experience with breechlock exchanger

PresentationPresentation

OnOn

Experience with Breech-Lock ExcahngersExperience with Breech-Lock Excahngers

At At

IOCL, Mathura RefineryIOCL, Mathura Refinery

Presented ByPresented By

K.K. ChattopadhyayK.K. Chattopadhyay

Chief Inspection Chief Inspection ManagerManager

Mathura RefineryMathura Refinery

Indian Oil Corporation Indian Oil Corporation LimitedLimited

Mathura Refinery - Green Refinery Clean RefineryMathura Refinery - Green Refinery Clean Refinery


IntroductionIntroduction Introduction

These are the exchangers with Breech-Lock Closure system.

First invented developed by Standard Oil Co. Of California. The first Breech-lock exchanger came in service in 1966. The Rights of technology remain with Chevron Research Company of California

Finds applications in refinery units operating at high pressure and temperature with hydrogen rich streams such as Hydrocrackers & DHDT, Hydrotreaters, Gas Compression, Ammonia Synthesis and Miscellaneous uses.

Advantages : Reliable High Pressure Performance Sealing Easy dismantling / Re-assembly for Inspection Avoidance of High Stressed zones in Pressure parts. In-service Sealing of Internal Gaskets.

Inspection Frequency - Once in 10 years or “as per need basis”.

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Breech-Lock Exchangers at Mathura RefineryBreech-Lock Exchangers at Mathura Refinery

Sl No. UnitEquipment Tag no. Comm. in Opened on

1

DHDT

301-E01A

2005

Not opened since commissioning

2 301-E01B Not opened since commissioning

3 301-E01C Not opened since commissioning

4 301-E01D Not opened since commissioning

5 301-E01E July'07 and Oct'11

6 301-E01F Aug'08 and Oct'11

7

OHCU

7-E-1A

2000

July'09

8 7-E-1B July'09

9 7-E-4 Not opened since commissioning

DHDT Breech-Lock Exchangers 301-E-1 E/F opened twice to rectify minor leakage during operation of these Reactor effluent Vs Feed exchangers. Leakage creates difficulty in limiting S within specified 50 ppm in Effluent .


07-E-1 A/B ((Reactor Effluent / HP Steam Generator) in OHCU

o The exchangers were opened after “heat efficiency” came down. The pre-heat came down by 17 C. Fouling was suspected due to possible carryover of scales from upstream. o Job was awarded to M/S C R Asia.o While opening the TLR (Threaded Lock ring), some seizing of threads was suspected in top exchanger.o After opening, it was observed that the ACME thread of TLR was damaged. (Total 09 threads out of total 12 nos.).o The corresponding threads of Shell channel was also found damaged (Outer 03 nos. of thread).o As local repair was not possible, the exchanger shell was cut from bottom-side nozzles (shell & tube nozzles) and sent to L&T, Powai.o The TLR was replaced. The inner thread of Shell channel was repaired by welding and machining.o The exchanger shell was brought back and re-welded in its position. Job was carried out by L&T.o The diaphragms were found damaged and were replaced.o Exchangers were tested and put back in operation.

o The jamming was attributed to gradual leakage thru diaphragm which washed away the Anti-seizing compound between the threads

Experiences with Breech-Lock exchangers at MRExperiences with Breech-Lock exchangers at MR


301-E-1 E/F (Reactor Feed vs Effluent) in DHDT

These two exchangers have leaked multiple times in operation. The leakage occurred after Unit tripping or after emergency depressurization. The leakage is from the diaphragms which separate the shell side & tube side products.

The Unit was commissioned in April 24, 2005. The first leakage observed after 17 days after emergency S/D of the Unit. The diaphragm was tightened externally. Subsequently, additional tightening of diaphragm was done externally in Sept-05. Tightening was again tried in Dec-06. But leakage rate increased. In July-2007 S/D, the exchangers were opened, diaphragm changed. In Sept 2008, the Exchanger was opened again and tested In 2009 Jul-Aug Shutdown, attempt was made to open the exchangers. However, some jamming of threads was suspected. The attempt was given up. In Sept-2011, the exchangers were opened again. Diaphragms were found damaged. Diaphragm of 301-E-1 F was changed. The diaphragm of 301-E-1E was rectified and put back. As on January, the exchangers are again suspected of leaking in service.



Experiences with Breech-Lock exchangers at MRExperiences with Breech-Lock exchangers at MRRoot–Cause of Leakage Problem

The issue of repeated leakage was taken up with Process licensor M/S AXENS

Salient Points The leakage occurred/leakage rate increased only after tripping of Feed Pump or after Emergency depressurization was carried out.

It was observed that in above cases, the Cold flow from Feed Pump 301-P-1 A/B stops – but Hot Effluent flow from Reactor does not stop. In absence of Cold Feed flow, the temperature of tube side increases beyond the design temperature.

The differential pressure between T/side and shell side also increases in such cases.

The metallic diaphragm cannot retain its flatness as its strength decreases with higher temperature.

There is also a possibility of “Excessive temperatures lead to excessive internal dilations and would most probably be the root cause of the gasket deterioration and subsequent failure”


EquipmentDesign

TemperatureTemp.

April 09Emergency Temp.

May 09E- 01 A TS 420 388 399

E-01 B TS 400 384 392

E- 01 CTS 370 379 385

E-01 D TS 340 374 377

E-01 E TS 300 365 370

E- 01-F TS 250 348 343

EquipmentDesign

TemperatureTemp.

April 09Emergency Temp.

May 09E- 01-F SS 190 226 235

E-01 E SS 250 349 341

E-01 D SS 300 371 372

E- 01 C SS 340 376 377

E-01 B SS 370 382 386

E- 01 A SS 400 385 394

The Temperature increases beyond the design Temperature in both shell and Tube side.

The increase is more in case of 301-E-1 E/F.

The data is from April 09 tripping – taken from PHD Server and extrapolated as the temp data goes beyond the measuring scale of the Temp. gauge


The pressure on shell and tube side as well as the differential pressure between these two sides remains within design range


Remedial Measures Envisaged in Past

Process licensor had asked for some minor changes in operating methods to take care during tripping of Feed pump or emergency Depressurization to lessen the impact. Same has been done. In addition, It was suggested to take the issue with the OEM to solve the issue. Accordingly, the issue was taken up with L&T. However, no headway could be made despite best efforts.



Present Experience

In 2011 Sept-Oct S/D, the two leakage prone exchangers 301-E-1 E & F were opened. The experience gained in this shutdown is presented below :

Problem with Opening of the exchangers Earlier, opening of Breech-lock exchangers used to be a difficult job. However, with better understanding and experience, this problem has been overcome.


1. A square plate was welded with outer ring. 2. The TLR part was heated up to 300 C.3. With use of special fixtures, the opening was

easy.

Square plate for welding with outer ring

Special Fixtures for opening TLR


Present Experience

Observations :

1.No difficulty in opening. Mech. Maint is confident that they can do the job of opening without aid from any external agency.2.No damage to TLR / ACME thread etc. observed.3.The Diaphragms were found distorted.4.There was some FeS scale deposit in the shell side.5. The shell side sealant strips were found damaged.6. While inserting the bundle of 301-E-1 E, a small plate attached between baffle plates became loose. It damaged the gasket face of shell. The repair was carried out by L&T as per their detailed procedure.7. The diaphragm of 301-E-1F was replaced with new one. The diaphragm of 301-E-1E was re-used,8. The testing procedure was followed as below a) The shell side test - this is to check whether the gasket joint is ok or not. b) After this test, the TLR was fixed. c) This was followed by combined shell & Tube test – at 1.33 times of design pressure, keeping the differential pressure with the design limit. d) This was followed by tube test.




On the shell side: The recycle gas rate must be maximized on the shell side (no spill back, compressor at full load). The effluent air cooler must also be run at full capacity (No more temperature control required).On the tube side: The last quench should be used to cool down as much as possible the effluent of the second reactor to minimize the temperature excursions. It can be opened wildly. The by-pass of the shell side of the exchanger E-02 (temperature control of the stripper inlet temperature) must be minimized to evacuate as much as possible of the duty through this exchanger.




Process licensor had asked for some minor changes in operating methods to take care during tripping of Feed pump or emergency Depressurization to lessen the impact.

On the shell side: The recycle gas rate must be maximized on the shell side (no spill back, compressor at full load). The effluent air cooler must also be run at full capacity (No more temperature control required).On the tube side: The last quench should be used to cool down as much as possible the effluent of the second reactor to minimize the temperature excursions. It can be opened wildly. The by-pass of the shell side of the exchanger E-02 (temperature control of the stripper inlet temperature) must be minimized to evacuate as much as possible of the duty through this exchanger. In addition, It was suggested to take the issue with the OEM to solve the issue. Accordingly, the issue was taken up with L&T. However, no headway could be made despite best efforts.



Thank you



In Case of deformation of Diaphragm, leakage will take place

experience with breechlock exchanger

Documents

refinery units

exchanger shell

breechlock excahngersat

breechlock closure system

opened on1dhdt301e01a2005not

tlr threaded lock ring

nozzles shell tube nozzles

inner thread of shell