blue
chemical
cold
concept
conduit
construction
delivery
distribution
drain
ecology
energy
engineering
equipment
factory
faucet
flue
gas
gasoline
gate
hot
hydrant
industrial
industry
isolated
oil
petrol
petroleum
pipe
pipeline
piping
plant
plumb
plumbing
power
processing
red
refinery
sanitary
sewerage
stopcock
supply
tap
transit
transmission
tube
tubing
two
valve
water