Split Case Pump – Strip Assess & Rebuild Case Study

Introduction

Berg Engineering was requested by the client to strip and assess then overhaul one Thompson Kelly & Lewis Model SDS-DV, 400/500-715 PUN2 at a pump station.

At the end of this page you will also find an overview of our scope of work as well as our proposal for the overhaul.

EQUIPMENT ASSESSED – Thompson Kelly & Lewis Model SDS-DV, 400/500-715 PUN2

Scope of Works

The Scope of works was broken down into two main elements including
Stage 1: Cleaning & Disassembly
Stage 2: Findings

Stage 1 Summary : Cleaning & Disassembly

Stage 1 work includes:-
• External inspection upon delivery
• Mark orientation of all joints
• Dismantle

Results:

Upon initial inspection of the pump on delivery a lot of debris was found on the bottom of the pump. The pump looked to be in reasonable condition, all joint were match marked ready for disassembly. On the disassembly it was found the DE bearing housing was stuck on and various methods and push and pull jigs were manufactured to remove this from the shaft.

Stage 2 Summary : Findings

After disassembling the DE bearing housing of the shaft it was found that the type 6 bearing had totally collapsed and the inner race had welded itself to he inner housing it was also found that the inner housing had at some stage spun on the shaft and snapped the key.

A specific reason for this failure could not be pin pointed but contributing factures could be a mix of incorrect tolerancing, lubrication issues and assembly issues.

A bearing specialist has been involved with a assemble solution for the rebuild including new tolerance and set up.

Shaft:

After disassembly of the shaft it was found that the shaft had been spray metal repaired before and was disbonding from the parent material underneath. This was around the area that the inner housing had spun on the shaft and could have been a contributing factor.

Impeller:

The impeller was found to be in reasonable condition with no issues of cavitation or corrosion.

Casings:

After splitting the pump half it was found that a coating had been applied to the inner surfaces of the pump after further investigation into this, the client had advised that this pump has had various performance issues and the OEM had some time ago altered and remodelled the inner volutes of the pump to improve on efficiency. This was done by Corrocoat with a Corroglass 632 filler with a Fluidglide top coat.

Some of the fluidglide top coat was found to be worn away in some areas as well as minor damage in others that will require repairing.

Corroded areas:

These were also found around some of the wear ring areas and excessive clearance on the wear ring groove width was also found in the casings

Recommendations

• Replacement of casing and impeller wear rings in Nitronic 60 material
• Refurbishing NDE mechanical seal (please see refurb scope below)
• Refurbish DE mechanical seal and rebuild with supplied Chestertson seal kit
• Replace all bearings, use existing bearings supplied first and replenish stock with new bearings
• Sandblast paint externals of pump with 75um layer of interzinc primer then paint top coat with green 200um layer of interplus 1180
• Supply new coupling with pump bored and keyed to suit pump shaft (information required for the motor shaft to bore and key)
• Replace all hold down studs with ASTM A193 B16 studs and nuts with ASTM A194 grade 4 heavy hex nuts (please note that the current nuts were 316 stainless)
• Replace all gaskets, o-rings and fasteners
• Replace and refurbish drive end bearing housing components to restore to correct tolerancing
• Metal spray and grind shaft for the DE bearing housings, sleeve, coupling and mechanical seal diameter on the NDE
• Rebuild the corroded areas as fill groove of casing wear ring with Belzona 1111
• Machine 0.25 of split face on top and bottom housing faces then bore through for the wear ring and bearing sleeve diameters
• Frost blast internal lining of pump housings then apply the Belzona 1341
• Assemble pump and hydro test to 2925 KPA

NDE Mechanical Seals:

• Clean all parts
• Grind and lap stationary face in tungsten
• Grind and lap rotary face in tungsten
• Fit new nitrile O-rings
• Polish sleeve and other seal componenets
• Manufacture new PTFE bush
• Fir new stainless plugs for flush and quench ports
• Assemble and pressure test in accordance with API 682

MDR Index

DE Bearing Housing Rebuild Procedure and Tolerancing:

HM926740‐HM926710
Bore:
4.500” TO 4.501”
114.300 MM TO 114.3254 MM

Shaft Fitting Dimensions:
CONE SEAT DEVIATION +0.0025”, +.0015” +0.0635 MM +0.0381 MM

SHAFT OD MACHINE TO 114.330 MM TO GIVE A LIGHT TIGHT FIT.
OD:
9.000” TO 9.001”
228.600 MM TO 228.6254 MM

Measure cup od and make housing size for size to give a transition fit.

Lap bore with 600 grade emery if cup is too tight until cup will slide in.

LM739749‐LM739710
Bore:
7.500” TO 7.501”
190.500 MM TO 190.5254 MM

Shaft fitting dimensions:
Cone seat deviation +0.0025”, +.0015” +0.0635 MM +0.0381 MM
Shaft spacer (SE420262 OD) Grind bearing seat to 190.540 MM to give a light tight fit.
OD:
10.125” TO 10.126”
257.175 MM TO 257.2004 MM

Measure cup od and make housing size for size to give a transition fit.

Lap bore with 600 grade emery if cup is too tight until cup will slide in.

Work Scope:

• Refurbish pump in accordance with the finding of the strip and assess report
• Replacement of casing and impeller wear rings in Nitronic 60 material
• Refurbishing NDE mechanical seal (please see refurb scope below)
• Refurbish DE mechanical seal and rebuild with supplied Chestertson seal kit
• Replace all bearings, use existing bearings supplied first and replenish stock with new bearings
• Sandblast paint externals of pump with 75um layer of interzinc primer then paint top coat with green 200um layer of interplus 1180
• Supply new coupling with pump bored and keyed to suit pump shaft (information required for the motor shaft to bore and key)
• Replace all hold down studs with ASTM A193 B16 studs and nuts with ASTM A194 grade 4 heavy hex nuts (please note that the current nuts were 316 stainless)
• Replace all gaskets, o-rings and fasteners
• Replace and refurbish drive end bearing housing components to restore to correct tolerancing
• Metal spray and grind shaft for the DE bearing housings, sleeve, coupling and mechanical seal diameter on the NDE
• Rebuild the corroded areas as fill groove of casing wear ring with Belzona 1111
• Machine 0.25 of split face on top and bottom housing faces then bore through for the wear ring and bearing sleeve diameters
• Frost blast internal lining of pump housings then apply the Belzona 1341
• Assemble pump half and hydro test to 2925 KPA

NDE Mechanical Seals:

• Clean all parts
• Grind and lap stationary face in tungsten
• Grind and lap rotary face in tungsten
• Fit new nitrile O-rings
• Polish sleeve and other seal componenets
• Manufacture new PTFE bush
• Fir new stainless plugs for flush and quench ports
• Assemble and pressure test in accordance with API 682

REBUILD REPORT

Repair of Casing Halfs

The Internal coating of the pump housing was coated in with a Corrocoat system with a Corroglass 632 filler with a Fluidglide Top coat. The top coat was worn away in some areas as well as corrosion issues around the split lines and volute area.

There was also corrosion issues around the casing wear rings the groove and diameter that the wear rings located in had excessive wear and were not locating correctly this was also causing low efficiency on the pumps performance.

To repair this Berg Engineering has repaired the corroded areas with Belzona 1111 building this areas back to the original surface and then machined the casing back to the correct tolerances. The Casing half’s were then coated with a two coats of Belzona 1341 Supermetalglide.

Casing half’s frost blasted for application of Belzona 1111 and 1341

Casing half’s frost blasted for application of Belzona 1111 and 1341

Application of Belzona 1111 to corroded areas of lower case

Application of Belzona 1111 to corroded areas of top case

Machining of split faces on CNC borer to achieve 100% flat mating faces

Application of Belzona 1341 first coat on to casing top half

Application of Belzona 1341 top coat on casing top half

Finish machining of the new nitronic 60 impeller wear rings to size on shaft prior to balancing, total
indicated shaft run is 0.025mm

New fittings for shaft sleeve location

Pump assembled with cover plates on ready for hydro testing

Pump complete ready for despatch with coupling locked up