Monday, January 3, 2011

Barbeque Burner Valves

Quick Hint -- WEDNESDAY, JULY 20, 2011

If you've arrived here because you were seeking help with barbeque valves that are stiff to turn, I can save you some reading.

Just pull the knobs off and lubricate the valve stems with WD-40 where the stems enter their bushings. (Don't overdo it; you don't want to flood the valves with WD-40.) That will most likely restore smooth, easy operation. The innards of the valves are unlikely to ever give any trouble.

If you'd like to know more, please be my guest and read on.

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If you've ever wondered what's inside a barbeque burner valve, wonder no more. Here's one taken apart. (It's for a side burner on a low-end Thermos model.)

The conical valving element in the centre of the photo is the key to the valve's smooth, quarter-turn operation. When turned 1/4 turn CCW from its 'off' position, the hole in the side is fully aligned with a hole in the valve seat that exits to the jet. In the 'off' position, the hole is completely covered by the wall of the valve seat. In between is everything in between, from a low flame to fully on. It's about as simple, reliable and durable a piece of gear as can be.

Another key element is the dark grease you can see on the brass 'cone'. The grease acts as both a lubricant for smooth operation, and as a sealant. (We're dealing with very low pressure here -- about 1/2 PSIG[1]. Layers of o-rings are not called for.)

I looked into 'gas valve grease' on the internet, and such a thing can be had. When I went to the local appliance parts place and asked about it, they'd never heard of it. That makes me suspect that a lot of these things get discarded and replaced because of stiff operation, when they could easily be restored to perfect condition at little cost.

Since I can't easily get the 'proper' grease, I'll use MOLYSLIP on it after I've cleaned it up; it's the right colour, at least. (By the way, I know of no other field than lubricants, grease lubricants especially, that's so loaded with 'secret' formulae and miscellaneous techno-bushwah. Try and educate yourself about grease lubricants and see how much progress you make.)

All that said, in actual fact these valves probably very seldom need to be dismantled. Stiff operation, especially on a barbeque that stays outside, is likely to originate in the stem that the knob attaches to. WD-40 will deal with that without dismantlement.

The little spring in the photo does two things -- it keeps a seatward bias on the valving element, and it forces the stem up into its detent at the off position.

The jet is just an orifice. It was installed here with a hardening sealant. I'll use Permatex Ultra Grey on it when I reinstall it. (Teflon tape is for tapered threads only. These threads are straight.)

Finally, note the barbed hose nipple. (It takes 5/16" I.D. tubing.) Do you see anything magical or 'special' about it? I don't. And that brings me to the subject of barbeque hose replacement.

Barbeque Hoses

I hadn't owned my Thermos barbeque very long before a raccoon chewed the hoses. (It must have been an adolescent one still learning its way around in the world, discovering what all could be eaten. I guess I should be pleased that I was able to provide it with some education.)

The hose installation looked pretty straightforward to me, but embossed on the regulator was this: "REG-HOSE UNIT IS FACTORY SEALED DO NOT REPLACE HOSE ONLY"

Oh my, the voice of authority telling me that the raccoon had rendered a perfectly good regulator and two valve assemblies worthless. I wasn't buying it.

I went to Canadian Tire, and for $2.10/foot bought three feet of 5/16" I.D., 50 PSI fuel/emission tubing. It fit the barbed nipples perfectly, and has served me well for over six years now. Following is a photo of the two types of hose:

Above is the original hose; below is the replacement. They're both 5/16" I.D. They have about the same wall thickness. The original hose is slightly stiffer.

From what I've seen of barbeque fuel-delivery components, they're both durable and serviceable. I've never seen a failure of a sealed regulator unit, which is not to say that they never fail, but a salvaged working one could be used for a replacement if it ever came to it.

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1. PSIG stands for Pounds-force per Square Inch Gauge, as opposed to PSIA -- Pounds-force per Square Inch Absolute. When you're measuring a tire pressure, you're reading PSIG; i.e. pressure relative to atmospheric pressure.

At sea level, a column of air one inch square the full height of earth's atmosphere weighs about 14.7 pounds. Everywhere on the face of the earth, the atmosphere is pressing on everything with about that amount of force. (It's less the higher up you are, obviously. At the top of a tall mountain, there's not so far to go to the top of the atmosphere.)

So a 35 PSIG tire pressure at sea level would be 49.7 PSIA -- the tire is inflated relative to its immersion in a surrounding atmospheric pressure of 14.7 PSI.

PSIG is almost always expressed as just 'PSI', as you can see done on the FUEL/EMISSION hose in the photo.

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The main burner valves are little different in construction, but they feature some enhanced functionality. They have three detented positions, and a greater arc of rotation -- about 210 degrees, compared to 90 degrees for the side burner valve.

The first detent is the 'off' position.

About 80 degrees CCW from there is the 'light' position detent where the valve is fully open.

About 125 degrees CCW from 'off' is the 'HI' position detent. That appears to be a slightly throttled back 'fully open'.

At the end of CCW rotation is a 'low' setting. Here, the valve cone's side opening that's been in play for the 'light' and 'HI' settings is closed off, and a second, much smaller opening provides the path out to the jet. So, you have a fixed 'low' setting. I imagine the idea is to provide a reliable low setting that needn't be fiddled with to arrive at.

These valves are exquisite machinings that look like they can and should last forever.

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