Page 42 - Diamond Products Catalog

SYSTEM OVERVIEW
40
© Copyright 2014 Boart Longyear. All rights reserved.
1. Casing & Rod Shoes
The casing and rod shoes are threaded to the end of the outer drill string for penetration through overburden. It assists in seating the outer drill string into the bedrock, providing
a tight seal for the drilling fluids to return to the surface. A casing shoe can be used to ream the casing downward when advancing a casing string in an existing hole with the rod string still in place.
The casing shoe inside diameter is flush or has clearance to the inside diameter of the casing which allows free passage of the core barrel through the shoe. Casing shoes are available in standard and heavy duty versions. The heavy duty version has an oversize outer diameter and 6mm crown height.
2. Casing Bits
These are less commonly used and differ from casing shoes in that the inside diameter of
the casing bit is smaller. It does not permit the passage of the core barrel due to the overlap of dimensions.
Casing bits are used when deep or difficult overburden is encountered or to ream over rod strings when stuck in the hole.
Casing Advancer Shoes (Not Shown)
The casing advancer shoe is designed much like a typical casing shoe but has an oversized outer diameter which allows for a roller cone to pass through the inner diameter and provides clearance for the extra cuttings generated. Use the heavy duty shoe for this application