Pilot goes out when fryer reaches set temp. and shuts-off.

If both the main burner and pilot shut down at 200F, the high limit is bad. If only the main burners shut down, the thermostat is bad.

You could have a weak pilot or thermopile. If the thermopile is not heated correctly by the pilot, it cannot generate enough millivolts to open the gas valve. The same is true if the thermopile is faulty. Thermopiles consist of several junctions of which only some may go bad causing low millivolt output. Millivolt output with the thermostat off and pilot lit should be around 600 millivolt, you can check with a DC multimeter set on MV across the two wires coming from the thermopile. Remember, the thermopile has to be heated by the pilot thoroughly before you will get the full millivolt reading and the thermostat must be off. Cleaning the pilot assembly is often helpful, thermopiles are inexpensive and relatively easy to change. Of course, other problems can cause this issue as well, but the above are most common.

Hi limit device trips prematurely (should only trip when oil temp reaches 450F). Check if the hi limit sensing bulb (located inside the fryer tank, between fire tubes) is not touching the fire tube because if it does, it will sense the heat from burner flame which is much higher than oil temp.

I assume it is a gas model. There are 2 thermostats. One is adjustable, you set your temp, it sounds like it has gone bad.. The second thermostat is the high limit thermostat. When it reaches 450 degrees F, it will shut down the pilot and main flame to prevent a grease fire. It may be possible that someone has hooked the thermostat up wrong. Next time you fire it up, disconnect one of the thermostat wires that has the temperature knob. If the flame goes out, the thermostat is bad,

Set the thermostat to 350 degrees,get a thermometer and put it in the oil,when the unit shuts off look at the temp of the oil.If the temp of the oil is higher then the thermostat is bad if not the hi-limit may be.Let me know.

You will need someone who is qualified in commercial gas appliance repair to fix this.
Liabilities would render this out of reach for anyone else.

Hi there, it sounds like your thermopile, for the pilot, is failing during use, when this happens, the small DC voltage it generates is less than the gas valve requires to stay open, and shuts off the pilot, which shuts off the main burners. Another thing that could be happening, is the hi limit is opening prematurely, instead of shutting of the pilot at 450 deg. it now is opening at 325, or 225 or 250. Sometimes the sensing bulb gets broken where it pass's through the oil tank causing this symptom. If you temporarily bypassed the hi limit to test this also, and it still goes off, you need a thermopile. If it stays on, check your temp with a reliable thermometer, and see if it reads fairly close to your setting, if so, then you need a hi limit.
Hope that helps, and thank you.

I had a very simular problem. My fryer would do exactly as you described, but sometimes the pilot light would stay on until the burners tried to re-ignite and then it would go out.
I finally had to call the gas company. They took the pilot light apart and cleaned it. The fryer works perfect now.
Hope this helps!
Ken

your problem is the thermostat is bad.the reason it shuts down is that it trips the hi limit.the hi limit is a saftey device that shuts the system down so the oil doesnt get too hot and catch on fire.remove all the oil from the tank and you should see 2 skinny metal bulbs one is the hi limit bulb the other is the t-stat bulb,make sure they are secured to the bracket.if the t-stat bulb isnt you will also have this issue,simply reattach it.let me know.