Capstone: the all-position plate test

Ten weeks after Marta drew the plan on the whiteboard, Devon tests. The test is the CWB all-position plate test for SMAW with backing: four 10 mm (3/8 in) groove coupons, one each in the flat, horizontal, vertical and overhead positions, welded with E4918 low-hydrogen electrodes under the eye of a CWB examiner, visually inspected, and then cut and bent. If all four pass, the CWB records him as qualified for groove and fillet welds in all positions with SMAW and the F4 electrode group, for Hartwell's CSA W47.1 certification, for two years. This capstone follows the test day from preparation to the last bend, and then looks at what the result allows Devon to weld.

The test procedure

A welder qualification test is welded to a procedure, and the procedure sheet is handed to the welder before the test. Elena Marchetti's test procedure for Devon's test gives:

The plates are cut and bevelled from one batch of plate with heat numbers recorded, and Devon prepares them himself, the same way he has prepared forty practice plates. Lucia checks each assembly before it goes in the stand: bevel angles, root opening at both ends and the middle, the backing tight with no gap, tacks on the backing outside the tested length, and the pre-set. Each plate is marked with Devon's welder number and the position, stamped into the plate outside the weld area so that the identification survives cutting.

Test morning

The CWB examiner arrives at eight. She checks Devon's identification, the test procedure, the electrodes in the oven and the oven's temperature, and the four assemblies. She tells him the rules: the plates will not be moved once he starts; he may grind and clean between passes but not touch the cap once it is done; each coupon must have at least one tie-in in the middle; and she will be watching the whole time. Marta is not allowed in the booth.

Devon starts with the plates he finds easiest, so that he can settle into the rhythm. He takes the electrodes out of the oven a few at a time and keeps them in a portable rod warmer, checks the interpass temperature with a crayon before each pass, and keeps a log on a card clipped to the stand: pass, current, start temperature. He chips every pass completely, grinds every convex root and fill pass, and makes his tie-in on each coupon at about the middle of a fill pass, grinding the crater to a taper first, the way he has practised since week three.

# Test day log: interpass checks and heat input for each coupon (mm, C)
coupons = {"flat": [("root", 20, 22.5, 125, 150, 70), ("fill", 140, 23.0, 130, 150, 55), ("fill", 190, 23.0, 130, 150, 55), ("cap", 220, 23.0, 125, 150, 60), ("cap", 235, 23.0, 125, 150, 60)], "horizontal": [("root", 20, 22.5, 120, 150, 75), ("fill", 120, 23.0, 125, 150, 50), ("fill", 170, 23.0, 125, 150, 50), ("fill", 205, 23.0, 125, 150, 50), ("cap", 215, 22.5, 118, 150, 45), ("cap", 225, 22.5, 118, 150, 45), ("cap", 230, 22.5, 115, 150, 45)], "vertical": [("root", 20, 22.5, 102, 150, 100), ("fill", 125, 23.0, 108, 150, 75), ("fill", 175, 23.0, 108, 150, 72), ("fill", 215, 23.0, 110, 150, 70), ("fill", 240, 23.0, 110, 150, 68), ("cap", 210, 23.5, 112, 150, 160)], "overhead": [("root", 20, 22.5, 112, 150, 80), ("fill", 110, 22.5, 110, 150, 60), ("fill", 150, 22.5, 110, 150, 60), ("fill", 185, 22.5, 110, 150, 60), ("fill", 205, 22.5, 110, 150, 60), ("cap", 215, 22.5, 108, 150, 55), ("cap", 225, 22.5, 108, 150, 55), ("cap", 235, 22.5, 105, 150, 50)]}
TMAX = 250
for name, passes in coupons.items():
    hot = [p for p in passes if p[1] > TMAX]
    his = [60 * v * a / (1000 * (length / (s / 60))) for _, _, v, a, length, s in passes]
    print(f"{name:10}: {len(passes)} passes, highest start temperature {max(p[1] for p in passes)} C ({'over' if hot else 'all within'} limit), heat input {min(his):.2f} to {max(his):.2f} kJ/mm")

flat      : 5 passes, highest start temperature 235 C (all within limit), heat input 1.10 to 1.31 kJ/mm
horizontal: 7 passes, highest start temperature 230 C (all within limit), heat input 0.78 to 1.35 kJ/mm
vertical  : 6 passes, highest start temperature 240 C (all within limit), heat input 1.15 to 2.81 kJ/mm
overhead  : 8 passes, highest start temperature 235 C (all within limit), heat input 0.79 to 1.34 kJ/mm

The log shows that Devon kept every pass under the interpass limit, which he did by stepping out from under the overhead plate between passes and by waiting a few minutes before the vertical cap. The vertical cap has the highest heat input of the day, as expected for a slow weave.

The overhead plate

The overhead plate is the one Devon is most worried about, and it is the one where his training shows. On the root, he feels the coating touch both bevel edges all the way along and watches the corners, not the arc. The root comes out slightly convex, and he grinds it. On the second layer, the plate starts to hold heat, and the pool at the end of the second pass gets larger than he likes; he stops, steps out, chips, and waits until the crayon tells him the plate is down to 200 °C (400 °F) before the next pass. The cap goes on in three stringers, the middle one run quickly. When he steps out from under the plate for the last time, his shirt is soaked and his shoulder aches, and he cannot tell from below whether the cap is any good.

Visual inspection

When the plates have cooled in air, the visual inspection is done before any cutting. Each plate is checked on the face and, after the backing is knocked or ground away at the ends, on the root side, against the visual criteria from lesson 5.

# Visual inspection of the test coupons against the cap criteria (mm)
LIM = {"reinforcement": 3.0, "undercut": 1.0, "width_past_edge": 3.0}
coupons = [("flat", 1.5, 0.0, 2.0, False, False), ("horizontal", 2.0, 0.5, 2.5, False, False), ("vertical", 2.0, 0.5, 2.0, False, False), ("overhead", 2.5, 0.8, 2.5, False, False)]     # (coupon, max reinforcement, max undercut, max width past bevel edge, cracks, unfilled craters)
for name, reinf, uc, wid, cracks, craters in coupons:
    faults = []
    if reinf > LIM["reinforcement"]: faults.append("reinforcement")
    if uc > LIM["undercut"]: faults.append("undercut")
    if wid > LIM["width_past_edge"]: faults.append("cap width")
    if cracks: faults.append("crack")
    if craters: faults.append("crater")
    print(f"{name:10} reinforcement {reinf} mm, undercut {uc} mm, width past edge {wid} mm: {'pass' if not faults else 'FAIL ' + ', '.join(faults)}")

flat       reinforcement 1.5 mm, undercut 0.0 mm, width past edge 2.0 mm: pass
horizontal reinforcement 2.0 mm, undercut 0.5 mm, width past edge 2.5 mm: pass
vertical   reinforcement 2.0 mm, undercut 0.5 mm, width past edge 2.0 mm: pass
overhead   reinforcement 2.5 mm, undercut 0.8 mm, width past edge 2.5 mm: pass

All the coupons pass visual inspection. The overhead cap is the closest to a limit, with 0.8 mm (0.03 in) of undercut at one edge near the tie-in, under the 1 mm (1/32 in) limit but enough that Lucia notes it and shows it to Devon afterwards. It is the edge pass he ran slightly hot when the plate was warm.

Cutting and bending

The coupons are cut on the band saw: the ends discarded, and from each coupon one root bend and one face bend specimen. Devon is not allowed to prepare his own test specimens; Lucia grinds the backing and reinforcement flush, finishes the grinding marks lengthwise and rounds the edges, with the examiner watching. The specimens go into the jig one at a time, each bent through 180 degrees around the plunger.

# Bend results for the test coupons (mm): largest opening, total of openings over the small size
SINGLE, TOTAL, SMALL = 3.0, 10.0, 1.0
results = [("flat", "root", []), ("flat", "face", []), ("horizontal", "root", []), ("horizontal", "face", [0.5]), ("vertical", "root", []), ("vertical", "face", [1.5]), ("overhead", "root", [0.8]), ("overhead", "face", [])]
passed = {}
for coupon, kind, openings in results:
    worst = max(openings, default=0.0)
    total = sum(o for o in openings if o > SMALL)
    ok = worst <= SINGLE and total <= TOTAL
    passed.setdefault(coupon, True)
    passed[coupon] = passed[coupon] and ok
    print(f"{coupon:10} {kind:5} bend: largest {worst:.1f} mm, total {total:.1f} mm -> {'accept' if ok else 'REJECT'}")
print("coupons passed:", ", ".join(c for c, ok in passed.items() if ok) or "none")
print("coupons failed:", ", ".join(c for c, ok in passed.items() if not ok) or "none")

flat       root  bend: largest 0.0 mm, total 0.0 mm -> accept
flat       face  bend: largest 0.0 mm, total 0.0 mm -> accept
horizontal root  bend: largest 0.0 mm, total 0.0 mm -> accept
horizontal face  bend: largest 0.5 mm, total 0.0 mm -> accept
vertical   root  bend: largest 0.0 mm, total 0.0 mm -> accept
vertical   face  bend: largest 1.5 mm, total 1.5 mm -> accept
overhead   root  bend: largest 0.8 mm, total 0.0 mm -> accept
overhead   face  bend: largest 0.0 mm, total 0.0 mm -> accept
coupons passed: flat, horizontal, vertical, overhead
coupons failed: none

Every bend passes. The vertical face bend shows a single small opening, a pore about 1.5 mm (1/16 in) across that opened under the bend, well inside the 3 mm (1/8 in) limit; Lucia guesses it came from the tie-in, and when the specimen is examined closely, the pore sits right at the restart. The overhead root bend, the one Devon feared most, shows a tiny opening under 1 mm (1/32 in), along the line where the root met the backing. It is acceptable, but it tells him that the overhead root is still the place where he is closest to the edge.

What the qualification covers

The test result is recorded on a welder qualification record, which lists what the welder may now weld. The record is as important as the test, because it sets the limits that Glen uses when he assigns work.

# Positions qualified from the plate groove tests passed (after the D1.1 / W47.1 pattern for plate)
GROOVE = {"1G": {"1G"}, "2G": {"1G", "2G"}, "3G": {"1G", "2G", "3G"}, "4G": {"1G", "4G"}}
FILLET_FROM_GROOVE = {"1G": {"1F"}, "2G": {"1F", "2F"}, "3G": {"1F", "2F", "3F"}, "4G": {"1F", "2F", "4F"}}
def qualified(tests):
    g, f = set(), set()
    for t in tests:
        g |= GROOVE[t]; f |= FILLET_FROM_GROOVE[t]
    return sorted(g), sorted(f)
for tests in (("1G", "2G", "3G", "4G"), ("3G", "4G"), ("3G",), ("4G",)):
    g, f = qualified(tests)
    print(f"tested {'+'.join(tests):12} -> groove {', '.join(g):14} fillet {', '.join(f)}")
t = 10
print(f"plate thickness range from a {t} mm test: as recorded by the CWB with the test result")

tested 1G+2G+3G+4G  -> groove 1G, 2G, 3G, 4G fillet 1F, 2F, 3F, 4F
tested 3G+4G        -> groove 1G, 2G, 3G, 4G fillet 1F, 2F, 3F, 4F
tested 3G           -> groove 1G, 2G, 3G     fillet 1F, 2F, 3F
tested 4G           -> groove 1G, 4G         fillet 1F, 2F, 4F
plate thickness range from a 10 mm test: as recorded by the CWB with the test result

Devon's four coupons qualify him for groove and fillet welds in all positions on plate, with backing, with SMAW and the F4 electrode group. Because the test was made with backing, he is not yet qualified for open-root groove welds; that is a separate CWB test, which he will take during the pipe course. The qualification lasts two years, and after that it is renewed by a check test in the vertical and overhead positions. Hartwell's CWB records are updated the same week, and Glen adds Devon to the list of welders he can assign to groove welds.

A second test the same day

Devon is not the only welder testing. Rob Haldane, a journeyperson on the Riverside erection crew, is taking his two-year check test: a vertical and an overhead coupon. His vertical coupon passes. His overhead root bend opens 4 mm (5/32 in) at the tie-in, along a line of slag he did not clean out of the crater before restarting. Under the check test rules used at the test centre, a failed check test means Rob must weld complete vertical and overhead coupons again. He is philosophical about it: he has welded overhead for eleven years and still made a beginner's mistake at a restart, because he hurried. The examiner books him for a retest the next week.

Lucia uses Rob's specimen in her talk with Devon afterwards. Experience does not make a welder immune to defects; habits do. The crater of every restart is chipped and ground, every time, on a test or on production work, by an apprentice or by a welder of twenty years.

Looking back over the course

On the last afternoon, Marta and Devon go through his practice log together. Forty-one practice plates, sixty-three bend specimens, twelve failed specimens on the board in the bay. His pass rate in the first four weeks was under 60 percent; in the last three weeks, it was over 90. His most common failures, in order, were cold corners on the root, slag at restarts and, overhead, a root that did not reach the backing. Each of them was cured the same way: by understanding exactly what caused it, changing one thing in his technique, and testing the result by bending or cutting the plate.

Glen's first assignment for Devon as a qualified groove welder is the bearing stiffeners on the last two Riverside girders: complete joint penetration groove welds at the bottom flange, welded in the vertical position with the girder on its side. Marta checks the first one. After that, she leaves him to it.