Does your excavator lack the power to lift spoil, does your snow plow drop under its own weight, and is there a puddle of oil growing under your machine? Hydraulic cylinders are the true "muscles" of the system, performing the heaviest mechanical work. Due to the immense forces they encounter, they are subject to natural wear and tear or mechanical damage.
Buying a new cylinder or selecting seals for its regeneration requires precision. BRhydraulic experts have prepared a complete guide that will help you accurately measure your cylinder and avoid the most expensive ordering mistakes.
1. Three dimensions you must know (Piston, Rod, Stroke)
When ordering a replacement, it's not enough to just provide the "overall length." For the new cylinder to fit and have the correct force, you must measure three key parameters with a caliper:
-
Cylinder bore diameter (Piston diameter): Please note – do not confuse this with an internal combustion engine! In power hydraulics, the bore diameter (e.g., 100 mm) refers to the internal diameter of the tube (i.e., the diameter of the piston itself, hidden inside). This dimension is responsible for the pushing force. If you cannot disassemble the cylinder, simply measure the outer diameter of the tube – usually, the wall thickness is 5 to 10 mm.
-
Piston rod diameter: This is the shiny, extending element (chromed rod). You can easily measure it from the outside. The rod diameter determines the pulling force and the cylinder's resistance to buckling (bending) under heavy loads.
-
Cylinder stroke: This is the difference between the fully retracted and fully extended cylinder. In other words, it is the length of the "shiny" part of the piston rod that extends from the tube during a full working cycle.
2. Retracted length and mounting types
Once you have determined the forces and stroke, the cylinder must physically fit into the machine's frame. The key parameter here is the retracted length, most often measured from the center-to-center of the mounting holes.
Be sure to pay attention to the mounting type. In agricultural and construction machinery, we most often encounter:
-
Eyes with spherical bearings (GE): These allow for minor compensation of lateral play and protect the piston rod from bending.
-
Clevis mountings: Common in smaller precision cylinders.
-
Flanges: Used in industrial presses for rigid attachment of the cylinder to the frame.
3. Where do failures come from? (What to avoid)
Cylinders most often fail for two reasons:
-
Scratched piston rod: If deep scratches appear on the shiny surface, the damaged chrome will "cut" the seals with each retraction, causing leaks. In such a case, merely replacing the seals will only help for a few days.
-
Transverse forces: A cylinder is designed exclusively for linear operation (pushing and pulling). If the machine's mechanism is worn and lateral stresses occur, the piston rod will bend or seize in the gland.
Summary and free tool
Replacing a cylinder with a new one of identical dimensions guarantees that the machine will regain its former power. In the BRhydraulic.eu online store, you will find a wide selection of standardized double-acting cylinders for agricultural, construction, and industrial machinery.
Are you wondering how much force (in tons) your new cylinder will push with at a given operating pressure? To simplify and automate these calculations, we have made an application available to our customers here: hydraulic calculator
