Work carried out on 21G62 between Nov 2015 - Feb 2016

21G62 Overhaul and gathering of data that can be trended over time.


20160126: Joe

Edwards

Maintenance

Supervisor, Sem

Logistics Milford

Haven

FULL REFURBISHMENT OF

DOUBLE ENDED CLASS 2

HYDROCARBON PUMP SET

21G62, INCLUDING

DETAILED ANALYSIS OF

WEARING PART

DIMENSIONS & CONDITION



Executive Summary

Following an HSE investigation into the sites approach to ageing plant condition monitoring

in December 2012, it was deemed that there were shortcomings in regard to the approach

taken to proving that the sites rotating equipment was safe to use, as it was most likely

operating beyond its intended design life.

At the time of the investigation, the majority of the pumps had been in service for circa 45

years, albeit in reduced capacity when compared to the period when the site was a running

refinery.

In order to prove the ageing centrifugal hydrocarbon pump sets fitness for service, there

were a number of changes implemented with effect January 2013, with further condition

monitoring methods being implemented periodically, as follows:

Seal failure rates were documented from this point onwards, the aim being to help

better predict when a seal failure may occur, and take steps to prevent loss of

hydrocarbon due to such failures.

An ultrasonic thickness inspection regime was commenced, the aim being to build up

thickness loss data on: pump casings, pump set non-return valves and isolation

valves. This data can be trended over time to build up thickness loss data and

develop a resulting inspection frequency.

A programme to refurbish all hydrocarbon pump sets was implemented, the aim

being to gather dimensions of all internal wearing parts so that these could be

analysed and a future refurbishment regime based on the wear rate seen.

Further condition monitoring methods have since been implemented, such as

vibration monitoring and thermography, which also help to build up a picture of a

pumps’ internal condition and justify its use whilst it awaits full refurbishment.

Table of Contents Executive Summary ............................................................................................................................. 2

Removal from situ and strip down of unit .......................................................................................... 3

Findings of strip down ......................................................................................................................... 9

Gathering of data to be trended over time ...................................................................................... 10

Manufacturers guidelines ................................................................................................................. 13

Wear ring dimensions ....................................................................................................................... 14

Rebuild of unit ................................................................................................................................... 16

Conclusions ....................................................................................................................................... 18



Work carried out on 21G62 between Nov 2015-Jan 2016

Removal from situ and strip down of unit

To progress the site wide pump refurbishment programme, 21G62 was removed from situ

complete to undergo full refurbishment.



To progress the ongoing condition monitoring programme on ageing plant, the pump was

completely stripped to assess condition of all internals.



Seal flush pipework, and bonnet bolts removed:



The shaft was then removed complete:



Findings of strip down

As was the case with a similar units, (21G87X & 21G50X), the area of shaft that the seal runs

on has developed surface corrosion, causing interference on the R.S.R. internal diameter, in

turn preventing it from moving up the shaft to meet the S.S.R. as the faces wear over time.

This has the potential to allow seal seepage in the future if not addressed.

Surface corrosion on shaft



Gathering of data to be trended over time

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

as follows:

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

Areas of shaft that R.S. R runs on coated and machined, (see Appendix 1)



Impellor wall thickness measured:

Readings were taken from 5 points on each side of the impellor, (clockwise from point 1):

Drive End:

Measurement point Thickness

1 0.412”

2 0.336”

3 0.431”

4 0.411”

5 0.380”

Average thickness = 0.394”

Non Drive End:

Measurement point Thickness

1 0.427”

2 0.429

3 0.413

4 0.395

5 0.418

Average thickness = 0.416”



Replacement 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

2.752” 2.750” 0.002” 0.002” interference fit, bearing warmed to shrink fit onto shaft.

Bearing External

Housing bearing sits into

Difference in size

Comments

5.909” 5.911” 0.002” 0.002” clearance fit into bearing housing, fitted with bushlock to ensure outer race doesn’t turn. Correct thickness gasket used on bearing retaining cover to ensure size for size fit of bearing into recess.

Shaft & Bearing Dimensions (Non Drive End)

Shaft External

Bearing internal

Difference in size

Comments

2.752” 2.750” 0.002” 0.002” interference fit, bearing warmed to shrink fit onto shaft.

Bearing External

Housing bearing sits into

Difference in size

Comments

5.909” 5.911” 0.002” 0.002” clearance fit into bearing housing, fitted with bushlock to ensure outer race doesn’t turn. Correct thickness gasket used on bearing retaining cover to ensure size for size fit of bearing into recess.

A third party inspection company are used to carry out U/T thickness checks of any parts

that have been identified as an area that could potentially deteriorate over time, eventually

leading to a loss of containment, analysis and graphing of this data can be found within the

‘Asset Integrity System’.



Manufacturers guidelines

When the pump next comes out of service, the internal measurements can be taken again

and an inspection frequency worked out based on the further loss in thickness or wear, if

any, versus time since last measurements taken.

The manufacturer’s guidelines state the following under point 3 of the ‘Recommended

Inspection Schedule’ section:

‘Wearing parts – Check by periodical inspection and simple hydraulic test. A simple

hydraulic test is at suction lift not exceeding 10 ft., and at a specified speed, close discharge

valve and take reading on pressure gauge on pump side of valve. Drop in pressure against

reading when pump was new indicates excessive clearances in the pump.’

Having taken into consideration the manufacturers inspection guidelines, 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, eg. drop in outlet pressure, unless future

procedures implemented to address the issue of ageing plant deem the manufacturers

inspection recommendations insufficient.

In addition to the measurement of bearing versus shaft dimensions and impellor wall

thicknesses detailed above, all other pump internals were inspected for wear, see below

wear ring dimension table:



Wear ring dimensions

Wear ring dimensions (Drive End)

Inner impellor wear ring (D.E)

Pump body wear ring

Diametrical clearance

Comments

11.000” 11.025” 0.025” Above process pump minimum tolerance, see below chart.

Outer impellor wear ring (N.D.E)

Pump casing wear ring

Diametrical clearance

Comments

11.000” 11.025” 0.025” Above process pump minimum tolerance, see below chart.

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

If a comparison of the wear ring clearances is taken it can be seen that the minimum

diametrical clearances, D.E & N.D.E, adhering to API 610 are above the lowest tolerance:

D.E: Diametrical clearance = 0.025” (Min is 0.022” for this size wear ring)

N.D.E: Diametrical clearance = 0.025” (Min is 0.022” for this size wear 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.



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

none were found:

On other similar units, in addition to the measuring and documenting of thicknesses,

bearing interferences and wear ring dimensions, additional work was carried out on the seal

to pump casing joint, although this was not required in this case:



Rebuild of unit

The shaft was reassembled and refurbished seals set to the compression stipulated in the

manufacturers recommendations:

For future reference, approx. 40mm gap between the rear of the spring carrier and the

outer edge of the impellor securing nut gives the correct spring compression:



The latest NRV strip down to obtain sizes and clearances between moving parts was

performed on 27/1/2015, details and analysis of which can be found within W/O:1027326.

The strip down of the NRV will be performed 2 years from the date of the units’

reinstatement following this refurbishment, this is based on analysis of wear rate data

showing very little change in internal clearances when on an annual inspection.

In addition, the NRV, isolation valves and pump casing of all in service hydrocarbon pump

sets are subject to annual U/T thickness checks also. Details of the latest UT inspection can

be found within W/O:1026382, no areas are considered a cause for concern, analysis and

graphing of this data can be found within the ‘Asset Integrity System’ also.

The bonnet was put back into place using an in-house made 0.75mm thickness gasket,

which is the same thickness gasket in place when the pump was removed, and end play of

the shaft compared to when it came out still measured at 0.002”.

A satisfactory pressure test at 100psi was performed upon reassembly of the unit:

The unit was reinstated at pump station 5, alignment was carried out and the motor was

shimmed and adjusted via jacking bolts to bring within correct tolerances, a hard copy of the

alignment report is available in the maintenance records office and is also attached to the

work order relating to this unit on Agility, and the ‘Asset Integrity System’.



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 data that can be trended over

time, helping to establish a future inspection frequency.

Further external UT thickness assessments of all areas checked in this write up will be

carried out on an annual basis. During future strip down of the unit, internal

thickness/clearance and wearing part dimension measurements repeated.

Upon interpretation of the latest UT report, there are no areas where a significant loss in

thickness of isolation valves body/bonnet, NRV body/bonnet or pump casing when

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

been taken in a repeatable manner to ensure gathering of meaningful data that can be

trended over time has been obtained.

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

electronic copies are attached to the UT PM work order on the site maintenance scheduling

system ‘Agility’, and logged within the ‘Asset Integrity System’.

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, (or 2 yearly in the case of the

NRV, this may be further adjusted based on the wear rate seen):

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

Additional condition monitoring to be carried out upon strip down of unit:

Shaft dimensions and condition

Condition and wall thickness of impellor

Diametrical wear ring clearance measurements repeated

Work carried out on 21G62 between Nov 2015 - Feb 2016

Documents

Transcript of Work carried out on 21G62 between Nov 2015 - Feb 2016