1. 2014 - MRO Dry Gas Seal Reliability Improvement
WELCOME TO
MRO
Dry Gas Seal Reliability Improvement

2. Presenter
Presenter: Ali Shallwani
Career Summary:
Rotating Equipment Specialist at Nova Chemicals (2014-onwards)
Rotating Equipment Engineer at Saudi based petrochemical company ( )
Machinery Engineer at Pakistan based fertilizer plant ( )
Career Highlights:
Vibration Diagnostics, Initiatives related equipment design and performance improvement, RCFAs, FMEAs, PHAs

3. Problem Statement Low buffer flow for dry gas seal
Primary Seal /Buffer Gas Supply
Primary Seal Gas + Separation Seal Leakage
Separation Seal Supply

4. Application Service: CO
Machine: 7 Stages Integrally Geared Compressor (Steam Turbine Driven)
Specific Stage: 7th Stage
Operating Profile: 65barg Discharge Pressure

5. Internals
Rotating face with spiral profile (uni-direction seal – specific case)
Stationary face (spring supported)
Espey rings or barrier seal
Sleeve

6. Significance
In case of low buffer flow – there is potential of oil ingress into the seal housing.
Potential failure of seal assembly
Equipment shutdown

7. Description Description Seal Type 2.937” Single Speed 27426 rpm
Design Temperature
-20C / 150C
Static Design Pressure
75 bara
Dynamic Design Pressure

8. Description
N2 is used as buffer gas – which then escapes through the primary vent (to the flare).
N2 pressure should be essentially maintained at recommended value to achieve this desired flow rate.
As standard design, there is no trip security associated with buffer flow.

9. Troubleshooting
The seal gas system for this specific set-up was checked. The important fittings and installations on the system includes transmitters, control valves and orifices.
The low buffer flow was observed on 7th stage of the equipment – the remaining 6 stages were healthy.
Potential leakage within the system was checked.
Restriction within the system was to be checked.

10. Inspection The seal was disassembled for inspection.
All internals were found in stable condition.
The espey rings through which the buffer gas flows were found slightly rubbed against sleeve surface.

11. Modification
The type of espey ring was modified such that grooves were introduced to ensure continuous supply for N2 in case of tight clearance / contact.

12. Outcome
The desired flow rate through espey ring was achieved – and reliability of the overall system was ensured.