16
receiving vessel. Additionally, agitation – typically lateral
for articulated units – of the haul truck bed or transit mixer
drum assists in spreading the load to avoid occluding the
slickline discharge orifice.
With wet transfer, it can be critical to follow the line
preparation with active loads before the line dries or the
‘milk’ flashes (initial set of the grout film). The transfer
schedule must consider the need to keep a primed line,
such that repeated preparation must be enacted if the line
sits idle long enough to begin drying or flashing. The flash
set will be very dependent on the ground and ambient tem-
peratures and relative humidity, as well as the airflow in the
transfer line.
Receipt confirmation is important to confirm the
dropline remains open and clear. With dry transfer, oper-
ational delays between loads typically can occur without
compromising subsequent transfer.
Transfer Completion/Washdown
Completion of a dry transfer cycle calls for confirmation
there is no remnant material susceptible to entering the
dropline from the surface station feed stream. A double
check would entail an empty hopper and appropriate gates
or caps to the dropline.
Completion of a wet transfer cycle, whether on-shift,
cross-shift, etc., calls for a rigorous cleanout wash of the
system. Upon transferring the final scheduled load for the
cycle, it is recommended to send no less than one load-
equivalent volume of water through the system, with
positive confirmation at the boot/discharge area. It can be
effective to minimize cementitious scale by washing a nom-
inal 225 kg (500 lb) of clean aggregate down the line with
the initial wash out water. Additionally, the cleanout ports
on the boot should be actuated with air/water as appropri-
ate, to assist visual confirmation by the underground opera-
tor of a clear device and line.
Upon completion of washdown, typically it is appro-
priate to cap or plug the lines to minimize airflow and the
concomitant tendency to dry the line. As a minimum this
is at the surface station. It may be effective to also do so
underground, with a breakaway plug at the bottom station
in the event of errant material fall.
Ventilation/Dust Control
Whether wet or dry, it is prudent to cap or plug the sys-
tem when idle, due in large to preventing errant material
transfer. These components, caps and plugs, can also serve
as ventilation fittings. As noted in Ventilation, ventilation
controls are appropriate whether the system has upcast or
downcast flow. Though some arrangements can be handled
remotely, it is common that caps and plugs are handled by
the slickline operators, with or without mechanical assist.
When dust suppression or collection is appropriate, it
is common to actuate those controls in advance of or upon
material transfer, to continue for some time after active
transfer or until the dropline/slickline is capped. The resid-
ual or follow-on ventilation can be gauged from ventilation
models and confirmed with actual operation. The need may
vary with specific material, as well as weather conditions
which affect bank or stockpile moisture.
MAINTENANCE PROCEDURES
The basic or conventional maintenance aspects of these
transfer systems are common with other underground min-
ing stationary maintenance concerns (10). Selected specif-
ics will be addressed here in brief.
A preliminary general statement on maintenance safety
is warranted, following the operational concerns noted ear-
lier. These transfer systems can be characterized by open
holes, overhead loose material, suspended loads, con-
fined spaces, with stations and operators remote from one
another. That nature directs that well-organized and coor-
dinated maintenance is fundamental to safe and successful
execution. Along with diligent planning, a principal aspect
of coordination can be thorough Lockout Tagout Tryout
(LOTOTO) procedures.
Surface Station
Surface station maintenance follows from that performed
for conventional material handling plants – as appropriate
for the coarse, fine, wet, dry, cementitious, or non-cementi-
tious material being handled. If the system entails mixing as
part of the surface station, then full plant maintenance will
be involved. If only a hopper and slickline collar are pres-
ent, then the wear surfaces, plugs, and wash down fixtures
will be predominant components for attention.
Slickline
Transfer line maintenance is a significant aspect of system
integrity, with replacement the predominate task. Selected
wear life is presented in Table 1 for various media and pipe
material. That history suggests that for coarse aggregate
in hardened transfer pipe, serviceable life can range from
approximately 71,400 t (80,000 ton) to nearly 446,400
t (500,000 ton) before the initial failure. A documented
concrete/shotcrete transfer life was slightly lower, but still
substantial. Accessible lines can be repaired or have select
segments replaced, typically needed near the bottom of the
system. Repairs or segment replacements of the documented
receiving vessel. Additionally, agitation – typically lateral
for articulated units – of the haul truck bed or transit mixer
drum assists in spreading the load to avoid occluding the
slickline discharge orifice.
With wet transfer, it can be critical to follow the line
preparation with active loads before the line dries or the
‘milk’ flashes (initial set of the grout film). The transfer
schedule must consider the need to keep a primed line,
such that repeated preparation must be enacted if the line
sits idle long enough to begin drying or flashing. The flash
set will be very dependent on the ground and ambient tem-
peratures and relative humidity, as well as the airflow in the
transfer line.
Receipt confirmation is important to confirm the
dropline remains open and clear. With dry transfer, oper-
ational delays between loads typically can occur without
compromising subsequent transfer.
Transfer Completion/Washdown
Completion of a dry transfer cycle calls for confirmation
there is no remnant material susceptible to entering the
dropline from the surface station feed stream. A double
check would entail an empty hopper and appropriate gates
or caps to the dropline.
Completion of a wet transfer cycle, whether on-shift,
cross-shift, etc., calls for a rigorous cleanout wash of the
system. Upon transferring the final scheduled load for the
cycle, it is recommended to send no less than one load-
equivalent volume of water through the system, with
positive confirmation at the boot/discharge area. It can be
effective to minimize cementitious scale by washing a nom-
inal 225 kg (500 lb) of clean aggregate down the line with
the initial wash out water. Additionally, the cleanout ports
on the boot should be actuated with air/water as appropri-
ate, to assist visual confirmation by the underground opera-
tor of a clear device and line.
Upon completion of washdown, typically it is appro-
priate to cap or plug the lines to minimize airflow and the
concomitant tendency to dry the line. As a minimum this
is at the surface station. It may be effective to also do so
underground, with a breakaway plug at the bottom station
in the event of errant material fall.
Ventilation/Dust Control
Whether wet or dry, it is prudent to cap or plug the sys-
tem when idle, due in large to preventing errant material
transfer. These components, caps and plugs, can also serve
as ventilation fittings. As noted in Ventilation, ventilation
controls are appropriate whether the system has upcast or
downcast flow. Though some arrangements can be handled
remotely, it is common that caps and plugs are handled by
the slickline operators, with or without mechanical assist.
When dust suppression or collection is appropriate, it
is common to actuate those controls in advance of or upon
material transfer, to continue for some time after active
transfer or until the dropline/slickline is capped. The resid-
ual or follow-on ventilation can be gauged from ventilation
models and confirmed with actual operation. The need may
vary with specific material, as well as weather conditions
which affect bank or stockpile moisture.
MAINTENANCE PROCEDURES
The basic or conventional maintenance aspects of these
transfer systems are common with other underground min-
ing stationary maintenance concerns (10). Selected specif-
ics will be addressed here in brief.
A preliminary general statement on maintenance safety
is warranted, following the operational concerns noted ear-
lier. These transfer systems can be characterized by open
holes, overhead loose material, suspended loads, con-
fined spaces, with stations and operators remote from one
another. That nature directs that well-organized and coor-
dinated maintenance is fundamental to safe and successful
execution. Along with diligent planning, a principal aspect
of coordination can be thorough Lockout Tagout Tryout
(LOTOTO) procedures.
Surface Station
Surface station maintenance follows from that performed
for conventional material handling plants – as appropriate
for the coarse, fine, wet, dry, cementitious, or non-cementi-
tious material being handled. If the system entails mixing as
part of the surface station, then full plant maintenance will
be involved. If only a hopper and slickline collar are pres-
ent, then the wear surfaces, plugs, and wash down fixtures
will be predominant components for attention.
Slickline
Transfer line maintenance is a significant aspect of system
integrity, with replacement the predominate task. Selected
wear life is presented in Table 1 for various media and pipe
material. That history suggests that for coarse aggregate
in hardened transfer pipe, serviceable life can range from
approximately 71,400 t (80,000 ton) to nearly 446,400
t (500,000 ton) before the initial failure. A documented
concrete/shotcrete transfer life was slightly lower, but still
substantial. Accessible lines can be repaired or have select
segments replaced, typically needed near the bottom of the
system. Repairs or segment replacements of the documented