Cleaning in place / cooling with surface water

[Yobbo]

Hi,

Do any of you have experience with cleaning in place of plate heatexchangers in combination with natural surface water? We want to prevent the build-up of fouling due to biological growth of organisms. I see a lot of applications in the food and beverages industry. But there the circumstances may be different and more defined. I am confronted with an almost absolute requirement that no cleaning chemicals are allowed to land into the outlet pipe of the cooling system. The emission license doesn't give any maximal concentrations, that are being allowed. Thereupon the use of the natural water as a cooling resource is already under heavy environmental discussion. The latter is more a political thing, but quite sensitive. Taking all this into account I wonder whether cleaning in place is feasible. Unless any of you can give me a hint about proven possibility to clean in place a plate heatexchanger on the cooling water side. without a risk of contaminating the lake, where the cooling water is pumped back to. Can I assume that CIP in combination with food or beverages is thus secure, that my worry about emitting chemicals in the lake is just neglectable risk?

Let me take the opportunity to wish you all a healthy and prosperous 2011.

Karel Postulart, The Netherlands
Nuon Power Generation

 

[rmw]

By plate heat exchanger do you mean plate and frame (PHE)?

If so, where they originated was the dairy industry where the requirement is that all equipment is disassembled and steam cleaned daily. They later progressed into industrial uses.

First, you should make sure that you have a good straining system on the cooling water. Your PHE mfg'r will be able to tell you the largest particle that the plate passages will permit to pass through. Any thing larger than that, and the PHE will become a VERY GOOD strainer.

That done, you could arrange valving so that you can back flush the CW side by reverse flow. That won't really do anything for biological growth, however. Look at Alfa Laval's site and GEA Ecoflex's site in their sugar section to see if they have any examples of that type of valving. I know that they have schemes for that type of back flushing on PHE's that handle dirty flow streams, but I don't know if they show it on the site (and I'll let you do the looking.)

Make sure that your design velocities are where the mfg'r recommends that they should be. The biggest mistake I see made in PHE application is that the velocity, especially the dirty side velocity isn't designed to be high enough to take advantage of the plate's ability to stay clean.

Back to the original question, based on my first comment above, you have the best of all worlds with respect to cleaning without having any objectionable effluent in that your Hx is designed to be disassembled and cleaned. Use it like it was designed and watch the tubular Hx guys cry.

rmw