white liquor and weak black liquor pump replacement

University of Victoria Faculty of Engineering

Summer 2005 Work Term Report

White Liquor and Weak Black Liquor Pump Replacement Justification

Eurocan Pulp & Paper Co. A Division of West Fraser Mills Ltd.

Kitimat, BC

Derek Wakita 12345678

Mechanical Engineering [email protected]

September 7, 2005

in partial fulfillment of the requirements of the B.Eng. Degree

Supervisor's Approval: To be completed by Co-op Employer I approve the release of this report to the University of Victoria for evaluation purposes only.

The report is to be considered NOT CONFIDENTIAL CONFIDENTIAL (select one)

Signature Position Date Name (print) E-Mail Fax # If a report is deemed CONFIDENTIAL, a non-disclosure form signed by an evaluator will be faxed to the employer. The report will be destroyed following evaluation. If the report is NOT CONFIDENTIAL, it will be returned to the student following evaluation.

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Feedback on work term report (Marker: Sean McConkey) Graded A+ Very well written report, excellent structure, English use. Typical mechanical engineering problem. Occasional misused or misspelled words (their/there, for instance). Could use Appendices for pump data, etc. Marks were removed for missing sections, and results section, however both were minor deductions. Other concerns include: Report should be double–spaced, or 1.5 spaced (line spacing) Report should include a glossary

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Table of Contents Tables................................................................................................................................................................... ii Figures ................................................................................................................................................................ iii Summary............................................................................................................................................................. iv 1.0 Introduction.................................................................................................................................................... 1 2.0 Problem.......................................................................................................................................................... 2

2.1 White Liquor Pumps (421-021,022).......................................................................................................... 2 2.2 Weak Black Liquor Pumps (412-002,020) ................................................................................................ 4 2.3 Safety ......................................................................................................................................................... 5

3.0 Considerations ............................................................................................................................................... 6 3.1 Soft Start .................................................................................................................................................... 6 3.2 Variable Frequency Drives (VFD’s).......................................................................................................... 6 3.3 Recirculation.............................................................................................................................................. 7 3.4 Pump Layout.............................................................................................................................................. 7 3.5 Modify Existing System ............................................................................................................................ 9 3.6 Pump Type............................................................................................................................................... 10

4.0 Cost Comparison ......................................................................................................................................... 11 5.0 Conclusion ................................................................................................................................................... 13 6.0 Recommendations........................................................................................................................................ 14 7.0 References.................................................................................................................................................... 15

Tables Table 2.1 – White Liquor Pump 412-021 Timeline [2]....................................................................................... 3 Table 2.2 – White Liquor Pump 412-022 Timeline [3]....................................................................................... 3 Table 2.3 – Weak Black Liquor Pump 412-002 Timeline [5] ............................................................................. 4 Table 2.4 – Weak Black Liquor Pump 412-020 Timeline [6] ............................................................................. 5 Table 3.1 – Soft Start Costs/Pump....................................................................................................................... 6 Table 3.2 – VFD Costs/Pump.............................................................................................................................. 7 Table 3.3 – Control Valve Pricing ....................................................................................................................... 7 Table 4.1 – Maintenance Costs for 412-022 [8] Table 4.2 – Maintenance Costs for 412-021 [9]............. 11 Table 4.3 – Maintenance Costs for 412-002 [10] Table 4.4 – Maintenance Costs for 412-020 [11].......... 11 Table 4.5 – Maintenance Costs of All Four Pumps Regarding Two-Year Payback ......................................... 11 Table 4.6 –Assortment of Costs......................................................................................................................... 12 Table 5.1 – Estimated Project Costs .................................................................................................................. 13 Table 5.2 – 2 Year Payback Cost Comparison ................................................................................................. 13

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Figures Figure 2.1 – Pump Chart for White Liquor Pumps [1]........................................................................................ 2 Figure 2.2 – Goulds Pump Chart for Weak Black Liquor Pumps [4] ................................................................. 4 Figure 3.1 – Start-up of White Liquor Pump [7] ................................................................................................. 6 Figure 3.2 – P&C of New Proposed System ....................................................................................................... 8 Figure 3.3a – Layout of Existing System ............................................................................................................ 8 Figure 3.3b – New Layout #1 .............................................................................................................................. 9 Figure 3.3c – New Layout #2 .............................................................................................................................. 9 Figure 3.3d – New Layout #3 .............................................................................................................................. 9

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Summary The white liquor pumps and the weak black liquor pumps that support the M&D digester have been consistently failing in recent years. Failure of these pumps results in pulp production downtime as well as maintenance costs. Failures include several power end problems as well as bearing, shaft, and seal problems. The pumps are also situated in a compact environment where maintenance personnel often work on one of the pumps while they are adjacent to another that is in operation. The main problems associated with the pumps are believed to be caused by the high head requirements followed by a low flow usage resulting in the pumps not being well situated on their design curves. In addition, the current white liquor pumps are obsolete and maintenance personnel are having issues with spare parts. This report reviews several options that may prevent such maintenance problems as well as outlining a recommended solution for the system. The report will recommend a solution to the problem that is justified by the fact that it will cost the company less money to fix this system than not, within a two year period (a two year payback). The recommended pumps are Goulds pumps which have addressed power end, seal and bearing problems. The pumps would require recirculation lines in order to operate within their design parameters. The white liquor pumps would use an orifice for the recirculation line while the weak black liquor pumps would use a control valve. Furthermore, three pumps would be used in the designated area for a more spacious layout that would be safer as well as easier for maintenance on these pumps. The three pumps would include a white liquor pump, a black liquor pump, and a swinger pump that could be used for either application. The cost to carry out this project is estimated at $106,780.00 allowing a 1.85 year payback when compared to the average maintenance costs over the past five years.

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1.0 Introduction Founded in 1965 Eurocan Pulp & Paper Co. was constructed in 1967 and began producing paper in 1970. Eurocan has produced high quality unbleached linerboard and sackkraft paper worldwide for nearly 35 years. Eurocan is ISO 9001 registered and is committed to producing high quality paper to its customers while operating in a safe manor. In fact, Eurocan has set both safety and production records for the company over the past couple of years. The goal of this report is to understand why the white liquor pumps (421-021,022) and weak black liquor pumps (421-022,002) are failing and to figure out a possible solution that will result in better performance, reduced maintenance costs as well as better control of the system. The primary function of the pumps is to pump liquor to the M&D digester where the liquor mixes with sawdust to break down the wood fibers. This mixing process produces pulp. After the liquor has broken down the pulp in the M&D digester, the pulp is moved to the washing line where the liquors are removed. Pulp then goes into the papermill where it will be turned into paper. The M&D digester is a high pressure environment which adds a high head to the pumping process. This high head and low flow combination make choosing a suitable pump unusually difficult. Within the last ten years, hundreds of thousands of dollars have been spent on repair and maintenance to the four pumps. Such repairs results in downtime and thus affects pulp production. A breakdown of the pump failures as well as a cost summary is discussed later in this report. It has been realized that there is potential for the pumps to be situated in a modified arrangement. With a revised layout, maintenance on the pumps could be accomplished in a proper ergonomically correct manner as the present configuration could lead to soft tissue issues.

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2.0 Problem Several problems exist with the weak black liquor and white liquor M&D pumps. The layout of these pumps is such that they are in close proximity to one another, generating difficulties and safety concerns in their maintenance and repair. When one of the pumps breaks down, the backup pump is used. While this backup pump is running, maintenance on the broken pump is generally done while working adjacent to the operating backup pump.

2.1 White Liquor Pumps (421-021,022) The current white liquor pumps are Sulzer 3x2-10 pumps and are not well suited for their application. The pump chart can be seen in figure 2.1. The operating conditions favor a pump with a low flow as well as a high head. Originally, the pumps were specked to handle a flow of about 160 usgpm. With the current pulp production, an operating valve controls the flow, allowing an average 120 usgpm. As the flow decreases, extra force is exerted on the bearings, shaft, and motor.

Figure 2.1 – Pump Chart for White Liquor Pumps [1]

On the morning of February 22, 2005 pump 412-022 failed when the impeller cap screw sheared from the shaft. Failure was believed to be due to the high initial torque created by the on/off switching of this pump that had occurred earlier. Later that day, the backup pump, 412-021 failed. The failure of this pump resulted in a coupling breaking into several pieces. This failure was believed to be due to the taper-lock hub being machined to fit the pump shaft.

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Several other failures have occurred with these pumps, most due to power end problems. A list of several of the problems occurring with the pumps over the last twenty years can be seen in table 2.1 and 2.2.

Table 2.1 – White Liquor Pump 412-021 Timeline [2]

Time Line - 412-021 PUMP - White Liquor to Sawdust DigestorNOTE: There may be undocumented failures.

198519861987198819891990199119921993199419951996199719981999200020012002200320042005

FailuresRepair PumpPower End ProblemBearing SealRotating ElementPump SealCouplingBroken BoltPiping alignmentRunning hotChange Motor

Table 2.2 – White Liquor Pump 412-022 Timeline [3]

Time Line - 412-022 PUMP - White Liquor to Sawdust DigesterNOTE: There may be undocumented failures.

198519861987198819891990199119921993199419951996199719981999200020012002200320042005

FailuresRepair PumpPower End ProblemBearing SealRotating ElementPump SealCouplingBroken BoltPiping alignmentRunning hotReplace Motor

As the timeline indicates, several problems are occurring with the power end and pump seals. It is also worth noting that rotating element problems are occurring much more frequently. There are numerous reasons explaining the possibilities of these failures. Operations generally control the white liquor flow to about 120 gpm which is much less than that of which the pump was designed. When the flow is reduced, extra pressure is put onto the shaft, contributing to rotating element, power end, and sealing failures. Some of the following problems can also occur with the wrong lubrication. The oil type may not be suitable for the high revolution of the motor (3600 rpm) and can cause bearing failures. Many power end problems may have been due to the improper fitting of the impeller on the shaft. Mill crews have been welding the impeller cap screw to the shaft as well as machining the taper-lock hub key way in order for it to fit the shaft. The pipe structure may also be putting pressure onto the pumps, which may result in sealing failure.

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2.2 Weak Black Liquor Pumps (412-002,020) The current weak black liquor pumps are models 3196 LT and 3196 LTC 2x3-13 pumps from Goulds. Although the pumps appear to sit well on the pump chart, (figure 2.2) the pumps are continuously failing in the power end and seal. This may be because operations usually run the pumps at a reduced flow than that of which the pumps were originally designed to handle. In fact, at times the pumps are running completely off of the pump chart.

Figure 2.2 – Goulds Pump Chart for Weak Black Liquor Pumps [4] A Time Line of some of the failures for these pumps can be seen in the following two tables.

Table 2.3 – Weak Black Liquor Pump 412-002 Timeline [5] Time Line - 412-002 PUMP - WEAK BLACK LIQUOR TO SAWDUST DIGESTOR

NOTE: There may be undocumented failures.

198519861987198819891990199119921993199419951996199719981999200020012002200320042005Failures

Repair PumpPower End ProblemBearing SealRotating ElementPump SealCouplingBroken BoltPiping alignmentRunning hotChange Motor

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Table 2.4 – Weak Black Liquor Pump 412-020 Timeline [6] Time Line - 412-020 PUMP - BLACK LIQUOR TO SAWDUST DIGESTER

NOTE: There may be undocumented failures.

198519861987198819891990199119921993199419951996199719981999200020012002200320042005Failures

Repair PumpPower End ProblemBearing SealRotating ElementPump SealCouplingBroken BoltPiping alignmentRunning hotChange Motor

From the timeline it is quite evident that several problems are occurring with the power end and the pump seal. These problems are also becoming a lot more frequent as the pumps are aging. Problems for these weak black liquor pumps are believed to be the same as that of the white liquor pumps. Piping arrangement, lubrication type, and reduced flows are believed to be contributing to sealing problems, impeller and shaft repair, as well as other power end problems.

2.3 Safety/ Ergonomics There is a less than ideal situation regarding the existing layout of the four pumps. With the current layout of the pumps, maintenance often works on a broken pump while sitting in close proximity to the backup pump while it is running. Due to the high heat that these pumps emit as well as the fact that the there are rotating parts, better arrangement of these pumps is favorable. As a result of my observations the mill reviewed its Safe Work Procedures to ensure that work could be performed safely. On February 22, 2005 pump 412-022 failed when the impeller cap screw sheared from the shaft. Failure was believed to be due to the high initial torque associated with the on/off switching of the pump. Following the failure of pump 412-022, pump 412-021 was run until it failed later that day. The failure of this pump resulted in a coupling breaking into several pieces. This failure was believed to be due to the taper-lock hub being machined to fit the pump shaft.

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3.0 Considerations The following section considers several solutions that were well thought-out in an attempt to better develop the existing system while decreasing maintenance repairs and downtime.

3.1 Soft Start With a soft start added to each motor, the start-ups would release less torque on the pumps. The decrease in the initial torque on the pump would result in a decrease in wear on the shaft, impeller and power end. When the pump starts, there is a great load initially applied to the pump due to the high rpm of the motor and low initial flow of the liquid. Indicated below is the start-up load during the day of February 22, 2005 when the pumps had failed.

Figure 3.1 – Start-up of White Liquor Pump [7] Table 3.1 outlines the costs associated with adding a soft start to each pump.

Table 3.1 – Soft Start Costs/Pump Description Cost

Size 5, 200 HP Soft Start $5000 Labor: 16 hrs @ $80/hr $1280 Drawings (revisions) $640

TOTAL $6,920

3.2 Variable Frequency Drives (VFD’s) Including a VFD to each of the motors would allow a softer start-up for each pump. The softer start-up would permit less torque applied to the pump, resulting in longer shaft and impeller lifetime as well as reducing power end problems. The VFD would also allow the motor to run more efficiently with the fluctuating flows, resulting in longer motor life as well as power savings. Indicated in table 3.2 is an estimate of the costs associated with installing a VFD. The detailed costs are based on previous projects associated with VFD installation and is based on installation of one VFD.

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Table 3.2 – VFD Costs/Pump Description Cost

125 HP VFD $22,300.00 Engineering & Elec. Installation $10,000.00

TOTAL $32,300

3.3 Recirculation Considering that the white liquor pumps are sitting in an unfavorable position on their pump curve, and the weak black liquor pumps are running at a flow lower than that of which they were designed, recirculation would be a proper solution to get the adequate flow volume out of the pumps. With recirculation, the pumps would produce a sufficient flow for the required head that they must achieve. In order to control the amount of flow coming through the recirculation line, a control valve or an orifice would need to be installed. The recirculation line would also have to be at a reasonable distance away from the pump to prevent overheating of the fluid (greater than 10’). The costs associated with installation of a control valve are as indicated in table 3.3. In the next section, figure 3.2 outlines a P&C of the recirculation line added.

Table 3.3 – Control Valve Pricing Description Cost

2” Control Valve $8270.00 2” Magtube $1800.00 Transmitter $1800.00 Elec. Engineering & Installation $7,000.00

TOTAL $18,870.00

3.4 Pump Layout Due to the compact area where the pumps currently exist, a new, more spacious layout would promote proper ergonomically correct maintenance. Instead of comprising of a weak black liquor and white liquor pump with each having a spare, three pumps could be used. Included would be a weak black liquor pump, a white liquor pump, and a swinger pump that can run either fluid. Below in figure 3.2 is an outline of the P&C of the system.

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Figure 3.2 – P&C of New Proposed System

Outlined below is the current configuration of the pumps as well as three proposed layouts.

Figure 3.3a – Layout of Existing System

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Figure 3.3b – New Layout #1 Figure 3.3c – New Layout #2

Figure 3.3d – New Layout #3

3.5 Modify Existing System In order to maintain the existing system a recirculation line for each piping arrangement (one for weak black liquor and another for white liquor) are recommended to be installed. There would be less power end problems, due to reduced pressure on the pumps; however, several parts would need to be changed. These parts would include the shafts, which have become warped over the years and have been problematic with impeller fittings and taper-lock hub key way fittings. All four pumps would remain in there current layout and the configuration. Due to the different operating ranges of the pumps, the option of using three pumps with one pump being a swinger, could not be used. The swinger pump would have to be the Goulds’ weak black liquor pump and there would be difficulties when the swinger pump is utilized as a white liquor pump.

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3.6 Pump Type The two different suppliers considered for pump selection were Sulzer and Goulds. The Goulds pumps were chosen because their supplier had suggested using the same pump for both applications. By using the same type of pump, three pumps could be utilized, instead of having four pumps (one white liquor pump, one weak black liquor pump and a spare for each). It is also worth noting that the pump sits on a better location for the Goulds pumps than compared to the Sulzer pumps. The Goulds pumps have also addressed power end problems by using an oversized shaft and bearing assembly, which will significantly increase the lifetime of the bearings and seals. The design was created for high load applications that can be seen with these pumps and is intended to minimize shaft deflection. The suggested Goulds 3196LTX pumps are comparable to several other Goulds pumps that are located in the mill, preventing any problems that may be associated with having additional spare parts in stores.

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4.0 Cost Comparison The following tables consist of the maintenance costs associated with each of the pumps over the past fifteen years. Costs are associated with work order tracking by reliability.

Table 4.1 – Maintenance Costs for 412-022 [8] Table 4.2 – Maintenance Costs for 412-021 [9]

412-022 Pump Repair Frequency/Cost

6,19813,460

7,4367,0876,6697,968

29,596

7,104

16,64116,014

48,17318,406

0 10000 20000 30000 40000 50000 60000

1990

1992

1994

1996

1998

2000

2002

2004

Dat

e

Cost ($)


2,9852,0423,181

7,8023,809

974916,940

19,8369,047

5,0897,098

4,7578,423

77730,509

17,310

0 5,000 10,000 15,000 20,000 25,000 30,000 35,000

1990

1992

1994

1996

1998

2000

2002

2004

Dat

e

Cost ($)

Table 4.3 – Maintenance Costs for 412-002 [10] Table 4.4 – Maintenance Costs for 412-020 [11]


14522,922

4,7146,320

11,1765,468

435410,645

14,79627,75029,043

10817

0 5000 10000 15000 20000 25000 30000 35000

1990

1992

1994

1996

1998

2000

2002

2004

Dat

e

Cost ($)


15,63521032,384

4,601593

31257,408

5605,044

30,90227,070

2,8608,187

18,3617308

2,012

0 5,000 10,000 15,000 20,000 25,000 30,000 35,000

1990

1992

1994

1996

1998

2000

2002

2004

Date

Cost ($)

Table 4.5 – Maintenance Costs of All Four Pumps Regarding Two-Year Payback 412-021 412-022 412-002 412-020 TOTAL 2 YEAR TOTAL Avg. cost/year over the past 10 years

$11,222.50

$13,216.50 $11,426.60 $11,082.50 $46,948.10 $93,896.2

Avg. cost/year over the past 5 years

$10,312.80

$17,586.40 $17,317.60 $12,757.20 $57,792.00 $115,584.00

Costs in 2003 & 2004

$31,286.00

$64,187.00 $56,793.00 $25,669.00 $177,935

An assortment of the total costs associated with Section 3.0 as well as the installation costs for the pumps is outlined in table 4.6.

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Table 4.6 –Assortment of Costs Description Cost

Soft Start per Pump $6,920 VFD per Pump $32,300

One Control Valve per Recir. $18,870.00

Concrete Demolition $3160.00

New Concrete & Labor $13,500.00

Mechanical $23,000.00

Gould’s white liquor pump $15,970.00 Gould’s weak black liquor

pump $15,970.00

Sulzer white liquor pump $11,153.00

Sulzer weak black liquor pump $12,282

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5.0 Conclusion The recommended pump selection would be the Goulds pumps. These pumps are recommended over the Sulzer pumps in view of the fact that they sit better on the design curve. It is also worth noting that the 4196LTX Goulds pump model has addressed power end problems, that are often associated with low flows and high head, by over sizing the shaft and bearing assembly. By using the Goulds pumps, three pumps can be used instead of four and a revised layout can be chosen with better access to the pumps in that area. The recommended layout would be New Layout #3. This layout is recommended because it permits adequate access to the pumps in the area as well as having a safe layout. However, a new lifting device would be needed for the farthest pump (pump in Northwest corner). It is also recommended that a recirculation line be added to the weak black liquor line as well as the white liquor line. The recirculation line would need to be at least ten feet in length so that the fluid does not overheat. An orifice could be used for the white liquor line permitting about 50 usgpm to flow through the recirculation line. However, a control valve would be needed for the weak black liquor line because of the fluctuation in flow that the pumps tend to operate at. Careful consideration should be taken to ensure that the piping arrangement is well supported. Adequate pipe support should be added to the suction and discharge sections near the pump to allow less strain on the pump. Proper lubrication should be used to allow for the greatest achievable lifetime of the bearings and power end. Lubrication type may be crucial to extending the maintenance life of the pumps, especially with the high rpm and high heat environment of the motors. Below is an estimate of the costs associated with adding the above requirements outlined in this section.

Table 5.1 – Estimated Project Costs This can be compared to the two year pay-back that was indicated earlier.

Table 5.2 – 2 Year Payback Cost Comparison 2 YEAR TOTAL Avg. cost/year over the past 10 years $93,896.2 Avg. cost/year over the past 5 years $115,584.00 Costs in 2003 & 2004 $177,935

It is optional to include soft starts to each pump allowing for softer start-ups and possible extended life of the power end and bearings. The associated cost per soft start is $6,920 per pump.

Description Cost Pump Costs $47,910.00

Civil/Structural $17,000.00 Mechanical $23,000.00

Control Valve/ Recir. $18,870.00

TOTAL $106,780.00

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6.0 Recommendations It is recommended that careful consideration be made with piping arrangement when installing these pumps. Careful consideration must also be ensured during the installation of the pumps as the alignment of the pumps will be crucial to their performance. Considering that the pumps have a 3600 rpm motor, an improper alignment during installation could result in deflection of the shaft. Spare parts should be reviewed with the stores/inventory management area to ensure that there are spare parts for the pumps in the event that they may fail. Similar pumps have spare parts in the Stores Department, but it should be reviewed to make sure that exact fittings will fit the new pumps. Although this report has been reviewed and approved by the Operations and Maintenance Departments it should be reviewed with them once again before the installation of the system. The Reliability Department should also attend any meetings involving the installation of the pumping system as they possess a great deal of knowledge attaining to extending the lifetime of the equipment. Any drawings involving the current system should be revised to incorporate the new layout and piping arrangement and obsolete drawings should be marked up and moved into the obsolete section of the drawing filing system.

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7.0 References [1] Ahlstrom Pump Catalog, 1970. [2] R.Todd, Eurocan Reliability Engineering Report, 2005. [3] R.Todd, Eurocan Reliability Engineering Report, 2005. [4] R.Todd, Eurocan Reliability Engineering Report, 2005. [5] Goulds Pump Catalog, 1970. [6] R.Todd, Eurocan Reliability Engineering Report, 2005. [7] R.Todd, Eurocan Reliability Engineering Report, 2005. [8] R.Todd, Eurocan Reliability Engineering Report, 2005. [9] R.Todd, Eurocan Reliability Engineering Report, 2005. [10] R.Todd, Eurocan Reliability Engineering Report, 2005. [11] R.Todd, Eurocan Reliability Engineering Report, 2005.

white liquor and weak black liquor pump replacement

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