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The crownblock disposition is often determined with the
hoisting system construction. Such designing is determined with
the necessity of drilling pipe central disposition and an attempt to
move the sheaf’s working way closer to the hoisting drum central
part.
Though there are many crownblock models, including two-
level blocks with rectangular upper sheaves, the most widespread
models for the modern drilling system are parallel and one-level
blocks. Other construction used on towers have specifically
designed disposition. On the drilling rig, where you have
additional inner space, the linear sheaves disposition is applied.
Not only drilling ends are attached to the main crownblock
rod, but also sand line pulleys. At present time, during drilling
operations, the crownblock’s sand line pulleys are hanged up
under the crownblocks close to wire ropes. Actually the sheaf’s
disposition is determined with the bailing drum’s location, though
hoist and V-shape window have specific location.

Travelling blocks

Most modern blocks have parallel common sheaves
disposition. The main requirements needed for the stability
ensuing is that the block must have low centre of gravity, because
in case of any block’s deviation or movement while drilling can
make boring technicians’s job more complicated. It must be at a
low level, leaving more space for round-trips. Smaller block’s
sizes make it lighter, making it very important for the modern
mobile equipment.
On the other hand the very light hook can’t assure the
drilling line’s friction force. Like all drilling equipment two block
models, especially the travelling one, must be projected from a
very durable material for transporting ductile oil products.
Following such requirements, the block and hook are
constructed as one unit. Though such construction provides tighter

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