Submersible & Borehole – Case Study

Introduction

Berg Engineering was requested by the client to strip and assess then overhaul one submersible pump for a pump station.

The Scope of works was broken down into two main elements including:
• Stage 1: Cleaning & Disassembly
• Stage 2: Measure and Record

EQUIPMENT ASSESSED – 16 CGH 2 Stage Submersible Pump

Stage 1 Summary: Cleaning & Disassembly

Stage 1 work includes:
• External inspection upon delivery
• Marking orientation of all joints
• Dismantle
• NDT of shaft

Results:

• Heavy corrosion found on both the motor adaptor plate and motor skirt
• Mild corrosion was found on all machined flange faces
• Pitting and scoring was found in the bearing bush bores
• Pitting on shaft diameters as well as wear predominantly on one side of shaft was found
• It was found that the strainer body and suction piece was not two separate pieces
• Found that all pump item were coated in a polyamide type coating
• Top case bearing had been replaced with a aluminium bronze bearing rather then a ferobestos bearing on the last refurbishment
• No issues found after MPI and UT of shaft

Motor adaptor skirt

Motor adaptor plate

MPI of shaft

Polyamide coating on all components

Scoring & pitting in bearing bust bores

Pitting in shaft

Stage 2 Summary : Measure & Record

Stage 2 work includes:
· Measuring of critical diameters and components
· Size checks of all fasteners

Results:

· Runout out of bearing locations on shaft up to 0.12 because of wear on one side
· Wear ring sizes were found to be 70mm greater then stated on drawings supplied
· Approximately .7 – .8 diametrical clearance in the wear ring areas
· Approximately 0.2 taper front to back on wear ring areas

Recommendations

· Replace all fasteners with A4-40 grade fasteners
· Replace all keys
· Replace O-rings
· Replace all ferobestos bearings with aluminium bronze bearings
· Replace aluminium bronze wear rings with 316 grade stainless wear rings
· Skim impeller wear ring area true
· Weld repair and machine motor adaptor plate and skirt
· Skim all casing bearing bush diamters
· Manufacture new shaft
· Sandblast and paint components in Interzone 485
· Dynamic balance shaft assembly to G2.5 at 1500 RPM

Motor Report

Workscope

· Dismantle motor
· Clean, measure and inspect mechanical components
· Perform electrical testing on all components
· Supply comprehensive report on findings

EQUIPMENT ASSESSED – Hitachi Submersible Pump Motor 12” 150HP

Make: Hitachi
Serial No: G89331H
Frame: 12”
Output: 150 HP

Voltage: 415
Current: 240 A
Frequency: 50HZ
Speed: 1500 RPM

Bearing – Drive End: Sleeve Carbon Bearing
Bearing – Non Drive End: Sleeve Carbon Bearing

Electrical Tests – Main Stator:

IR to earth 1kv: 62MΩ @ 500v

Resistance: 146mΩ x 3

Surge Comparison: Ok @ 1960v

The stator winding has passed all static testing and was found with minimal contamination. The winding has been clean, baked and inspected with no concerns found.

Incoming view

After wash and bake

Damaged Leads

Rotor:

The main rotor is in serviceable condition passing visual inspections and growler testing.

4.0 Mechanical Checks
· The mechanical measurements are as follows
· DE Bearing Journal: Ok – 79.92mm
· NDE Bearing Journal: Ok – 79.91mm
· DE Bearing: Ok – 80.015mm
· NDE Bearing: Ok – 80.015mm – Small chips and damage
· DE Shaft Extension: Run out 0.01mm

Both motor sleeve bearings have been found reusable however the thrust bearing has been received damaged and will require replacing.

Thrust bearing

Sleeve bearing

Shaft seals, require replacing

Damaged seal coupling

Conclusion

We have found the motor to be in average condition in need of a few repairs as outlined below to bring this motor back to a serviceable condition.
· Replace the thrust bearing with OEM parts
· Supply and fit new seals and seal coupling
· Clean and overhaul all parts
· Replace motor leads and gland

Rebuild Report

Scope of Works

· Replace all fasteners with A4-40 grade fasteners
· Replace all keys
· Replace O-rings
· Replace all ferobestos bearings with D-glide FC bearings
· Replace aluminium bronze wear rings with 316 grade stainless wear rings
· Skim impeller wear ring area true
· Weld repair and machine motor adaptor plate and skirt
· Skim all casing bearing bush diameters
· Manufacture new shaft
· Sandblast and paint components in Interzone 485
· Dynamic balance shaft assembly to G2.5 at 1500 RPM
· Replace the thrust bearing with OEM parts
· Supply and fit new seals and seal coupling
· Clean and overhaul all motor parts
· Replace motor leads and gland
· Final assembly

2nd stage assembly

Pump section final assembly

2nd stage assembly

D-Glide FC bearing bush

Final Motor Test Results

OUTGOING – MAIN WINDING

IR to earth: 1500MΩ

Resistance: 146mΩ

Surge Comparison: Pass

Final Motor Test Results

AC TESTS – LIGHT RUN

RPM: 1490

Volts: 415

L1 amps: 83

L2 amps: 84

L3 amps: 81