Freeze Dryers and Freeze Dried Food (Part 2)

[JimR]

Is anyone having trouble with moisture when storing items in mason jars using the food sealer? I did some chopped onions, green onions and chopped celery and they where completely done but after two months in the jars they have softened up. Also did peaches and stored in Mylar bags but when I opened them they had softened up as well. I am not finding any cold spots when I take them out of FD. They seem dried. Any suggestions would be appreciated. I am concerned I will open my bags down the road to find they are not good to eat.

Here are a few things I do to reduce this problem.

I pull my food out of the machine about 10 minutes BEFORE it turns off and beeps “complete” I do this so the food is still warm. It is easier to feel the cold or cool pieces of food. Even “cool” pieces mean that not all of the water has been removed. I also break the large pieces of food and check for a crisp break, not a bending.

I take each tray, after checking for done, and immediately put the food in a gallon zip-lock bag. I remove as much air a possible and seal the bag. Each tray gets it’s own zip-lock bag. I check each bag once per day for a minimum of 2 days, usually 3-4 days. If the food does not soften up then I will package in Mylar with Ox-absorber (long term) or vacuum in Mason jars without Ox-absorber (shorter term). Note: Ox-absorbers can not work in a vacuum so don’t waste one.

If you find a bag that is part or whole softening up just put all of food from that bag back on a tray and put in your freezer to be re-processed your next session.

I have opened FD’ed food that I vacuumed in Mason jars 5 months later with food still crisp. Note: if you vacuum in Mason jars put a ring on jar after vacuuming tightly and check your lids once a month to make sure they are still sealed. If you have been vacuum packing in Mason jars for very long you will have noticed that sometimes the seal doesn’t last.

As a side note, if you are in “food production” mode, as I am most of the time, here is how I run one session per day for many days in a row.

1. I prepare and pre-freeze my food trays. I have 4 to 8 trays, with food, in my freezer ready to put into the machine at any one time. I put one food per tray and try and mix the types of food so I don’t have too much water in the machine. My goal is to have my FD’ing session last between 18 to 24 hours. No more. This you will have to play with until you know what combinations of food to process together.

2. I start my FD’er sessions at about 4pm. After I start the machine I set the Freezing cycle to about 7-8 hours. This will have the machine go into the “drying” cycle at around 11pm. Or start later with a shorter Freezing cycle IF you have a very good pre-freeze of your trays. Warning: make sure you have closed the drain valve or you will not be happen in the morning.

3. When I get up in the morning I check the machine and see how much longer the “drying” cycle has to go to finish. If the machine shows “Drying” and the timer is below 6 hours left I set a timer or alarm after that time plus 10 minutes. This will alert me 10 minutes fore the machine turns off.

For those who don’t know, after the 7 hour timer goes to zero the machine will go into a 20 minute “cooling” before it shuts the vacuum pump off and beeps “complete“. I try to remove the food 5-10 minutes BEFORE the machine shuts the pump off as noted earlier.

4. I pull the food, check for done, and if done, put each tray into Zip-lock bags as described above.

5. At about 30 minutes before I’m ready to start my next session that same day, I remove all ice/water from the chamber, including any water on the trays (top), turn machine on to pre-cool and start all over again.

You can process a lot of food this way if you want to go into “production” mode, such as when produce is in season or you get a great buy on meats and other foods.

One more quick note: All FD’ed food will soften after opening as the food will start to absorb moisture from the air. If I can’t use all of the food after I have opened the container (Mason jar or Mylar bag) I will take the remaining food and vacuum seal in Mason jar immediately.

As usual, sorry for the long post.

[Rett]

Thank you guys for responding. I will try what JimR does as I also run the machine 24/7 when I have it. My family shares the freeze drier on monthly cycles. I used O2 absorbers in Mylar bags but not in mason jars as you all recommended. Maybe scallions just don't work well as they moistened in the jars. Thanks again.

[Rett]

What might be the cause of the freeze dryer staying in cooling mode? It doesn't go to the heat cycle. I also noticed oil spray around the pump. Oil level not over filled. I turned the machine off and turn freezer dial to zero but it goes to cooling mode and won't go to heat cycle. Any suggestions would be appreciated.

[Gypsyman]

Is the oil spray coming from the pumps exhaust (handle)? If the unit is staying in the cooling mode and you have oilmist coming from the pump exhaust then you most likely have a vacuum leak. Check your hose connections, pump oil drain, and door seal.

 

Richard

Edited June 3, 2015 by Gypsyman (log)

[Deryn]

If you haven't been messing with your hose/pump drain connections since the unit last ran fine (and you definitely closed the water drain hose), then the problem is probably the door seal. Stop the system, open the door, pull the seal out a bit all the way around and close the door again firmly to re-seat the seal. You can also try to run a piece of paper around between the door and the seal to make sure there are no holes. Remember to do the 2 step turn on the handle.

 

I know this is basic stuff but believe me I have made all these seemingly simple mistakes and had a mess of oil spewing from the exhaust and/or something else strange happening such as low pressure or no heating, etc. - and it can be frustrating. One thing I have done to contain the mess a bit, should it happen, is to loosely fasten some paper towel over and around the exhaust exit point - allowing some air in and out but stopping the oil spray from getting anywhere except into the paper towel.

 

Somewhere, on the HR site, there is a video I saw at one time showing a good way to seat the seal for reliable results. Not sure where it is but you might want to go see if you can find it.

 

Another thing I found is that, at first, till I got a better handle on the machine, I should do exactly what HR told me to do - which is basically set it and forget it - don't try to 'understand it' or adjust it at all. I had all sorts of problems when I tried to set things myself at that point. And I always freaked out when it was time for the pump to come on, for fear it would spew oil - which it did a few times till I relaxed and just shut things down for a second and reset the seal on the door (which was the culprit about 99% of the time for me). Every time I set things manually, something new and baffling seemed to happen - and like you seem to have experienced, I also had the heating cycle not come on at least once. I thought it was supposed to come on almost immediately once things were frozen, but, no .. sometimes it doesn't .. but that is usually ok.

Edited June 3, 2015 by Deryn (log)

[TonyC]

Hello All,

I've been away tinkering and would like to report some of my efforts to streamline my freeze dryer process.

 

We had a 13.7 Cu Ft Frigidaire Freezer fail recently and I had to replace it with another in a hurry to save about $1500 worth of food.  I considered discarding the freezer but instead decided to make it a staging freezer for our freeze dryer.  I purchased a new compressor on eBay ($80) and replaced the defective one.  I also discovered that the freezer had a bad relay on the control board that also needed replacing so I searched and found the part for $10 and replaced the defective one on the board.  These new freezers only use 3.5 ounces of freon and the tolerance is critical.  It take lots of patience to get it right - 1 ounce over and you will destroy your new compressor... it took me several days with gauges to get it right.  Anyway, it now runs great and I have modified it to streamline our preparations and allow for flexibility in keeping the Freeze Dryer running 24/7.  I figure if it runs for several years I'll get my money out of the repair costs.

We now have 6 shelves that hold 3 trays each of food that we have prepared for freeze drying.  The freezer brings the food down to -10F and doing this cuts 3 hours off the freeze dryer cooling cycle (from 9 hours to 6 hours) before the vacuum drying process begins.  The picture shows the the top half of the freezer.  I left the bottom half stock.

 

On the Freeze Dryer front, I've been trying to optimize the process time and improve quality.  I've added a cutoff valve to the vacuum pump input port (I'm still experimenting with a modified check valve).  This allows me to isolate the running pump and then release vacuum in the chamber to check the progress of the food.  We are pushing the limits of the machine by completely (maybe even overfilling) filling the trays.  The risk here is that if the chamber walls ice up too heavily the ice becomes an insulator and the freeze drying process will slow to a crawl until the ice is thawed. Discovered this the hard way!

Anyway, There are 3 benefits that I have found to the installation of the valve:

1. The valve allows me to check to see how much ice has accumulated, and defrost the system if necessary.  I simply remove the trays to the freezer, then defrost the system, and restart the drying process.  It is amazing how quickly the newly defrosted system removes the last of the water from the food.
2. The valve also allows me to isolate the pump before the freeze dryer shuts down automatically.  This insures that oil vapor in the pump chamber can not be drawn back into the food chamber due to the high vacuum state in the food chamber.  I am not sure that this is happening, but I prefer to be safe rather than sorry.
3. When I installed the valve I also removed the restrictive stock pump input tree.  It had different two diameter ports on it, a 1/4" and a 3/8" (OD thread, the actual diameter of the port orifice was much smaller).  The port itself was quite restrictive.  I have been experimenting with different size vacuum hoses and fittings in an effort to speed up the vacuum cycle.  I discovered that even with a restrictive 1/4" port, a 1/2" inside diameter hose dramatically increased the efficiency of the pump (I tried 3/8" hoses and things slowed way down - HarvestRight engineers got this absolutely correct!).  I then went a step further and replaced the restrictive tree with a 1/2" inside diameter valve and input plumbing.  A very large increase in performance was achieved.  I have not objectively measured the difference, but it is quite a bit faster.  When the pump first kicks on, it takes significantly less time to start seeing 990 mTor and in less than 3 minutes after seeing 990 mTor, 500 mTor is reached.

Here's a picture of the difference in port diameters.  On the left is the original input part, on the right is its replacement.  Doesn't look like much of a difference, but it is!

 

 

I've also added an oil catch can that does a wonderful job of trapping oil vapor exiting the exhaust of the pump.  Now instead of coating the area in a fine oil mist, the oil settles into the can.  The clear tube on the side of the can lets you know how full the can is.  I routed the exhaust from the catch can to a home made catch can that consisted of a jar with two ports with steel wool inside.  I wanted to see just how much oil would escape the newly install catch can and collect in the jar. 

I've run the system in countless tests including over filling the pump and running the pump without a load (both result in lots of oil spitting out the exhaust port of the pump).  I've drained the catch can twice, once with over 5 oz  of oil in it, but have not collected any oil downstream in the jar so the system is performing well.  I bought the catch can on eBay for $15.89 including shipping! It included all mounting hardware, gaskets, hoses, and clamps. I did put rust resistant steel wool in the can (though the drain plug) to add surface area for the oil vapors to attach to.

I have one last thing left to modify... I had to remove the pump handle  (which is also the pump exhaust port) when I upgraded the input port.   I noticed some rust in the interior of the pipe.  This is due from the high humidity from the vacuum chamber as the moisture that doesn't freeze to the chamber walls runs through the pump and exits via the handle exhaust port.  I'll probably replace it with a brass handle of equivalent diameter in the near future. 

AFTER PICTURE - Notice the diameter of the plumbing coming out of the pump housing

 

BEFORE PICTURE - Notice how small and restrictive the original stock plumbing going into the pump housing is

 

I have a list of parts available from your local Lowes and Home Depot to make the valve mod or to simply eliminate the restriction at the pump input.  I can list them if anyone is interested.  The valve was $12 and the four assorted brass fittings were around $20.  To find the catch can, follow the link or search on "Oil Catch Can"  on eBay -  BILLET ALUMINUM RACING ENGINE OIL CATCH RESERVOIR TANK/CAN+HOSE INDICATOR BLACK .  (Disclaimer here:  I have no relationship with this seller other than purchasing his inexpensive catch can and being happy with it.)  

 

There is plenty of room on the pump housing skirt to mount the bracket (I drilled and tapped two 1/4" holes for the mounting bolts.) without risking damage to the pump oil reservoir. 

 

I still get a slight hint of the smell of the oil when the pump first starts, but no where near what it was.  We use oil catch cans on turbo or supercharged cars, and the idea works for this vacuum pump as well.   Hope this helps someone...

 

Have fun!  and Kindest Regards,

 

Tony

[Gypsyman]

Very nice work Tony. Great find! 

 

I'm building a custom cabinet/stand for my HR dryer. While I've been working on the cabinet I've also been playing with various inlet and exhaust filters for the pump too. When I received my dryer I was impressed with the build quality of the dryer itself but appalled by the cobbled together hardware store exhaust demister that HR supplied for the vacuum pump. Just some cheap pipe fittings with what appears to be a hunk of copper scouring pad shoved into it. They didn't even take the time to clean the shavings out of the hand drilled holes in the plastic cap.

 

 

This shows the HR "demister" beside a filter that I carry in my store for another application. 

 

 

Perfect fit. Clean, simple, professional looking and washable.

 

 

Once the cabinet is done I'll be adding versions of the filter shown below for both the pump inlet and exhaust.

 

 

 

[Deryn]

Wow! Will you (TonyC and Gypsyman) come and live at my house for a while? Bring your families.

 

I wish I even understood everything you have done, TonyC - but I am certainly impressed. I do get why you did it, mind you. I certainly am not handy enough (and I am 'handy' but just not this mechanically inclined these days) to be able to 'do' what you have done - or even know enough to source the parts, especially when I am in Canada.

 

And, Gypsyman, I like your elegant solution for what I too have noticed about the pump exhaust 'mister' - mine looks exactly like the original in your picture - the holes not even cleaned out. Does the new 'filter' actually trap the oil spray so it doesn't go all over the place? And if so, how often do you take it off and wash it out?

 

Thank you both. Keep experimenting, please (not that I could stop you, I am sure).

Edited June 5, 2015 by Deryn (log)

[TonyC]

Gypsyman,

 

That looks like a K&N Air Filter!  I may put that on the end of my catch can.  Do you have the model number handy?

 

I considered some type of water separator before the pump, but I found that any restriction at all on the input side of the pump tended to make the drying cycles much slower.  I actually added a modified passive check valve that looked promising, but proved to add too much resistance and drying time increased.  I then figured I could reduce the hose size to 3/8" since the pump input is only .277".  This proved to be a false assumption.  That's when I decided to open up the input to the pump by removing the stock pump input tree.

 

Here's a picture of both sides of the tree

 

The stock configuration of the vacuum hose and pump input is as follows (all Inside Diameter (ID) measurements):

• Stock Hose Inside Diameter  .68"
• Input Tree 3/8" port  .277"
• Base of the Input Tree that threads into housing   . 369"
• 3/8" Pipe Thread Brass Nipple   .5"
• 1/2" Pipe Thread Brass Nipple   .59"

 

So looking at the above picture you can see that the flow diameter from the chamber to the end of the hose is .68" ID.  It is reduced to fit on the pump input tree which is then constricted to .277".   I replaced the entire tree with 1/2" brass (.59" ID) down to the pump housing which is a 3/8" Pipe Thread so I drop down to .5" ID entering the pump housing.

 

I really was quite suprised to find that flow constriction occurred so easily.  As mentioned above, I had replaced the stock Harvest Right hose with a Yellow Jacket 3/8" vacuum hose and the dry time increased substantially.  This caught me off guard for several reasons.

1. I presumed that the smaller 3/8" hose wouldn't matter as the input constriction was .277"  at the pump input tree.
2. And once the initial air is pulled from the chamber you are dealing with molecules so no large volume of air is flowing.  I feel absolutely no air flow from the exit of my catch can after the initial first 2 minutes of vacuum pull.

I was proved WRONG.  Live and Learn!

 

Gypsyman, when you have your cabinet built and filters in place I'd love to see your results and compare notes.  You may have a better design and I am all for learning from each other.

 

Good Luck

 

Tony

 

 

 

[Gypsyman]

Deryn,

 

This simple filter seems to work very well. I noticed a slight tacky feeling on the counters in the downstairs kitchenette where I run the dryer. That concerned me. If it was fogging the kitchenette even slightly the when the HVAC system for the house was running there was a possibility that it was being sent all thru the house. Not acceptable to me in any form or fashion. S0, I started messing around with exhaust filtration ideas.

 

If you don't have any vacuum leaks then the initial vacuum pull down is when the pump is most likely to "smoke" or mist from the exhaust port. The amount is minute but adds up over numerous runs. I've been washing the filter every 10 to 15 batches. That tells me that even though I'm not seeing oil mist during the initial pull down it is still there to some extent. 

 

TonyC,

 

The filter shown is a filter that is built for us but any PCV or valve cover breather filter with a 3/4" stem should work just fine. I was just trying find a simple solution that was easy to install for those that weren't happy with the HR supplied breather.

 

I really like your catch can idea as we use something similar in our industry on the older trucks. If people decided to use that particular catch can I could machine up a handful of billet aluminum mounting brackets that would allow a simple bolt-on installation using the factory pump cover bolts.

 

 

I have a tendency to over build and over think everything. Anal by nature. Just ask my wife. =) The Visi-Mist and Visi-Trap filters that I will be using when the cabinet is done are probably overkill but I like to experiment.

 

The pump inlet will be run thru a Visi-Trap with a  5 micron Poly-Pro element which is supposed to be good for high volumes of solids and particulates. I'm hoping to catch as many particles as possible before they make it to the pumps oil chamber. I suspect that the majority of the pump oil contamination is happening during the initial pull down faze of the system.

 

The exhaust will be run thru a Visi-Mist with a low-resistance micro-fiberglass coalescing filter. The clear housing should promptly show if we really are getting a large volume of oil mist/fogging during the initial pull down of the system.

 

I had the laser shop cut cooling perforations in both sides of the cabinet to match the pattern on the freeze dryer and allow airflow for pump cooling. I also tracked down a handle for the door that matches the handle on the dryer. Should give it a nice factory look. Super excited to see if it comes out as nice as I hope it will. I'll post photos of the cabinet and filtration system as soon as it's complete. Shouldn't be much longer now.

Edited June 5, 2015 by Gypsyman (log)

[Gypsyman]

I need to clarify my earlier reply to Daryn's question. I noticed the tacky kitchen counters using the HR supplied breather. That's why I started testing pump exhaust filters.

 

Apparently my brain was going faster than my fingers.

 

Richard

[TonyC]

TonyC,

 

The filter shown is a filter that is built for us but any PCV or valve cover breather filter with a 3/4" stem should work just fine. I was just trying find a simple solution that was easy to install for those that weren't happy with the HR supplied breather.

 

I really like your catch can idea as we use something similar in our industry on the older trucks. If people decided to use that particular catch can I could machine up a handful of billet aluminum mounting brackets that would allow a simple bolt-on installation using the factory pump cover bolts.

 

post-79543-0-31226600-14334.gif

 

As far as inlet restriction versus pull down time. Have you logged any timed tests between the 3/8" hose and the 1/2" hose/fittings? Since we're only working with a few cubic feet of air it's seems odd that such a small restriction would make such a large difference in pull down time to a given vacuum level. Keep in mind that exhaust restriction could effect pump pull down time too. I'll run some timed tests when I get mine put back together on the new stand. You have my curiosity peaked with this one. =) If you decide to do any timed tests I'd like to compare notes on the result.

 

I have a tendency to over build and over think everything. Anal by nature. Just ask my wife. =) The Visi-Mist and Visi-Trap filters that I will be using when the cabinet is done are probably overkill but I like to experiment.

 

The pump inlet will be run thru a Visi-Trap with a  5 micron Poly-Pro element which is supposed to be good for high volumes of solids and particulates. I'm hoping to catch as many particles as possible before they make it to the pumps oil chamber. I suspect that the majority of the pump oil contamination is happening during the initial pull down faze of the system.

 

The exhaust will be run thru a Visi-Mist with a low-resistance micro-fiberglass coalescing filter. The clear housing should promptly show if we really are getting a large volume of oil mist/fogging during the initial pull down of the system.

 

I had the laser shop cut cooling perforations in both sides of the cabinet to match the pattern on the freeze dryer and allow airflow for pump cooling. I also tracked down a handle for the door that matches the handle on the dryer. Should give it a nice factory look. Super excited to see if it comes out as nice as I hope it will. I'll post photos of the cabinet and filtration system as soon as it's complete. Shouldn't be much longer now.

 

 I look forward to seeing your work.

 

When I installed the 3/8" Yellow Jacket hose  (I really like the idea of finger tight knurled hose fittings) I was still using the stock input port configuration on the pump.  I use this hose all the time when I pull a vacuum on refrigeration and AC systems here at home.  The hoses are high quality and do not leak.  I hate cheap vacuum hoses amd guages!  They are simply not worth the aggravation. 

 

Anway, The dry cycle was 12 hours longer then normal and I was frantically looking for vacuum leaks.  The vacuum pressures were much higher then normal as well for the time required, and the cycle from 500mTor to 620mTor took longer to pull down and faster to climb.  The colling cycle would climb to 790 mTor before topping out.  Prior to this I was topping out at 750 mTor. The system was acting as if it were iced up.  I finally stopped the test at 290 mTor and reattached the larger diameter stock hose.  I was tehn able to complete the drying cycle within 6 hours at 50 Mtor.  I pulled the food at this poiint and vacuum packed it.  I then changed out the input port to the larger ones.

 

Regarding the catch can, I removed the aluminum ports and drilled them out to remove material to make the ports larger.  I was still not near the 1/2" ID that I had on the input side, but I tried the can anyway and it has not appeared to make a difference. ( I considered that it would just as you have )  It was installed in both scenarios and previous to the hose swaps and port changes.  I did not notice any adverse effects from the catch can.  The restrictions don't seem to be as big a problem on the output side of the pump.  The can is about 1/2" thick on the top and bottom so it would be trivial to simply drill out the ports and install 1/2 ID brass fittings and a larger hose.  I may end up doing just that now that I think about it

 

For a test to be valid I'd need to have fresh oil in during both tests and freeze dry the exact quantity of identical food, or alternatively, simply pull a vacuum on the empty chamber to 500 mTor - again with fresh oll each time.  But this last test would not tell you the degree of impact the increased pump efficiency would have on the total drying cycle.

 

This gets complicated, but consider these facts, If the pump is more efficient you may not see a diffence in cycle time with food in the chamber.  Here is why.  The more water vapor pulled out of the chamber the slower the climb to the cooling point at 620 mTor and the faster the drop to the warming cycle trigger point at 500mTor.  The cycles could theoritically be the same lenth, but the more efficient pump would be pulling more moisture from the chamber during each cycle thus requiring less total cycles to remove a given amount of water in the food.  (My head is begining to hurt!)  This also ties in with how efficient the cooling chamber and the heating elements are.  There are a lot of variables to consider.     

 

The short answer to your question is is that I did not test back to back with the exact same paramenters. 

 

On another note, I did see particulates that came from the interior of the handle that had fallen into the pump exhaust port housing area when I removed the handle.  I will be replacing the handle as it is rusting internally after only 5 months usage.  I have already replaced the pump splash plate with an aluminum piece, but now instead of orange used oil I'm seeing a charcoal color in the oil so the T6061 alumium is oxidizing as well.

 

I may try painting the original mild steel piece with rust inhibitied paint...after I have tested to insure the oil has no adverse affects on the paint.  I've already sandblasted it to remove all the surface rust.  Or I may simply have a friend make me a stainless steel replacement piece.

 

Your project sounds very interesting and quite elaborate.  I looking forward to seeing your progress.

 

Tony

[Gypsyman]

Great data Tony. Agreed on all points. I'm going to save your post for future reference.

 

Since exhaust restriction didn't seem to have any effect on your results I wonder if the 3/8" hose was icing slightly internally up by the chamber causing further restriction? I have all of my hoses covered in split loom so it never occured to me to check for hose for icing up at the chamber connection point.

 

Considering the amount of moisture we are pulling thru these pumps I think pump corrosion is going to be an ongoing problem for all that use their units heavily. I've actually considered going to a cheaper pump and just scrapping them when the corrosion gets too bad. Short of that I think splash plates and handles are going to be a common maintanance item. Maybe we should consider having splash plates molded from HDPE or something similiar. I wonder if just powder coating the original steel plate would fix the issue? Hmmmmmm..........

 

Here I go thinking too much again...

Edited June 5, 2015 by Gypsyman (log)

[Deryn]

Plasti-dip? Is that stuff still made?

[Gypsyman]

I think so. Another good idea. =)

[TonyC]

I have an old unopend can of it in the garage... Red too!

[TonyC]

BTW, These funnels are a great addition for adding oil to your pump. The largest one is perfect for pouring new oil into the pump housing.

 

The smallest one is great for pouring oil down the stock intake port while the pump is running to clean out the pump housing.

I do this every time I change the oil.  Here's how you do it:

 

1. Drain your pump oil and replace the oil cap
2. Remove the hose from the top of the pump
3. Place the smallest funnel into the port ( the other two won't fit )
4. Open the drain port and have a container under the pump to catch the oil
5. Turn on the pump and pour 5-10 ounces of your filtered used oil into the funnel
6. Turn off the pump and let the residue oil drain out
7. Every 3rd oil change I remove the cover and clean up the interior of the pump

You'll be amazed at the crude that comes out of the pump.

 

I now use the middle size funnel instead of the smallest one for flushing my pump due to the larger intake port.

 

They are stainless steel and worth the $9.75 price from Amazon... Search on " Norpro 3-Piece Stainless Steel Funnel Set "

[TonyC]

Gypsyman,

 

I just ran a pulldown test using the larger port on the pump.

 

Here are the results: (Time Points are total, not additive)

 

Time           mTor

5:30 min      960

9 min           500

12 min         400

 

The vacuum bottomed out at 400 mTor before heading up.  This was with used oil on its 3rd cycle and a warm pump.  I'm not sure that this means anything in that it is not a definable / repeatable test as I had food on the trays & dirty oil, and at 500mTor the heating elements kicked on during the test.

 

I think a better test would be to simply run the pump and see how long it takes to pull a complete vacuum on an empty chamber with the tray rack removed.  I'd still have to consider ambient temp, atmospheric pressure, etc at the time of the test, but it would be a lot easier to repeat with some consistency.

 

On another topic,

 

What do you think of the idea of installing a T fitting on the input of my pump and routing the the drain of the catch can into it.  This would allow me to empty the catch can oil back into the pump oil simply by turning on the pump and opening the valve.   The vacuum should pull the oil from the catch can back into the pump.  Any reason not to do this?

 

The upside is no messy draining necessary of the catch can. 

 

The downsides as I see them are:

• possible vacuum leaks if not done right
• possible oil contamination (not sure about this one)
• I have to reconfigure my pump input again   

Comments?

[Gypsyman]

I'd have to wrap my brain around this one a bit but it seems like the open to atmosphere inlet when the drain is open (and the pump is running) would cause a lot of the oil to be sprayed out of the exhaust.

 

Maybe you could mount the catch can higher than the pump. Then you could just open the drain valve with the system turned off and let the catch can drain back down into the pump. Might work?

 

Richard

 

[TonyC]

I have just completed some very interesting vacuum timing tests on my unit.  I have been testing different configurations on my system a great deal, and as a result I’ve been removing and reinstalling my vacuum hose quite a bit lately. 

 

I started to notice a drop in performance and wanted to determine where the problem was.  I suspected the hose, but I had replaced a great deal of the original hardware that connected the hose to the pump and a leak could show itself in any of the joints. 

 

This was also our first summer using the freeze dryer and I wasn’t sure what the 90F+ days with 90%+ humidity might have on performance.  I have noticed a great deal of moisture dripping off the door gasket when the system was running. 

 

No matter the source of the problem, I intended to isolate and correct it. The dry time was simply taking much too long.

 

While I was performing the diagnostic test I also decided to see what impact the catch can had on the system.  I used the timer on the Harvest Right Unit to time the results of 3 distinct tests.  I removed the heat tray frame from the unit for all testing and used default settings of 7 hour dry time.  Once XXX mTor was reached (below 0 mTor) I closed the valve on the pump and let the system sit for 5 minutes to test for leak down.  Some initial settling is normal in the vacuum pressure, but a steady drop in vacuum unacceptable.

 

Here are my results:

 

Test Configuration 1

• Original Hose
• Catch Can Installed
• Pump Oil temp 95F

Results

• Time to 0 mTor          6:34 or 26 Minutes
• Time to XXX mTor      6:29 or 31 Minutes
• 5 Minute Leak Test    020-030 mTor

 

Test Configuration 2

• Original Hose
• Catch Can Removed
• Pump Oil temp 110F

Results

• Time to 0 mTor          6:28 or 32 Minutes
• Time to XXX mTor      6:24 or 36 Minutes
• 5 Minute Leak Test    010-020 mTor

 

Test Configuration 3

• New Hose
• Catch Can installed
• Pump Oil temp 112F

Results

• Time to 0 mTor          6:48.5 or 11.5 Minutes
• Time to XXX mTor      6:47.5 or 12.5 Minutes
• 5 Minute Leak Test    XXX-000 mTor

Analysis

• The Catch Can works well (catching the oil vapors) and does not negatively impact the system.  I have no idea why the time went up on the second test.  This was mildly surprising to me.  I am not sure if it was a result of removing the catch can or not.  I may run a few more tests to see if the result is repeatable.  If so than it is the catch can making the difference in time.
• Even a slight leak makes a big difference with the system performance.  The hose leak was negligible, but it was enough to dramatically increase the freeze dry cycle times.

In the FWIW category, Oatey Silicone Plumbing Grease Item # 30219 is great for aiding in the sealing of the hose connections.  I place it on the brass threads and mating surfaces to keep wear to a minimum.  It will also seal any imperfections in the mating surfaces. It is waterproof, non-staining and nontoxic.  It does not dry.

 

[TonyC]

After my 6th cycle on this oil change, I opened up my pump and cleaned up the insides.  The aluminum shield replacement is holding up much better then the original mild steel one.  Only a few 1/2" circles with slight  discolorations on the top of the plate.  I took it off anyway and replaced it with the original one that has been painted with rust proofing primer and paint.  I also replaced the mild steel allen head screw that held the plate with a stainless steel one.  The screw was looking pretty nasty. 

 

If the painted plate holds up to the high water content and heat I will be using the same paint on the pump body inside the oil chamber.  Ther pump housing was very rusty this time around.  I have a feeling that rust is a going to be a major problem with these pumps.  The moisture doesn't help and I'll focus on that after I get the rust under control.  Anyway, there was very large amount of gunk in the bottom of the unit this time around - a mix of oil and water that had jelled into a nasty slow flowing semi-jello state.  It did not drain out of the pump...  I had to remove the cover to get to it.  Yuck!

 

After receiving my new hose, I have begun experimenteing with the old one.  I cut it in half and added a modified 3/4" brass check valve. I used a 3/4" PEX fitting to secure the hose to the check valve.  Getting the hose on the 3/4" PEX fitting was a bear and getting the rings over the fitting before crimping them was almost as hard.  I modified the check vlave to remove 70% of the spring tension.  It still seals when air is not pushed through it, but it takes precious little effort to hold the valve open.  It now rattles when shaken like an auto PCV valve.  I'll test it later this week.

 

Tony 

[harrisgo]

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

[Deryn]

Welcome to eGullet, harrisgo! And to our world of freeze-dryer owners!

 

Did your loads actually dry, and dry properly? If so, I would not worry immediately about whether the pressure gauge indicates below 500 mtorr or not - since 500 mtorr usually kicks off the reverse cycle anyway. On the other hand, if your oil is milky, I would try changing it completely as that is usually an indication that there is water in the oil. If there is no oil spray, it probably is not 'leaking'.

 

You did check to be sure that the drain valve was completely closed too? Also, does your pump settle down into a constant hum once it has started up? (I suppose there is a possibility you have a pump problem but I don't know enough about those to answer that.)

 

While I hope that the more 'technical' members here will pipe up soon to help you more than I can, I also suggest you give HR a call and ask them what they think/how to resolve the problem if there really is one.

[harrisgo]

Hi Deryn,

 

i had run another FD test with only 2 trays of apples yesterday. In the vacuum/drying stage, the readings can reach up to 500 mtorr after 7 minutes the pumps starts and the goes back up again. Then after next cycle, the system can only reach minimum 580 mtorr (the next 5 cycles as i can remember), and after that in only reach 610/620 mtorr and goes up to 990/xxx mtorr (these cycles kept repeating). There is no vacuum leak as i can recall: no leak in the door seal (i checked that even the single paper cannot slip pass the seal before the drying stage begun), no leak in the vacuum in the hose, the vacuum drain had been closed, and most importantly there is no oil mist coming out of the oil demister.

 

There is a different sound for the pump though. The first 10 minutes of running, the pump was in the constant hump, but it was far LESS noise compared to the rest of the cycle where there are a bit of the trickling sound sometimes.

 

I opened up the case of the pump and turns out there are little bit of rust (2 bolts inside the cartridge were rusted) and water vapor. I don't know if this the main problem that my pump is not working properly to pull a deep vacuum. 

[Deryn]

So, you changed out the milky oil before you ran those apples through? And then you opened up the pump?

 

Given all that, it certainly sounds as though your food will never dry since the vacuum must move between 500 or below and 600 or above to kick in the next cycle. The way you described the mtorr cycling now still sounds like a leak somewhere to my uneducated ears - it always has been the case on my system when that sort of thing happened. However, your description of the pump noise sounds backwards to me - mine usually makes a cycling louder noise at first and then settles into a (not quiet but steady) hum.

 

You might try PM'ing TonyC or Gypsyman before you call HR. Neither has posted lately and I am not sure they have been reading this thread for a while but a PM may reach them. Those guys really know a lot more about these pumps than I am ever likely to.

 

Not sure whether the pump warranty is voided by opening the pump up though so if you call HR perhaps you won't want to mention that at first till you are sure.

 

Have you ever had ANY run go to the end and the food seemed to be dry as it should be?

 

When I first got my machine, I watched it wayyyyyy too much (once the pump started) and panicked several times when I didn't understand exactly what was going on. I soon learned it was 'magic' that no one yet has completely explained to the point that I totally understand it - but so far so good - it worked to do the job it was supposed to do whether I understood it or not.

 

Wish I could help you more but someone - either here or at HR - CAN I know. I just want to see you happily talking about all the foods you have dried successfully - and soon. I know the frustrations when one spends so much money and something doesn't work well from the beginning. However, your system IS under warranty and HR has been great in the past (as far as I know they still are) about responding to customer issues.