Auto Draw Off Question

[mapleman3]

When the last section gets near syrup and starts to foam... More air is there and my temp on the controller goes down therefor not reading the syrup correctly. is that normal and do you set lower? My probe is straight up and down and 1/4 inch off the bottom near the other dial therm probe. Any help ?

[Haynes Forest Products]

I think the probe is the problem. You want more of it in the syrup running horizontaly or at a slight angle. close to the bottom. Can you put a T in the draw off plumbing and have the probe on the level side and the auto draw on the downward part of the T That way the finished syrup will be passing the probe as it exits the finish pan and be completely submerged? If the T is a s close to the drawoff box and the probe is going thru the T into the box and into the pan you should get the best reading.

[Lwood]

I've seen that when I get a little niter on the bottom of the pan near the draw off, causing what appears to be foaming. But have not had that issue when there was no niter build up. It seems to drop my temp by about 2 degrees if I remember right.

[mapleman3]

I may have been a bit premature on it... it seems to be fine, i have tweaked it and now it's pretty precise. here are pictures (links) to my draw off... yes I copied the Marcland and bought a marcland valve.. built it for half the cost. the only thing is the controller I bought doesnt allow o.1deg F resolution, but does in Celsius.... so I use it in that... just had to make a conversion chart, not a big deal

http://picasaweb.google.com/lh/photo/WBGwayBtA4Yb8UMsQStEFg?feat=directlink

http://picasaweb.google.com/lh/photo/XOPKrBdZQXx3M9oz3vqQwA?feat=directlink

http://picasaweb.google.com/lh/photo/CdrPtmhZ_zqxF8YeSzKxjQ?feat=directlink

http://picasaweb.google.com/lh/photo/MWL7yyQpI_htX7OeFGZPng?feat=directlink

[twofer]

I may have been a bit premature on it... it seems to be fine, i have tweaked it and now it's pretty precise. here are pictures (links) to my draw off... yes I copied the Marcland and bought a marcland valve.. built it for half the cost. the only thing is the controller I bought doesnt allow o.1deg F resolution, but does in Celsius.... so I use it in that... just had to make a conversion chart, not a big deal


What are using for your temperature sensor? I'm using a similar PID and if I switch it to a PT100 RTD sensor I can get .1° resolution. Haven't done it yet though since I had some thermocouples lying around and I'm cheap. :)

[mapleman3]

I am using a PT100 but this controller does not give a decimal on F no matter what.

[Grade "A"]

I am using a PT100 but this controller does not give a decimal on F no matter what.

Use the setting pt10.0 instead of pt100 it should give you the tenth of a deg. your looking for.

[Amber Gold]

Jim, can you post a parts list? I may build one for next season.

[Haynes Forest Products]

Mapleman3 What type of controller did you use. I have a few Watlows that Im wondering if they would work. What is the things that are most important


1)sensitivity

2) on-off increments

3) temp range

4) can it be thrown across the room and servive:o

5) How long of a temp probe lead do I need so if I do throw it across the room so it wont unplug:lol:

What would you do differant as far as componants

[farmall h]

Haynes, I was wondering the same thing in regards to the watlows. New watlows are 275-350 $ depending on model (that's is at my company's cost). They also require what is called a quench arc for installed as electrical surge protection. I think the Watlow may be too sophisticated for a draw-off application.. My Central Out Door Boiler has a LOVE Control to activate the solenoid on the damper...this may be more suited for a draw-off control and they are 115v. I believe the Watlows vary in voltage. Just thowing it out there.:)

[Haynes Forest Products]

Farmall I have two and they both have relays in them that can activate a solonoid valve. Its the increments that I hear are the problem. Do you need 1/10 of a degree and the ability to program the differance in? Plus barometric......YIKES who can do this.

[twofer]

Farmall I have two and they both have relays in them that can activate a solonoid valve. Its the increments that I hear are the problem. Do you need 1/10 of a degree and the ability to program the differance in? Plus barometric......YIKES who can do this.

That's exactly what I've been working on. I have some experience programming microcontrollers and controlling SSR's based on temperature readings. My plan is to build an evaporator controller that will auto draw off, report volume levels in the bulk tank/tanks, and control the blower for over/under fire air.

In addition to all that geekiness I plan on having the controller log all it's measurements to a remote database to evaluate performance over the long term and for record keeping.

Below is a crappy picture of the controller that I built to control the heating of my home and the operation of my wood fired gasification boiler/thermal storage.

http://img6.imageshack.us/img6/5715/img5873k.jpg

It's an ambitious plan and maybe I won't get it to work but I plan to give it my darnedest.

[Haynes Forest Products]

I have a Watlow model 965 and it has a book that comes with it YIKES.
I also have a vertical probe liquid level and dual pump controler never used.
Inline flow sensors and air actuated SS ball valves and all sorts of gadgets that take someone better than me to hook up.

[twofer]

Forgot to add that I also plan on integrating a barometric pressure sensor to automagically adjust the draw off temp. And yes I did say "automagically". :)

[Haynes Forest Products]

Your a dang SHOW off. Now lets get it done so I can be the first on the list to get one. I do better with things that have levers and peddles than buttons and LED readout:emb: Make it simple without all sorts of crappity this thats and other things.

[Squaredeal]

Twofer. Awesome. I've wanted to do that since I saw several large evaporators wired that way up in Quebec and reading out on a laptop. Problem is I can't build anything that doesn't involve a hammer.

[twofer]

Heh

I promise this is not to show off but rather let people know what I've been working on in hope of maybe spurring some ideas or get others involved who have more experience than I.

As I get parts of it completed I plan on posting my progress and getting your guys' opinions.

[Haynes Forest Products]

I still dont know what the main criteria should be for the controller. So many have all sorts of programs and over rides and bells and whistles. What is the main items to look for and want. If you dial in a set temp and the probe reads the temp and the controller reacts to the temp by activating a valve thats good BUT at what increments should it then close the valve 1/10th of a degree or 1 degree? It would be nice if it showed actual temp with desired target temp and yes a simple overide button to exend the drawoff. I would think that if it actuated and stayed open to long that could be a problem. So I would want it to have a very small window of temp to react to.I THINK.

I was watching the rig at Roth Sugar Bush operate and with the size of the evap and the concentrate they push thru it the valve never completely closed. It was a modulating paddle valve that really just opened and closed and back open slowing the syrup at the draw off.

[twofer]

My goal is to have temperature resolution down to 1/10th of a degree. This way we ensure that when that valve opens up the only thing coming out is syrup that is finished. As far as the sampling interval, my goal is to have the temperature evaluated at a minimum of once per second and maybe even twice. At that rate the maximum amount of time the valve would be open and pouring near syrup or over syrup (not sure what you guys call it) is one second. I've never run a large rig before so I don't know if that is too long or too short and is going to bounce the valve. At any rate whatever problems come up with timing can be dealt with in the programming since there is almost 100% flexibility there.

I do plan on having a simple switch on the front of the controller housing where the valve can be triggered to open manually.

[jrthe3]

jim them are same parts i used to build my auto draw off mine works great have not had any probs are you useing it as a on off or are yiou useind the pid i built two draw offs and will be posting one for sale shortly as soon as i get pics

[farmall h]

Haynes I don't know....I' am just a parts purchaser for my company...I just want an Auto draw-off for next season. I here they draw-off in small batches consistently. 2 degree range and set them per the hydrometer after the 1st draw then your golden for the rest of the night (or day). Shut valve @ 215 open at 217 degree. or what ever hydrometer/temperature matches after 1st drawoff manually. That is the way I understand it...never used one before. Seems rather low tech.

[Haynes Forest Products]

Thats what I want something just slightly smarter than me....OH crap that could be a rock. I guess I do want alarms and the ability to shut the burner down when Im MULTY :emb: TASKING

[Brent]

Jim

Back to your first question. I have seen this happen in my rig and will take a guess at what is happening.

We boil until the sugar content is increased enough to get the boiling temperature above 212 Deg. Once a steam bubble is created, there is no sugar factor involved any more, just a bubble of steam. The more foam there is the more plain old steam at 212 there is. I have watched my temps go up and then as the foam gets higher the temps go down. Then add a drop or two of defoamer and the foam goes down, the temps go up and the auto draw off opens.

For the guys talking about building draw offs, I think the sampling rate will take a back seat to the speed with which temperature changes are conducted through you prope to the thyristor inside it. On mine there is a lot of things start to happen when the temp hits the pre-set to open the valve.
- I think there are temperature differences in the pan between where my probe is about 3" from the draw off port, to the syrup that is in the middle of the pan, 12" or so from the draw off port. Once the valve opens a crack, that hotter syrup from the center of the pan causes the temp to go up a bit so the valve opens even more, then the syrup from the far corner starts to ge pushed through and the temp starts to drop and the valve will start to shut. Depending on a whole mess of factors, like is the sugar shack door open with cold air blowing on the last partition in the syrup pan, and did I just fire the rig or is the fire stable, and did I put a real big log up close to the pan somewhere blocking heat etc ... the temperature sensor can get all kinds of operator errors introduced.

The bigger your rig the better all these factors will get averaged out. On a little 2 x 6 rig, they make for large ( 0.5 deg ) swings in pretty short order.

So this year I had the probe in the pan and the auto-valve laying on the floor and just monitor the display and audible alarm and drew off manually.

[farmall h]

Brent, all that you said makes sense. I would almost say that an oil fired rig would have the advantage...consistent temperatures = controlled environment. Plus, now that I think more about it..kinda takes the fun out of it!

[Brent]

I don't think there's any question that an oil rig would be more consistent but I'm not so sure that the corners of the syrup pan would be as hot as the middle ... never having run one.

[twofer]

For the guys talking about building draw offs, I think the sampling rate will take a back seat to the speed with which temperature changes are conducted through you prope to the thyristor inside it. On mine there is a lot of things start to happen when the temp hits the pre-set to open the valve.


I had planned on using an RTD with a 1/8" sheath in order to try and minimize the amount of lag time. What is the thickness on the sheath for your probe?

That didn't sound right.... :lol:



- I think there are temperature differences in the pan between where my probe is about 3" from the draw off port, to the syrup that is in the middle of the pan, 12" or so from the draw off port. Once the valve opens a crack, that hotter syrup from the center of the pan causes the temp to go up a bit so the valve opens even more, then the syrup from the far corner starts to ge pushed through and the temp starts to drop and the valve will start to shut. Depending on a whole mess of factors, like is the sugar shack door open with cold air blowing on the last partition in the syrup pan, and did I just fire the rig or is the fire stable, and did I put a real big log up close to the pan somewhere blocking heat etc ... the temperature sensor can get all kinds of operator errors introduced.

The bigger your rig the better all these factors will get averaged out. On a little 2 x 6 rig, they make for large ( 0.5 deg ) swings in pretty short order.

So this year I had the probe in the pan and the auto-valve laying on the floor and just monitor the display and audible alarm and drew off manually.

Do you think if you extended the probe further into the middle of the pan you might get a better average temperature?

[Brent]

Most are only a few microns thick :D

but the one in the temperature probe is only 1/16 and likely less. It's hard to measure accurately because of the way it's crimped. That doesn't sound right either.

You're going to get errors in a small syrup pan regardless of where you put it. You have to find a spot that is going to be consistent with the way your draw off opens according to the temperature rise above the trigger temp, the size holes in your vavle etc. Take samples as it begins and ends the draw to see what the density is and make adjustments. Most auto draw offs are made for big rigs, like 3 x 10 and larger and have too big a port and open too wide for a small 2 x 6 with a 2 x 2 syrup pan. At one point I put a manual ball vavle on mine because it was emptying half the pan.

[Sugarmaker]

I like our Marcland a lot and you guys making your own get a lot of credit.
When I first set mine up I put the temp probe as close to the draw off as possible. For some reason I was drawing off too big of batches. Moved the probe 12 inches from the draw off and I get much smaller batches drawn off. Note this seems to be about the hottest spot in that section of the finishing pan.
Jim, Very nice job on the build of the draw off. I am sure you will like it.
Regards,
Chris

[farmall h]

Sugarmaker, I think the probe goes near the same location as a thermometer in the pan.

[Tom Cook]

Here are the parts you will need to make that controller: 1-dtb4848rr & 1-rtd (pt100) probe www.bb-elec.com/product_family.asp?FamilyId=246&Trail=164&TrailType=Main

[lpakiz]

Tom,
I can't seem to locate the PT 100 probe--is that available from these folks?