Explain Single & Double acting hammers with neat sketch.
hammers-pump and compressor • 3.2k  views

Single Acting Hammer:

  • In single acting pile driving the ram of hammer is raised by the steam or compressed air when works on the underside of the piston.
  • When the ram reaches the top of upward stroke, the pressure of the steam or air is released, which results in the fall of the hammer by gravity.
  • The weight of ram of these hammers are generally available in the range of 1.5 to 10 tonnes, thus making overall weight of hammer between 2 to 20 tonnes.
  • The number of blows per minute are generally around 60.
  • These hammers can also be used under water, where the hammers are lifted and dropped in an enclosed casing.
  • As they deliver heavy blows at faster speed, the time required for driving operation is lesser as compared to the drop hammers.
  • The speed of driving is slower than that of double acting hammer hence it is less suitable where very fast driving of lighter piles is required.
  • These hammers cost less than double acting hammer but need more investments.

Double acting hammer:

  • This is similar to single acting hammer except that steam or air acts on both sides of piston in this type of hammer.

  • Steam or air raises the ram to the top of the driving stroke and then drives it down in its downward stroke.

  • This also increases the speed of downward motion and thereby increases the number of blows per minute.

  • In this case steam or air is admitted above the piston, after piston reaches to the top during its upward stroke.

  • During the same time the fluid is allowed to escape from the underside of the piston.

  • The speed of the ram is about 100 blows per minute.

  • The energy delivered by each blow is about 20% more due to steam pressure assisted gravitational force during downward stroke.

  • These hammers are capable of fast driving of light or medium heavy piles in hard soils.

  • These are also suitable to drive steel sheet piles.

Below is the diagram for both Single & Double acting hammer:-

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