Some of the most important information on Engineering drawings, are general notes. This is so easily overlooked, but may convey very important information and instructions to the person reading the drawing.
General notes in Engineering Drawing commonly consist of a set of standard notes or instructions, specific client specifications used when carrying out the work, certain test criteria during and at the completion of the work and some general information specific to the work.
The notes may vary from one drawing to another, however, some instructions will remain standard. We can also add additional instructions as required by the engineer or specific processes in the fabrication process. Below is a standard outline of possible information that can be considered general notes on an Engineering Drawing
General Notes
Notes are very general and will be directed to activities that is applicable to the overall project. An example of a general note could be “REMOVE SHARP EDGES”. This instructs the fabricator to remove sharp edges on all the components manufactured.
Examples of general notes:
- REMOVE SHARP EDGES
- MACHINING AS INDICATED
- ALL FLANGE BOLT HOLES TO STRADDLE PRINCIPLE CENTER LINES OF SHELL
- ALL WELDED CONSTRUCTION
- MINIMUM 6 mm FILLET WELD FOR ALL UNSPECIFIED WELDS
- ALL STAINLESS STEEL COMPONENTS TO BE PICKLED & PASSIVATED AFTER WELDING, GRINDING OR MACHINING
- ALL COMP.PADS TO BE TESTED TO A PRESSURE OF 50kP
These are only a few of the general notes that may appear on a drawing.
Specific Client Specifications
In this section, every client will have specific specifications that will be applicable to specific activities.
As an example, if the completed assembly needs to be painted before installation, there will be a specific specification that will address what type of paint, how thick, and in what way it has to be applied.
The company that does the work for the client needs to know that they should use the specification as a guideline to do the painting. If the drawing does not list the specification, the manufacturer may not know that the completed assembly needs to be painted to a certain standard.
Non Destructive Examinations
During, and at the end of the work, certain tests should be performed. This section will instruct what tests should be performed and to what extent they should be performed.
An example of a NDE note set would be as follows:
100% VISUAL & DIMENSIONAL INSPECTION DURING ALL STAGES OF WORK
100% PT/MT ON ALL WELD PREPARED AREAS
100% PT/MT ON ALL COMPLETED WELDS
100% RT ON ALL COMPLETED PRESSURE WELDS
These notes are very dependent on the specific work that will be done.
Existing Conditions or Materials
Existing conditions of the material that is worked on may need to be identified or qualified. If, for example, it is required to do wall thickness measurements prior to welding on a specific part of the shell, this needs to be listed.
On statutory equipment (that is equipment where the design and operation is governed by law, eg storage tanks, heat exchangers, boilers, etc) the existing material needs to be confirmed before there can be welded onto it. Certain other factors should also be taken into account like post weld heat treatment cycles and other conditions that may have an effect on the repair philosophy.
Fabrication or Repair Procedures
It is the design engineer’s responsibility to create a repair or design philosophy that is code compliant. This should be turned into a step by step to follow procedure that should be included on the drawing. Having the procedure on the drawing gives instructions to the craftsman on what needs to be done when.
Commodity or Serial Numbers
Commodity or serial numbers indicate a standard part that can be requested from a store. If the part in question is a standard part that will be mass produced to be readily available in a store, the commodity or serial number needs to be shown on the drawing
Conclusion
Often times clients will have their own standard and general notes that they require to be on the drawings. When doing work for a client, request their drawing standards or discuss with the deign engineer what general notes needs to be on the drawing.
