Become the Hydraulic Cylinder Expert By Learning its Nitty-Gritty

The hydraulic cylinder is an intricate yet heavy-duty system. The significant applications of hydraulic cylinders are in material handling machines like crane, trucks, and agricultural machines like transfer stations, road sweepers, trucks etc. They also get used in general industrial devices such as drilling equipment, roof bolters, underground vehicles, and so on. If you use equipment based on the hydraulic system, then it helps if you have an adequate understanding of the system. So, keep reading this blog to explore the nitty-gritty of hydraulic cylinders.

Since hydraulic cylinder performs heavy and loaded tasks, they work with high pressure. But, such high pressures are subject to change with each cylinder. PSI is a unit to measure pressure, and it stands for Pressure per Square Inch. Generally, any system that exceeds the operating pressure of 1K PSI falls under high-pressure systems. 6K PSI is the more general interpretation of high pressure, and the same will get considered for discussion, further in this blog.

1 – Design of the cylinder

A designer may produce a cylinder with specific ideas for each unit, like what functions the unit will do and how it should get performed. But when an operator starts using the machine, he/she may use it in a completely different way that may lead to the machine’s under-performance. Below are some cylinder design considerations.

• A cylinder may need load-holding valves. Counterbalance and pilot operated check valves hold the cylinder in a position, but they can impose extra load on cylinder’s components. With back pressure on the pilot port, the load holding valve setting will increase.
• The speed of the cylinder and the flow going into it should get considered while deriving port and plumbing size. Speed also helps determine if cushion designing is necessary.

2 – Interface between rod and piston

The interface between rod and poison is the most challenging to manage for many. The bore of the cylinder and rod’s diameter often get decided from a lower-pressure design. If the fastener or an interface area is tiny, then it may lead to premature failure of the interface.

When a cylinder has a short stroke and doesn’t have extreme side loads, then it should at least have a pilot-operated check valve firmly attached to the barrel. It will prevent the load from dropping even if the hose to the cylinder gives up. Operators may operate the grapple so that the hydraulic cylinder bears high extension forces while acting against threads.

3 – Cylinder components

You are likely to pay attention to the interface between rod and piston and ensure that it is robust. Also, the materials used for rod and piston should have adequate strength. Ideally, the barrel needs to get engineered using a material that has excellent yield strength, adequate weld-ability, and impact bearing capabilities. It’s mandatory if you want to use the cylinder at lower temperatures.

Other essential aspects to consider are head gland attachment and welding procedure. The most reliable design of the head gland attachment is the one that is capable of handling maximum load when extended by pressure and the highest stopping load too.

4 – Sealing

Choosing the material for sealing and guiding the rod and the piston is perhaps the most challenging part of the high-pressure hydraulic cylinder. A cylinder that gets employed at off-highway equipment is prone to high-pressure during operation, which may shorten seal life. The right use of step-cut or lap-cut wear rings, zero-split wear rings are a better alternative than buffer seals.

The pressure-velocity value of the sealing material is also vital while doing high-pressure sealing. Each sealing material will have a unique PV value following various contacting materials.

5 – Assembly

While you are assembling components of the cylinder, keep in mind to use oils and greases that are contact-friendly with the hydraulic fluids in the machine. It would help if you did not go for materials that have mineral-based additives and thickeners.

When you want to redesign the cylinder to be able to handle working pressures, then you can use FEA or similar tools to reverse-engineer faulty components and pass new designs. Note that component design, the material used, and the assembly method that worked for 5K PSI will not necessarily give quality results at 6K PSI.

To summarize

The most critical dimensions of a hydraulic cylinder are a design of the cylinder, rod to piston interface, cylinder components like head gland attachment, sealing and finally, assembling. You can have a closer look at each of these aspects by reading the information mentioned in this blog. It will help you understand the hydraulic system better and enable you to locate its problem and derive solutions as well.