10
or hold back material which might slough into the borehole
and compromise readings and service life.
With any borehole configuration, hole alignment is
critical for the same reasons as mentioned for shaft-installed
transfer lines. The borehole should be drilled directionally
in order to achieve an unswerving alignment.
Borehole—Grouted in Place
In some installations, planned Service life, line weight, and
other considerations may indicate a grouted-in-place trans-
fer line is preferrable. A variation on, or extension of, this
approach is to install an oversized line into which a smaller
diameter line(s) can be inserted if/when the first line wears
through to the point of becoming unserviceable. Further to
that may be an opportunity to use the borehole casing itself
as the initial transfer line.
If the system ventilation characteristics indicate such,
a vacuum break and/or pressure relief can be built into
the collar or sub-collar of the borehole. Conversely, the
pipe collar can be elevated such that the ventilation and
washout piping is above grade, making for readily acces-
sible components for construction as well as operation and
maintenance. Serviceability of the vent component(s) can
be enhanced if a reduced diameter collar insert is used in
the system, as discussed in Borehole–Collar Suspended and
indicated in Figures 2 and 3.
Figure 3. Concept sketch, collar insert to borehole collar-suspended slickline
or hold back material which might slough into the borehole
and compromise readings and service life.
With any borehole configuration, hole alignment is
critical for the same reasons as mentioned for shaft-installed
transfer lines. The borehole should be drilled directionally
in order to achieve an unswerving alignment.
Borehole—Grouted in Place
In some installations, planned Service life, line weight, and
other considerations may indicate a grouted-in-place trans-
fer line is preferrable. A variation on, or extension of, this
approach is to install an oversized line into which a smaller
diameter line(s) can be inserted if/when the first line wears
through to the point of becoming unserviceable. Further to
that may be an opportunity to use the borehole casing itself
as the initial transfer line.
If the system ventilation characteristics indicate such,
a vacuum break and/or pressure relief can be built into
the collar or sub-collar of the borehole. Conversely, the
pipe collar can be elevated such that the ventilation and
washout piping is above grade, making for readily acces-
sible components for construction as well as operation and
maintenance. Serviceability of the vent component(s) can
be enhanced if a reduced diameter collar insert is used in
the system, as discussed in Borehole–Collar Suspended and
indicated in Figures 2 and 3.
Figure 3. Concept sketch, collar insert to borehole collar-suspended slickline