64 inches in diameter and preferably made of a rigid material the hollow helmet or helmets and the pipe to be inserted are preferred to be up to approximately 120 inches in diameter and may be 160 or up to 190 inches in diameter the hammer 12 is preferably a high energy impact hammer generally 60 000 260 000 foot pounds such as one used in large offshore vertical piling construction projects in use the hammer hits approximately 40 60 blows per minute and can drive 30 feet of large diameter pipe on average in about 35 minutes however unlike offshore construction the hammer is used horizontally rather than vertically several elements must be in place to ensure that the hammer operates as intended larger hammers may be used as necessary up to 500 000 foot pounds fig1 a shows a schematic diagram of the high force horizontal pile driver 12 used to drive the pipe casing 110 and the drive hammer set up when driving horizontally to counteract against the increased pressure in the gas buffer a constant tension loading device pull down force is required to keep the hammer housing 112 firmly on the anvil a spring arrangement 116 is located between tension wires 114 and the hammer 118 to prevent too high shock loads.