Underwater wet welding

(time specifications for weld seams)

High-quality welding under water requires careful preparation of the weld seam and calculation of the weld time involved.

Multiple-layer stitch bead

a) In order to obtain an a-dimension of 6 mm, 3 beads are necessary in the horizontal and vertical position, as follows:

Vertical position: 1 root and 2 final runs with a 3.25 mm "Thyssen Nautica" electrode
Vertical position, falling: 1 root and 2 final runs with a 3.25 mm "Thyssen Nautica" electrode

In order to obtain this specification, a stretch energy of approx. 1.5 KJ/mm is recommended (where water is approx. 10 metres deep). With a 3.25 mm electrode, this results in a welding speed of approx. 900 cm/hour. The stretch energy equals welding voltage (U) x welding current (I) : welding speed (mm/sec). The welding speed lies between 2.5 and 3.0 mm/sec.

b) In order to obtain an a-dimension of 8 mm, 5 beads (1 root, 2 filler layers and 2 final runs) are necessary in the horizontal and vertical position, falling. The conditions and welding speeds referred to above remain unchanged.

If 900 cm/hour is converted to 3 beads, this results in a weld output of 3.0 m/hour excluding seam preparation and electrode changes or fitting and provisionally fastening the sheet metal. This does not include the time required for replacing divers.

Temper-bead technique

It can be assumed that a physically fit underwater welder is capable of processing 80 to 100 electrodes sized 3.25 mm in a single shift (approx. 4-5 hours in summer) without using a flex grinder. In winter, divers wearing heated suits should be capable of achieving the same output.

The temper-bead technique involves laying a bead with an initial length of approx. 70 mm with a half electrode length and within a period of one minute. Before the minute elapses, the weld-overlaying process must be commenced using a thinner temper bead. The electrode test is used for this. 100 electrodes then correspond to a total seam length of approx. 7 metres (per shift).

Where the a-dimension of the seam is 8 mm, it can be assumed that a root layer (1 tempered bead) covered by a final run (usually 2-3 tempered beads) needs to be laid. Converted into output per shift, this corresponds to approx. 2 metres of full weld seam.