DGS report new (PDF)

Kuwait Oil Company

BS-131 Dry Gas Seal K-2102 RCA Report
June 12, 2017
Presented by:
Equip Sup & Reliability Operations Support (Gas) Group

DGS RCA Report

TABLE OF CONTENTS
SECTION 1

3

1. EXCUSIVE SUMMERY

3

1.1 INTRODUCTION
1.2 PROBLEM DEFINITION
1.3 FAILURE SIGNIFICANT
1.4 FAILURE HISTORY
1.5 INVESTIGATION METHODS
1.6 CONTRIBUTE FACTORS

3
4
7
8
9
10

SECTION 2

12

2. ROOT CAUSE ANALYSIS

12

2.1 RCA INTRODUCTION
2.2 RCA SCOPE
2.3 RCA TEAM
2.4 RCA CASE 1
2.5 RCA CASE 2
2.6 CORRECTIVE ACTION PLAN
2.7 CONTROL PLAN

SECTION 3
3. APPENDICES

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15
17
18
19
20
20

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Chapter 1
EXCUSIVE SUMMERY

1.1 Introduction
A Booster Station is part of an oil-field facility installed to fully utilize the
separated gas from the Gathering Centers. The compressed gas and
condensate are transmitted separately through pipelines to Mina Al-Ahmadi
LPG Plant.
There are two phases to implement this duty, each phase has three
compressor units (trains) connected in series LP1, LP2 & HP. The compressors
which made by GE is BCL type (for LP1 & LP2) driven by industrial GE gas
turbine frame 5. Compressor is considered to be the heart of the station &
any unexpected failure will directly impact in to the final production .The
DGS which made by John Crane fixed on both DE & NDE sides function is to
prevent compressed gas

from leaking to atmosphere , its tandem

arrangement with labyrinth design as shown figure 1.
To insure that good performance function of DGS, dry gas & separation air
should provide without contamination at specific flow / pressure during
running or offload condition

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Figure 1

1.2 Problem Definition
In Dec – 2016 DE & NDE Dry gas seal cartridge were replaced due to high LEL
on secondary vent, so the old seal has been sent to John crane facility for
inspection.

DGS was serviced one year and two months , the next failure was
catastrophic & face broken into piece in March 2017 with only 3 months of

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service where the seal service life should be 3-5 years at normal operation
condition (Figure 2).
Figure 2

In our analysis we will study the two cases separately, based on John Crane
inspection reports (Appendix) the seal was exposed to contamination, this
contamination will go between stationary & rotatory part inside the seal at
the same time between two face as a result the spiral grove on mating ring
will not be able to build separation pressure & contact face will occur. The
main evidence in the report showing running marks on metal seat & mating
ring as result of contamination.
Treatment of gas should be implemented by eliminate condensate &
contamination before enters the seal, and this consider to be function
filtration system. As same as the treatment should implement to the process
gas by minimizing condensation using inlet scrubber .
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On another hand at 9th March 2017 we have visit the site to trace causes of
this issue and condensate was found on both separation air filter & seal gas
filter.
and once we remove the separation air filter we found filter saturated with
water in addition drops of water was stick on the filter shell wall, also
condensate gas found on the seal gas filter side which evaporate quickly .
The second failure occurred in march 2017 on DE side of the same
compressor which happened in short time ( less than three months ) has a
different scenario . As per John crane inspection report attached at appendix
show that matting ring fractured and carbon ring was worn-out due to
rubbing (Figure 3 ).

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In this case the contamination considered to play week contributed factor if
we noted the time to fail is only three months plus the both seal exposed to
the same gas inlet parameters and there is no failure reported on NDE side.
In our RCA report we consider over compressed as strong evidence of failure.

1.3 FAILURE SIGNIFICANT

At last failure on March 2017, the compressor was forced outage for 7 days ,
there was potential daily production losses of 250 MSCFD discharge from HP
compressor . Further the DGS repairing at John crane facility and new seal
was installed.

Figure 4 illustrate the replacement cost & potential down time for DGS.

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Figure 4

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1.4 DGS failure History
As seen in figure the BS-131 commissioned in 2007, at 2015 the DGS was
replaced at Major inspection so almost 8 years of service without fail. After
replacing the seal it was stand one year & two months only.
The next failure in 2017 is unique & has different scenario, its stand only for
less than three months as showing in figure 5.

12/13/2016

DGS failed & replaced
4/30/2007

3/3/2017

4/11/2015

DGS Replaced during MI DGS catastrophic DE failure

BS-131 Commissioning

1/1/2008

1/1/2009

1/1/2010

1/1/2011

1/1/2012

1/1/2013

1/1/2014

4/07

1/1/2015

1/1/2016

1/1/2017
10/17

Figure 5

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1.5 INVESTIGATION METHODS
Our investigation is built on collecting data since 2015 from Major inspection
until date, we have reviewed maintenance reports, Data sheets, following
procedure practices & daily operation & maintenance activity, we also did
site visits & meetings with different sections in order to gather the most
possible information which will help us to complete RCA. We are trying to
use only proved information & attested evidences certified with images &
documentation. Our main source of information will be:
1- Site visit & sampling for condensate & contamination.
2- Normal images & thermographic images for seal piping system
3- Meeting with different departments such as maintenance, operation,
instrument , vendor & GMSR
4- Documents like maintenance procedure, instrument report, events report
& drawing.
5- Chemical sampling Result of substance collected inside failed DGS
reported by JC.
6- Fuel Gas analysis report.

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