Sievert blowtorch - regulators and hose failure devices

I managed to pick up a Sievert blowtorch kit from eBay, though instead of a regulator it has the Sievert 305401 hose failure device. This has the POL (left hand thread) connector to connect it directly to a propane bottle.

My question is, do I need/would I benefit from a separate regulator? I notice that many torches only have the hose failure device, so does this mean that the pressure is controlled by the torch valve?

Many thanks in advance,

Mike

The maximum pressure for Sievert torches is between 2 an 4 Bar. I have no idea what or how the hose failure device works. But I would certainly use a regulator. The propane bottle pressure is around 120 pounds per square inch at normal temperature. This rises rapidly with temperature and as far as I remember, it is over 300 pounds per square inch at 100 degrees Fahrenheit.

I would use a regulator for peace of mind, even if Sievert consider the hose failure device is sufficient.

Andrew.

Sievert explain that a Regulator is always needed and the Hose Failure Device is an optional extra:

Sievert 305401 Hose Failure Valve - Not a regulator itself but can be combined with the above. Recommended for use with long hoses when there could be a risk of the hose being damaged. Cuts off the gas when a leak is detected.

Presumably the valve shuts when it detects maximum output from the cylinder, as might happen if a hose were severed. I guess leaving the regulator out would make the flame very difficult to control.

Dave

Mike, I contacted Sievert last year about the function/use of their HFVs. I got the following reply:

"Thank you for the enquiry. Whilst the HFV are not regulators in the truest sense they give some regulation due to the way they operate. If you wanted to be certain of the pressure and have the safety benefit of an HFV I would recommend using the 306311. This will enable you to adjust the pressure between 1 and 4bar and have the HFV function.

**LINK**"

Dunno what ‘normal temperature’ is supposed to be, but if propane were a gas, rather than a vapour, and ‘normal temperature’ was 20 Celsius (293K) then the pressure at 100F would only be about 127psi.

Sorry for the odd units but SI units actually work much better! That is according to Gay-Lussac's Law.

Edited By not done it yet on 19/09/2020 14:04:06

The 305401 is also known as the HF3. It does incorporate a pressure reduction device. The limitaion is that it is not adjustable or well regulated (1.5- 4 Bar ). The fact hat it hs a POL fitting tells you it is not intended to be used with a regulator as regulators do not have POL output connectors. Sievert do sell HFs with adjustable regulators.

The HF-3 is sae to use as is. Most uses do not need the additional control of a regulator.

Robert G8RPI.

An addition to my earlier post which, in my rush, I did not consider that the vapour pressure of the propane is now above a warmer liquid, so its pressure will be higher than determined by `GL’s Law. Up to 170psi - still little more than half of 21Bar (300psi).

Many thanks again to all who posted, particularly Bill Phinn and Robert Atkinson 2. You both confirmed what I suspected.

Doing a little more research, it seems that many of Sievert's torch kits come with no 'regulator' as such, but just the hose failure device, including all the roofing kits such as those stocked by Screwfix, as well as the needle-flame jeweller's torch kits (so it must be reasonably good at keeping a steady flame!).

I found the following link which gives instructions on torch kits and even lists the 305401 hose failure device in the Regulator column

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwj116fj8_TrAhXNbsAKHUAvDMo4FBAWMAB6BAgEEAE&url=https%3A%2F%2Fwww.cousinsuk.com%2FPDF%2Fproducts%2F8586_kit%2520instructions%2520a5%25202014.pdf&usg=AOvVaw3R5twUb0-1Q41CQ_4coSPb

Being second hand and fairly dirty, I intend to give the torch and hose a wash with some detergent before cautiously trying it (probably outside until I'm completely confident with the controls!).

Once again, many thanks to everyone. Now... does anyone happen to know where I can find my glasses are that are usually on the coffee table in my lounge?

Mike

Edited By Mike Donnerstag on 19/09/2020 15:08:21

Edited By Mike Donnerstag on 19/09/2020 15:08:35

Edited By Mike Donnerstag on 19/09/2020 15:08:58

Edited By Mike Donnerstag on 19/09/2020 15:14:48

NDIY, your assumption of the Gay Lussac law is incorrect. This applies only if the cylinder contains just gas. For a liquid and gas scenario then you need to apply the Clausius-Claperyon law. This gives a much higher pressure than the simple Gay Lussac law which is gas phase only.

Checking published data, my remembered figure of 300psi at 100 to 105 degrees Fahrenheit is not far from the correct value.

Andrew.

You are right about GL, but I later corrected that to 170psi @100F (actually 172psi and straight from the internet).  Still far short of the 300psi at the temperature you originally quoted. Keep moving the goalposts, if you must.

Edited By not done it yet on 19/09/2020 17:09:47

You must use a regulator. Depending on your use, I would reccommend that you use 2 gauges in your set up, the more so if you are drawing off gas at a fast rate. One for the bottle pressure 0-300psi and a second 0-80 or 100psi for your reduced or line pressure. I have known bottle pressure to rise to 150psi or above on a hot day. Fast evaporation of the liquid gas will soon chill the bottle and the bottle pressure drop and if the bottle is less than half empty this may not take long. Then your line pressure will drop and if you are half way through a job cause problems. The answer is to A)warm the bottle, or B) Have 2 or more bottles coupled, close no1, whilst opening no2. Always start on no1. This will enable you to get all the gas out of a bottle - you would be supprised at how much gas gets sent back due to freezing bottles.

As for the operation of HFV, they are set to pass a set amount of gas - if this is exceeded - a hose has come off or burst then the valve will shut.

I have a catalogue from a firm called weldabillity that lists all you will need.

Good luck, Noel

Andrew and ndiy

This might be a reasonable compromise: gives additional useful info. and appears to come from a reliable source:

**LINK** : https://flameengineering.com/pages/propane-information

MichaelG.

Update...

I have tried the Sievert kit with a small (3.9kg) propane bottle and can confirm that it works perfectly with the hose failure device as the only 'regulator'. In fact, I found that the jewellery supplier Cooksongold supply a 'beginner's torch kit' which, like my kit, is only regulated by the hose failure device. My thinking is that, if it's stable enough to do silverwork, it should be good enough for my purposes. My burner (a 28mm burner giving 7.7kW) is far more powerful than the jewellery burner (a 17mm burner giving 0.25kW), and I only intend to use the torch for applications where my MAPP gas torch isn't man enough.

Once again, many thanks to all who replied.

Mike