Leakage of the reboiler of the naphtha splitter

[ponderer]

We have a naphtha splitter in our refinery.

The splitter separate naphtha into light and medium naphtha.

Recently we encounter leakage of the reboiler in this splitter.The steam then enter this column and contaminate the light naphtha with water.

We want to know the root cause of the incident.

Is it a corrosion problem? or manufactural fault?

Which refinery has the same experience as us?

 

[TD2K]

Impossible to answer since you have provide no information what you have seen in the exchanger.

Tube leaks are not uncommon either where the tubes have been rolled into the tubesheet or due to corrosion of the tube itself. If you have vibration on the tubeside, you can have physical damage to the tubes due to them vibrating where they go through the baffles, essentially the tubes have a hole worn in them.

Please provide some more information regarding the leaks and we might be able to help you more.

 

[ThomasEun]

As TD2K said, ponderer did not open the leakage history sufficiently.

In general, the reboiler leakage can be presumed the following root causes.

1. In Mechanical and Manufacturing Point of View
(1) Wearing of the tube at baffle holes due to the tube vibration
(2) Weak rolling at tubes to tubesheet at manufacturing shop
(3) Thinning of tube wall due to the strong rolling at manufacturing shop
(4) Weak seal welding of the joint between tubes to tubesheet

2. In Corrosion and Materials Point of View
(1) Crevice corrosion between tubes and tubesheet
(2) Erosion corrosion at the end of the tubes due to turbulent flow
(3) Erosion corrosion around the deposit and Under-deposit corrosion
(4) Unsuitable in tube material selection

3. In Process and Operation Point of View
(1) The tight contact between tubes to tubesheet can be loosed by high thermal cycle.
(2) Chemical analysis of each side fluids
(3) Temperature records

I think the root cause analysis is impossible without shutdown. The following basic investigations are needed.

1. Where (Which part) is leaked?
2. Whether the leakage is due to corrosion or mechanical?
3. Which side (shell or tube) is initiated?
4. To review the operating history and records
5. To review the repair history of the reboiler
6. To draw the damage map if the leakage has multi-locations
7. To check the deposit (location, height, area, and composition) on the tube inside
8. Chemical analysis of deposit
9. Microstructure analysis of leaked parts

Please inform me (thomaseun@shaw.ca) or TD2K more detail information if you need further response.

Thomas

 

[ponderer]

Thanks for your teaching.

As we not yet has the chance to shut down the plant for repairing the heat exchanger. I can not privide more detailed information of the leakage.

I will post the detailed information when we finish inspection of the heat exchanger.

 

[pmureiko]

There are a lot of mechanisms for tubing to leak as listed above. I consider corrosion to be the most likely. If the reboiler operates with a level of condensate, then those tubes will be exposed to carbonic acid and corrode. The carbonic acid is formed when carbon dioxide in the steam reacts with water. This can be verified by if the corrosion is located on the lower level tubes and not on the tube above the condensate level.

 

[pmureiko]

P.S. You can check this by getting a sample of your reboiler condesate and measuring the pH.

Good luck.

 

[reactorshell]

1. Is the feed to the splitter hydrotreated?
2. Any history of fouling and corrosion in the unit?
3. Any analysis on water accumulated in overhead receiver if any?