NSTM 074 and NAVSEA 505 Welding and Piping Overview

Purpose of NSTM 074 Vol 1

To provide Navy guidance for welding processes and inspection.

Common welding processes covered

SMAW, GTAW, GMAW, and FCAW.

SMAW

Shielded Metal Arc Welding.

GTAW

Gas Tungsten Arc Welding.

GMAW

Gas Metal Arc Welding.

FCAW

Flux-Cored Arc Welding.

Preheat

To reduce the risk of cracking and improve fusion.

Interpass temperature

Temperature maintained between successive weld passes.

Post-weld heat treatment

To relieve residual stresses and improve properties.

Porosity in welds

Trapped gas from contamination or improper shielding.

Undercut

A groove melted into the base metal next to the weld.

Preventing undercut

Use proper technique and reduce travel speed.

Slag inclusion

Nonmetallic solid trapped in the weld metal.

Importance of proper joint fit-up

To ensure penetration and strength.

Filler metal selection

To match base metal properties and service conditions.

Common weld positions

Flat, horizontal, vertical, and overhead.

Welder's qualification test

A test to verify skill in producing sound welds.

Welder requalification

If they haven't welded in 6 months or fail inspection.

Weld bead appearance

Surface shape and smoothness of the weld.

Safety equipment for welding

Helmet, gloves, apron, and eye protection.

Ventilation importance during welding

To prevent exposure to harmful fumes and gases.

Hot work

Any activity involving open flame or heat-producing equipment.

Precautions for hot work

Fire watch, fire blanket, and gas-free certification.

Weld inspection methods

Visually and using NDT methods like PT, MT, and RT.

PT inspection

Liquid Penetrant Testing for surface cracks.

MT inspection

Magnetic Particle Testing for surface/subsurface flaws in ferromagnetic metals.

RT inspection

Radiographic Testing using X-rays or gamma rays.

Documentation required for welds

WPS, welder qualifications, inspection reports.

Weld reinforcement

Excess material above the base metal surface.

Crater in welding

A depression at the end of a weld bead.

Avoiding a crater

By backfilling before arc termination.

Weld cleaning necessity

To remove slag, spatter, and contaminants.

Incomplete fusion causes

Improper technique or low heat input.

Handling a weld defect

Documented, evaluated, and repaired if needed.

NAVSEA 505

Design, installation, and testing of shipboard piping systems.

Class I piping systems

Vital to ship safety and require highest level of control.

Class II piping systems

Less critical systems but still important for operations.

piping run

A continuous stretch of pipe between two connection points.

expansion loops

To absorb thermal growth and reduce pipe stress.

proper pipe support spacing

To prevent sagging, vibration, and failure.

hydrostatic testing

Testing a system with pressurized water to check for leaks.

pneumatic testing

Testing using air or gas when water cannot be used.

pneumatic testing usage

For systems where water introduction is not acceptable.

pressure testing requirements

All joints must be complete and visually inspected.

brazed joints

Used in copper-nickel or copper systems.

pressure class marking on flanges

Class rating such as 150, 300, etc.

pipe hanger

A device that supports and secures piping.

riser in piping

A vertical segment of pipe.

reducer

To connect pipes of different diameters.

pipe schedule significance

Defines the wall thickness of the pipe.

elbows

Used to change direction of piping.

gate valves

To start or stop flow; not for throttling.

check valves

To allow flow in one direction only.

documentation for piping systems

Installation drawings, test reports, and material certs.

primary concern with Class I systems

Preventing catastrophic failure under operational stress.

cleaning piping systems

They must be flushed and cleaned before testing or service.