Two cylinders with the same bore and stroke will look different, one being a welded cylinder and the other a tie rod cylinder. The differences go beyond appearances. How a cylinder handles pressure and how easily it can be serviced can impact how well it integrates with the machine it is paired with. Understanding this up front can help avoid re-design work.

Tie Rod Cylinder Design

Tie rod cylinders use tie rods to connect the end caps of the cylinder. The tie rods run along the barrel of the cylinder. Because the end caps of the cylinder are separate, the cylinder can be disassembled with ordinary tools. With seals being one of the main causes of friction loss in systems, the ability to easily swap seals can improve the efficiency of a system. This is one of the many reasons tie rod cylinders are favoured in factory systems.

Welded Cylinder Design

Welded cylinders get their name because the end caps of the cylinder are welded to the barrel, as are the mounts. A welded design results in a more compact cylinder that is able to handle higher loads. Along with having a smoother exterior, a welded cylinder is able to handle shock loads better. Welded cylinders are often found on the mobile equipment.

Strength and Size Comparison

Tie rod cylinders are usually rated for moderate pressures and are similar to standard industrial duty units. Welded cylinders can be designed and fabricated for greater strength to handle higher pressures and more rigorous applications, and provide a space saving design, as there are no tie rods protruding from the barrel. The trade-off is that a welded cylinder is more difficult to open for repair, requiring more careful planning with the selection of seals and the fluid system in order to minimize the potential for contaminant ingression into the system.

Comparison

When choosing between a tie rod cylinder and a welded cylinder, a machine designer generally has a few questions. Is it easy to service the machine or is the compact size more important? Will the cylinder be shocked and fielded? What is the operating pressure of the system? For typical applications and service, tie rod cylinders are less costly and more serviceable. For heavy duty and more compact designs, a welded construction is more applicable. It is beneficial to consult with the hydraulic cylinder manufacturer early in the design process, as often mounting styles, stroke, and the location of inlets and outlets can be tailored to the application, as opposed to designing a machine and trying to fit a catalog part.

Cylinder Life

Details such as the seal selection and a well-machined gland determine how long a cylinder lasts. Scoring of the rod can be minimized by the use of a hard chrome plate. A properly honed barrel or cylinder liner helps the seals to operate smoothly. Improper or poor alignment and side loading accelerate wear on even the best cylinder, and should be designed with equal consideration.

Working with a Supplier Who Builds the Product

Based in Coimbatore, India, Teutonic Engineering makes hydraulic cylinders in various constructions and builds custom cylinders to order. Using a single source supplier for the cylinder, seals and associated items such as power packs and valves helps ensure that a machine’s specifications remain consistent.

Final Thoughts

There are various points of view on the subject. Some advocate the use of welded cylinders while others favor tie rod construction. In choosing a cylinder for a machine, looking at the available space and the service plan as well as the duty cycle gives the machine builder a good chance to pick a cylinder to get the job done and keep it working.