Oil well pumps are downhole equipment for pumping oil. The liquid it sucks contains sand, wax, water, gas and corrosive substances, and it works underground at hundreds of meters to thousands of meters, and the internal pressure of the pump may be as hig
Frame scaffold first appeared in the United States in 1946, the main form for the door and ladder, with installation disassembly is simple, safe and reliable performance, economic benefit is remarkable, and many other advantages.