Hydrocyclone Feed Pumps

Ceramic Impellor & Liner Trial

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 8^th 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 17^th 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 26^th 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

26^th August 2008

 

Similar Further Reading:

Maximum Life