BASO valve schematic? Troubleshooting?

[Tim Allen]

Does anyone know where I could find a schematic of the internal workings of a BASO valve?  I just want to understand how it it supposed to work, I'm NOT proposing try to repair it myself....

Obviously when you press the red button, that opens up gas flow to the pilot system. But does that also open up flow through the main part of the valve to rest of the system downstream? Or does that part of the valve only open when the thermocouple is sending voltage, and the magnet moves?

If the thermocouple IS sending appropriate voltage, why would the pilot system shut down when you release the red button? If you are getting appropriate voltage, isn't the magnet supposed to move and keep the valve open even once you release the red button?

I've read about, and tried, "poking" the magnet by  spiking the voltage, heating the tip of the thermocouple to red hot.

I've cleaned the contacts between the thermocouple and the valve body.

I've check the thermocouple for appropriate voltage, and I've done some cleaning of the thermocouple tip (but maybe could do more).

Something is still not working right.....  So back to my may question: Does holding the red button down open the valve to gas flow through to downstream of the valve (not just to the pilot system)?

Thanks for any ideas.

Tim

[NoArtist]

I believe that the entire gas supply for both the pilot and the main burner is controlled by an electrically activated valve controlled by a thermocouple.  That's really about all there is to the system.  If the temperature sensor at the pilot is not hot enough to show that the pilot light is really on, no gas will flow to either the main burner or the pilot.  The only other part of the system is the red button, which is just a simple momentary bypass  valve to provides an easy way to light the pilot.  It only supplies gas to the pilot though, not the main burner.  With most of these valves there is even a mechanical lockout that only allows you to depress the red button and light the pilot with the manual control valve for the burner in the off or pilot only position, so that the appliance does not suddenly start up while you are still lighting the pilot.  As always, exercise extreme caution around any gas appliance, and contact a knowledgeable professional if there are any issues. Also be aware that parts on most of these systems are not interchangeable. So, even if there are user replaceable parts, you will need to insure that you have the exact right replacement parts.  

So, if the pilot light lights when you press the red button, but then goes off when you release it, there are usually only four common reasons. 1. You did not hold the button long enough, so the thermocouple did not get hot enough. 2. The pilot light is not heating the thermocouple well enough to work due to alignment or flame issues. 3. The thermocouple is bad. or 4. the main switch is bad. 

Given your tests so far, (heating the thermocouple with an external source), 1, and 2, are probably not the issue. Cleaning the contacts was also a good move. It is still possible that you have a bad thermocouple. That is the most common failure point since it sticks directly into the flame and deteriorates over time.  But a stuck or corroded valve is also a possibility.  That is something that just should not be second guessed. If you have not tried replacing the thermocouple, you might try that. Otherwise it is time to replace the whole thing.  

[Tim Allen]

19 minutes ago, NoArtist said:

...the red button ... only supplies gas to the pilot though, not the main burner.  ....

Thanks for this, which is what I wanted to know, and confirms a hypothesis I had, and helps me focus further troubleshooting efforts.

[neilestrick]

Correct, the main line will not open until the thermocouple has heated enough. The red button only allows gas through to the pilot. The only time I've seen a red button not hold is because of a bad thermocouple, but I suppose it's possible for the main valve to break down. Try a new thermocouple, and double check that all your connections are tight.

Is this a new setup or old?

[Tim Allen]

Relatively old.   I think the thermocouple is delivering "marginal" voltage -- enough to open the main valve (sometimes), but not enough to keep the pilot flame burning (if that makes any sense).

 

[neilestrick]

I've know kilns that needed a new thermocouple every 4 to 5 firings. Something about the setup just burned them out quickly. The pilots were probably too close to the burner port. Try a new thermocouple.

[Bill Kielb]

BASO valve pilots generally are set within 1/4” of the burner to pass the turn down test and reliably light the burner. Line of site infrared from kilns is tough on this setup. I agree, often ends up unreliable and we are forever measuring 20 or so open circuit millivolts and wondering if the valve will hold reliably.

[Tim Allen]

FWIW, this is an Olympic DD-12 kiln. There are two groups of 3 burners, one on the left side and one on the right. Each group of burners has it's own pilot "bar." Each pilot bar also has associated with it a thermocouple with it's own dedicated pilot flame (separate from the flames that come from the pilot bar to light the burners). All six burners are fed from a single manifold fed through a chain of four valves: (1) electric valve powered by a set point controller; (2) BASO valve for the left side pilot assembly; (3) BASO valve for the right side pilot assembly; (4) manual valve for controlling flow to the burners.

Here is a picture of the pilot/burner arrangement on the right side of the kiln (although it is the left side that is giving me trouble right now). The pilot "bar" is the horizontal pipe with all the little holes emitting small flames. The thermocouple and it's own flame are mounted to the angle just to the right of the front-most burner:

And here is a picture of the valve chain (in which you can also see some of the left side pilot assembly). The angled venturis are the ones that feed the pilot bars. Each of the BASO valves has two gas leads, one for the pilot bar burner, and one for the separate flame powering the the thermocouple. Both supplies have needle valves for adjustment. It's the first BASO valve (and it's associated thermocouple) that's giving us trouble right now.

We first fired this kiln in late March 2014, and have fired it approximately twice a year since then. It's outside in a metal shed, but with a gravel floor (we put the sheet metal down on the ground to try to prevent dust from getting sucked up into the kiln. The kiln legs are resting on steel plates to spread the load over the gravel.

 

[Bill Kielb]

On 4/17/2019 at 8:54 AM, Tim Allen said:

FWIW, this is an Olympic DD-12 kiln. There are two groups of 3 burners, one on the left side and one on the right. Each group of burners has it's own pilot "bar." Each pilot bar also has associated with it a thermocouple with it's own dedicated pilot flame (separate from the flames that come from the pilot bar to light the burners). All six burners are fed from a single manifold fed through a chain of four valves: (1) electric valve powered by a set point controller; (2) BASO valve for the left side pilot assembly; (3) BASO valve for the right side pilot assembly; (4) manual valve for controlling flow to the burners.

Here is a picture of the pilot/burner arrangement on the right side of the kiln (although it is the left side that is giving me trouble right now). The pilot "bar" is the horizontal pipe with all the little holes emitting small flames. The thermocouple and it's own flame are mounted to the angle just to the right of the front-most burner:

And here is a picture of the valve chain (in which you can also see some of the left side pilot assembly). The angled venturis are the ones that feed the pilot bars. Each of the BASO valves has two gas leads, one for the pilot bar burner, and one for the separate flame powering the the thermocouple. Both supplies have needle valves for adjustment. It's the first BASO valve (and it's associated thermocouple) that's giving us trouble right now.

We first fired this kiln in late March 2014, and have fired it approximately twice a year since then. It's outside in a metal shed, but with a gravel floor (we put the sheet metal down on the ground to try to prevent dust from getting sucked up into the kiln. The kiln legs are resting on steel plates to spread the load over the gravel.

 

Hmm, thanks seem to have lost one whole post here. The post said that the red button is a mechanical means to raise a solenoid which then allows a swing check to open the main gas through the valve body. 10 mv is typically needed to hold the solenoid open. The actual BASO specs are below. My suggestion is do a closed circuit test and monitor the coil holding voltage. Generally the thermocouples fail. BTW, pilot flame tips look a bit yellow in the picture, might just be the picture.  Area that the thermocouple is in also looks flashed over and yellow as well. Is this natural gas and have you measured the thermocouple output?

 

[Tim Allen]

Hi Bill,

The fuel gas is Propane.

I am not sure the photos capture the flame colors accurately.

The thermocouple from the troublesome left side gave an open circuit voltage of 30 mV when heated with the distal end of a MAP torch flame, and about 24 mV when heated  by the regular pilot flame (red button taped down to allow gas flow to the pilot, end of thermocouple removed from the valve body for voltage measurement). These measurements after some minimal cleaning of the tip.

Not sure how I would measure the closed circuit voltage? I guess I would need some kind of connector to insert between the valve body and the end of the thermocouple that would allow me to insert the probes from my mulitmeter?

[Bill Kielb]

Yes, they actually make a test kit. Sometimes valuable as watching these operate reveals they cannot maintain sufficient current when loaded  and any wavering of the flame around the thermocouple trips the valve.  Not many of these in use for gas fired appliances anymore so a test kit is probably not very popular at this point.

Thermocouples are cheap and this one could be switched  for new  or better yet switching it with your known good valve may indicate it is bad or that the valve requires more output to remain open than the good valve.

Since this kiln has a history I would guess it is possible that sufficient moisture could have entered the system and potentially affected the first downstream valve and explain if and why this valve would need more operating current than the other.

I think switching and observing might tell you more in short order without buying the test kit, lots of speculation here. Just an add it’s probably a good idea to have a couple of spare thermocouples on hand in the event one failed just prior to firing or worse during a firing.

[Bill Kielb]

@Tim Allen ok we have waited, any discoveries?

[Tim Allen]

Heh heh.  Wendy ordered a new thermocouple from the local distributor --  she'll pick that up on Monday.  So we will try again on Tuesday. Re-arranging the order of the valves in the valve train seems like a big job, and if we are going to go to those lengths, I would probably just get a new valve to replace the troublesome one -- if a new thermocouple doesn't resolve the trouble....

[Bill Kielb]

I say just switch the thermo couple from one valve to the other don’t move the valves

[Tim Allen]

Update:

Swapping thermcouples sounds simple but they have different lead lengths, so the TC from the left side would not work on the right side. Leaving the TC's in place and just swapping them at the valves would require swapping the pilot system gas plumbing at the valves as well.... with already formed tubing cut to length, that would be a lot of work.

So we got a new thermocouple, and got that installed (see my other thread on removing the old TC).

Started up the left-side pilot system and it was immediately obvious that the pilot flame on the TC was crap. Adjusting the needle valve on the gas TC pilot gas supply offered no improvement. Still had to tape the red button down to keep the pilot burning, but gas was flowing through the valve, so we started the pilot system on the left side (much better pilot flame on that side), and then lit all six main burners to "candle" the kiln for a bit to try to dry things out.

Everything was looking good, except for the crappy pilot flame on the left-side TC, but the kiln was running, so we started the firing. We check on it every 15 minutes, and on one of those checks after about two hours, we found the kiln had died. We tried to re-light it, but gas would not flow through the first BASO valve anymore.

Wendy took apart the gas supply to the left side TC pilot flame, blew everything out with compressed air to clean it all up, put it back together, but no joy -- the pilot flame was still all yellow, no blue....

So either there is some sort of problem with that pilot "burner" still, or the problem is within the BASO valve -- not supplying the right gas pressure or something. We are still having to tape the red button down to keep the pilot flame burning.

Our next step is to get a tech from our gas supplier out to take a look to see if they have any insight (a delivery truck driver from the company was filling a propane tank at our house when we tried firing the kiln last week, and he offered some helpful suggestions then).

The kiln is still loaded with "unfired" wares (it only reached about 700F before quitting -- we fire to Cone 10).

[Bill Kielb]

Clean out left side pilot orifice, it’s very tiny.

Next time If you have to test  simply use your manual  light and tape it down trick. That way you only need to unscrew each thermo couple and screw it into the other valve. (No valve moving or piping moving) The picture you originally sent looked yellow and flashed anyway so it seems likely a dirty pilot orifice. Take that side assembly off and clean it out thoroughly there is probably a spider web in there. Don’t forget the orifice is at the end of the tube, clear it with something soft and blow backwards through it, also make sure to clean everything  as often spiders will build a web in the assembly itself just after the orifice. See below, everything comes apart and can usually be cleaned in a few minutes.

 

 

[neilestrick]

I agree. Spiders love burners. If that doesn't work, those little pilots are cheap and easy to replace.

[Tim Allen]

I wasn't there, but two techs from our gas supplier showed up this morning, and Wendy showed them the kiln. Not something they deal with everyday, so they were very interested in it. They observed that the pilot was a "lazy flame," took the assembly apart and noted that it did not appear to have a gas orifice. They called Olympic to find out if it was supposed to have one and to get the specs, then one of them went looking for one in their truck. Meanwhile the other tech looked around on the sheet metal under the kiln and found the one that had somehow fallen out.  They installed the orifice in the pilot assembly, and it works! And we don't have to tape the red button down to keep it running, either....

They did recommend some maintenance on the whole pilot bar assembly.... we have a problem with the bar burners getting "coked" up with carbon deposits later in a firing (when the main burners are turned up), which I think might be due to gas density effects changing the mix ratio as the propane tank ices up, and thus the supplied gas is colder.... We should probably get a larger tank or a dual tank set-up to reduce the freeze up.

 

[Mark C.]

sounds like problem fixed when orfice was reinstalled  after falling out.

[Bill Kielb]

8 hours ago, Tim Allen said:

I wasn't there, but two techs from our gas supplier showed up this morning, and Wendy showed them the kiln. Not something they deal with everyday, so they were very interested in it. They observed that the pilot was a "lazy flame," took the assembly apart and noted that it did not appear to have a gas orifice. They called Olympic to find out if it was supposed to have one and to get the specs, then one of them went looking for one in their truck. Meanwhile the other tech looked around on the sheet metal under the kiln and found the one that had somehow fallen out.  They installed the orifice in the pilot assembly, and it works! And we don't have to tape the red button down to keep it running, either....

They did recommend some maintenance on the whole pilot bar assembly.... we have a problem with the bar burners getting "coked" up with carbon deposits later in a firing (when the main burners are turned up), which I think might be due to gas density effects changing the mix ratio as the propane tank ices up, and thus the supplied gas is colder.... We should probably get a larger tank or a dual tank set-up to reduce the freeze up.

 

Hopefully you were able to watch them do it so next time it should be easy. Since the orifice fits over the tubing and into the pilot assembly it must have fallen out when they disassembled it.  No other possible way to remove it. Good that it’s fixed. If not here is one of many you tube videos that show what it looks like with no orifice.