Dawson HPH 1200, User Manual

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3.5 Using the hammer underwater
It is possible to drive piles with this hammer underwater. However, the hammer must be prepared
correctly in order to do so - it can not be used underwater in standard format.
The work involved is briefly as follows:-
a) The stroke adjuster ‘slot’ in the leg guide must be sealed with a cover.
b) The insides of the hammer should be suitably greased to minimise the effects of corrosion.
c) The gaps between hammer casing, leg guides and top cover must be sealed with silicone mastic.
d) The inspection holes near the bottom of the hammer casing must be plugged.
e) A threaded compressed airline port must be added in the bottom end of the hammer casing or leg
guide.
f) The hammer must be run in conjunction with a 35/70 c.f.m. (100 psi) air compressor.
g) The hammer grease nipples must be greased after every pile drive to ensure ample lubrication.
NOTE: FOR DETAILED ASSISTANCE WITH THIS TYPE OF WORK PLEASE CONTACT
THE MANUFACTURER.
3.6 Wider or special pile sections.
The HPH 1200 hammer in standard format will drive a considerable range of steel piles. In some
applications, however, where sheet piles are particularly wide or perhaps boxed together it is
possible to use simple leg insert modifications and/or spreader plates to give improved pile coverage
reducing pile head stress and improving productivity rates.
A good example of this is with B.S.C. LX or Arbed PU type sheet piles. The standard leg inserts
can have “wing extensions” bolted on to correctly centralise the hammer on a single sheet pile.
Then either a special anvil can be used to give wider coverage, or, by dropping the inserts to a lower
set of location holes, a ‘spreader plate’ can be added below the standard anvil to give improved pile
coverage. This is a tried and tested technique (see figure 3).
With tubular piles, for example, the standard inserts can be removed and in place some simple bolt
on plates added to centralise the hammer on the tube (see figure 4). A further refinement, if
necessary, is to weld a ring onto the underside of the anvil to give correct location on the tube.
PLEASE CONTACT THE MANUFACTURER IF YOU HAVE A SPECIFIC PILE DRIVING
PROBLEM - IT MAY HAVE BEEN DONE BEFORE!