NOTE: Figures and pdf version still required.

Raising instrument when working with hydraulic power pack

1. When the instrument is to be removed from the borehole, remove the Cutter Drive Unit and water swivel and place out of the way.

2. Connect the CDU hydraulic hoses together and lay out of the way.

3. Remove the short 2" casing adaptor rod on which the CDU sits.

4. Remove the short CDU cutter drive rod.

5. Slide a Ball Foot Clamp down the length of casing that is sticking up above the gate – there may not be a sufficiently long length exposed, so in this event slacken the clamp bolts on the gate and lower the rams a little.

6. In any event there is no need for the gate bolts to be tight – the BFC ensures that the casing is securely held at all times. The gate needs to be loose enough for the casing to pass through it without catching.

7. The instrument can now be lifted up using the rams.
   
   CAUTION: When the probe has been drilled in to stiff clay the forces on the Chinese Lantern can be very high. Although carrying out a test will relieve much of the skin friction, there can nevertheless be quite large forces restraining the Chinese lantern. When the instrument is lifted the effect is to pull the instrument through the Chinese lantern. It is important under such circumstances that the instrument be lifted slowly.
   
   Unfortunately when lifting the instrument, all the control valves are by-passed, so that maximum flow is available to lift the rams quickly. This is the normal requirement.

8. To lift the rams slowly requires some care:-

   • Cut the engine revs to a minimum.

   • Disconnect the hydraulic hoses from the water pump and link them together.

   • Put the water pump control lever down. This cuts in half the available flow for lifting the rams.

   • Now crack open the control lever that lifts the rams – try to take about 4 minutes to lift the rams about 0.5 metres. After this any friction on the CHL has been largely removed.

   • Now turn off the water pump control lever and increase the engine revs to lift the rams at the fastest possible rate.

9. When the instrument is being lifted care must be taken to ensure that the hose is rising as the rods rise. It is possible for the hose to become caught in the borehole and to ride over it with the instrument, with disastrous consequences.

10. At the top of the stroke, place one of the BFC support plates in position as shown in Figure [22]. A large wrench now rests on this plate and is used to grip the casing.
    
    Note:- The way to use the wrench is to have the jaws slightly slack, to hold the wrench at the end of the handle and to lift up the handle.
    
    When the weight of the casing is applied to the jaws they will 'window-frame', and will be jammed against the casing. In fact, although not recommended, it is usually possible to let go of the wrench at this stage.

11. The rams can now be lowered, the ball foot clamp on top ensuring that even if the wrench should slip, the casing cannot fall down the hole.

12. Note:- Good communication between the person operating the hydraulic controls and the person holding the wrench is important. If the HGF gate should momentarily catch on the casing then the rams will need to be stopped quickly to sort the problem.

13. Another difficulty that sometimes occurs is that the BFC will not slide down the casing smoothly, possibly due to mud clogging the BFC. It may be necessary to move it by hand down the casing.

14. What must be done is to arrange that a joint on the casing appears a short distance above the BFC. It may be necessary to have one or two short strokes on the rams before this occurs.

15. Break the joint on the casing with the large wrenches, and lift the length of casing over the inner rod. DO NOT LET IT FALL TO THE GROUND AND CLOG WITH MUD. Place it safely out of the way.

16. Break the joint on the inner drive rod and place it out of the way in a clean place.

17. Now continue with steps [7] to [16] until only the last length of casing remains on the instrument.

18. When the last length of casing shows, lift the rams to the top of their stroke. Now lift up the instrument so that most of it is now visible in the rams. Do NOT lift it so high that the top bearing adaptor becomes jammed in the gate.

19. Clean off as much of the mud as possible so that the instrument is not too slippery. It is probably easier to use a bucket of water and a scrubbing brush rather than attempt to pressure wash the instrument using the water pump.

20. The instrument must now be lifted out of the borehole, which cannot be done until the clamping gate is removed. BE VERY CAREFUL. Make sure before the gate is removed that all necessary adjustments to the instrument and cable have been made so the period of time that the instrument is vulnerable to dropping down the borehole is kept to a minimum.

21. Two people are required to lift the instrument out of the rams. One person looks after the length of casing and ball foot clamp, the other person grasps the instrument. Pull the instrument OUT of the gate then UP to lift it out of the well of the HGF.

22. Carry it to a safe position.

23. Replace the gate.

24. Lower the rams.

25. Place a board or plate over the borehole so that nothing can fall into the hole.

26. Turn off the engine.

Raising instrument when drilling under rotary rig

When the instrument is to be removed from the borehole, it is usually the case that the probe is still gripped firmly by the soil. What is needed is a slow steady pull until the adhesion of the ground is broken. A rapid pull will risk damage to the Chinese lantern. A slow steady pull can only be supplied by the head of the rig.

Another factor to consider is that any pull ought to be on the outer 2" casing, but in fact the drill rig is coupled to the inner rods. The inner RW rods are quite strong but any pull is transferred to the bottom bearing in the shoe of the instrument.

The safe way of operating is now described.

1. Start by removing the rotary adaptor hardware as if for the addition of a new length of casing and rod (see Changing a rod).

2. Screw the male LH 2"/female RW adaptor into the top of the casing. Slide a ball foot clamp over the length of casing, and allow the clamp to sit on a plate or similar support.

3. Screw a length of RW rod to the coupler and pass through the head of the rig. Tighten the collet.

4. Now use the head to pull slowly and steadily on the instrument until the seal with the ground is broken and the probe moves easily. Although the pull is on the RW rods the load is transferred to the 2" casing.

5. Once every thing is moving freely it will be easier to use the winch to pull the equipment from the ground. Undo the free length of RW rod, and remove.

6. Remove the male LH 2"/female RW adaptor and couple the special swivel directly to the 2" casing string.

7. All lifting is now done with the winch. How much casing to remove depends on the height of the mast and what is most convenient to handle.

8. Lift up a suitable length of casing until the joint to be broken is clear of the ball foot clamp. Break the joint with large wrenches, and lift the 2" casing up until the equivalent joint in the RW rod is exposed.

9. Break this joint with the small wrenches, and remove out of the way the length of casing and RW rod as one piece. Make sure that the correct joint of the RW rod is broken, so that the 2" casing is always male thread down, and the inner RW rod is always female thread down. This avoids confusion later.

10. Repeat the process until the probe can be lifted clear of the borehole.

11. It is of great importance at all times to ensure that the hose and cable assembly comes back with the instrument. Hose and rods must always move together. It is easy to miss this, and the consequences can be expensive.