bolt
chemical
chemistry
clean
clear
closed
color
connection
connector
construction
control
crane
distribution
energy
engineering
equipment
factory
flowing
gas
gear
horizontal
image
indoors
inoperative
instrument
looking
metal
natural
optical
part
physical
pipe
pipeline
power
pressure
pump
repairing
reserve
screw
steel
structure
surveillance
technology
tube
tubing
valve
view
watching
yellow