How to Measure a Hydraulic Cylinder?

Do you own a hydraulic cylinder? Taking measurements of various parts of a hydraulic cylinder is sometimes necessary. It can assist in finding a perfect replacement for your hydraulic cylinders.

Before you take the measurements of the hydraulic cylinders, you must know the various tools and instruments needed to measure them.

Today, we’ll discuss the various steps to measure the hydraulic cylinder and provide a detailed overview of the different aspects of measuring tools.

Tools required to measure a hydraulic cylinder

Measuring a hydraulic cylinder is only possible with the necessary measurement tools. Take a look at the detailed functionality of each tool listed below:

Calipers: Calipers are the measuring tools that calculate the diameters and dimensions of the different components. They often measure the piston rod diameters. Common examples include Digital or Vernier Calipers.
Measuring Tape: The measuring tape is a free-end tape that measures the length of the hydraulic cylinders. Users measure the stroke length along with the retracted and extended length of the cylinder.
Micrometer: Micrometers act as an accurate alternative tool to calipers. It gives more precise measurements regarding the outer diameters of the piston rod. They can be either digital or mechanical micrometers.
Thread Gauge: Thread Gauge can measure the thread size of the hydraulic cylinder. It helps understand the hydraulic cylinder connection sizes and types.
Bore Gauge: Do you want to measure the internal diameter accurately? A bore gauge goes into the cylinder barrel and measures its inner dimension directly.
Depth Gauge: A depth gauge can measure the depth of the seals and grooves in the cylinder. The analog or digital gauges can speed up the measurement process and fetch flawless measurements.
Dial Indicator: If you have any misalignment or irregular movements in the hydraulic cylinders, dial indicators show it instantly and provide better protection.
Pressure Gauge: For the hydraulic cylinder pressure measurements, you need the pressure gauge. It is a quick and efficient tool for verifying working pressure.
Protractor: The protractor helps with angle measurement for various purposes. For example, you can assess the mounting angles of the hydraulic cylinders.
Safety Tools: Keep your gloves and other safety tools ready. When measuring, you must wear them and do the measurements safely. Also, keep a note of your measurements in a handwritten diary.

Steps to measure a hydraulic cylinder

Step 1: Find out the Nameplate

The nameplate contains the data about the hydraulic cylinders. It can ease your tasks and deliver quick details about the hydraulic cylinders.

Take a thorough review of your hydraulic cylinder.
Look at its parts and components and validate if a nameplate is available.
Also, check online resources to know where the nameplate or hidden information lies.

What if there is no nameplate? Don’t get disappointed. Extensive physical measurements of each part will be taken in the following steps.

Step 2: Measure the Bore Diameter

The bore diameter is the inner diameter of the cylinder barrel. Note that while the piston operates inside the barrel, the piston diameter incorporates seal clearances and tolerance fits, so it should not be strictly confused with the raw barrel ID.

If the cylinder is not assembled: Measure the internal diameter of the barrel directly using an inside caliper or bore gauge.
If the cylinder is assembled: Measure its external diameter (OD), then subtract twice the wall thickness of the tubing from the measurements:

Bore Diameter = External Diameter − (2 × Tubing Wall Thickness)

For example, if the external diameter is 2.0 inches and each tube’s wall thickness is 0.5 inches, the overall bore diameter will be 2.0 − (2 × 0.5) = 1.0 inch.

You can assess standard industry tubing sizes in the table below:

Outer Diameter (OD)	Wall Thickness	Resulting Bore ID
2.00”	0.25”	1.50”
2.50”	0.25”	2.00”
3.00”	0.25”	2.50”
3.50”	0.25”	3.00”
4.00”	0.375”	3.25”

Step 3: Measure Rod Diameters

The cylinder rod is one of the most crucial parts of the cylinder. It exerts the force generated through the fluid movements. So, the wrong size or slight mistake can result in inaccurate measurements and incompatible rods that might cause accidents.

Technically, it is a straightforward task with the vernier or digital calipers. However, you can make your readings more accurate by using a micrometer.

Step 4: Measure the Retracted Length

The retracted length of the rod provides accurate measurements of the closed cylinder. You must first retract the cylinder rod completely and measure the length.

Measurement Reference: Always measure from center-to-center of the mounting pins (Pin-to-Pin Center). If flange mounted, measure from the mounting face to the rod end pin center.

Retracted length helps in the accurate replacement of the hydraulic cylinder assembly.

Step 5: Measure the Extended Length

The extended length of the rod is the same as measuring the retracted one except for one thing—you have to extend the rod fully.

Pull the rod out of the cylinder and take it to its maximum length. It is the highest extended length of the rod. Get your measuring tape and check the overall extended length of the cylinder using the same pin-to-pin reference points as Step 4.

Step 6: Calculate the Stroke

The stroke length of a cylinder is the overall measurement of the distance through which the cylinder rod travels.

To find the precise stroke length, calculate the difference between the extended and retracted lengths:

Stroke Length = Extended Length − Retracted Length

When equipment is non-functional: If your hydraulic cylinder is not installed, separate or move the rod to measure both extended and retracted pin-to-pin lengths. Minus the retracted length from the extended length to get the precise stroke.
When equipment is functional: If the hydraulic cylinder is installed, check if you have the manufacturer’s manual, or carefully measure the maximum exposed shaft travel distance during full operation.

Step 7: Understand the Rod End Style

Understanding the rod end style can sometimes be essential. There are many rod end styles, but you often interact with the three most common ones:

Standard Male
Standard Female
Intermediate Male

Measure the rod end style and examine the thread. For impeccable measurements, use a standard thread gauge and vernier caliper. Compare the measurements to the standards set by the NFPA.

Step 8: Know the Mounting Style

Since you have to mount a hydraulic cylinder, check its style. There are many styles of mounting the cylinders, but you should consider the following:

Flange Mounts
Side Lug Mounts
Pivot Mounts (Clevis / Pin)
Trunnion Mounts
Tie Rod Mounts

When replacing the cylinders, you have to consider the mounting options. Your replacement must have either the same or a compatible mounting option.

Step 9: Identify Your Hose Port and Location

Hoses are the channels that bring the fluid to the cylinder and help in simplified operations. Each port comes with thread connections.

Scan all your thread types and sizes before you deploy them in your hydraulic cylinders:

Hose Sizes

¼-inch
⅜-inch
½-inch
¾-inch

Thread Types

SAE (O-Ring Boss)
NPT (National Pipe Thread)
JIC (Joint Industry Council)

If the thread and cylinders are incompatible, you can’t fix them without an adapter.

Step 10: Environmental Impact

Treat the environmental factors, such as working temperature or dust control, as crucial. They can alter your findings or make your components incompatible. These factors are essential for choosing proper seal materials during replacement.

Step 11: Measure Working Pressure

The final step in the hydraulic cylinder measurements is the pressure rating. Usually, pressure is visible in the manufacturer’s manual guide or nameplate.

A standard-duty hydraulic cylinder typically operates at a pressure of 1,500 to 3,000 PSI. On the other hand, heavy-duty applications or jacks may reach up to 10,000 PSI or more. Ensure your replacement unit meets or exceeds the operating pressure rating of your system.

Key Features to Attend in the Hydraulic Cylinder Purchasing Attempt

Look at the Cylinder Type: Choose between Single-acting cylinders (one-way force), Double-acting cylinders (two-way force), or Telescopic cylinders (long stroke in confined spaces).
Consider Bore Size: Larger bore sizes yield higher surface area, directly increasing force output for a given pressure (F = P × A).
Check Operating Pressure: Match the rated working pressure to your system output to prevent potential structural or seal failures.