Figure 8-14. - Assembly of 10- and 20-foot sections.
4. The lines that handle the piles and the hammer (called the PILE WHIP and the HAMMER WHIP) are reeved (passed) over the sheaves at the head of the boom, and the ends are brought down to the foot of the leads and lashed. Enough slack in each whip is reeved through to ensure that the boom can be topped up to the vertical height of the leads without also straining the sheaves.
5. The leads are raised by topping up the boom.
6. When the leads are raised to the vertical position, lead braces or spotters (catwalks) are then attached.
7. The hammer is placed in the leads, as shown in figure 8-16. The leads are raised off the ground by topping the boom; the hammer is placed under them; the leads are lowered onto the hammer; and the hammer whip line is attached to the pin on top of the hammer.
Figure 8-15. - Lead adapters connected to the boom tip.
Figure 8-16. - Placing hammer in leads.
8. The driving cap or follower block is a cap that rests on the top of the pile being driven. It slides freely in the leads to steady the pile and to receive and transmit the impact of the hammer. The cap, as shown in figure 8-17, has a sling of wire rope, so the cap and the hammer may be drawn to the top of the leads out of the way when a pile is being positioned for driving.
The three main types of pile-driving hammers are the DROP hammer, the STEAM, or PNEUMATIC, hammer, and the DIESEL hammer. A drop hammer is a block of metal run up to a specified height and then dropped on a cap placed on the butt or head of the pile. Drop hammers weigh from 1,200 to 3,000 pounds.
Figure 8-17. - Placing pile cap in leads.Continue Reading