The pile hammer should be used only by well trained and experienced personnel. Before using the hammer all instruction and safety manuals should be thoroughly reviewed by all operating and maintenance personnel. These references are an invaluable source of information and should be retained by the owner for future study and to train new employees. Copies of these manuals should be kept with the hammer at the construction site for ready access. Additional copies are available from Vulcan.
Safe use of the pile hammer, as with any machine, is dependent upon the skill, knowledge and concern of those who maintain and use it. Because of the wide variety of environments and applications in which this machine may be used, a comprehensive description of detailed rigging and operating techniques within this booklet is not possible. (Specific requirements should be addressed to Vulcan’s engineering department.)
For reasons mentioned elsewhere, no one should be any closer to the hammer during driving than is absolutely essential. All workmen should wear safety clothing including hard hats, safety shoes, safety glasses and hearing protection.
Before, and periodically during usage, a complete inspection should be performed on the hammer and all associated equipment to insure operational integrity. The associated equipment includes items such as the compressor and/or boiler, hoses and hose couplings, leaders, support and lifting equipment and all rigging, etc. On the hammer, particular attention should be given to sheaves, pins, retaining bolts, hose couplings, the valve mechanism, all keys, ram point, pile cap, and the lifting points. Supervisors should be certain that all inspection and maintenance is properly done.
During the driving operation and whenever the hammer is moved, constant supervision and inspection should be provided. If abnormalities are observed, driving should be stopped immediately. One example would be that of the loss of one or more ram keys. If both keys are missing, then the ram would obviously no longer be connected to the piston. Without the ram to slow the acceleration of the piston on the up stroke, the piston may impact into the cylinder head with catastrophic effects. Another dangerous situation would be to continue hammer operation without a piling seated in the pile cap. In this event, the entire force of the falling ram could be absorbed by the hammer’s columns, base and pile cap. Few such strokes could be sustained without severe damage to the hammer. Obviously, such destruction would be hazardous to anyone in the vicinity. Also, the cylinder head lifting points (sheave, axle, pins, keys and nuts) should be continuously checked for worn, loose or missing parts. Damaged or missing components oif this assembly could cause hammer to disconnect from rigging and fall.
The effects of unregulated steam or air pressure may also create a risk. As noted elsewhere, failure of any of the hose couplings, while under pressure, could be very dangerous. In addition, operation at pressures either higher or lower than specified design should be avoided since structural damage to the hammer or inefficient operation may result. Obviously, all air or steam supply hoses must be properly sized to avoid undue flow restrictions.
Damage to the pile, pile cap, ram point and piston can occur if the alignment of the hammer and the pile is not correct. That is, the central axis of the hammer should be in alignment with the central axis of the pile and the pile end should be square and uniform. If the error in alignment is great, the hammer will receive an unbalanced structural loading which could result in either a fatigue failure in the hammer or a significant shortening of its useful life. Obviously, this type of condition could be both expensive and dangerous, but can be avoided with reasonable care.
A common pile driving criterion is to drive until a certain number of blows per foot of pile insertion is achieved. This measure is based on the amount of energy delivered with each stroke of the ram. In a single acting hammer, the energy is dependent upon the falling weight and stroke length. Since falling weight is constant, only changes in stroke length can affect the energy delivered. Therefore, if a variable stroke hammer is used, it should be noted that the blow count taken is compared to the proper stroke energy, i.e., the blow count criterion will vary with the stroke length used. The supervisor should correlate the blow count criterion and the stroke length. Otherwise, pile damage, added expense, or inadequate pile installation could result. It should also be noted that significant deviations in pressure delivered to the hammer from the recommended pressure may affect the actual operating stroke length and thus influence the energy in each blow of the hammer.
Since the pile hammer is such an extremely powerful machine, it is conceivable that even with normal operation, surroundings at the driving site could be damaged. Operators should take every precaution to see that exhaust from the hammer and vibration of the earth are not a threat to the area surrounding the driving site. Failure to do so could be unsafe and possibly lead to expensive property damage.
As an additional precautionary measure, a pre-pile driving survey could be made.
Given the respect it deserves, the pile hammer should provide years of safe service. However, the ultimate safety and reliability of the hammer rest in the hands of the user.