User's Manual

LMPL20 • 17
3. Where pre-poured inverts are used be sure to attach the correct feet size and set the laser in the center
of the invert (Fig. 26).
4. Use an optical level or rotating laser level to obtain the elevation from the elevation rod or (See Fig. 26)
5. Add the cut amount obtained from the stake to the elevation obtained by the optical level or laser.
6. This dimension is the distance from the optical level or laser to the invert of the pipeline - so subtract
the distance from the invert to the center of the laser spot.
7. Place the grade rod in the manhole at the correct elevation and position the laser at the correct height
in relation to the grade rod.
8. Note that the grade rod can be positioned on the top of the LMPL20 and a correction of - 2.78
inch (70.5mm) is required.
How To Set The Grade
To set grade follow procedures as described in section “Grade” page 8.
How To Establish and Set Line or Direction
Procedure 1 (Fig. 27)
1. Set the LTU or Transit over the centerline of the pipe using a plumb bob and offset measurement.
2. Position the sighting scope of the transit so that the vertical crosshair is aligned to the next
manhole position of line stake.
3. Plunge the sighting scope into the area where the laser is set up and position the laser pivot or
alignment crosshair point.
4. Bring up the scope so that the vertical crosshair is in the position of the open trench in front of the laser
where the laser spot will project.
5. Using the remote control RC20 drive the line adjustment left or right until the laser spot Is in line with the
vertical crosshair In the scope.
6. The laser housing and the laser spot in front of the laser are now aligned with the axis of the pipeline
stakes and pipe laying can begin.
Procedure 2 (Fig. 28)
1. Mount the Manhole Mount Transit Tower (optional) to the manhole and position the optical
instrument or transit directly over the centerline of the pipeline.
2. Drop a plumb bob down from the optical instrument and position the pipe laser at the pivot point
directly under the plumb bob.
3. Align the optical instrument by the vertical crosshair to the next manhole position stake.
4. After locking the horizontal rotation, plunge the scope into the trench at a convenient spot to view the
laser spot.
5. Using the remote control RC20 drive the left or right direction control until the laser spot is aligned with
the crosshair in the optical instrument.
6. The LMPL20 is aligned with the pipeline axis and pipe laying can begin.
Procedure 3 ( LMPL20 )
1. Position the LMPL20 exactly in the center of a poured invent or centerline marked on the bottom
of the manhole so that the pivot point is on the centerline.
2. Attach the loose end of a plumb bob cord to the notch on the LMPL20 at the pivot point.
3. Extend this cord to the top of the manhole and so that the cord is supported over the thumb of the
operator. The free end with the plumb bob then hangs from the thumb of the operator.
4. Using the cord from the thumb to the plumb bob as a guide move the thumb left or right until both sides
of the cord are vertical and aligned with the next manhole stake.
5. Using the remote control RC20 drive the left or right direction control until the laser spot is aligned with
the both of the vertical cords.
6. The LMPL20 is aligned with the pipeline axis and pipe laying can begin.