3d
abstract
background
blueprint
chemical
connection
design
drawing
engineering
engineering drawing
equipment
facility
factory
faucet
fitting
fuel
furnace
gas
heavy
illustration
industrial
industry
large
line
machinery
metal
oil
orthography
outline
perspective
pipe
pipeline
piping
plant
plumbing
power
pressure
silhouette
sketch
steel
symbol
technology
tube
tubing
valve
wire frame
wireframe