work carried out on 21g80 between october 2014 - mar 15
TRANSCRIPT
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
Work carried out on 21G80 in between Nov 2014 and March 2015
Following the work order 1022235, raised on 15/2/14, 21G80 pump was removed complete
from situ and brought to the main workshop.
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
Under the site wide pump refurbishment project, aimed at addressing ‘ageing plant’
condition monitoring, the pump was completely stripped to assess condition of internals.
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
Drive end bearing assembly removed complete:
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
Drive end mechanical seal removed:
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
Non-drive end casing bolts removed:
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
Pump up-ended and jacking bolts used to seperate:
Scale build up required substantial force to separate casing from main body of pump,
wedges needed in addition to jacking bolts:
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
Shaft and impellor removed complete:
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
Non-drive end bearing assembly stripped:
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
Drive end white metal bearing assembly stripped also:
Mechanical seal assembly removed both ends:
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
Pump shaft now separate from assembly:
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
Shaft set up in lathe:
Impellor positioning/locking sleeves were worn in localised areas, possibly due to fretting of
seal assembly:
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
Area of shaft under locking sleeves also in poor condition:
Metal spraying technique used to repair damaged areas of shaft and locking sleeves, see
appendix 1 for metal spraying/machining report performed by 3rd party:
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
Impellor checked for signs of damage and overall condition found to be very good
It was difficult to measure the impellor wall thickness as the external surface sloped away
from the impellor edge, but no major variations were apparent, and thicknesses varied
between 8mm – 10mm.
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
New wear rings fitted, (see table later in write up for clearances):
All components were cleaned and their condition assessed:
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
The condition of the seal plate to casing gasket face was assessed and machining was not
deemed necessary.
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
Once all components were clean and prepared:
The pump was set up for reassembly:
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
Casing painted prior to reassembly:
Impellor, spacing collars and shaft sleeves installed on shaft:
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
Ensuring the impellor was located in the same position as prior to dismantling:
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
Rebuilt shaft inserted into pump body using an in-house made 0.75mm thickness gasket,
which is the same thickness gasket in place when the pump was removed, end play of the
shaft compared to when it came out still measured at 0.001”
Drive end bearing and seal assembly installed once shaft centralised:
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
Followed by installation of non-drive end of assembly:
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
And drive end bearing and seal assembly:
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
Following full reassembly of unit:
A pressure test was performed:
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
At this point, it was found that there was a problem with both seal assemblies leaking,
meaning the pump had to be dismantled to investigate. As nothing was obviously incorrect
with the installation of the seals, a seal manufacturer visited site to provide guidance. It was
suggested by the AES Seals representative, (Steve Salter), that the reason for the seals not
performing correctly was most likely due to porosity in the metal sprayed coating on the
shaft sleeves, and upon further investigation this did appear to be the case:
With an area of the coating seemingly cracked, as well as porous:
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
Following identification of the above defects, the shaft sleeves were sent to AES seals where
they were recoated with a Chrome Oxide coating, see Appendix 2, difference in appearance
as below:
The pump was again reassembled and pressure tested:
And seals inspected for leakage, none found, proving that the initial shaft sleeve coating was
the problem as suspected.
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
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
1.875” 1.877” 0.002” 0.002” clearance fit between shaft and ID of white metal bearing.
Bearing External
Housing bearing sits into
Difference in size
Comments
4.330” 4.332” 0.002” 0.002” clearance fit into white metal bearing housing.
Shaft & Bearing Dimensions (Non Drive End)
Shaft External
Bearing internal
Difference in size
Comments
1.574” 1.573” 0.002” 0.002” interference fit, bearing warmed to shrink fit onto shaft.
Bearing External
Housing bearing sits into
Difference in size
Comments
4.330” 4.332” 0.002” 0.002” clearance fit into bearing housing, fitted with bush lock to ensure it doesn’t turn.
When the pump next comes out of service, the bearing vs shaft diameter measurements
can be taken again to establish a wear rate and resulting inspection frequency. As this is a
water pump only, a UT inspection of the pump set was not performed.
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
In addition to the measurement of bearing vs shaft dimensions detailed above, wear ring
dimensions following their replacement can be seen below:
Wear ring dimensions (Drive End)
Inner impellor wear ring (D.E)
Pump body wear ring
Diametrical clearance
Comments
6.980” 7.010” 0.030” Above process pump minimum tolerance, see below chart.
Outer impellor wear ring (N.D.E)
Pump casing wear ring
Diametrical clearance
Comments
6.980” 7.010” 0.030” 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
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 = 0.030” (Min is 0.017” for this size wear ring)
N.D.E: Diametrical clearance = 0.030” (Min is 0.017” 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.
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
A strip down of the non – return on the discharge to obtain sizes and clearances between
moving parts was carried out, see Appendix 3, and a function test was carried out by means
of opening the discharge valve and the casing drain, no significant amount of water flowed
from the drain proving the NRV is working as it is intended to.
The unit was put back into position at pump station 24, 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 within the ‘Asset Integrity System’, in the
maintenance records office and is also attached to the work order 1024195 within CMMS
Agility.
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 wear data that can be trended
over time.
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:
Alignment of unit.
Visual oil analysis and change.
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 vs bearing dimensions and condition
Condition and wall thickness of impellor
Diametrical wear ring clearance measurements repeated
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
Appendices:
Appendix 1:
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
Appendix 2:
21G80 Overhaul and gathering of data that can be trended over time
21G80 Overhaul and gathering of data that can be trended over time
Appendix 3: