Hello all

An event for me - first time into a mine:

http://weldsmith.co.uk/temp/mine/231109_condurrow.html

The compressed air pipe - not that thick wall - about the same as a
scaffold tube...
That could be "got" in one pass with a cellulosic stick ("6010" SMAW) ?

I am used to rebuilding the railings around storage and construction
barges when they are wiped off in collisions.
I'd usually start at the bottom and come up to the top welding "in
one". No prep. - about 2mm gap - so can "blow a keyhole" and bring
the keyhole around and up to the top. That is much better than a
6013/"rutile" "butt-fillet" (a surface bead with neglible
penetration).
[In the UK most have never heard of 6010's, or if they have they are
"aren't they some sort of special pipe-welding rod?" (sic.) - all
common welds are made with 6013/rutile - high-spec welds with 7018's]
But is that spec. good enough for a compressed air pipe at 6Bar?

To weld a compressed air pipe up against the rock - can you cut it
square to the half-way point, then have a "triangular-ish" cut-out to
the front, with a fitting insert?
So you can either weld around the back outside if you could get the
rod in, watching the root penetration from the front? Or more likely
given right up against the rock - weld from the inside / bore around
the rear half, so the penetration bead is on the outside and the rough
surface is on the inside. Then do two full-penetration welds to
weld-in the "triangular-ish" insert on the front half of the pipe -
welding from the outside?

"Richard Smith" wrote in message news:lyil6avw8a.fsf@void.com...

> all
>common welds are made with 6013/rutile - high-spec welds with 7018's]
>But is that spec. good enough for a compressed air pipe at 6Bar?

----------------------

I've seen yield as low as 25KSI given for water pipe made from unknown
scrap.

Common US water pipe is rated for 300 PSI.

"Jim Wilkins" <muratlanne@gmail.com> writes:

> "Richard Smith" wrote in message news:lyil6avw8a.fsf@void.com...
>
>> all
>>common welds are made with 6013/rutile - high-spec welds with 7018's]
>>But is that spec. good enough for a compressed air pipe at 6Bar?
>
> ----------------------
>
> I've seen yield as low as 25KSI given for water pipe made from unknown
> scrap.
>
> Common US water pipe is rated for 300 PSI.

I'm thinking of the girth welds. That said - pressure not more than
100psi - and girth welds are at exactly half the stress of
longitudinal seams (geometric effect).

I once went to try to radiograph some 5mm (3/16th-inch) plate seam
welded in one pass with cellulosics

(* (/ 25.4 32) 6) ;; 4.762499999999999
(* (/ 25.4 16) 3) ;; 4.762499999999999

But when at the Co. with the radiography bunker, none of their welding
machines, all inverters, would run a 6010, even "open-arc".

With very little "subject contrast" by having that uniform 5mm
thickness including barely different across the weld, and then only
that 5mm thickness, I was going to be able to use some very contrasty
fine-grained photographic paper. Hopefully fantastic sharpness to
"run the question to ground". But was not to be. So never got to see
how sound are those one-pass welds in much greater thickness than is
met in Welding Procedure Specifications for eg. pipe welding.

"Richard Smith" wrote in message news:lyo7g1ph2k.fsf@void.com...

I'm thinking of the girth welds. That said - pressure not more than
100psi - and girth welds are at exactly half the stress of
longitudinal seams (geometric effect).

--------------------------------

I remember that tank stress problem from college, but not how to calculate
it.

"Jim Wilkins" <muratlanne@gmail.com> writes:

> "Richard Smith" wrote in message news:lyo7g1ph2k.fsf@void.com...
>
> I'm thinking of the girth welds. That said - pressure not more than
> 100psi - and girth welds are at exactly half the stress of
> longitudinal seams (geometric effect).
>
> --------------------------------
>
> I remember that tank stress problem from college, but not how to
> calculate it.

"Hoop stress" is the circumferential stress
The longitudinal stress is is related to the "pi.r^2" area
Seeing diagrams is best.
If I wrote the equations here it would not "bring it ot life"
Having "got it", you can forget the formulae but do the diagrams and
re-derive the equations.

"Richard Smith" wrote in message news:lyleb4kbp5.fsf@void.com...

"Jim Wilkins" <muratlanne@gmail.com> writes:

> "Richard Smith" wrote in message news:lyo7g1ph2k.fsf@void.com...
>
> I'm thinking of the girth welds. That said - pressure not more than
> 100psi - and girth welds are at exactly half the stress of
> longitudinal seams (geometric effect).
>
> --------------------------------
>
> I remember that tank stress problem from college, but not how to
> calculate it.

"Hoop stress" is the circumferential stress
The longitudinal stress is is related to the "pi.r^2" area
Seeing diagrams is best.
If I wrote the equations here it would not "bring it ot life"
Having "got it", you can forget the formulae but do the diagrams and
re-derive the equations.

--------------------------------

The valuable simplification I learned from it was that the sum of forces on
the end supports of a curved surface ("reaction"), such as an arch, can be
treated as though it was a straight beam, instead of having to integrate one
component of the force resolution across the curve.

https://toolbox.igus.com/motion-plastics-blog/how-to-calculate-surface-pressure-for-plain-bearings
"..the simple calculation that uses the bearing length and diameter is
ultimately the more practical and precise one."

When I designed the hydraulic bucket loader for my tractor I used brass
water pipe for the pivot pin bearings because the calculated maximum
pressure was excessive for sintered Oilite. When I took it apart after
several years of clearing snow and hitting rocks etc under it one pin was
slightly bent from an accident but the bushing to pin clearance had barely
changed.

On 10/11/2023 19:02, Richard Smith wrote:
> "Jim Wilkins" <muratlanne@gmail.com> writes:
>
>> "Richard Smith" wrote in message news:lyil6avw8a.fsf@void.com...
>>
>>> all
>>> common welds are made with 6013/rutile - high-spec welds with 7018's]
>>> But is that spec. good enough for a compressed air pipe at 6Bar?
>> ----------------------
>>
>> I've seen yield as low as 25KSI given for water pipe made from unknown
>> scrap.
>>
>> Common US water pipe is rated for 300 PSI.
> I'm thinking of the girth welds. That said - pressure not more than
> 100psi - and girth welds are at exactly half the stress of
> longitudinal seams (geometric effect).
>
> I once went to try to radiograph some 5mm (3/16th-inch) plate seam
> welded in one pass with cellulosics
>
> (* (/ 25.4 32) 6) ;; 4.762499999999999
> (* (/ 25.4 16) 3) ;; 4.762499999999999
>
> But when at the Co. with the radiography bunker, none of their welding
> machines, all inverters, would run a 6010, even "open-arc".
>
> With very little "subject contrast" by having that uniform 5mm
> thickness including barely different across the weld, and then only
> that 5mm thickness, I was going to be able to use some very contrasty
> fine-grained photographic paper. Hopefully fantastic sharpness to
> "run the question to ground". But was not to be. So never got to see
> how sound are those one-pass welds in much greater thickness than is
> met in Welding Procedure Specifications for eg. pipe welding.

Richard,

I had a look to find out what the problem might be running 6010 on
inverters and came across this thread
https://forum.weldingtipsandtricks.com/viewtopic.php?t=16665 , it
suggests adding an old transformer welder in the circuit to add
inductance to get it to run 6010. I expect my old MaxArc rectifier might
do the same as it's just a full wave rectifier in a box with a large
inductor for smoothing.