background
bolt
chemical
chemistry
color
connector
construction
control
design
element
engineering
equipment
faucet
fitting
flat
fuel
gas
gasoline
gauge
icon
illustration
industrial
industry
isolated
line
metal
meter
oil
petrol
petroleum
pipe
pipeline
piping
plumbing
pressure
pump
refinery
set
sewage
sewer
sign
steel
supply
symbol
tap
technology
tube
valve
water