Lots of excellent info--thanks very much!
On Tue, Jul 5, 2016 at 7:13 AM, Peter Fairbrother <zenadsl6186@xxxxxxxxx>
wrote:
On 05/07/16 05:44, Nels Anderson wrote:
Any idea what the purity and consistency of MAP-PRO is?
Ah, one of my pet subjects. If tl,dr; sorry where off-topic.
Going by MSDSs:
BernzOmatic MAP-PRO is 99.5% propene, with 0.5% propane. :)
Rothenberger MAPP*gas or MAPP* gas (where the * is a TM in a circle
symbol) (no, it isn't really MAPP gas, it's like american Pyrex; they
changed the formula to something completely different and less useful, but
reused the name as it had commercial value - which has a whiff of fraud to
me) is about 35% propene and 65% propane. :(
As is Rothenberger MAPP-Pro :(
However Rothenberger MAP-PRO is 99.5% propene, with 0.5% propane. :)
I think the different Rothenberger gasses may be distributed in different
countries.
MAP-Plus is about 20% propane, 30% dimethylether, 50% propene.
Apachi gas is supposed to be >99% propene - it may now be a reliable
source, but it wasn't always >99% propene, they changed the formula.
As to other brands, you would have to check: but in general MAP-PRO is
99% propene, with <0.5% propane. Which is good :).
MAP-Pro is usually similar. But MAP-PRO is the most reliably likely to be
99% propene.
But this is mostly from MSDS's. "You don't get what you expect, you get
what you inspect" (Randall Clague, I believe)
As we've
discussed previously, commercial "propane" is actually a geographically
varying mixture of propane and butane, among other things.
Yes, though pure(ish) technical grade propane is available, eg for hot air
balloons, refrigeration, aerosol propellent, and so on.
The one which varies a lot is, in theory, LPG or liquified petroleum gas -
actually if it's labelled propane it _should_ be >85% propane, some ethane
and propene, and <2.5% butane, although very often it isn't.
If you only want a small quantity, Coleman propane is said to be 100%
propane, but I'd take that with a pinch of salt.
BernzOmatic propane is supposed to be >95% propane, <5% propene, which it
probably is.
As a practical matter, if a company is selling both butane and propane in
similar lines, then the propane will usually be mostly propane, with little
enough butane in that that you don't get distillation (as gas is withdrawn
from the cylinder the propane boils off first, leaving butane) in normal
use - check first, but for practical rocketry purposes, unless you are
trying for orbit, this is usually sufficiently close to pure propane not to
matter much.
Almost all fuel gasses will have a trace of ethyl mercaptan added.
What do welders use these days when they need something hotter, now that
MAPP is no longer available?
It is not totally unavailable, but it is hard to find - there are no North
American sources, but small quantities are made in Brazil, Russia, and one
of the Scandanavian countries, I forget which. Probably India and China too.
Some use MAP-PRO, which doesn't really work well for welding especially
welding steel; not hot enough, too much hydrogen - some use "magic
ingredients" like acetone, dimethyl ether, hexane or iso-octane, which in
my limited experience don't work at all - some like me find UN1060 (same as
old MAPP gas) under different names wherever we can and carefully hoard it
- unfortunately, many suck wind.
But then there is always acetylene, in cylinders or from calcium carbide.
In India they use a Kipp's-like apparatus to drip water on carbide to make
acetylene for local car repairs and so on. But it is a lot less convenient
than MAPP gas.
I believe there is a specialist MAPP/UN1060 supply for underwater welding
and cutting on oil rigs and the like, where acetylene can't be used because
it becomes explosive below 25 feet under >15 psig pressure, but afaik that
is kept within those companies which do oil rigs.
Oh, one more safety thing about propane and propene - if you splash a
little liquid butane on your hands, it will normally do no lasting damage.
If you splash a little liquid propane or propene it is _much_ more likely
to do freezing damage. Be aware.
Let's be careful out there.
-- Peter Fairbrother
On 07/04/2016 10:18 PM, Peter Fairbrother wrote:
Propene aka propylene is widely used by plumbers and the like, sold
under the name MAP-PRO.
When Linde stopped making MAPP gas (methylacetylene/propadiene
stabilised with propane)firms like BernzOmatic and Rothenberger
started supplying propylene under the name MAP-PRO as a substitute.
It works ok-ish for a hotter gas-air flame than propane, but unlike
MAPP it isn't much use for oxy-gas welding. I digress.