21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

Work carried out on 21G72 in June/July 2013

The pump in question was removed complete from situ at pump station 5 and set up in the

workshop for full refurbishment to be carried out.

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

To improve the knowledge of ‘ageing plant’ condition monitoring, the pump was completely

stripped to assess condition of all internals.

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

Rotary and stationary faces of mechanical seal found to be in good condition:

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

Once stripped the condition/dimensions of all pump internals were measured and assessed

as follows:

Shaft measured in all areas for any throw, less than 0.001” measured

Bearing internal diameters measured, (drive end and non – drive end) and compared to

external measurements of shaft, see tables below for measurements:

Shaft & Bearing Dimensions (Drive End)

Shaft External

Bearing internal

Difference in size

Comments

2.754” 2.753” 0.001” 0.001” interference fit, no breakdown of area where bearing sits.

Bearing External

Housing bearing sits into

Difference in size

Comments

5.906” 5.907” 0.001” 0.001” clearance, fitted with bush lock to ensure no chance of race turning in housing, no evidence of this happening previously.

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

Shaft & Bearing Dimensions (Non Drive End)

Shaft External

Bearing internal

Difference in size

Comments

2.953”

2.951” 0.002” Note: Shaft metal sprayed/machined to give correct interference fit with bearing I.D. summary of this can be found at end of report as Appendix 1.

Bearing External

Housing bearing sits into

Difference in size

Comments

5.119” 5.120” 0.001” 0.001” clearance, fitted with bush lock to ensure no chance of race turning in housing, no evidence of this happening previously.

A third party inspection company, (Silverwing), were used to carry out U/T thickness checks

of any parts of the pump assembly that were identified as an area that could potentially

deteriorate over time, eventually leading to a loss of containment.

Referencing the report SEM 30 the following observations were noted for comparison at the

next inspection, their positioning means they are most likely to wear from the pumping

process or are low points that would lead to the greatest loss of containment should they

fail:

Points 1 – 15 of Volute casing:

Average thickness of this area is currently 27.22mm

The thinnest measured thickness of this area is 22.8mm - not a cause for concern, to be

compared at next inspection.

Points 1 – 12 of pump casing in area behind back end of impellor:

Average thickness of this area is currently 21.7mm

The thinnest measured thickness of this area is 20.3mm – Pitting in this area of depth up to

4mm was noted, although even if this were to be in the thinnest area it would still leave

16.3mm of thickness remaining, not a cause for concern, a comparison will be taken against

measurements taken at next strip down to monitor deterioration.

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

Point 5 of identified as inlet valve in report, (is actually re-circulating valve)

Average thickness of valve of body and bonnet is currently 20.3mm

Thickness of point 5 is 24mm – not a cause for concern, to be compared at next inspection.

Points 31 – 34 of inlet MOV 155:

Average thickness of this area is currently 25.7mm

Thinnest area in this location is 24.9mm – not a cause for concern, to be compared at next

inspection.

Points 17-19 of outlet MOV 156:

Average thickness of this area is currently 25.9mm

Thinnest area in this location is 25.3mm – not a cause for concern, to be compared at next

inspection.

NRV thickness measurements are available in the Silverwing report.

All external measurements can be taken again without requiring the pump to be stripped or

taken out of service, and if any loss in thickness of the casing has occurred, used as a basis

to determine when the unit should be stripped for internal thickness measurements to be

taken again also. The first repetition will be a year from the time of first inspection, and the

inspection frequency adjusted thereafter based on the further thickness check results.

Although a manual is not present on site for this particular pump, the following paragraph is

stated under the ‘Complete Overhaul’ section of a similar size single ended centrifugal pump

such as the pump in question:

‘Frequency of a complete overhaul depends upon the hours of operation of the pump, the

severity of the conditions of service, the materials used in the pump construction, and the

care the pump receives in operation. It is not necessary to open your pump for inspection

unless there is definite evidence that the capacity has fallen off excessively or there is

indication of trouble inside the pump or in the bearings’ – (See note below).

Note: Recent vibration monitoring training has taken place on site, once the equipment to

carry this out has been purchased and monitoring systems are in place, it can be used as an

indicator to determine whether there is ‘trouble inside the pump’ or if there are any bearing

issues.

Having taken into consideration the manufacturers recommended overhaul guidelines for a

similar pump, it is not intended that this pump will come out of service for another overhaul

until there is any evidence of the symptoms highlighted in the above paragraph.

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

In addition to the measurement of the differences in pump body casing thickness loss and

bearing versus shaft dimensions detailed above, all other pump internals were inspected for

wear including wear rings, see below table:

Wear ring dimensions

Inner impellor wear ring (D.E)

Pump body wear ring

Diametrical clearance

Comments

12.850” 12.884” 0.034” Above process pump minimum tolerance, see below chart.

Outer impellor wear ring (N.D.E)

Pump casing wear ring

Diametrical clearance

Comments

12.845” 12.881” 0.036” Above process pump minimum tolerance, see below chart.

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

Wear Ring Diameter in Inches Minimum Diametrical Clearance Recommended by API 610 Standards, (in inches”)

1 - (Anything under 2” diameter has same minimum clearance by API 610 standards)

0.010

2 - (Anything under 2” diameter has same minimum clearance by API 610 standards)

0.010

2.000 – 2.499 0.011

2.500 – 2.999 0.012

3.000 – 3.499 0.014

3.500 - 3.999 0.014

4.000 - 4.999 0.016

5.000 - 5.999 0.016

6.000 - 6.999 0.017

7.000 - 7.999 0.018

8.000 - 8.999 0.019

9.000 - 9.999 0.020

10.000 - 10.999 0.021

11.000 - 11.999 0.022

12.000 -12.999 0.023

13.000 -13.999 0.024

14.000-14.999 0.025

D.E: Diametrical clearance = 0.034” (Min is 0.023” for this size ring)

N.D.E: Diametrical clearance = 0.036” (Min is 0.023” for this size ring)

Although there are no maximum wear ring tolerances documented, a ‘rule of thumb’ is to

change wear rings for new if diametrical clearance doubles the minimum, meaning that D.E.

& N.D.E. of this unit are currently within minimum and ‘maximum’ tolerances.

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

The condition of the impellor was assessed to see if there were any cracks or distortion and

none were found:

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

In addition to the measuring and documenting of thicknesses, bearing interferences and

wear ring dimensions, additional work was carried out on the seal plate to pump casing

joint:

As can be seen from the photograph the face in question had a poor surface finish and there

were signs of pitting also, this could lead to leaking when put back in commission.

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

The decision was taken, as with all recent refurbishments, to have this face machined back

to a smooth finish:

In addition to dimension and condition gathering on pump casing and all internals, this

pump has in place a ‘Yarway’ recirculation valve that acts as a non-return for the main outlet

line, whilst allowing a flow back into the inlet manifold when pumping against a closed

valve. To ensure the Yarway valve was working correctly it was stripped also:

The bonnet was removed carefully using stud bar to slowly release spring tension.

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

Condition of sealing faces found to be very good:

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

As the setting of the valve is governed by the rating of the spring, it requires no calibration

when re-assembling.

Additionally, the 4” 300# NRV on the recirculation outlet port of the Yarway was showing

signs of wear in the moving parts so was changed for new, the wear on this can be

monitored periodically:

Sizes of internals of new NRV as follows:

(A) Hinge pin O.D.

(B) Flap hinge I.D.

Clearance Comments

0.470” Hole in arm: 0.496” Hanger holes: 0.492”

Arm: 0.026” Hanger: 0.022”

To be monitored periodically for any change in dimensions

(C) Clack central pin O.D.

(D) Central Clack hole I.D.

Clearance Comments

0.990” 1.015” 0.025” To be monitored periodically for any change in dimensions

In house NRV inspection card is attached as Appendix 2 at the end of this report.

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

N.D.E. Bearing positioning

It was noted that when the N.D.E bearing cover was removed that there was an

unexpectedly large gap in between the outer race and the spigot on the bearing cover,

when measured this was 0.485” in size. After consultation with on-site engineering

consultant John McIntyre, it was determined that the N.D.E. is designed to have a gap

between outer race and spigot on the cover to allow for thermal expansion, but the

positioning of the bearing on the shaft meant that the outer race had barely entered the

machined area of the casing.

This could lead to increased risk of the outer race turning and causing damage, as well as

the possibility that it might not be supporting the N.D.E. end of the shaft properly.

The decision was taken to install a spacing collar behind the bearing in question in order to

correctly position it on the shaft, meaning the outer race was then fully inserted into the

machined are of the casing minimising the risk of it turning, whilst providing better support

for the N.D.E. of the assembly.

A management of change, number 1000014, was put in motion detailing the need for a

collar to be put in place on the shaft, dimensions of spacing collar necessary to position

N.D.E. bearing where it should sit in machined area as follows:

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

Gap between outer race and end of machined area (including gasket): 0.673”

Spigot on cover: 0.188”

Gap between spigot and cover prior to installation of collar: 0.485”

To allow a 0.060” gap, (as agreed with John McIntyre), in between outer race and spigot on

cover the collar must be of length 0.425”.

Other dimensions of collar:

I.D. 2.951”

O.D. 3.220”

Pump was reassembled using custom made casing gasket:

Type R spiral wound gaskets (no inner or outer ring) of following dims:

I.D: 540mm

O.D: 563mm

Thickness: 4.58mm

Methods that will be used to monitor condition of this pump unit over time:

Condition monitoring to be carried out in line with annual PM:

UT thickness checks of inlet isolation valve body and bonnet

UT thickness checks of outlet isolation valve body and bonnet

UT thickness checks of non-return valve body and bonnet

UT thickness checks of pump casing

Strip down of internals of non-return valve and measurements taken to establish

whether there is a change in the tolerances since last measurements were taken,

also visual inspection of seats to identify any damage

Condition monitoring to be carried out upon strip down of unit:

Shaft dimensions

Condition of impellor

UT thickness checks of pump body behind impellor

Pressure test of non-return valve

Diametrical wear ring clearance measurements repeated

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

Conclusions

The pump has been refurbished to a high standard, taking into consideration condition of all

internals and measuring all areas that will be able to provide ‘trendable’ data. Further UT

thickness assessments of all areas checked in this write up will be carried out in line with the

pumps next annual maintenance and/or strip down of the unit, from this a thickness loss

rate, (or progression towards failure), can be established and a resulting inspection

frequency.

Upon interpretation of the Silverwing reports, there are no areas where a significant loss in

thickness of isolation valves body/bonnet, NRV body/bonnet, pump casing and pump body

compared to the nominal thicknesses is a cause for concern. These measurements have

been taken in a repeatable manner to ensure meaningful ‘trendable’ data can be gathered

over time.

Hard copies of the Silverwing reports are available in the maintenance records office, also

electronic copies are available upon request.

Additional photos – (pump reassembly):

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

A Hydrostatic test was carried out on the pump following assembly:

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

No Leaks apparent from mechanical seal, casing gasket or any vent/drain pipework.

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

Appendix 1

21 G 72 Overhaul and ‘trendable’ data gathering.

21 G 72 Overhaul and ‘trendable’ data gathering.

Appendix 2