1. METHANATOR FEED/EFFLUENT EXCHANGERS
Presented By
Taha R Sheikh
Management Associate( Projects)
Case History And Way Forward

2. E-209(A/B) Location 200 area (Benfield area)
Ammonia Plant
200 area (Benfield area)
South of the Benfield towers
Series configuration after C-209

3. E-209(A/B) Process E-209 A Syn gas from C-208 C-209 E-209 B E-212

4. Tube Failure history Corrosion of tube from external (shell) side
Tube leakage caused synthesis gas to bypass around C-210
Carbamate formation in synthesis gas compressor loop

5. Inspection history Lake Charles 1965 Replacement in 1987
Tubes 3/4” OD, 14 BWG ,SA-214(CS)
Tubesheet A-105-II (CS forged)
Replacement in 1987
Tubes ¾” OD, 14 GA, SS-316
Tubesheet (Fixed) TS C-1/2 Mo
Tubesheet (Floating) TS 1-1/4Cr-1/2Mo

6. Inspection history Pre mobilization 1995
Inspection conducted by M/s Industrial Technical Company (ITC) at Lake Charles, USA
20% tubes inspected around existing plugged tubes
Major damage
(>50% loss) tubes
Moderate damage tubes
Already plugged tubes
Exchanger 21
100 27
E-209 A 58
123 09
E-209 B

7. Inspection history E 209 B 1998 51 leaked tubes found in SFT
& TTS seal weld leakages
51 Tubes were plugged
Unsuccessful Weld repair of TTS joints
Failed attempts of PWHT
bypass line across shell installed

8. Inspection history 1998 - 2007 E 209 A 1998
Exchanger taken in service without any internal inspection
2001
Heavy Sludge accumulation on shell side.
Pressure drop of 13psig in 10 min from shell side
No repair done
2003
Pressure drop of 3.5psig in 30 min from shell side
Again no repair done.
Till 2007
Exchanger was in service with leakage

9. Replacement in Ammonia BMR
To Increase the ammonia plant capacity to 1570 MTPD
Designed and manufactured by Descon Engineering in year 2007
Design was reviewed by Haldor Topsoe.

10. Enhanced exchanger design
2 Identical Horizontal Shell & Tube Heat Exchanger (BEM)
Having Process gas on both tube and shell sides.
Design pressure 30 kg/cm3.
Design temperature 400˚C.

11. Enhanced exchanger design
Tube
Material SA-213 T12 (1Cr0.5Mo)
Number Nos.
Tube sheet
Material SA-182 F-12 Cl.2
Thickness mm
Shell
Material SA-387 Gr.12 Cl.2 (1Cr0.5Mo)
Thickness mm
Diameter mm
Total length 6991 mm

12. Findings in 2012
No inspection was conducted Until August/September 2012
Flow hindrance across Synthesis Gas compressor(K-306 A)
leakage in E-209A confirmed by Laboratory analysis In September 2012
Boroscopy was conducted of E-303 A/B
Leakage was detected across E-209 A/B tubes

13. Inspection history 2012 E-209 A
Dismantled in September 2012 (gas curtailment)
Benfield solution came from bonnet / tubes
Benfield scale on both tubesheets
SFT and hydrostatic testing revealed 119 leaked tubes
Leaked tubes were plugged by hammering
Final hydrostatic-test passed

14. Inspection history E-209 A 2012
East end Tubesheet – Tubes choked due to Benfield deposits

15. Inspection history E-209 A 2012
West end Tubesheet – Benfield coming from leaked tube

16. Number of tubes to be plugged
Inspection history
M/s Stamicarbon
TA-2013
Performed eddy current inspection of both the exchangers
Defect category
Number of tubes to be plugged
% in E-209 A
% in E-209 A+B
> 50 %
927 (+119) 29 15
> 60 %
756 (+119) 24 12
> 70 %
474 (+119) 16 8

17. Inspection history E-209 A TA-2013
pulled out tube leaked having Under deposit corrosion on tube outer surface

18. Inspection history E-209 A TA-2013
Thinning on pulled tube outer surface due to under deposit corrosion

19. Inspection history E-209 A TA-2013
617 plugged tubes recommended in Stamicarbon report

20. Reasons for Benfield Carry over
High performance washing trays not in service in Absorber KO Drum (C-209)
Demister pads f CO2 Absorber (C-208) and Absorber KO Drum (C-209)

21. Explanation of Corrosion
Benfield solution droplets evaporates leaving Benfield scale on outer surface of tubes
Benfield salts are corrosive in nature and cause under deposit corrosion
Severe localized thickness loss which results in tube leakage.
Corrosion products promote further deposition and corrosion of tube material
No corrosive scale / deposits and corrosion occur after evaporation
No affect on E-209B tubes and upper portion of E-209A

22. Explanation of Corrosion

23. Recommendations
Improving efficiency of demisters of CO2 Absorber (C-208) and Absorber KO Drum (C-209)
High efficiency washing trays in Absorber KO Drum (C-209) to be taken into service regularly
Regular analysis of synthesis gas to E-209A
E-209A shell side washing with detergents
Replace the corroded tubes/tube bundle in E-209A with existing Grade T12 (1Cr1/2Mo) material

24. Thank you!