A Hydraulic Cylinder is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke. It has many applications, notably in construction equipment, manufacturing machinery and civil engineering. There are primarily two styles of hydraulic cylinder construction used in industry. One type is called the tie rod style cylinder, and the other type is the welded style cylinder.
What is a Hydraulic Cylinder?
Hydraulic cylinders get their power from pressurized hydraulic fluid, which is typically oil. The hydraulic cylinder consists of a cylinder barrel, in which a piston connected to a piston rod moves back and forth. The barrel is closed on one end by the cylinder bottom side chamber.
What are Tie Rod Cylinders?
Tie rod style hydraulic cylinders use high strength threaded steel rods to hold the two end caps to the cylinder barrel. This method of construction is most often seen in industrial factory applications. Tie rod style cylinders can be completely disassembled for service. The National Fluid Power Association (NFPA) has standardized the dimensions of hydraulic tie rod cylinders. This enables cylinders from different manufacturers to interchange within the same mountings.
What are Welded Hydraulic Cylinders?
These cylinders have no tie rods. The barrel is welded directly to the end caps. The ports are welded to the barrel. The front rod gland is usually threaded into or bolted to the cylinder barrel. This allows the piston rod assembly and the rod seals to be removed for service.
Welded Hydraulic Cylinder Advantages
Welded hydraulic cylinders have some advantages over tie rod style cylinders. Welded cylinders have a narrower body and often a shorter overall length enabling them to fit better into the tight confines of machinery. Welded cylinders do not suffer from failure due to tie rod stretch at high pressures and long strokes. The welded design also lends itself to customization.
More Capabilities
Welded body cylinders dominate the mobile hydraulic equipment market such as construction equipment and material handling equipment. They are also used in heavy industry such as cranes, oil rigs, and large off-road vehicles in above-ground mining. The smooth outer body of welded cylinders also enables the design of multi-stage telescopic cylinders.
Limited Capabilities
Tie rod cylinders are less complex regarding design and has limited options regarding customizability. Tie-rod cylinders are “off-the-shelf” items. They come in fixed bore sizes and stroke lengths that can reduce one’s design options when developing new equipment. Tie rod cylinders are less durable than welded hydraulic cylinders.
