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