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MODEL 220
HYDRAULIC
IMPACT HAMMER
I.
GENERAL INFORMATION
A. GENERAL DESCRIPTION
The J&M Model 220 Hydraulic Hammer is a Free-Fall hammer. The ram is lifted by
the hydraulic actuator and then allowed to free-fall, impacting the pile. The hammer
has been designed to provide maximum flexibility by enabling the contractor to vary
the energy range of the hammer to suit job conditions. The 220 hammer design
incorporates an all hydraulic control system, with no electrical or electronic controls
used, to ensure reliability and field serviceability. Further, without the need for
vulnerable umbilical cords, this unit is readily adaptable to alternate hydraulic power
sources.
The 220 hammer is normally powered by the same Model 175 power unit that
powers J&M Vibratory Hammers and J&M Earth Augers.
contractor to use a single power unit on jobs where both the Impact Hammer and a
Vibratory Hammer or Auger are needed. The Hammer can also be powered by any
source providing the required flow, pressure, cooling and filtration. The 220
Hydraulic Hammer delivers 46,000 ft-lbs (6359.7 Kg-M) of energy at its full stroke of
4'-0" (1.2M) at a blow rate of 40 blows per minute.
B. MAJOR COMPONENTS
The hammer system consists of 8 major components (Fig. 1) page I-4:
Hydraulic Actuator
Ram
Guide Structure
Lifting Bale
Drive Cap
Controls
Interconnecting Hoses
Power Unit
Hydraulic Actuator
The hammer is driven by the hydraulic actuator. The actuator is coupled to the ram
using a shock absorbing, self aligning, connection. Hydraulic oil flows from the
power unit, at pressure, to the actuator which accelerates the ram upward.
Attached to the ram is a trip bar which activates a trip valve after the ram has risen
a predetermined distance. Activation of the trip valve stops the flow of oil to the
actuator. The ram then decelerates and free falls to impact the pile. Power unit
energy is stored in a hydraulic accumulator while the ram is falling.
I-1
This permits the
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