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[Cwsrt]

Hi, good day to everyone!

I'm a new engineer assigned at our refinery's water treatment facility. Since i started until now, we have been receiving a lot of reports regarding the clogging up of our pumps' lube oil coolers at the refinery process area. There are also instances wherein the cooling water is not able to flow back to the return header (we have a recirculating cooling water system), thus we just drain the used cooling water to the refinery sewers.

I have come up with a number of hypotheses (as well as my insights) regarding this problem.

1.) The cooling water supply pressure may be insufficient to reach some pumps in the process areas. This may cause low flow of cooling water on "far" pumps and may result to inefficient cooling. This would then cause silica to precipitate and foul the cooling water line.
-if this is the case, however, why is it that only certain pumps are experiencing this problem. All "far" pumps should experience the same problem if this is the root cause.

2.) The cooling water return pressure may be too high. This may prevent the cooling water lines to enter the cooling water return header. This may also cause inefficient cooling and possibly silica deposition.
- Again, if this is the case, all pumps connected to the header should be affected which they are not.

3.)
Lube oil temperature may be too high for some pumps, such that it may cause the spontaneous deposition of silica and other precipitates.


Additional information:

Our cooling water silica is at around 150ppm
Total hardness is at 200ppm
pH is kept within a range of 8-8.5
Residual chlorine is kept at 0.2-0.5ppm (we are using continuous chlorination)
Ortho-phosphate level is also monitored at 8-10ppm
We also have a corrosion inhibitor and yellow metal passivator injection at the cooling water tower basins.

I hope these information are enough.

Can you please help me regarding this problem? Please comment on my suspected causes regarding their feasibility. Can you suggest methods or ways on how I can confirm the root cause, and find a suitable solution?

Comments and suggestions will be greatly appreciated. Thank you.