If you are like me, you may be having a hard time keeping the temperatures down on your propane smoker/cooker, hopefully you will find this article helpful
This article describes what a needle valves does, why you might need one, and some sources for obtaining one.
This is your basic LP Needle Valve:
The importance of proper installation of Needle Valves...
All well designed needle valves include an arrow shape, either machined, or cast into the main body of the needle valve. It is common to see needle valves, with the same or different threads on both the inlet and the outlet. So let us examine this arrow and it's importance. As with any pressurized gas or liquid, safety is paramount. Therefore we have discovered the reason for the arrow. As you can see in the illustration above, even though a needle valve may look similar from either end, the inside is very different.
In the above image, you see that if the gas is entering the valve from the RIGHT, and the valve is shut, there is no pressure on the seals around the valve stem and knob assembly. On the other hand, if the inlet was connected in error, with the gas supply coming in from the LEFT, in the illustration, then with the valve closed, the seals around the valve stem and knob would be under stress... NOT GOOD!!!!
Proper installation of a needle valve will ensure years of safe operation.
There are many sources for needle valves, and I can't really say one is better than any other, personally I've only ever installed one, but I know there are alot of fine folks on this site that have installed them on many different types of cookers and smokers
Here are some pictures of my installation:
And a close up:
Previous to installing the needle valve in my smoker, the temperatures, even at the lowest setting, would creep up to around the 270F range. Not that most anything can't be done nicely at that temp, but for those of us wanting the the preverbial "low & slow", that is a little too high.
The manufacturer of my smoker actually indicates to only turn on the propane bottle valve 1/4 turn so as to not fully open the propane bottle. With the needle valve, I am able to open it as much or as little as I want without having to worry about it. The valve on the bottle is more of an open/close anyway, and not for flow control.
Here is the before picture of my burner at night with the gas control knob set on LOW:
And after the needle valve installation:
Even with the poor shots from my camera, you can clearly see an obvious difference in the flame output.
Here are a collection of sites that carry different needle valves, I got mine from Adventures in Homebrewing as it was the cheapest with shipping ($12 and change), and what arrived was the Bayou Classic valve. HA!
Adventures in Homebrewing:
For those who don't want to mess with taking apart your existing propane lines, Bayou Classic offers several Propane Regulator Kits that have the Regulator AND Needle Valve already in place.
From what I found during my research, shop around, Amazon has the same product even cheaper.
** UPDATE 2/28/2013 **
It seems the vendor is no longer shipping the product shown in the above link.
After a quick search, this seems to be the correct assembly. (at least as of today, if someone orders it, please post a comment that it is indeed the correct one)
** UPDATE 3/18/2013 **
It seems the vendors on Amazon need to change their descriptions as they are shipping the adjustable regulator assembly versus the one with the needle valve. If you find a correct one, please post below for others to order, I'll update if I find another one.
If anyone has anything further to add, please feel free, this is just my attempt to help out where I can.
In hindsight, after buying the needle valve and additional fittings at my local Lowes to make it work, I would have spent just about as much by purchasing the entire regulator assembly from Amazon, and wouldn't have had to mess with the splicing.
** Also, before firing it up after making the mod, make sure to check all of your connections with soapy water to ensure that you don't have any leaks.