Commercial Pita Bread Oven Remodel

[seesoe]

hello forno bravo members, im new to the forum, however i been reading it for the past few days, pretty talented people out there making amazing wfo!!

i run a pita bread bakery with my dad, he has been doing this operation for almost 30 years now, he started with a pizza oven and manually taking pitas in and out, then he bought a commercial tunnel oven that was custom built.

the oven is about 12 feet long
runs on propane
has a variable 90 vdc motor for the slat bar conveyor
mineral wool isolation
total of 4 rows of burners, 2 on top 2 on bottom with pilot light (each about 10 feet long)
temps get up to about 850 degrees f
about 15 minutes to preheat

the bread takes about a minute and half to travel 12 feet and be cooked right, this is a long time for that distance, the pitas tend to dry out.

so im thinking to line the inside walls of the oven with firebrick, but im kind of limited on space. i think firebrick are standard 4x8x2",

could i expect to get much higher temps with the oven lined with firebrick? or would it not be worth it?

if so would i expect to get the same results if i stand the bricks up?

im trying to get the oven much hotter so that we can bake the bread faster, and save money on gas, and time baking, this would also not dry out the bread as much. also im planning on doing automatic ignition, with solenoids, and electric spark

any feedback or ideas would be appropriated!

thank you
seesoe
gainesville fl

[seesoe]

Re: Commercial Pita Bread Oven Remodel

pictures coming soon, sorry for the delay

i was also thinking of getting rid of the open flame burners (just holes in a pipe) and replacing them with infrared burners?

[nissanneill]

Re: Commercial Pita Bread Oven Remodel

seesoe,
I can't see any advantage of using the fire bricks in your commercial oven other than storing the heat that is in the tunnel.
Rather, I think (and without a better perception of the oven without photos) that I would look at insulation to hold the heat within the conveyor and maybe look at putting in reflective material above and below your burners, (even something as simple as a thicker aluminium foil).

i was also thinking of getting rid of the open flame burners

I would also check with your gas servicing people and possibly look into a little forced air into the system (rather than just the gas through the jets sucking in the air to burn). The effect would be like adding more oxygen to an acetylene torch, the more oxygen, the cleaner and hotter the flame.

Cheers.

Neill

[seesoe]

Re: Commercial Pita Bread Oven Remodel

nissanneill, thank you for the replay
radiant heat is what pita bread wants, it wants very hot and fast oven temperatures, kinda like super hot air flash cooking it.

sorry for the lack of detail, the gas inlet before it goes into the oven has a plate that i can turn and adjust how much air the fire gets, i have nice double blue flames on the bottom but trying to get the top calibrated still, just haven't had the time to mess with it.

im going to the bakery tomorrow, ill take some pictures and post them up tomorrow night.

you are right about the insulation, a major part of this remodel is to re-insulate it FULLY and properly with thick mineral wool, you'll see why it needs to be done from the pictures i post.


here is 2 links to professional commercial brick tunnel ovens (to get an idea of what the big boys use)
Bimatic s.a.r.l. Bakery Equipment Industry and Trade - Lebanon
FARHAT arabic & pita bread machines - bakery equipment Lebanon

thanks
cheers
seesoe

[seesoe]

Re: Commercial Pita Bread Oven Remodel

also on a side note, any possible way to calculate how much btu's the oven's burners give off?

[nissanneill]

Re: Commercial Pita Bread Oven Remodel

Sorry, can't help you there. Did a Google search and many state 30,000 bthu's from a double blue flame.
A friend of mine had a powder coating business where he used an electric element oven to fuse the powder. Two bakes a day was all he could do so he went natural gas fired. The gas pressure was 2 lbs/sq. inch which is the max permissible in commercial applications and double that allowed in domestic properties.
This increase in pressure would throw a flame 5 metres along inside a 10" steel pipe and would have it glowing red in a couple of minutes. Now 20 minutes per bake for each load (depending on product mass).
Check with your authorities as to having the pressure increased slightly to increase the flame size and temperature.

Cheers.

Neill

[drogers]

Re: Commercial Pita Bread Oven Remodel

Seesoe, I was up your way today in Micanopy. Tomorrow my wife and I are going to the botanical garden in Gainsville. Good day trips from Inverness. Enough of my weekend schedule.

What is the inlet and outlet area like for this oven, is it restricted fairly good to prevent heat loss ? What effect does the moisture given off by the combustion of the propane have on the bread, does it have a negative influence on the outside of the bread ? Would electrical resistance heaters be an option ?

[seesoe]

Re: Commercial Pita Bread Oven Remodel

Neill,
i actually got started with research at the custom powder coating ovens forum, very good info there on all sorts of things, like oven circuit controls, insulation, and all that kind of stuff.

yeah i couldn't find much of anything to calculate custom oven btu, it all goes off the brand name burner/element source.

pressure is a good idea, i'll check the regulator out back and see what its running at.


drogers,
the botanical garden is a beautiful place to go for a weekend, you two will enjoy it, if you like Lebanese food, (falafel gyro hummus) you should stop by our restaurant. its like half a mile off the exit and 1 or 2 miles from the garden, its called falafel king

i never went to the bakery today, but i attached an old picture that i have of the outlet of the oven. as you can see very old. the belt comes out and hands under the oven and goes back around to the inlet, this is a major heat loss, i will be removing the bottom of the what is now the oven bottom, and putting that under the belt circulating under the oven, that way it is part of the oven all the way and never looses to much heat. like i said the bread takes about a minute and half to bake as of now, so that a minute and a half the belt is exposed to normal air.

i did read about propane a while back, i think it burns a little on the dry side if im not mistaken, i don't really remember though, i don't think electric would be sufficient for pita bread, would take a lot of very strong elements

thanks
cheers
seesoe

[lwood]

Re: Commercial Pita Bread Oven Remodel

1lb of propane gives off 21,600 BTUs. Get you gas bill and find out how much propane you use in a given time period. It will probably be in some funky units like cubic meters or worse yet cubic feet. The web has tons of conversion tables for almost anything. lets say it is in lbs. So lbs of propane divided by 21,600 btu/lb of propane gives you BTUs consumed in a month. Convert that to the resonance time of the pita in the oven (how long does each pita stay in the oven). Assuming there is nothing else on the gas meter...that is your BTU consumption. Subtract 20% for inefficiencies and you have an estimate of the number you are looking for.

[seesoe]

Re: Commercial Pita Bread Oven Remodel

thank you lwood for the info

i finally got some spare time to go and analyze the whole situation carefully and take some pictures. the oven is in much worse condition than i thought. it needs to be reshelled completely from the ground up, there is a lot of openings.

i found out the bottom burners have a metal plate on top of the flame not to burn the bread, however the top burners do not, they need it though, when the bread over poofs and is baked then it gets burned because the flame is so close to it.

you'll notice there isn't much space as of now on the inside for bricks, that is why i was asking if it would suffice to put the bricks standing up. if not im thinking to add a strip of angle iron along the edge of the oven to support the bricks laying flat.

the propane tank is 100 gallon, however the company only fills it up to 80 percent, we use an average of 35-45 gallons a week. (tank is filled back to 80 weekly)

sorry for the bad pictures, i only had my phone on me, also you'll notice how old the oven is, its been in almost daily operation for about 22 years now

here is the link to the image (Oven Images)

thanks
cheers
seesoe

[seesoe]

Re: Commercial Pita Bread Oven Remodel

i just realized that the server wasn't allowing the pictures from being shown, but i fixed it now, you may find the images here at this link

also i placed an order for a digital multimeter and a 10 inch high temperature k thermocouple. im going to start logging some temperatures, i should have some numbers posted by the weekend.

open for any questions comments or concerns
thanks
cheers
seesoe

[nissanneill]

Re: Commercial Pita Bread Oven Remodel

Hi Seesoe,

i found out the bottom burners have a metal plate on top of the flame not to burn the bread, however the top burners do not, they need it though, when the bread over poofs and is baked then it gets burned because the flame is so close to it.

I built a conveyor drier which incorporated both Ultra violet and/or Infra red radiation to dry/cure screen prints. The infra red lamps were so hot (even though I had it thermostatically controlled, it would burn and destroy the textiles being cured. To overcome this, I put some expanded metal (I used aluminium but you might need to use some stainless steel due to the higher temperatures and melting points) directly beneath the lamps. Problem solved.
The perforations in the metal will still allow the heat to radiate to the breads but the flames will be prevented or severely limited.

Cheers.

Neill

[seesoe]

Re: Commercial Pita Bread Oven Remodel

yeah it is a pretty important feature to have in ovens, the bottom has it as you can see here, i was thinking i could just put a strip of stainless down the length of the burners, and simply mount it to the beams holding the burners, you can see what i mean in here and here

cheers
thanks
seesoe

[drogers]

Re: Commercial Pita Bread Oven Remodel

seesoe,
I had a chance to review your photos. Next time I am up in Gainsville I will give you a call. These are some of the observations and questions I came up with.

1. Could you just box in the return conveyor section and put some insulation over the box, as opposed to relocating the conveyor up into the existing oven area below the bottom burners ? A fabrication shop should be able to bend what you need out of light gauge mild steel at a minimum cost.

2. Can the discharge opening height be reduced without hitting the bread being discharged? This could be a major heat loss.

3. Is the distance between the conveyor deck, that the bread rides on, and the bottom of the top heater pipes sufficient to place a 3"x3" angle under each pipe ? The angle would be mounted like the letter "V" and would hang down about 2 1/4" from the cross supports that the pipe rests on. This would prevent directly "broiling" the bread, but still allow good heat circulation. The width across the "V" would be about 4 1/4", so you may be able to go with a different size angle. I thought of angle because it would be more self supporting.

4. Does the flue have any kind of manual or automatic damper ? If not, and if code allows, that could yield substantial savings. Without a damper you are discharging your heat almost as fast as it is being generated. These automatic units are also called barometric control dampers and are purely mechanical .

5. Could you install a larger propane tank? The larger the tank the less you and the dealer have in delivery charges. Delivery charges may not be listed seperately, but the are incorporated into what you are paying for propane. If you install a larger tank, and retain ownership of the tank then you can put your propane requirements out for bid. If you do not retain ownership then you cannot get competitive bids.

6. Does the cooling conveyor area after the oven cause a draft back into the oven because of the fans? Could this area be shrouded from the discharge of the oven ?

I hope some of these thoughts help you .
Don

[seesoe]

Re: Commercial Pita Bread Oven Remodel

I had a chance to review your photos. Next time I am up in Gainsville I will give you a call. These are some of the observations and questions I came up with.

thank you for your time. that would be great.

1. Could you just box in the return conveyor section and put some insulation over the box, as opposed to relocating the conveyor up into the existing oven area below the bottom burners ? A fabrication shop should be able to bend what you need out of light gauge mild steel at a minimum cost.

yeah, this is what i am planning on doing, however i didn't mean to say relocate the belt in the oven but to higher the belt rollers a few inches up so the belt wont sag as much and move the ovens sheet metal floor to under the belt, this way the return belt will always remain isolated in the main body of heat of the oven, you can see what i mean in here and here

2. Can the discharge opening height be reduced without hitting the bread being discharged? This could be a major heat loss.

we have little flaps that we can lower a bit more, but i am going to get rid of them and put something more efficient and have it continue down the edges of the discharge area, you are right it is pretty open, a good couple of inches on either side just wasted open, as shown here

3. Is the distance between the conveyor deck, that the bread rides on, and the bottom of the top heater pipes sufficient to place a 3"x3" angle under each pipe ? The angle would be mounted like the letter "V" and would hang down about 2 1/4" from the cross supports that the pipe rests on. This would prevent directly "broiling" the bread, but still allow good heat circulation. The width across the "V" would be about 4 1/4", so you may be able to go with a different size angle. I thought of angle because it would be more self supporting.

that is a good idea i would have to take some measurements and report back, the heat of the angle iron can act as a nice heat source to make the bread have a nice color on top

4. Does the flue have any kind of manual or automatic damper ? If not, and if code allows, that could yield substantial savings. Without a damper you are discharging your heat almost as fast as it is being generated. These automatic units are also called barometric control dampers and are purely mechanical .

no it is just a straight opening through the flue, i have thought about it though, later on when i get the oven nice and isolated to sustain heat, i am thinking about installing a PID system, like an oven controller, and i was thinking of putting a fan in the flue for the controller to control. the barometric dampers look interesting though i would have to get in contact with the city about it. ill see if i have some time to talk with them.

5. Could you install a larger propane tank? The larger the tank the less you and the dealer have in delivery charges. Delivery charges may not be listed seperately, but the are incorporated into what you are paying for propane. If you install a larger tank, and retain ownership of the tank then you can put your propane requirements out for bid. If you do not retain ownership then you cannot get competitive bids.

this is also a thought, the 100 gallon tank we have is leased but they only fill it to 80 percent every week they come out, and we use about half of that a week

6. Does the cooling conveyor area after the oven cause a draft back into the oven because of the fans? Could this area be shrouded from the discharge of the oven ?

not that i know of, i made sure to position the fans and an angle away from the oven like this "/"

thank you for the help, ill get back with more info as i get it.

cheers
seesoe