Topic: Low or High Pressure?

[DalPuri]

hi all,
    i've just bought a new gas stove  ;D

but am a little confused
its a low pressure burner 8.8kW. said to operate at a max working pressure of 37mbar, same as the regulator.
low pressure hoses have a max of 50mbar, and are usually black. but i see most people using these and bbq's
with an orange hose? (typically high pressure, max 17.5mbar)
i have read that you can use either or, but does that mean if i use an orange hose, i wont get as good a flame as
i would with a black hose?
please help ;D

[Peripatetic Phil]

its a low pressure burner 8.8kW. said to operate at a max working pressure of 37mbar, same as the regulator.
low pressure hoses have a max of 50mbar, and are usually black. but i see most people using these and bbq's
with an orange hose? (typically high pressure, max 17.5mbar)

I am confused : is there a misprint here ?  If low-pressure hoses are rated at a maximum of 50mbar, surely high-pressure hoses would be rated at a higher pressure, yet the figure you have quoted (17.5mbar) is only 1/3 of 50mbar ...

i have read that you can use either or, but does that mean if i use an orange hose, i wont get as good a flame as  i would with a black hose?

If you can use either, then it is definitely a low-pressure device (since you can obviously use an lp device with hp hoses, but not vice-versa), and I would not expect any significant different in performance.  The hose is rated for maximum pressure (without bursting), not maximum flow rate.

** Phil.

[DalPuri]

the figures are correct, thats why i'm confused
physics class was a long time ago

http://www.gasproducts.co.uk/acatalog/LPG_Low_and_High_Pressure_Gas_Hose_.html

[Peripatetic Phil]

OK, it took me a while to get to the bottom of this, but here is the definitive statement :

British Standard hose only must be used for passing these gases and it must be securely attached with hose clips to the ends provided. Low pressure hose, (which must show the number BS.3212/1) must be used only for pressures up to 50 mbar. High pressure hose (which must show the number BS.3212/2) can be used for all pressures up to 17.5 bar.

The devil lies in the detail : look very carefully at the last line, and you will see that the units are bars, not millibars !   As regards performance, the wider the hose the greater the maximum flow rate, so just choose a wider bore in preference to a narrower one.

[Update] Two more ideas of possible relevance / interest :

1) Butane is normally regulated at 28 mbar, propane at 37mbar.  A regulator set to 37 mbar can, in certain circumstances, momentarily allow pressures up to 52 mbar to be reached, as a result of which the HSE have stipulated that hose suitable for pressures up to a maximum of 50 mbar cannot be used, since there is an (infinitesimally small) chance that the hose could rupture.  Of course, the likelihood of this occuring in real life is far less than the risk of your being abducted by aliens, but facts is facts and the hose is rated at only 50 mbar whilst there is a finite risk that the pressure might briefly exceed that by a whole 2 mbar.  Use your own judgement here !

2) In a static system, the pressure in a pressurised system will be identical both at the outlet of the regulator and at the inlet of the burner; once the burner tap is opened, however, the system ceases to be static, and the pressure at the outlet will exceed the pressure at the inlet by an amount which varies with a number of factors, of which pipe bore is one.  With all other factors constant, the pressure drop will be the lowest (and therefore the burner will generate the greatest heat) when the bore is large; with a smaller bore, the pressure drop will be greater, and the burner less effective.  Therefore go for the widest bore that you can, ensuring (of course) that it is compatible with the outlet of the regulator and the inlet of the burner.  It may be that these two are already givens, and that you therefore have no choice in bore size unless you can also source two suitable (and approved) bore reducers.

** Phil.

[DalPuri]

cheers phil

it was gettin to be like one of those spot the difference pictures.
i was browsing and searching for hours yesterdee, and all it was, was the (m) : ;D

so i suppose i could push to 10mm with clips to get the max flow. but no doubt end up getting  the standard 8mm
like everyone else.

thanks again, frank.

[Peripatetic Phil]

You are very welcome, Frank : I have lost track of how many sources I consulted before suddenly realising that the 17.5 was bars and not millibars !

** Phil.