Plate and Frame Heat Exchanger for Purified Water

[dtreacy]

I am hoping to install an Alfa Laval double walled plate heat exchanger onto our site purified water distribution loop. The heat exchanger will function as a trim cooler maintaining the loop and tank temperature at 15 degC, it will also be used as a batch heater for thermal sanitisation at 85 degC.
My concern is that the FDA guide to inspection of heat exchangers talks only about shell and tube type heat exchangers.
Can anyone tell me if they have a double wall plate and frame heat exchanger installed on their purified system.
Or why I should not use one.

Regards
Daragh

 

[zhangbd]

Dear Daragh

Did you mean the double-sheet exchanger?

We have double-sheet exchangers installed in out purity water 80C and 20C production system, and I know why you plan to install a same one on your distribution loop, maybe that the ambient temperature is higher than 30C and with purpose of 85C sterilization

I think the double sheet heat exchanger is necessary for your purity water loop because the double sheet type of exchanger could prevent your system from medium mixing.

zhangbd

 

[HEC]

Dear Daragh,

I am familliar with plate H/X and the double wall variety. The application is mainly in the Dairy industry for pasteurisation. Zhangbd is correct in stating the double or plate configuration is to prevent cross contamination of the two mediums.
The FDA guide refers only to shell&tube style H/X's as the seal areas and potential dead flow areas are greatly reduced compared to plate H/X. Is the water loop for Sterile (Injectable) or Pure water system? If it is for a Sterile or WFI loop I would recommend using a Shell & Tube H/X for this reason. For a Purified water loop the plate H/X although not ideal is suitable. Increased testing may be needed during validation to ensure no build up of contaminant or bio load.

HEC

 

[dtreacy]

HI all

It’s a difficult one alright, the opinion seems to divided USA (Shell & Tube) / Europe (Plate & Frame).

Anyway I've gone ahead and purchased a double walled plate & frame H/X. It will be used on a purified water loop, providing normal operations temperature control and thermal sanitisation of the distribution system.
I've also checked locally and the industry is split 60% 40% between shell and tube and plate and frame.

As a mechanism to provide greater confidence in the plate and frame H/X , the control system will monitor the pressure differentials between the utilities and product sides ensuring that the product side pressure is maintained above the utilities side. Also a leak detection device will be fitted to provide an alarm if a leak is detected from the unit.
With regards the seal area and dead flow area.
1) I am confident that I have enough documentation to cover the seal area issue.
2) However I am not to sure how to approach the dead flow area issue. Is there a mechanism to prove that there is no dead flow areas in the heat exchanger?

Any ideas?

Regards
Daragh

PS
Many thanks for your help.

 

[HEC]

Daragh

It sounds like you have most bases covered in relation to leak detection and the like. The application on purified water rather than sterile water is comforting.

One of the dissadvantages of the seal area is the additional maintenance and inspection required. What material has been specified for the seals.

A crude method for determination of any hold up would be to pass a salt solution through the PHE. Then monitor the rinse out time and profile for the reducing conductivity (salt concentration). A sharp reduction would indicate a well flushed system. A long tailing off reduction in conductivity would indicate areas where the salt is difusing out and therefore dead flow areas. This test is quite subjective and may require some benchmarking against some other known systems. This procedure may not be acceptable to operations as it does purposely introduce a contaminant into the system.

As stated previously you may need to put in place additional bio load monitoring during the validation of the system.

Hope this is of use to you
HEC