Pile Hammer, Pile Driving Equipment
Pile hammer is very important Pile Driving Equipment. The operation of installing a pile into the ground is known as Pile driving. The oldest method of Pile Driving and the most widely used method is Drop hammer. In this method the hammer allows it to fall on to the head of the pile.
The most important advantage of pile rig, It pile accurately. It must be rugged and rigid enough to keep the pile and hammer in alignment and plumb inspite of wind, underground obstructions and the movement of the pile hammer.
Types Pile hammers
- Drop hammer
- Single-acting hammer
- Double-acting hammer
- Diesel hammer
- Vibratory hammer
This is the simplest type of hammer. The hammer, ram or monkey is raised by pulley and which and allowed to fall on the top of the pile. The drop hammer is simple but very slow this is used for small work only.
In this type, the hammer is raised by steam or compressed air and is allowed to drop on to the pile head. The hammer is usually have 10 to 100 kN weight.The height of fall may be about 60 to 90 cm. The blows may be delivered much more rapidly than in the case of drop hammer.
In this type, steam or air pressure is employed to lift the ram and then accelerate it downward. The blows are more rapid; from 90 to 240 blows per minute, thus reducing the time required to drive the pile, and making the driving easier. The weight of the ram may be 10 to 25 kN.
This type of hammer loses its effectiveness with wear and poor valve adjustment. The energy delivered in each blow varies greatly with the steam or air pressure. If the number of blows per minute is approximately the rated value, the pressure is probably correct.
Steam operation is more efficient, particularly with circulating steam generators. If the hammer is to be operated under water, which is possible with enclosed double-acting types, compressed air operation is necessary.
The advantage of power hammers is that the blows follow in rapid succession, keeping the pile in continuous motion and reducing the effect of impact, thus minimising the damage to the pile head.
This works on the internal combustion of diesel oil. This type is self-contained, economical, and simple. The disadvantage is that the energy per hammer blow varies with the resistance offered by the pile and is difficult to evaluate. Thus, the diesel hammer is best adopted to conditions where controlled energy is not critical.
A double-acting hammer activated by hydraulic pressure is somewhat faster and lighter compared to equivalent steam hammers because the operating pressure is much higher. The compact hydraulic pump system is easier to move than the bulky air compressor or steam generator.
A heavy single-acting hammer may be more effective sometimes than a light double acting hammer, since the hammer may bounce back due to high velocity, in soils of high resistance to penetration.
The driving unit vibrates at high frequency and thus, the driving is quick and quiet. A variable speed is used for the purpose of creating resonance conditions. Vibratory hammer allows easy penetration with small driving effort.
Most pile hammers require the use of driving heads, helmets, or ‘pile caps’ that distribute the force of the blow more evenly over the pile head. The number of blows required depending upon the material and weight of the pile.
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