The hydraulic cylinder seal kit prevents leakage and contamination, which helps prevent malfunctions. As a worn and torn part, they need to be replaced regularly. While the OEM seals can be expensive, how can to make sure you find a matchable one at a low cost? This guide will introduce three different methods so that you can deal with different situations.
What are Seal Kits Used for in the Hydraulic Cylinder?
Suppose a hydraulic cylinder is the muscle of your machine. In that case, the hydraulic cylinder seal kit is the intricate system of veins and ligaments that allows the muscle to function powerfully and without failure. Seals are subjected to immense pressure, constant movement, and extreme temperatures, making them high-wear, consumable parts that inevitably require replacement.
Hydraulic Cylinder Seal Kit’s Main Functions
- Preventing Leakage: This is the most obvious job. Seals stop high-pressure hydraulic fluid from escaping. This includes preventing external leaks and, just as importantly, internal leaks. An internal leak is the reason a cylinder can become weak or unable to hold a load, even with no visible dripping.
- Preventing Contamination: Seals also act as a barrier to the outside world. They stop dirt, dust, water, and grime from entering the hydraulic system as the piston rod retracts. This is critical, as contamination is a leading cause of premature failure for pumps, valves, and other expensive hydraulic components.
Types of Seals
A standard seal kit contains several types of seals, each with a specific job. To get a full overview of all the parts inside a cylinder, you can check out our detailed guide to hydraulic cylinder components. The most common seals you’ll be replacing include:
- Piston Seals: Located on the piston head, these are crucial for creating a pressure-tight chamber. They prevent fluid from bypassing the piston, allowing the cylinder to generate force and hold its position.
- Rod Seals: Found in the cylinder head (gland), these are the primary defense against external fluid leaks. They seal against the moving piston rod, keeping the hydraulic fluid inside the cylinder.
- Wiper Seals: As the first line of defense against external contaminants, the wiper seal is installed at the very end of the cylinder head. It acts like a squeegee, scraping dirt, mud, and moisture off the piston rod before it can be drawn into the cylinder.
- Wear Rings / Guide Rings: These low-friction bands are essential for preventing metal-on-metal contact between the piston and the cylinder bore, and between the rod and the cylinder head. They provide stability, absorb side loads, and extend the life of both the cylinder and the seals.
- O-Rings and Backup Rings: These are typically used for static sealing applications, such as sealing the connection between the cylinder head and the cylinder barrel. Backup rings are often used with O-rings in high-pressure situations to prevent the O-ring from being extruded into gaps.
3 Ways to Find the Right Seal Kits
Matching a hydraulic cylinder seal kit is far more complex than matching a bolt—a tiny difference in size or material can lead to complete failure. To eliminate guesswork, follow these methods, ranked from most to least reliable.
Method 1: Source by Part Number
This is the most accurate and highly recommended method. A part number match is a trustworthy fit.
Find the Part Number on the Cylinder Itself:
Inspect the body of the hydraulic cylinder for a metal nameplate, tag, or stamped number. This plate will typically list the manufacturer, a model number, and most importantly, a Part Number (P/N). Provide this number to your parts supplier. With this information, the team at FridayParts can identify the exact seal kit required with 100% certainty.
Find the Part Number from Previous Repairs:
If you or your mechanic has serviced the cylinder before, you might have the old packaging for the last hydraulic cylinder seal kit. The part number printed on that box or bag is your direct ticket to ordering the correct replacement.
Method 2: Source by Equipment Information
If you can’t find a part number on the cylinder, the next best approach is to use the information of the machine it belongs to.
Provide Detailed Equipment Information:
To do a successful lookup, you need to provide your parts expert with the following:
- Equipment Make: e.g., Caterpillar, Komatsu, John Deere, Bobcat, etc.
- Equipment Model: e.g., 320D (Excavator), D6R (Dozer), 580M (Backhoe).
- Equipment Serial Number (PIN/VIN): This is the most critical piece of information! Manufacturers often make mid-year changes or use different cylinder suppliers for the same machine model. The serial number is the only way to confirm the exact configuration of your specific machine as it left the factory.
- Cylinder Function: Tell the supplier which cylinder on the machine needs the kit. For example: “It’s the bucket cylinder on my Komatsu PC200.” Other examples include the boom, stick, blade lift, or steering cylinder.
Armed with this data, a professional parts supplier like FridayParts can cross-reference OEM databases to pinpoint the correct seal kit for your machine’s serial number.
Method 3: Source by Size
This method is complex, time-consuming, and carries a high risk of error. It should only be used when the first two methods are impossible. Precision is everything, so you must use a precision measuring tool like a digital or dial caliper—a tape measure will not be accurate enough.
Disassemble the Cylinder and Measure Key Dimensions:
Before you can measure anything, you’ll need to take the cylinder apart. If you’re new to this process, our complete guide on how to rebuild a hydraulic cylinder provides a detailed, step-by-step walkthrough. Once it’s apart, you’ll need to measure:
1. Bore Diameter: The inside diameter of the cylinder barrel. You can measure the outside diameter of the piston to get this.
2. Rod Diameter: The diameter of the piston rod that moves in and out of the cylinder.
3. Measure the Seals Themselves: Carefully remove every seal from the piston and gland, laying them out in the order they were removed. For each seal, you need to:
- Measure its Inner Diameter (ID), Outer Diameter (OD), and Height/Thickness.
- Take clear photos of each seal’s cross-section (profile). A U-cup seal has a different profile and function than a V-ring, even if their basic dimensions are similar.
Provide these precise measurements and photos to a specialized seal supplier.
A Strong Warning: Measuring old, worn seals is inherently risky. A compressed or shrunken seal will not give you an accurate dimension. A small measurement error or misidentification of a seal profile will result in a kit that doesn’t fit or fails immediately.
Summary
You can apply the following steps:
- First Choice: Always try to find the Part Number directly on the hydraulic cylinder.
- Second Choice: Use your machine’s full Model and Serial Number to have a professional parts supplier find the kit for you.
- Last Resort: If all else fails, perform highly precise measurements of the cylinder and the old seals, ideally with guidance from a hydraulics expert.
Don’t guess or settle for a “close enough” kit. The integrity of your hydraulic system is too important.
Stop the guesswork and avoid costly downtime. Whether you have a part number or just your machine’s serial number, the experts at FridayParts are here to help you find the exact seal kits you need, fast. Contact us today and get your machinery back to earning its keep.
