The tolerances should be designated in the Welding Procedure Specification and derived from the governing code.

The WPS is written from the governing code. We weld to AMS-STD-2219, D17.1, D1.1 and four customer weld spec.s. none of these specifications define these issues. In the past I've defined the length as a minimum and the pitch as a visual thing. Even looking in AWS B1.10 and B1.11 weld inspection spec. list nothing. Our customer has gone thru so many layoffs that the only responce they can give me is "do whatever the specification says". It'll only be a matter of time before a NADCAP auditor asks this question.

The length and size of the welds should be based on the loads to be transmitted and the allowable load per unit of weld (size). Code allowables and the base metal being welded must be considered. For instance, welds in carbon steel are usually as strong as the base metal, but the allowable load is based on some functionof the yield or tensile strength. Aluminum on the otherhand has to take into consideration any loss of mechanical properties as a result of the heat of welding, example: 6061-T6 tensile strength on wrought condition - 42ksi, after welding - reduced to 24ksi.

AWS D1.1 states that the minimum length of the fillet weld is four times its leg size. Stated another way, the maximum size of the fillet weld is one quarter of the weld length. The weld start and crater is included in the length, provided the crater is filled to the full cross section.

Does the wall thickness of the base metal matter in this case

abba7114, no. This was the callout on a customer supplied print. The question was brought up "what is the tolerance on the pitch and length" and I went looking for the answer. Our customer has eliminated their welding engineers so they were no help. This print is about 30 years old, no reinvention of the wheel going on here.
Nathan

You are describing an intermittant fillet weld. This question went to the AWS welding symbols committee several years ago. The intermittent welding symbol should not be used when precise location and length of weld is required, rather it should be interpreted as:

Weld size - size specified is the minumum leg size permitted
Weld length - the minimum length of each weld segment permitted
Unwelded spaces - pitch minus length = the maximum unwelded space between weld segments

With that in mind, in the absence of a workmanship standard, a continuous weld that has the proper size (leg dimension) would be acceptable even if the intermittent weld was specified as 4 inch (length) on 10 inch (pitch). The workmanship standard would be a requirement imposed by the customer or the fabricator could have their own "in-house" standard. The welding symbol, in itself, does not imply any standard tolerance, other than specifying minimum length and size. Even those minimum can be played with by the governing standard. For instance, AWS D1.1 Structural Welding Code/Steel allows the fillet weld to be undersized by as much as 1/16 inch provided it does not exceed 10% of the weld's length (paraphrased).

Hope this helps.

Al  

Sounds like something you want to address up front.  Hopefully, reason will prevail.