GXXXA and GXXXB pump Recovered Ore and Coke (ROC) slurry
to the hydrocyclones in Unit 550. The liners and
impellors regularly wear out. This causes repairs and
high costs.
Background
The pumps are Warman 4/3 CAH models. They have
rubber-lined casings and a rubber-lined impeller.
On
the 8th of October 2007, GXXXA tripped
twice. It stopped because the motor had become too hot.
Vibration readings taken on the following day showed
that a large vibration was occurring at the speed of the
pump.
Maintenance Technicians removed the pump’s cover. The
rubber lining was severely damaged.

The
vibration was caused by the impellor rotating past the
damaged section of liner.
The
motor had been overheating because its cooling fins were
caked up with mud. Maintenance hosed the motor down to
clean it.
The
maintenance history of G-XXXX A & B was investigated.
Already in 2007, the impeller and liners have been
replaced at least seven times. Average liner life is
5.3 weeks and in the last year has dropped to 3.7 weeks.
Work has begun on upgrading the pumps with a harder
wearing liner material.
A
ceramic impellor and liner has been trialed in the
GXXXXA hydrocyclone feed pump. This trial was done in an
effort to extend pump life, which has historically
averaged 5.3 weeks. The ceramic pump internals were
inspected after 17 weeks of service and were found to be
in good condition, with minimal damage to the impellor
and no noticeable damage to the bowl. It is recommended
that ceramic components permanently replace the existing
rubber components.
Introduction
The
GXXXX hydrocyclone feed pumps have operated with a
rubber liner since they were commissioned in 1992. Over
the last 9 years the average liner life has been 5.3
weeks. The last year has seen this drop to 3.7 weeks, in
2007, $26,500 was spent maintaining the pump.
Slurrytech, a company based in Perth, Western Australia,
has developed a range of ceramic liners and impellors
for abrasive slurries. The ceramic material is silicon
carbide and has performed well on other sites. The
ceramic liners are roughly twice the cost of the current
rubber liners, so a service life of three months would
be required to justify a permanent change.
Liner
Trial
A
ceramic impellor and liner were installed in GXXXXA on
17th March 2008 under change order K07-140.
The trial was done to determine whether a ceramic liner
would withstand the conditions and provide a
cost-effective alternative to the existing rubber
components.
The
pump was regularly inspected by Reliability during the
trial period. No change in performance or operation
(vibrations, noise etc) was observed.
The
wet end was removed for inspection on 26th
August 2008, 23 weeks after the trial commenced. During
this period was a six week outage caused by the gas
crisis, making the total running time 17 weeks.
Following the inspection the pump was rebuilt using the
ceramic components and reinstated as the duty pump.
Findings
The
ceramic impellor was is relatively good condition, with
minor damage to the vanes. The outer face of the vanes
showed signs of erosion, with gouges 1-2mm deep running
parallel to the direction of fluid motion. Chips of
ceramic were missing from the leading edge of some of
the vanes, probably the result of large solids (bolts,
rocks etc) in the slurry.
Despite this damage the impellor was still in very good
condition and was returned to service.

Image 1 – Ceramic Impellor

Image 2 – Inner Edge of Impellor Vane
The
ceramic bowl was in excellent condition, with no erosion
or impact damage to the main face. Minimal damage around
the inlet rim was observed. Apart from this minor
damage, the bowl was in ‘as new’ condition.

Image 3 – Ceramic Bowl
Conclusions
After 17 weeks of continuous service, the ceramic
impellor and liner were in excellent condition and were
returned to service. This is an excellent result
considering that historically the average liner life has
been 3.7 to 5.3 weeks. This result is suitable
justification to permanently replace the existing rubber
components with ceramic components.
Based on the wear to date, I would expect that the
ceramic liners will operate for at least 30 weeks,
possibly a year.
At a 30 week life the following
savings would be evidenced:
2007 spend = $26,500.00 =
26500/12 = $2208.33 / month.
2008 spend = $4500.00 / 30 x 52 /
12 = $650.00 / month.
Savings = $18700.00 / year per
pump.
At a 52 week life the following
savings would be evidenced:
2007 spend = $26,500.00 =
26500/12 = $2208.33 / month.
2008 spend = $4500.00 / 52 x 52 /
12 = $375.00 / month.
Savings = $22000.00 / year per
pump.
Also worth consideration but not factored into the
savings equation is that the pump efficiency is being
maintained over a longer time frame thereby providing
additional savings in power use and cost.
Recommendations
Replace existing
GXXXXA&B rubber liners and impellor with ceramic
components.
Investigate
whether other components will be affected by
corrosion due to the longer service life
Investigate
whether other slurry pumps would benefit from
ceramic liners.
Update
-
20 Jan
2009
Pump was inspected and found to be in same condition as
reported above with approx. 4 to 5% additional wear on
impeller eye and volute cutwater.
Ceramic parts were installed on 17 March 2008 with a
shut down period of 6 weeks for gas shortages, to date
pump has run continuously for a period of 35 weeks.
This equates to a life improvement of over 900% against
original parts and ongoing.
|
Original Life |
100% Life Benefit |
Current Life |
Life Benefit |
|
Weeks |
Weeks |
Weeks |
% |
Post 2007 |
3.7 |
7.4 |
35 |
946% |
Pre 2007 |
5.0 |
10.0 |
35 |
700% |
At a 35 week life the following
savings have been evidenced:
2007 spend = $26,500.00 =
26500/12 = $2208.00 / month.
2008 spend = $5500.00 / 35 x 52 /
12 = $681.00 / month.
Equating to savings of =
$18324.00 / year / per pump.
Accounting for current condition of parts and wear
allowance of 50% of new parts thickness projected wear
life is 65 weeks, this would potentially achieve the
following savings:
2007 spend = $26,500.00 =
26500/12 = $2208.00 / month.
2008 spend = $5500.00 / 65 x 52 /
12 = $367.00 / month.
Projected savings = $22092.00 /
year / per pump.
Reliability Engineer
26th
August 2008
Similar Further Reading:
Maximum Life