MIL-STD Welding and Maintenance Procedures Overview

Purpose of MIL-STD-22D

To standardize welded joint designs used in military fabrication.

Five basic types of joints

Butt, corner, edge, lap, and tee joints.

Groove weld

A weld made in a groove between the workpieces.

Fillet weld

A triangular cross-section weld joining two surfaces at right angles.

Backing strip

Supports molten metal during welding and ensures full penetration.

Weld reinforcement

Extra weld metal above the surface to increase strength.

Full penetration weld

Where maximum strength is required.

Partial penetration weld

Does not extend through the full thickness of the joint.

Field weld symbol

A flag on the reference line of the weld symbol.

Bevel groove weld

A weld in a joint with one side beveled.

Square groove weld

A groove weld with no joint preparation.

Root opening

The separation between workpieces at the bottom of the joint.

Flare bevel weld

Used on a round and flat piece, like a pipe to a plate.

Tail of a weld symbol

Contains welding process or supplementary information.

Contour symbol

Desired shape of the finished weld (convex, concave, flush).

Weld all-around indication

By a circle at the intersection of the arrow and reference line.

Throat of a weld

The shortest distance from the root to the face of the weld.

Leg of a fillet weld

The distance from the root to the toe of the weld.

Weld size in a fillet weld

Usually the leg length or throat dimension.

Slot weld

Fills an elongated hole in one piece to join it to another.

Plug weld

Fills a round hole in one part to fuse it to another.

J-groove weld

A groove with a single curved edge.

U-groove weld

Both sides of the joint have curved edges.

Joint fit-up

How parts are aligned and spaced before welding.

Importance of joint design

It affects weld strength, accessibility, and distortion.

Flare V-groove

Weld between two rounded surfaces.

Intermittent welding

Welds with breaks between segments.

Pitch in welding

The center-to-center spacing of intermittent welds.

Scarf joint

A long taper on both pieces for welding.

Corner joint

Two parts meet at approximately 90° forming an L.

Lap joint

One piece overlaps another.

Arrow side on a weld symbol

Weld is made on the side the arrow points to.

Other side in welding

Weld is made opposite of the arrow.

Combination weld

Uses more than one type of weld or joint.

Compound joint

Two or more joint types in one weld area.

Role of prequalified joints

Ensure joint design meets tested and approved standards.

Common cause of poor weld strength

Improper joint design or preparation.

T-joint

Two parts intersect at 90° in the shape of a 'T'.

Unequal leg fillet welds

When different thicknesses or load directions exist.

Welding position notation

It's usually noted in WPS or detail drawings.

MIL-STD-1627C

Standard procedures for corrective maintenance tasks.

Corrective maintenance

Actions taken to fix equipment after a failure has occurred.

Corrective Maintenance Task (CMT)

Steps, resources, personnel, and time estimates.

Standardizing maintenance procedures

To improve efficiency, safety, and consistency.

Task analysis in maintenance

To define what needs to be done and how long it will take.

Approval of maintenance task procedures

Engineering or QA authorities.

Maintenance documentation

Steps taken, materials used, time, and personnel involved.

Critical maintenance task

A task essential for mission capability or safety.

Task prioritization

By urgency and effect on system operation.

Tools used in task verification

Checklists, QA forms, and performance tests.

Importance of clear task sequencing

To prevent errors and ensure task flow.

'As-found condition'

The state of equipment before corrective action.

'As-left condition'

The state of equipment after maintenance is complete.

Role of the maintenance planner

To ensure all resources and steps are available for the task.

Task performance evaluation

By comparing outcomes to standards and time estimates.