The proposed weld as I arrived on-site:
These are rings at the inside top of tubular piles at a marine construction site.
At the best of times it would be difficult to do the "underside" weld
inside a tube about 760mm diameter.
Add to this - the piles are almost full of sand and water. Going
inside the pile to weld the lower "z5" welds in the PD position - with
air supply for the welder; safety provisions; etc - would have
been problematic and expensive. Add the water to within a metre of
the rings and the situation becomes hopelessly problematic.
The team leader handled it well - I pointed out that a welder working
from the top could "weld in-the-mirror" - and he got a quote from a
welder experienced in "welding in-the-mirror". For which the price
was unattractive...
The solution presented by the lead contractor was inevitable:
That's one bigger "top" weld in the PB position, readily done from top access.
Comparing the two, side-by-side:
The "single z8 weld" is very "doable".
A new challenge then presents itself. Explaining...
The team has a construction barge with pedestal crane "built-in", which saves weight, so "packs a lot of punch" in terms of tonne-metres of lift for draught in the water. Plus has its own small tugboat, so also small draught, paired to the barge.
Therefore remunerative niche - get into the piles near the shore.
Good stream of work - but that brings the challenge.
The task:
That is the challenge - you have that immutable two hours and not a
minute more to do the work.
Run-out of time - you have to abort the work and get out fast, because
the barge and tugboat must not become grounded.
There are other tasks of oxy-flame cutting plus "fitting" accurately
on some surfaces.
It is always the case that the faster the welding, the more
advantageous the working situation.
Must be "stick" (SMAW) because you are exposed to the elements.
Gasless Flux-Cored wire welding? No - the wire and equipment could
not survive the seaspray.
In fact - due to pressure of time, on the 2 hours, the welder had to
throw the stinger, return-clamp and oxy-fuel torch into the sea for
the barge crew to haul aboard by the hoses and cables.
The largest electrodes available were the 5mm diameter version of the "7018" "Basic" calcium-carbonate rods.
The job did get surely the best 240A current setting to be had.
My colleague did the flame-cutting, fitting and welding in 1~1/2hours. Doing just the "top" "z5" weld.
By feeling their way in nudging the silt bottom of the marine site, the barge team could give me 2~1/2hours.
I had to point-out - with the "z8" welds I was depositing
2.5 times the amount of weld metal. Along with the same
flame-cutting and fitting. So I was giving them at least as good a
deal as my colleague.
Herein lay the problem - the barge crew did not know whether to
believe me, wondering whether I was trying to bamboozle them...
Here is the crucial argument - linked as a PDF presenting typeset the mathematical case .
That linear ratio of 5:8 (=1.6) is the increase in strength going from "z5" to "z8". Well, that is to be assumed, all other things being equal.
But not the ratio of metal deposition...
Which is 1:2.5
The area ratio of 25:64
So all things being equal that would be two and a half times the
welding time.
Not applicable here - but a general principle comes into view.
To get the needed strength, where possible make your welds long
(full-length?) and small. Rather than skip (intermittent) welds with
a bigger fillet size...
Because the strength is obtained with less weld metal.
This was realised when building the "Liberty ships" in the early 1940's.
I achieved the weld as a 2-run weld, as follows:
This matches the recommendation in the Lincoln Foundation's "The Procedure Handbook of Arc Welding".
First run fillet-corner / root run but flicking the electrode out
horizontally to spread the weld to 8mm leg-length horizontally.
Spreading the weld metal, leaving quite a low first run.
Then second run straight-run no manipulation in the new corner on top
of the first run.
The tide waits for no-one!
Therefore - I had to accurately control fillet weld leg-length to
I had an 8mm plate fillet gauge with me.
Given how crucial it was to meet spec. but minimise welding time.
(my experience - only plate fillet gauges work - all more complex
devices not working in the real world)
The intention is to reinforce the message : accurate fillet weld size control is crucial to master early when learning welding.
(R. Smith, 15Dec2023, 16Dec2023 (eds), 16Dec2023 (weld dets.))