the air box and tube clamp as shown in the
sketch above.
The air box and tube clamp assembly are now set up to blow the foam plug through the
tube, the foam plug will help to deposit an even coating of lubricant to the inside walls
of the tube. Connect the air as for normal blowing. Make sure there are personnel at
the other end of the tube run, and that they are aware that the air is to be turned on.
Make sure that a suitable device is fitted (a catcher is available from CBS Products Ltd;
speak to our sales department for details) to obviate injury should any object be
expelled from the far end of the tube. When the foam plug has been expelled from the
far end of the tube run, cable can be installed into the tube.
Note:
when the air is turned off, after checking the tube integrity and sending the foam
plug down the tube to spread the lubricant. It may take some time for the pressure in
the tube to dissipate, time must be allowed for the pressure to fall back to low levels.
