Freeze Dryers and Freeze Dried Food (Part 2)

[TonyC]

It's been a while since I have posted.  I've been busy testing and refining my machine and my process.  The result have been encouraging but I still ahve a ways to go.

 

I posted this picture several months ago about rust in the pump oil chamber and what I was attempting to do about it. You can see the rust still on the original plate even after I had cleaned and dried it.  The first two were replacement plates that I was considering.

 

I finally got around to sand blasting my original plate and painting it with rustoleum rust inhibitor primer (the brown stuff) and rustoleum red. I painted it over several days this summer when my garage was very hot upstairs to let the paint bake.  I've been running this red replacement part now for a while.

 

I have found that if I defrost my freeze dryer 8-10 hours into the dry cycle, that I do not get as much water buildup in my pump, and freeze dry cycles complete faster.  I think that maybe the ice that builds up on the freeze dryer walls insulates the chamber and also sublimates into the air just as the water in the food does. 

 

I was able to go 20 cycles between the last oil change and this one and my freeze dryer still reached 0 mTor even on the 20th cycle with the same oil.  I typcially add a little bit more oil than the 22.5 oz required to allow me to drain a little of the water out as the pump cools and the oil and water separates.  If I add any oil during this time it is theoil that I catch in a cup and let sit and stratify.

 

So after 20 cycles I opened up my pump and here is what I found!  This was before I cleaned things up.

 

 

Note the rust build up on the unprotected pump housing (My splash plate used to look this bad as well), but look how nice the splash plate still looks.  Based upon this successful test I am going to dissassemble my pump housing and powder coat the exterior of the pump housing..

 

I am also experimenting with catching the water vapor before it reaches the pump.  My first two attemps failed, but now I know what doesn't work!  Still playing in this area and I'll report back when I have a viable solution.  

 

Tony

Edited July 30, 2015 by TonyC (log)

[TonyC]

Hi all,

My FD machine had arrived a week ago and since then i have tried 3 batches of banana and avocado. But it seems i have a problem with the FD because it cannot reach below 500 mtorr and on cycle 1-9 the readings varied between 500 and 700 mtorr. I have checked all the possible leak cause at the machine and the the vacuum pump, but nothing seemed to be the problem (as all seems leak proof to me). One thing i noticed that the oil in the pump were milky. Do anyone have the same problem as me or should i do a full oil draining in the vacuum pump? Thanks before.

NB. I did pull off the rubber gasket when the Machine arrived, but i managed to put it back and i checked during the freezing and drying process that there is no leak from the gasket seal.

Cheers,

Harris

 

Hi Harris,

 

Congratualtions on your purchase of a freeze dryer!

 

It seems to me that if your unit is cycling between 500 and 700 mTor that you are in stage 2 of the drying cycle.  Depending on how wet your food is this cycle can run for 36 hours.  If you have overloaded your trays the cycle will never end.  If your food slices are thicker than 3/8"  your food will take much longer to dry.

 

As a TEST load a single tray lightly with bananas sliced 1/4" thick short ways so you end up with 1/4" thick circles on the tray.

Insert the tray and start the cycle.  This should result in a cooling phase of 9 hours (if your prefeeze 6 hours), a drying phase of a varying time limit but probably 7-9 hours and a post drying phase of 7 hours.  Watch the FD and see if you drop below 500 mTor.  This means you have entered the 3rd phase of the fd process - (post drying).  

 

I have noticed on my FD that if I over load the tays with food that the FD will never exit the 2nd stage of the process. Instead you'll see a great deal of icxe on the walls and the heating tray will be difficult to remove due to ice buildup. To correct this pull the trays and put them in your freezer, and then defrost the freeze dryer.  To do this: 

1. Remove the rubber gasket,
2. pull the heating tray out if you can and lay it up on the top of the FD (I have a towel on top of my unit to protect everything).  I do not disconnect it. 
3. I then use a fan and blow air into the chamber until I see the ice turn clear. 
4. use a flat blade screw driver to loosen the ice.  I can complete this job in 10 minutes. (Do not turn the FD on within 5 minutes of shutting it off, this will damage the compressor.) 
5. Wipe down the inside of the unit with a towel,
6. reinsert the heating tray stand,
7. reinstall the rubber door gasket,
8. turn on the unit,
9. reinsert your food and close it up,
10. set the freeze timer down to 1 hour and your done.

In an hour your unit will again be below zero (about -15F) and the pump will come back on restarting the drying process.  BTW, This is now a part of my routine and my food dries much much faster than before. Within 8 hours of doing this your mTor reading should be well below 500 and you should be in the 3rd stage of the drying cycle.  If this doen't work, you can vacuum test the unit using the following method.  

 

You should be able to pull a complete vacuum on your system as a test.  Here is how.

1. Leaving your freeze dryer empty
2. Remove the heating tray from the unit and unplug it
3. Close and lock the door - not need for the pad
4. Turn on the unit and zero the freeze time, the pump should come on.
5. In 7-8 minutes you should see the XXX on the screen drop to 990 mTor.  It should drop relatively quickly to 500 mTor.
6. Within 30-45 minutes you should be seeing 0 mTor or XXX mTor ( I see the lower limit within 20 minutes on my unit with fresh oil & a clean oil chamber)

If you do not see this level of performance, you need to look for leaks.  It doesn't nee to be a big leak to cause poor vacuum performance. 

 

Check the following:

1. Vacuum hose connections - both ends need to be tight.  I use a 14" Cresent adjustable wrench.  Insure the hose is SNUG.  If the clear part of the hose can move at all ( up or down, or spin radially) the hose needs to be tighter.
2. Insure that your drain valve is fully closed.
3. Check and adjust your door if necessary.  When closed you should see a very narrow contact patch on the door.  It won't be wide but it should be consistant all the way around the door.   As the vacuum becomes strong the contact patch should grow to over well over 1/4" wide.

Report back what your results.

 

Tony

[Deryn]

Thanks, Tony - for your Harris post. I knew you would be able to help him more than I could. Please check back once in a while - I feel quite lost when my technical gurus are not here.

 

As for what you have done with your pump - snazzy red! When you have all this figured out, I will just have to send you my pump so you can do all the mods for me - but I am certainly enjoying your experimentation reports!

[TonyC]

Thanks, Tony - for your Harris post. I knew you would be able to help him more than I could. Please check back once in a while - I feel quite lost when my technical gurus are not here.

 

As for what you have done with your pump - snazzy red! When you have all this figured out, I will just have to send you my pump so you can do all the mods for me - but I am certainly enjoying your experimentation reports!

 

Hi Deryn,

 

Here is my first pass on a Vapor Trap... it is an old whole house water filter that I modified.  It failed to reduce the moisture in the oil...  I'm in the process of modifying it to catch and suspend the moisture in the container long enough for desiccant beads to absorb the water.  The air flow comes into the inlet, down the central pipe to the bottom of the screen and filters up through the beads and out the top.

 

I added this inline and filled it with 1/8" desiccant beads.  When blue they are dry, they turn pink when full of moisture.  Heat them up and they release moisture and turn blue again.

 

This is it all hooked up.  I didn't see any measureable drop in vacuum pump efficiency so that is a plus.

 

And after running the pump through a cycle this is what I got... almost all of the moisture passed through the unit and into the pump.

 

I removed the unit and left it open to air with the hoses attached... in 3 days all the beads were bright pink.  So the concept will work if I can trap the moisture long enough to allow the beads to do their thing.

 

Next step is to machine quilt several layers of quilt batting in a donut configuration - maybe 10 or so to get 3-4" of material, enough that they will trap/absorb the moisture and allow the beads to function.

 

This may not work either, but it is fun trying.

 

Tony   

[TonyC]

Deryn,

 

Have your tried freeze drying all natural peanut butter?  I'm thinking that it will go to powder and reconstitute with water. But I have not tried it yet.

 

Tony

Edited July 31, 2015 by TonyC (log)

[harrisgo]

Hi Tony,

 

Thank you very much for the explanation!

 

I have figured out that the issues are the mostly the water vapor the system of the pump, it caused great deal of rust in my pump. Your great experiment about coating the pump house might be worth to try aswell. I would like to know the result of the several layers configuration of quilt battling, as it is might cause an efficiency loss of the vacuum i think.

 

And yeah about the icing build up. Can you tell me more, especially when do you stop the FD process-defrost it-and turn it on again? Do i need to check it within 7 hrs after the drying phase starts?

[Deryn]

No, I haven't yet tried drying peanut butter. I think either fully homogenized or a natural one (with every bit of oil you can get squeezed out of it removed) 'might' sort of dry (although I am not sure how much of its content is water, not oil). Butter doesn't do well (if it is just butter, as opposed to mixed in with other foods) as we all know but maybe peanut butter, with its solid base (peanuts) would do better. 

 

I believe that peanut butter powder is made either by spray drying or maybe by never allowing the peanut mixture to not quite ever reach the oily state in the grinding process. If I knew what the commercial process was I might know a bit better whether we have a decent chance to replicate it in our home freeze-dryers. That said, I am not sure we would ultimately find a cost savings over buying a pre-made #10 can so I would do it only as a fun experiment. I'll report back here if/when I try it.

[TonyC]

Hi Harris,

 

re: Defrost Time

 

There are three phases that HarvestRight uses to define the FD process

• Phase 1 - Cooling - Only the Freezer is running
• Phase 2 - Drying - The cycle time between 500 mTor and the upper limit (can be as high as 800 mTor)
• Phase 3 - Post Drying - The final period when the drying timer begins counting down and the vacuum reading is 500 mTor or less

Depending on the food and how much / wet it is determines in what cycle I defrost.  It is from 8-10 hours from when Phase 2 begins. If the food is high in moisture (typically the heavier the tray the more moisture in the food) the FD may still be in the phase 2 drying period, but with lighter less wet foods it may be in phase 3. 

Note: I have actually had my FD stay in Phase 2 indefinitely from too much ice buildup.  This happens when you overload the machine with too much wet food.

 

My freeze dryer is rarely not running so defrosting in mid cycle is not an inconvenience for me.  Defrosting in the middle of the process simply means that there is less ice to remove at the end of the process.  I've gotten to where I have the system back up and running in 15 minutes or less.  After defrosting the unit and restarting, the Phase 3 Post Drying cycle begins very quickly.

 

I added a valve just in front of my vacuum pump inlet that allows me to check the food without shutting down the FD or pump.  I simply close the pump valve, open the FD drain valve and check my food. 

 

If the ice isn't heavy I close the FD door, close the drain valve, and open the pump valve.  I don't want to turn off the FD if I don't have to. 

 

If the ice build up is heavy I turn the unit off, pull out the food and place in a nearby freezer, remove the tray heater and place on top of the FD, and use a fan to defrost the unit.  I then wipe down the interior and reinstall everything, close the drain valve, and start it all back up.  I set Phase 1 cool time to 1 hour and have found the walls of the FD chamber will be at -20F by that time. 

 

I keep a $10 thermometer in the freezer so I am aware of where the temps are all the time.  After watching it for a while you start to see a pattern emerge.  I use an Accu-Temp indoor / outdoor model purchased at WalMart - the most inexpensive model they had.  I place the sensor under the tray in the bottom of the FD chamber and the display between the door and the black insert.  It sits on the rubber gasket.  It reads to -50F.

 

Re: Vapor trap 

I'll let you know the results of my batting experiment when I get the time to try again.  But first I'm going to powder coat my pump housing.  That means dissasembly of my pump for a day or so. Sand blasting the exterior of the pump, cleaning it all back up in prep for the coating, applying the coating and then reassembly.  I must be sure to keep all the abrasive sand blasting powder out of my pump internals, otherwise I ruin my pump. I'll replace the bolts with stainless steel ones that resist rust and humidity.  

 

Tony 

[Canon4me]

I purchased a HR FD late last year and because of our basement being torn up have not used it until the first time last night. Read the manual front and back and also Part 1 of this never-ending thread in this forum. Much helpful info on this forum that really can't be found elsewhere. We have a large country garden and would like to FD as much of the produce as we can. Started the HR last night about 2030. Got up this morning and the unit is a little noisier coming from the pump. There is some condensation on the gasket with some dripping on our cart is in. The pump seems to making more noise than it did last night before I went to bed. Before I started it I went through all the preliminary steps and I've got them all covered. Just wanted to know if this is normal? By the way, I have four trays of uncooked green beans in it now.

http://i154.photobucket.com/albums/s271/photogman/image.jpg1_zps9c5u6ynf.jpg

http://s154.photobucket.com/user/photogman/media/image.jpg2_zpswyga47f5.jpg.html

[Canon4me]

Two more pics of the moisture.....

http://i154.photobucket.com/albums/s271/photogman/image.jpg2_zpszldovuiq.jpg

http://i154.photobucket.com/albums/s271/photogman/image.jpg1_zpsxxuscrfn.jpg

Before I started the unit, I went around the gasket and did the paper test and it was tight all around with no chance of air infiltration or sign the gasket wasn't tight.

[Deryn]

Hi Canon -

 

Is it a humid day/time of year where you live? The air around the outside of your dryer is warmer than it is inside (particularly during the initial freeze cycle) so moisture will condense out of the air on the gasket. That causes the drips. I put a piece of paper towel under my door edge because that often happens to me too as I live on the coast. It isn't a seal problem and won't affect your drying run.

 

I am not a pump expert but the noise increasing rather than settling down (or after it has settled down) would bother me more than condensation on the gasket. Is the system cycling properly between 500 and 600 mtorr (or going below and above those two numbers)? Is the oil at all milky (on your first run it should not be but who knows)? Is the drain valve closed? Is there any oil (probably a very fine spray) coming from the pump exhaust valve? (If the latter, you may have a minor air leak - check your pump connections carefully and tighten what you can).

 

You say you started the system at 10:30 pm. That was just on the freeze cycle - right? So the pump wasn't even working then - and wouldn't be for about 8 or 9 hours (since it doesn't come on till the freeze cycle is done) which brings us to this morning, correct? And when you got up the pump was actually running I would guess? Maybe I am not quite understanding exactly where you are in the cycle. I hope you can clarify - there may be no problem at all.

Edited August 2, 2015 by Deryn (log)

[Canon4me]

Deryn, thanks for your reply. 2030 is 8:30 pm. I looked in the round window of the pump and the oil does not seem cloudy. It is right at the line going across for level. The vacuum currently is going back and forth from about 680 to 700 nT. I have all time settings left at default factory settings. The indoor humidity is around 47%. Thanks for your help. I'm in the learning curve.

http://i154.photobucket.com/albums/s271/photogman/image.jpg2_zpsuugxoe5l.jpg

http://i154.photobucket.com/albums/s271/photogman/image.jpg1_zpsbnkcmlcl.jpg

[Deryn]

Deryn, thanks for your reply. 2030 is 8:30 pm. I looked in the round window of the pump and the oil does not seem cloudy. It is right at the line going across for level. The vacuum currently is going back and forth from about 680 to 700 nT. I have all time settings left at default factory settings. The indoor humidity is around 47%. Thanks for your help. I'm in the learning curve.

http://i154.photobucket.com/albums/s271/photogman/image.jpg2_zpsuugxoe5l.jpg

http://i154.photobucket.com/albums/s271/photogman/image.jpg1_zpsbnkcmlcl.jpg

Doh - you are right. Getting my 2nd cup of coffee now. I should know better about that time - I worked in air traffic ops for many years. My bad.

 

1) Please confirm for me. The pump was NOT on when you went to bed then (unless you didn't go to bed until the wee hours of the morning), right?

 

2) The numbers on the readout panel should be going back and forth from at or below 500 mtorr to at or above 600 mtorr (and then back down again). If it is stuck above 600 mtorr and never cycles back down, there is probably some kind of small leak somewhere. That means it is not pulling a good vacuum. Check all your pump hose attachments (including the drain closing under the oil level) and get them as tight as you can.

 

Note: It does take a few minutes to cycle - this is not an 'instant' up/down thing. And when the pump first starts up and is noisy till it settles down into a proper hum, it can take a few minutes to get the whole cycle smoothed out.

 

I know how confusing and scary that first run can be. I went through it all too - and had someone calling me to reassure me late at night when I panicked. Hang in there. Check those closures first.

 

Once you get those right, from now on, probably the only things you will have to check if there seems to be a leak will be: the door (which you say is good but it is usually the issue), the drain valve and that little nut under the oil display window (if you have opened it to drain out any oil). My first run, that oil nut was the culprit.

Edited August 2, 2015 by Deryn (log)

[Deryn]

It just occurred to me that I am not sure how many posts you need to have before you can post freely as many times as you want in a day. If you cannot respond here, try PM'ing me. If you don't post again shortly I will try to contact you by PM and give you my email address if necessary.

 

(edited to add: sent you a PM)

Edited August 2, 2015 by Deryn (log)

[Canon4me]

I just came in from working in the garden and it said it was heating and at about 500 mT. It just went to cooling and jumped up to 640mT. I noticed when it is cooling there is no time but there is when it is heating. You were correct, when I started it up last night and before I went to bed the pump was no running, only when I woke up this morning. With this forum software am I able to load up an audio file? If not, I could email you a short ten sec audio clip recorded with my iPhone. I may send that to Harvest Right tomorrow to confirm that the pump is sounding/working correctly. When I tightened all the fitting up, I tightened them to what the specs said 1/4 to 1/2 turn tighter than hand tighten. I'm afraid to tighten it any tighter. I have a reputation in this household for stripped engine bolts (5 point and aircraft bolts). It seems like I always want to tighten them up until they bleed. Not good to do when you are messing with a $4k piece of equipment.

[Deryn]

If you are still worried about the pump noise, send me that audio file and I will have a listen to it for you. You have my email address in that PM I sent you.

 

Sounds as though the machine is working though and that there aren't any leaks after all.

[Canon4me]

44 minutes of drying time left in this cycle at 180-200 mT. 22 hours into this process thus far at 1830.

Question: since my wife and I both work, is it ok to leave this going unattended? And when it finishes freeze drying, does it shut off by itself?

Edited August 2, 2015 by Canon4me (log)

[Kerry Beal]

44 minutes of drying time left in this cycle at 180-200 mT. 22 hours into this process thus far at 1830.

Question: since my wife and I both work, is it ok to leave this going unattended? And when it finishes freeze drying, does it shut off by itself?

It shuts off the vacuum cycling - the freezer comes back on - and as I recall it beeps, and beeps and beeps. The food when removed is cold and so risks condensation forming on it. 

 

What I tend to do is watch for it to start the countdown timer once it has finished phase two and moves on to phase three. If it's going to be another 5 hours and I'm going to be at work for 8 then I turn up the timer so it's finishing after 8 hours instead of 5. Then I can unload when it's warm rather than cold. I generally find if it hasn't started the countdown timer by the time I leave for work that I don't need to worry about it until I get home. I do the same thing overnight so it's finishing up when I get up in the morning so that damn beep doesn't wake the house overnight.

[Deryn]

What Kerry said.

Canon - Sorry I didn't manage to get back to you in a timely manner. Hope it all worked out ok.

With only 44 minutes left to go, given that what you were drying was a load of green beans, I think I might have shut the machine down for a minute and checked to see if they were dry at that point, as they well might have been. I don't think the machine is that precise that it resets itself based on dryness except at the end of a cycle - it just finishes the cycle and then checks to see if it should do another 7 hours. Someone please correct me if I am wrong about that though.

But, that said, Kerry's summary of what she does is what many of us do if there is a chance we won't be around or if we know we may be sleeping when, per the timer, we expect the load will be finished.

You can't get drier than dry so no harm is done as far as I am aware (other than a bit more electricity being consumed) if you run it for days after everything is dry as a bone. But, definitely warm it up a bit (if the beeper is telling you it finished by itself) before you unload, to prevent condensation.

Edited August 3, 2015 by Deryn (log)

[Kerry Beal]

The whole wet dirty oil thing has been a source of angst for me - particularly the spraying oil all over the house if the vacuum isn't complete. And dislike the changing of the oil as well - when it reaches the point that I can't even see the level of vacuum oil in the pump because of the dirt. I can get hubby to take the pump apart for me and clean it - but then he starts muttering about how this can't be good for the pump and all.

 

So I did some research and decided that I wanted a diaphragm pump of some sort for it so that moisture wouldn't be an issue - contacting the guys at HD they explained I would need a pump that could get down below 200 mTorr (0.2 Torr) which is 0.3 millibar or 0.000266 bar. It needed at least 6 cfm.

 

I concluded that Edwards XDS scroll pump or Vacuumbrand mv 2 or 10 nt vario would be workable options if I could get one and adapt it to the 1/2 inch hose on the FD unit. 

 

I found an Edwards XDS 10 for a fraction of the price new and picked it up when I was in Washington in April.

 

Fortunately hubby used to work with high vacuum systems so was able to figure out what I needed to hook it up and while I was up north he finally got around to checking to make sure it worked and hooking it up for me. 

 

 

 

So today is it's maiden voyage. I'll keep you posted.

 

I'm going to go and do a little reading on gas ballast and figure out what I should be setting that to.

 

 

[Deryn]

I can certainly relate to the pump/oil spraying/changing angst (especially without a handyman around the house any more). I look forward to hearing how the experiment goes, Kerry. Crossing my fingers it is a great success! Thanks to your husband for helping you get it hooked up.

[Kerry Beal]

I've put a very small load in there this time - it's basically half a thin layer of rhubarb puree that I made and put in the freezer before I went north.

 

I let it freeze for about 3 hours, then turned on the pump. Took several minutes to come down to pressure - the timer started and is continuing to count down! It remains around 440 - 450 mTorr. Pump is pretty quiet compared to the vane pump.

 

So this batch will be finishing tonight around 7 - 7:30 as I picked 7 hour drying time.

 

Spoke with Matt at HR - he says that the lack of cycling at this point is due to the small quantity of liquid in there. Full trays will cycle. 

 

So off to the grocery store to find a few more things to freeze dry in round 2 - I scream, you scream....

[Canon4me]

Little unrelated....can anybody make a recommendation for a vacuum pump/food saver to suck out the air on mason canning jars for which I will store some of my freeze dried food?

[Kerry Beal]

Do you own a food saver of any sort now?

[Canon4me]

No, I do not own a foodsaver. Maybe there is something better out there. I really don't know.