problem in chocolate factory

[mike8181]

I have a problem with the scaling of pipes (carbonate,chalk.lme formation). The water tests show that the ph is ok, german hardness is ok . Also theres a blackening of stainless steel r 316 L and corrosion of the injection moulding press which is made of a cu-al-ni-fe alloy. I use sodium hydroxide as the cleaning agent and a boost of hydrogen peroxide to clean the pipes and the stainles steel tanks. My suspects are the resin udes in the softening unit bayer lewatit s 1467 and the composition of the naoh / h2o2 mixture , maybe i need the correct mixture , i want to know the ideal mixture of naoh and h202 for cleaning 5000 litre tanks and the correct resin for the softening unit.

 

[HEC]

Need a bit more information, a common problem in the dairy industry is occurance of "milkstone". This is also a white build up. The solution in thhis case was to do a nitric acid based CIP on a weekly basis. Blackening of 316l ss sounds bad too. What are the exact process conditions that this is occuring under?


Mark Hutton

 

[mike8181]

The water used for cleaning is normal room temperature , the process water is 85 c . The pressure is 3 bar , velocity of water is 3ft/sec. The flow is not turbulent, i know that this type of flow causes scaling. The water used for cleaning is softened water ph 8-9 , german hardness 3.5 , I also understand that there should be some amount of hardness in process water as this develops a protective barier above the surface of the metal.My company is in the netherlands and I have contacted the ppl who make the press about the alloy , apparently its a popular choice. There is no substitute for the h202 , so im really clueless. The softening unit manufacturers claim that their unit works well and the water tests prove that the water entering and leaving the unit is ok.

 

[EdStainless]

Your pH sounds high. What is the rest of the water chemistry (TDS, alk and so on).
How much peroxide are you using? What is the concentration at the inlet and discharge?
Do you run the hydroxide and peroxide together, or one after the other?
Does the water start out at 85C, are there areas that are cooler than that?

You need to have some analysis done to find out what the deposits are. The black may be magnetite. If it is, and it is staying stuck to the tubes then leave it alone.
The only way to clean these (if they are what I suspect) is with nitric acid.
First you need to determine if the product is being effected.

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[777gne]

Did you say the the velocity of your CIP water is 3ft/sec? If so, I don't know that it would be causing all (or any) of your issues, but that's a very low velocity in most CIP situations (I have no experience with chocolate however).

7-10 ft/sec is a good rule of thumb for CIP velocity, otherwise as you say, the flow is not turbulent and there is not much "scrubbing" effect.