Plate & Frame Hex hot vs cold sides differential pressure

[Unotec]

Good day,

We have a problem with a crude oil cooler.

The oil comes from a high (80ºC) process at a relatively low viscosity (1.38cP). It is cooled down by water to about 40ºC, where the viscosity increases to about 7.33cP.

The problem is that, as the viscosity increases the differential pressure between the hot oil and cold water sides varies throughout the unit. Plate and frame, usually, allow for up to 6kPa pressure differential, which is very minimal.

We have busted couple plates.

In theory, the pressure drop throughout the unit should remain constant and minimal, but apparently it isn't.

Has anybody experienced similar problems to this scenario?

Cheers!

<<A good friend will bail you out of jail, but a true friend
will be sitting beside you saying ” Damn that was fun!” - Unknown>>

 

[pmover]

This type exchanger has small flow passages, which can be easily fouled or filled with debris if the process fluid (crude oil) is not clean. have the failed plates failed due to debris or fouling?

investigate/inquire with the mfg about maximum or allowable DP across the exchanger. there ought to be a data sheet for subject exchanger and if available, i recommend reviewing the data.

hope this helps.
-pmover

 

[itdepends]

6kPa DP between sides on a PHE is very small, we have industrial units from Alfa Laval running hundreds of kpA delta. This doesn't help you a lot but I'm surprised at the comment "usually allow up to 6kPa differential".

Are your units correct?

As a chem eng/metallurgist the first part of any answer I give starts with "It Depends"

 

[TD2K]

7 cP also doesn't seem that high of a viscosity to stop flow. The skin temperature of the oil would be lower but not enough that I would suspect a problem. Do you have any idea of the pour point of the oil?

 

[Unotec]

Just got back from site.

I verified and the mfgr specs are 6kPa differential on the sides.

Looking at the damage, yes it was caused by the bending of the plates due to the differential in pressures.

Apparently one exchanger was damaged when the oil got thick enough that the pressure drop was significant (the oil is cooled with the glycol) at the end plates (out for oil). The other was busted when they connected a pressure truck to flush it.

These are the less expensive and smaller footprint exchangers available. I guess it is time to look for other options..

Thanks for your replies

<<A good friend will bail you out of jail, but a true friend
will be sitting beside you saying ” Damn that was fun!” - Unknown>>