As you probably already read in my post regarding Welding in Ship Design, Hull Design engineers only propose a minimum, theoretical design throat thickness.
And even if they would want to provide the accurate one, most of them are not acquainted with the on-site procedures.
As follows, Shipbuilding engineers assume the responsibility to deliver a “real” throat. The real throat >= theoretical design throat.
To achieve this, they must take into consideration the right weld process and corresponding penetration.
In other words, the first thing to do is to check the information received from the Hull designer against the one available in the WPS (Welding Procedure Specification).
All WPS, stored in WPQR (Welding Procedure Qualification Record) are already approved by the Classification Society.
In conclusion, you are not allowed to weld outside the limits set in the WPS or with unauthorized welders.
For tack welding you must, always, follow the same rules and conditions as the welding itself.
On a lighter note:
A man answered an ad that read, “Hiring welders; $18-$24 per hour.”
When he arrived, he was asked to take a welding test.
He turned in 2 sets of welds. One was a great weld. The other was a real mess.
When the manager asked him what his reasons were for providing also a lesser quality weld, the man replied: “One is for $18/hr, the other one is for $24/hr.”