104 JT920/JT920L - OPERATION
ASSEMBLE BACKREAM STRING
104 JT920/JT920L - OPERATION
ASSEMBLE BACKREAM STRING
Determine Fluid Requirements
Backreaming is only successful when enough fluid reaches the
bore. The amount of fluid needed depends on size of bore,
pullback material, and soil condition.
This section describes how to find the minimum amount of fluid
needed in perfect conditions. Use more fluid than recommended
or the bore might be dry and unsuccessful.
1. Determine size of backreamer and outside diameter of
pullback material. Use APPENDIX, section B, to find amount
of fluid needed for each.
For example, you find that a 6 in (15.2 cm) backreamer
requires at least 1.5 gal/ft (19 L/m) and a 3 in (7.6 cm)
product diameter requires at least .4 gal/ft (5 L/m).
2. Subtract amount needed for pullback material from amount
needed for backreamer. This answer is amount of fluid
needed to drill each foot or meter.
You now find you need at least 1 gal for every foot (12 L for
every meter) drilled.
3. Multiply answer by distance per minute you plan to
backream. The answer is an estimate of amount of fluid you
will need for each minute of backreaming.
Now, if backreaming 2 ft/min (.6 m/min), you need at least
2 gal (7.6 L) for each minute of backreaming.
4. Estimate pressure you will be using.
5. Using APPENDIX, section C, select nozzles that, added
together, supply at least the amount of fluid per minute
needed for the flow and pressure you will be using. A
combination of nozzles that will supply more fluid per minute
is recommended.
Determine Fluid Requirements
Backreaming is only successful when enough fluid reaches the
bore. The amount of fluid needed depends on size of bore,
pullback material, and soil condition.
This section describes how to find the minimum amount of fluid
needed in perfect conditions. Use more fluid than recommended
or the bore might be dry and unsuccessful.
1. Determine size of backreamer and outside diameter of
pullback material. Use APPENDIX, section B, to find amount
of fluid needed for each.
For example, you find that a 6 in (15.2 cm) backreamer
requires at least 1.5 gal/ft (19 L/m) and a 3 in (7.6 cm)
product diameter requires at least .4 gal/ft (5 L/m).
2. Subtract amount needed for pullback material from amount
needed for backreamer. This answer is amount of fluid
needed to drill each foot or meter.
You now find you need at least 1 gal for every foot (12 L for
every meter) drilled.
3. Multiply answer by distance per minute you plan to
backream. The answer is an estimate of amount of fluid you
will need for each minute of backreaming.
Now, if backreaming 2 ft/min (.6 m/min), you need at least
2 gal (7.6 L) for each minute of backreaming.
4. Estimate pressure you will be using.
5. Using APPENDIX, section C, select nozzles that, added
together, supply at least the amount of fluid per minute
needed for the flow and pressure you will be using. A
combination of nozzles that will supply more fluid per minute
is recommended.
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