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HTST pasteurizer inspection

HTST Heat exchanger Plate pack visual inspection CIP cleaning Frequency of inspection Maintenance Cleaning

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#1 PegK

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Posted 08 July 2021 - 03:36 PM

Good morning Everyone, I am trying to write the maintenance schedule for our HTST (High Temperature Short Time) pasteurizer.  We pasteurize approximately 50,000lb of fluid milk 5-6 days per week, that is then processed into cheese. The plate pack contains approximately 80 gasketed plates. The entire system is cleaned CIP. How often do you open the plate pack on an HTST for visual inspection? Our State inspector recommends every 3-6 months. Our maintenance man says he has a letter from the company that built it stating every 12-18 months, and he was told some companies only open it every 5 years.   :shades: Maintenance and I are in a tug-of-war over the timing for inspection.   It had never been opened for 10 years, before I was hired.  Yes it was leaking!  New plate pack was installed and I would like to get them on track with regular checks. The food safety plan is a work in process, and I'm battling the, "We never had to do any of this before", attitude. Thanks for letting me unload, and for anyone who has HTST advice.  

 



#2 johnmcip

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Posted 08 July 2021 - 04:42 PM

What do you want to do, and what does maintenance want to do?

Recommendations are not requirements. I'm sure having a letter stating it may be checked every 12-18 months would pass fine with the inspector.

I would say you validate the frequency. Seeing as it was used for ten years without a check seemingly without incident it seems safe enough to do.

Check after 18 months. If there are leaks, do the next check at 12 months. Still leaks, do the next at six months. this way you can hone in on how long it takes to leak and subtract a month or so.



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#3 MDGMG

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Posted 09 July 2021 - 05:23 AM

Hell,

 

The quantity of  milk process is less compare, Most of the dairy industries open the HTST once a year as part of the preventive schedule. But daily monitoring frequency for leakage is advisable. 



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#4 Ryan M.

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Posted 14 July 2021 - 05:22 PM

Here's a question, when it was opened after not being opened for 10 years were any residues found on the plates?  Either product residues on the product side, or minerals, or other residues on the heating / cooling sides?

 

If no (I would be very surprised!) then I would follow what your maintenance team says.  However, typically this isn't the case....in various milk plants I've been in it is either as frequent as every 3 months up to a year.  It really depends on what you run through it, how long you run it at a time, and how it is cleaned more than anything else.



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#5 PegK

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Posted 19 July 2021 - 06:36 PM

Here's a question, when it was opened after not being opened for 10 years were any residues found on the plates?  Either product residues on the product side, or minerals, or other residues on the heating / cooling sides?

 

If no (I would be very surprised!) then I would follow what your maintenance team says.  However, typically this isn't the case....in various milk plants I've been in it is either as frequent as every 3 months up to a year.  It really depends on what you run through it, how long you run it at a time, and how it is cleaned more than anything else.

 

The residue on the milk side was tremendous after 10 years of build up.  Our inspector said he had never seen one so full of deposits.  The plates also had a very unpleasant smell of burnt milk or cheese.  Oddly enough my aerobic plate counts never went over 30cfu (<10cfu to 10cfu was the normal range).

I learned that the bacterial count is not a good indicator of cleanliness in the plates.  

 

The plate pack had leaked for years but they just ran with it since it was not enough to override pasteurization.  

 

At the second opening (10 weeks) there was discoloration on the product side indicating a protein buildup and a slight oily film in the corners.  I manually washed the plates to remove any residue.

We had a variable drive installed to boost the cleaning cycle.  Called in our chemical rep to test and adjust the concentrations of caustic and acid (both boosted from 1% to 1.5%)   

I wanted to boost the chemical concentration even more 1x a week for a few months (we always did a double strength caustic wash and acid rinse on the farm side during bulk tank wash), but the chemical rep said the caustic wash would not be more effective above 1.5%.   Is this true?

 

We also did a can test to time the volume of water pumped thru at each cycle, and are at our maximum.

 

One month later we opened it a third time to address the broken gasket we noted only a very slight discoloration on the product side (this is the beginnings of a biofilm to my eyes).  Whether I didn't get the previous proteins off by manually cleaning on the previous round, the chemicals are not doing a sufficient job, or we need a larger pump on the HTST, is yet to be known.

 

35 minutes caustic and acid cycles each @ 72C (161.6F)

 

Long story, short... I want to open it quarterly for visual confirmation of the cleaning.  I'm sure I will loose to maintenance wanting somewhere in the 1-5 year range.  Trying to come to a compromise.

 

Thank you very much for your input.



#6 Ryan M.

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Posted 20 July 2021 - 01:34 AM

The residue on the milk side was tremendous after 10 years of build up.  Our inspector said he had never seen one so full of deposits.  The plates also had a very unpleasant smell of burnt milk or cheese.  Oddly enough my aerobic plate counts never went over 30cfu (<10cfu to 10cfu was the normal range).
I learned that the bacterial count is not a good indicator of cleanliness in the plates.  
 
The plate pack had leaked for years but they just ran with it since it was not enough to override pasteurization.  
 
At the second opening (10 weeks) there was discoloration on the product side indicating a protein buildup and a slight oily film in the corners.  I manually washed the plates to remove any residue.
We had a variable drive installed to boost the cleaning cycle.  Called in our chemical rep to test and adjust the concentrations of caustic and acid (both boosted from 1% to 1.5%)   
I wanted to boost the chemical concentration even more 1x a week for a few months (we always did a double strength caustic wash and acid rinse on the farm side during bulk tank wash), but the chemical rep said the caustic wash would not be more effective above 1.5%.   Is this true?
 
We also did a can test to time the volume of water pumped thru at each cycle, and are at our maximum.
 
One month later we opened it a third time to address the broken gasket we noted only a very slight discoloration on the product side (this is the beginnings of a biofilm to my eyes).  Whether I didn't get the previous proteins off by manually cleaning on the previous round, the chemicals are not doing a sufficient job, or we need a larger pump on the HTST, is yet to be known.
 
35 minutes caustic and acid cycles each @ 72C (161.6F)
 
Long story, short... I want to open it quarterly for visual confirmation of the cleaning.  I'm sure I will loose to maintenance wanting somewhere in the 1-5 year range.  Trying to come to a compromise.
 
Thank you very much for your input.


So a few things…

1. With that kind of buildup you want to open quarterly and manually clean to remove as much residue as possible. An off smell is a bad, bad sign. Not sure if you mentioned it? But it is definitely worth looking into having the plates checked for leaks (pinholes). But that’s probably further down the road after you fix the cleaning.

2. Flow during CIP is critical on a heat exchanger. General rule of thumb is 1.5 times flow during CIP versus process flow.

3. I would check the TDS of the chemicals. They will specify usage range and temperature. Caustic should generally be around 180 unless you have additives in there which may be affected (usually not, but worth a check). Acid temp may be slightly high if it is a nitric blend. Nitric tends to gas off about 160.

4. May need more time during circulation. Caustic up to an hour. Acid generally around 30 minutes is good. Especially with the buildup you see since it sounds like it is mostly organic buildup and not mineral.

5. If you can got #2, 3, and 4 optimized and still see that kind of buildup you should insider switching the cycles where you do acid after pre-rinse and then caustic after the post rinse of acid. Logic is the acid will punch holes in the plate buildup making the buildup easier to remove with the caustic. I’ve done this before at a fairy I was at and it worked great.

I do think the most focus should be around flow rate, followed by correct temperatures and then longer cycle time for caustic.

#7 Ryan M.

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Posted 20 July 2021 - 01:37 AM

Oh…and you can have buildup and see clean micro on your finished product with fresh micro testing. Try testing the product after stressing product at elevated temperature, or later on in the shelf life. You will see your micro bloom. That’s a better indicator of the heat exchanger cleanliness. Got to be careful because the longer the buildup remains on the plates more chance of a biofilm and that’s much harder to remove. Biofilms can also slough off spores which germinate later in the product life cycle affecting shelf life.



#8 kingstudruler1

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Posted 20 July 2021 - 04:04 PM

I did my time in a fluid milk plant.  

 

HTST's were disassembled quarterly.    dye tested annually for cracks and pin holes.  as I recall we always found issues.  

 

a maintenance manager that only does maintenance on a  HTST / PHE every 10 years, isn't a maintenance manager.  that's almost shocking.   I was lucky my engineer was extremely good.   

 

id say you continue to take them apart at different periods to establish the frequency.  I don't believe a MFG will tell you "X" amount of time for cleaning and maintenance.  there are too many variables.   

Probably not much help.    







Also tagged with one or more of these keywords: HTST, Heat exchanger, Plate pack, visual inspection, CIP cleaning, Frequency of inspection, Maintenance, Cleaning

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