The Myth of Pressure Regulators

[Roger Caffin]

Hi James

> pressure regulator would make the flame a little more consistent. …
That has not been my experience in any way at all.

Cheers

[Roger Caffin]

Hi All

I have added some graphs of SOTO performance courtesy of Randulf Valle from the Norwegian outdoors magazine Friluftsliv, to whom full acknowledgement is made.

They show just what happens when you run a SOTO stove for a while at three different temperatures, compared to a typical upright. The short answer is the pressure regulator has almost ZERO effect on performance. Amusing.

Read for yourself.
Cheers

[Tad Englund]

Roger thanks for the graphs and addendum,
my favorite sentence of the whole article:

"On the other hand, the stove is very well made and works well. It would be a pity to discard it just because of the stupid marketing spin about the regulator"

Why do they have to push the "spin"? Just sell the stove for what it is- a good stove.

[Hikin’ Jim]

Excellent update, Roger, excellent. This is exactly the kind of hard data that unequivocally proves or disproves a proposition. Based on the testing, I'm surprised (and rather disappointed) that Soto made any claims at all for the regulator as regards it's ability to stabilize output or counteract the effects of cold. The one thing that the regulator seems to buy one is that the regulator will keep the stove under control in hot weather. Perhaps this is a safety feature, but said feature is completely unrelated to the claims that have been made for the stove.

Still, there is the outstanding question of why the Jetboil Sol performs better in cold weather than non-regulator valved Jetboil stoves. It will be interesting to see just how much heat is conducted to the canister. I could feel with my hand that some heat was making it down to the canister, but I lacked the equipment to tell just how much.

HJ
Adventures In Stoving

[Nick Gatel]

Interesting article, Roger.

I'm not a scientist. But I don't see the benefit of a regulator unless there are large variations in canister pressure in a very short period of time.

Now RV LPG tanks pose a different problem. Interior appliances are required by code in the US (and probably other countries), to operate at 11 inches of water column max, which is close to 1 psi. However many outdoor appliances operate at 15 PSI, so some RVs have special regulators that split the gas delivery between outdoor and indoor appliances. The typical "Coleman" camping stove and portable BBQs usually run at 15 PSI. Other types of LPG appliances run at different pressures and most have their own regulators. Makes the typical 20lb LPG tank quite versatile.

My tent trailer has low pressure exterior fittings. To run my Weber Baby Q bar-b-que, which had a built-in 15 PSI regulator, I removed the built-in regulator and run it just fine at 11" WC directly from the low pressure port. Same flame and performance as running it on a high pressure system with the built-in regulator. Wind does not affect it either.

Since I suspect most of the BPing canisters run at similar pressures, I don't see the advantage of a regulator and my gut feeling is that they are probably more prone to difficulties and/or failure than a simple jet. But then I just saw on TV that I need to use the same deodorant as Bear Gryls is I want to be a real man :)

[Roger Caffin]

Hi Jim

> I'm surprised … that Soto made any claims at all for the regulator
MSR have a similar pressure regulator on the Reactor, but they make NO claims for it. Yes, I think it is a safety thing for MSR.

Cheers

[Hikin’ Jim]

Speaking of claims made, one wonders exactly what is going on with the video put out by Soto.

HJ
Adventures in Stoving

[Roger Caffin]

Yes, well, I would imagine you or Stuart or quite a few others could fake that video just as easily. Start with nice hot canisters, open the SOTO up full bore and the other one barely enough, and then chill them down. So what?

But see the graphs from Randulf's independent tests for reality.

Cheers

[Hikin’ Jim]

Deliberate, outright fakery? Ouch.

HJ
Adventures In Stoving

[M B]

A needle valve is not a pressure regulator. It is a simple fixed restriction that generates pressure drop that is proportional to the square root of the flow.

A pressure regulator may be of 2 types, relative (ie pressure drop, ie relative to upstream pressure) or absolute (relative to atm pressure). In either case, it is an adjustable restriction orifice. The orifice size changes as needed to maintain the downstream pressure.

Not knowing anything about the overall pressure drop across jets and thru the stoves, it is theoretically possible for a pressure regulator with a large orifice to pass more gas with a lower dP than a small fixed restriction can. This would enhance low pressure operation when the pressure in the cannister is low. IE, it would be a function of the size of the regulators adjustable orifice, not the fact that it is a regulator.

Not saying this is or isnt the case, but it is possible that a regulator or stove could give a cold weather advantage in this way relative to standard needle valves. Of course, a larger manual needle valve would have the same benefit.

[David Thomas]

"A needle valve is not a pressure regulator. It is a simple fixed restriction that generates pressure drop that is proportional to the square root of the flow."

That's true until it hits sonic velocity (which gases can do at these pressures thru a small orifice). Then it is a constant mass flow, regardless of the delta P increasing.

[Hikin’ Jim]

Not knowing anything about the overall pressure drop across jets and thru the stoves, it is theoretically possible for a pressure regulator with a large orifice to pass more gas with a lower dP than a small fixed restriction can. This would enhance low pressure operation when the pressure in the cannister is low. IE, it would be a function of the size of the regulators adjustable orifice, not the fact that it is a regulator.

Stuart Robb advanced an explanation earlier (elsewhere on BPL) as to why Jetboils with regulator valves outperformed Jetboils with conventional needle valves. Essentially, if I understood Stuart correctly, he posited that the regulator made a larger diameter jet safe by limiting the gas flow when the canister pressure is high while allowing for improved gas flow when canister pressure is low in cold conditions.

HJ

[M B]

"That's true until it hits sonic velocity (which gases can do at these pressures thru a small orifice). Then it is a constant mass flow, regardless of the delta P increasing."

Im sure what you intended to say, was regardless of the delta P increasing due to any further downstream pressure drop for a fixed upstream pressure and temperature.

Changes in pressure or temperature, will of course still effect a change in flow rate across a choked restriction.

[Hikin’ Jim]

Not that there was necessarily any question as to the science, but it never hurts to have some field testing to either confirm or deny what we expect.

I posted this in the gear section, but I thought a link here might be salient for whomsoever might read this article. I took my Soto Microregulator OD-1R and a Monatauk Gnat out about a week ago for a little field testing in 31F/-0.5C weather at about 6000' elevation (~1825m). To eliminate some variables, I used 100% n-butane as my fuel. The boiling point of n-butane at 6000' is about 19F/-7C. In other words, I was testing in conditions where the ambient temperature was about 12 Fahrenheit degrees above the boiling point of my fuel.

I shot a video of the two stoves running side by side for a period of approximately 20 minutes. That video is posted on my blog: Advantages (?) of Regulator Valved Stoves, Part II. The video is in two parts, 1) the first 17 or so minutes (if you want to see the whole thing) and 2) the last 3 or so minutes (if you want to see how things turned out). For those not wanting to take the time for either video, my testing was entirely congruent with the article.

HJ
Adventures In Stoving

[Bryan Bihlmaier]

Roger,

I hope you don’t mind if I open up this topic again.  But would you mind please elaborating on an explanation of your opinion and experience whether Hikin’ Jim’s theory in the following blog post, and as mentioned previously in this thread, could be correct: A gas stove with a pressure regulator could safely use a larger-diameter jet without the possibility of a flame-out at higher canister pressures (higher temps).  This could potentially help low-temperature, low-canister pressure situations when the valve and jet needs to be less restrictive.

https://adventuresinstoving.blogspot.com/2016/12/gas-stoves-in-cold-weather-regulator.html

I am also assuming that, if a canister warming device such as a “Moulder” heat transfer strip, or old fashioned bowl of water, would eliminate the needs for a regulator valve which might only help at low canister pressures.  In my thinking, if a pressure regulator and larger jet orifice did actually help low-canister pressure performance, it would only benefit if you did not sufficiently warm the canister initially before starting the stove, and for the approximately 15 seconds until the Moulder Strip heated the canister enough to restore adequate pressure.

So basically, as I think about it, there might be a narrow band of canister temperatures at which the regulator valve could help, but the low canister temperature / pressure could be overcome across a much wider range of temperatures by using methods to keep the canister warm.

Thoughts?

[Roger Caffin]

Hi Bryan

The article all these comments are about does go into all that. I have to ask whether you have read the article yet, as I don’t know what else to explain.

That said, basically one of these so-called ‘pressure regulator’ valves is still just a needle valve, just like a conventional needle valve – but with lots of marketing spin and a higher price-tag. The difference is that you, the user, get to adjust the needle valve to regulate the flow over a period of half an hour rather than having the stove make a partial correction. Big deal!

The issue of ‘flame-out’ is controlled by the amount of air brought into the gas stream by the combination of gas velocity and air inlet size. A poorly-designed stove can have problems with this; a well-designed stove does not. That is a separate issue.

So – lots of marketing spin but negligible science or engineering. Actually, it was the advertising copy-writers for the retailers who went overboard: SOTO themselves were a bit more restrained.

HTH, Cheers

[Bob Moulder]

So basically, as I think about it, there might be a narrow band of canister temperatures at which the regulator valve could help, but the low canister temperature / pressure could be overcome across a much wider range of temperatures by using methods to keep the canister warm.

Yes. Pretend there is no — ahem — “regulator.”

;^)

[Bryan Bihlmaier]

Roger,

Yes,  I did read the article you wrote. That’s why I addressed this question to you. I understand completely the operation of a regulator valve as compared to a needle valve. But I did not see a discussion of whether or not there is a benefit to having a <u>larger jet orifice</u> which could allow more gas flow at lower canister pressures. Basically the pressure regulator valve could safely be allowed to open up wider in cases of low canister pressure, enabling a lower total system resistance and thus less pressure loss due to gas flow, when combined with a larger jet orifice. Hikin’ Jim suggests in his blog post that such a system with lower restriction (larger orifice) could become unsafe in the case of high canister pressures, if a needle valve were opened up all the way,  in which case there could be too little restriction in the system, allowing too high of gas velocity exiting the orifice.

So I guess my specific questions are, could a jet orifice which is too large lead to too high fuel/air velocity exiting the burner, which could lift the flame off the burner face and potentially “flame out” the stove? And, would a pressure regulator allow a canister stove to <u>safely</u> operate across a wider range of canister internal pressures versus a needle valve? And finally, how much benefit would that actually provide, given that there are external means of warming a canister  and increasing its internal pressure? I’m not sure how else to posit my questions.

[Roger Caffin]

Hi Bryan

No worries, I was just unsure.

Yes, it is entirely possible to get flame lift-off with a larger jet size. Been there and tried that. Commercial stoves come with a very limited range of jet sizes – typically 0.28 mm to 0.30 mm. That said, the size of the air inlets is an equal factor in this problem.

Basically the pressure regulator valve could safely be allowed to open up wider in cases of low canister pressure
This is pure spin, not fact. There is ZERO difference between a pressure regulator (PR) needle valve and a conventional screwed needle valve. Both make a variable pressure drop. Anything you can do with a pressure regulator valve you can do just as well, or maybe slightly better, with a conventional needle valve. You can totally empty a canister with a conventional needle valve – most of us have done so many times.

The only benefit to a PR valve is that you don’t have to adjust it half an hour later when the canister pressure has dropped a bit. But I never have my stove running for that length of time anyhow. Pure and total marketing spin, otherwise known as The Big Lie.

Cheers

[Erik Norseman]

Hi Roger,

Digging deep into stoves after reading the stovebench review of upright canister stoves. I’m particularly interested in the MSR Pocket rocket deluxe, which outperformed all the other upright canister stoves. From my understanding, this is due to the stove design, not the fact that is pressure regulated. It made me want to try the stove out, but I’ve seen in other places that many people deride pressure regulated stoves because they can actually inhibit the user’s ability to fine tune controls of the stove. I read through your article and the attached comments hoping to find a discussion of the disadvantages of pressure regulated stoves, and some were mentioned:

• potential failure points (complex parts)
• increase cost
• harder to maintain/clean (might not be a big issue)

But are they less efficient? Does a pressure regulator get in the way of controlling the stove to the exact amount of heat output desired, e.g. for simmering or just a more efficient burn?

The basic framing of this conversation seems to be along the lines of “some say pressure regulated stoves do magical things, but in fact they are essentially just a needle valve that adjusts the rate of flow (correct me if this is wrong term) automatically, i.e. nothing special, not worth the hype or paying extra for.”

What I’m wondering is in addition to NOT living up to marketing spin, do they in fact have distinct disadvantages when it comes to trying to increase fuel efficiency by running stoves at lower outputs, e.g. partially closing the valve, and/or do they struggle more to simmer? 

In short, what are the reasons to NOT buy a pressure regulated stove, if cost/weight etc. were more or less equal?

Cheers

[Jon Fong / Flat Cat Gear]

I have been testing a lot of stoves recently and have come to an interesting conclusion about pressure regulated stoves.  This is how I think they work; Roger and others can chime in.

Say the that a fresh, new canister holds 45 psi (I don’t know the exact amount (and that would temperature and ambient pressure related).  A micro-regulator limits the pressure that the stoves will see to say 15 psi.  It is the same concept as a scuba regulator: 3000 psi down to 150 psi.

So why do I think this matters?  After using several stoves, the regulated ones (PRD & Soto WindMaster) have much better flame control than non-regulated stoves (BRS 3000 & Fire Maple).  Unregulated stoves on high are loud.  So, my belief is that because unregulated stoves must operate over a large pressure range (0-45 psi) that it is difficult to optimize fuel efficiency.  Regulated stoves operate under a much narrower pressure range (0-15 psi) therefore it is easier to design around.  It is much easier to control the Pocket Rocket Deluxe compared to the Pocket Rocket2.

That being said, there are a lot of generalities, a Pocket Rocket 2 is going to perform better than the BRS 3000t (efficiency and time to boil).  You can dial back performance to increase efficiency.  I can boil 500 ml of 20 C water in under 3 minutes with the PRD as well as the Soto WindMaster while maintaining good fuel efficiencies.   Not one unregulated stove can do this (speed and efficiency).  So, these are a lot of observations and not a data driven, but sometimes, observations are fine.  My 2 cents.

[Roger Caffin]

My biased opinions about all this:

First, stove efficiency does not depend directly on the presence or absence of a pressure regulator. It depends on:
* how hard you run the stove: run it flat out and a lot of flame and heat goes up the side of the pot and is wasted.
* how wide the flame spread is: a wide flame spread needs a wide pot to avoid losing flame/heat up the side.
* what the pot diameter is: how much flame/heat goes up the side of the pot and is wasted.
* and whether you are using a good windshield: is the flame being blown sideways and missing the pot.
People have said this many times over here at BPL.

The issue of fine control is a good one. I am used to my stoves, all of which have a very fine needle valve so that fine control is very easy. If the stove you are using goes from off to flat out in a quarter turn (and some of them do), then fine control can be tricky. The argument that a regulator stove allows better fine control may have so truth in it. The argument that better fine control can lead to better efficiency relies on the user not bothering to set the flame carefully – which can happen when you are a bit tired of course.

Whether a pressure regulator stove is more likely to fail is not something I have any experience with. All I can say is that I have not heard complaints about this. Could they block up more? The question may not be relevant as all the regulator stoves I have seen are upright ones, and with upright stoves the dirt stays at the bottom of the canister.

a Pocket Rocket 2 is going to perform better than the BRS 3000t (efficiency and time to boil).
I would want to see real data from a controlled trial before I believed this. Better efficiency due to better control, maybe, but better efficiency PLUS shorter time to boil – no. I sometimes use a (genuine) BRS-3000T and I have never seen any problems – but I adjust it carefully and use it with a wide pot.

because unregulated stoves must operate over a large pressure range (0-45 psi) that it is difficult to optimize fuel efficiency.
Fairly obviously I am going to disagree with this as far as a direct link goes. There may be a link through the ease of adjustment, but that is a poor link as different users will have different willingness to adjust the stove.

I don’t like the old Pocket Rocket because it was too tall for stability and the pot supports were very weak. Also it had a very focused flame, which was not good for cooking (as opposed to boiling water). The new PR is a little better, but imho there are a lot of better stoves on the market. As the New PR is $110 on Amazon, it is also a very expensive stove compared to the alternatives. It is not light either.

Just my 2c. YMMV
Cheers

[Erik Norseman]

Thanks Roger, this helps a lot.

[Olivier A]

Specially when using pure propane (around 7.5 bar of vapor pressure at 21°C), or even more with propene (10.3 bar at 21°C), pressure is really higher than a 70/30 butane/propane mix (3.1 bar at 21°C). This can cause the flame to lift off the face of the burner because the gas flow become to fast, helped by  an air mix that could be sub optimal for some burners. This can be a safety hazard if the flame vanish, keeping unburned gas to flow out.

In this regard a gas regulator is helping for safety, keeping a reasonable maximum gas flow regardless the used gas. Another advantage is that it will help in keeping a good simmer control. Propane will be rarely used for a single burner portable stove, so the pressure regulator usefulness here is very questionable except for some special stoves that could be dangerous without it, but for larger dual burner stoves, sometimes used with propane canisters or large LPG tanks, a regulator is probably a good thing to have.

 

 

 

[Roger Caffin]

One of the reasons that a pressure regulator valve is used on large LPG tanks is that the stoves they are driving are designed for low-pressure gas. Such stoves could still be used without the pressure regulator, but it would be more tricky. Kitchen stoves are generally designed for low pressure.

A second reason for having a ‘pressure regulator’ on a large LPG tank is that it limits what some idiot can do when he opens the control valve right up without thinking.

Also, some pressure regulators have a safety valve inside them which senses a large flow rate and shuts off. That prevents a ‘blow-out’.

Flame lift-off is caused by the gas velocity (for the fuel/air mix) at the face of the burner being higher than the maximum flame velocity for that fuel/air mix. This can be caused by the air inlets being too large, or by the amount of fuel coming out of the jet being too large.

Cheers

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