How to Choose the Right Hydraulic Seal Kit for Your Equipment

Everything wears out over time. It’s a fact. Even software wears out and requires updating and occasionally cleaned of contamination and bugs. The same is true for each component of a hydraulic cylinder, down to the seals. If you own or work in a hydraulic cylinder repair facility, operate a mobile hydraulic repair service, or are the repair technician in a manufacturing facility that uses hydraulic cylinders, then you are critically aware of this fact.

The good news is that if you know the symptoms of worn seals, you can know just when to change them. Fortunately, there are hydraulic seal kits available for most makes and models of hydraulic systems that you may have. However, not all hydraulic seal kits are equal. For this reason, you must know what to look for in a hydraulic seal repair kit. This blog post will tell you the questions to ask and the answers you need to find.

Looking for the right seal replacement kit for your hydraulic cylinder? Ask the experts at CRC Distribution.  

The Role of Seals in the Hydraulic System 

For the purposes of this article, we will be discussing the dynamic seals in your hydraulic system. Before we get into it, here’s a quick refresher on the two different types of seals.

Static Seals

Static seals are the seals between components that are not in motion, like the cylinder bore and the end cap. This is a static joint. It doesn’t move. Static seals tend to last a long time.

Dynamic Seals

Dynamic seals are seals that move against another component. The seals in a piston, contained within a machined groove, move up and down the cylinder bore under the force of hydraulic fluid. They form the barrier between the outer diameter (OD) of the piston and the inner diameter (ID) of the cylinder bore. There are also rod seals contained within the gland, which are stationary. Under pressure from the fluid in the cylinder, the rod moves up and down against the rod seals. In both cases the seals prevent fluid and pressure from escaping the pressurized chambers in the cylinder bore.

The Importance of Regular Hydraulic Cylinder Repair

In terms of items on a hydraulic cylinder that wear, seals have one of the shorter lifespans. Most other components are made from machined steel or other durable materials. Seals are made from pliable materials, mostly thermoplastics and rubber. They serve as barriers, containing the enormous pressures that build up inside the hydraulic cylinder– sometimes as much as 10,000 PSI. Seals often fail before other components, in part due to the tremendous stress they experience and in part due to their less durable nature.

With this in mind, you should perform hydraulic cylinder inspection and maintenance regularly, paying special attention to seals. Failure to detect and replace worn seals typically results in one of two things happening:

Loss of Pressure, Power, and Efficiency 

Decreased hydraulic pressure will eventually affect the quality of whatever process the system is powering. The large hydraulic cylinders that raise and lower the blade or bucket of a bulldozer carry heavy loads of soil or rocks. If those cylinders have worn seals, the ability of that bulldozer to carry or move material is compromised. Failure could even endanger lives. Other industrial applications, including marine, transportation, aerospace, aviation, etc., all rely on reliable, consistent hydraulic power to move components, open gates, lower and raise landing gears, and activate other processes.

Risk of Damage to Other Components

A worn seal will eventually fail, allowing direct contact between the piston and the cylinder, or the rod and the gland holding the rod seal. At this point run the risk of scoring surfaces beyond repair. Parts might even seize and become immobile. Failure to replace worn seals can jeopardize the entire hydraulic cylinder assembly, with the potential to render it unusable.

Unsure about whether a seal kit can help solve your hydraulic cylinder problems? Contact CRC Distribution and ask our experts.

How to Tell If You Need New Hydraulic Seals

There are a few signs to look out for which may indicate that you need to inspect and replace your hydraulic seals.

Visible Leaks

A specific type of leak called “weeping” occurs at the front of the cylinder bore where the rod comes out on its downstroke. In outdoor applications and factory environments with debris and manufacturing dust, this leaking fluid will attract these loose particles and the assembly will become very dirty. This is an obvious sign that it may be time for a seal repair.

Gradual Loss of Hydraulic Pressure

Often, the loss in pressure is gradual and, at first, unnoticeable. If part of your hydraulic maintenance program involves a regular system pressure check, you will see this gradual pressure loss in your records. If you don’t do regular pressure checks, you are unlikely to notice this pressure loss until processes slow down to the point that operation is unsustainable.

Worn seals can also cause undue wear on pistons, cylinder bores, glands, rods, and other components. The damage to the seal could potentially come from metal shavings that get into the cylinder and work their way into a position where they can damage the seals, the piston's OD, or the bore's ID. Sudden events such as pressure spikes and power failures can also damage seals.

Inconsistency or Jerking Movements 

Another indicator that the seals are either worn or damaged is when the hydraulic system starts behaving erratically, characterized by jerking or inconsistent movements. This results in a loss of power or a lack of precision in whatever action your hydraulic system is powering. A well-functioning hydraulic system should run smoothly.

OEM Recommendations

Be careful to read any documentation that comes with your hydraulic system regarding maintenance. The manufacturer may have recommendations on seal replacement. It is best to follow these guidelines. Failing to do so may void all or part of the warranty on the system.

Piston Seals and Gland Seals 

There are two different areas where seals need to be monitored and sometimes replaced: piston seals and gland seals.

Piston Seals

The piston travels up and down the cylinder bore, creating pressure and driving a specific process. Although it looks like a tight fit, the piston never comes into contact with the bore. That minuscule space between the piston and the cylinder bore is filled and cushioned by the piston seal. Remember, the seal does two things:

• It keeps the piston and cylinder bore from making contact.
• It prevents hydraulic fluid, now under immense pressure, from escaping between the bore and the piston. Escaping fluid translates to escaping pressure.

There is a primary seal and often a secondary seal to provide added protection. On either side of the primary seal are guide rings, also known as wear rings. These rings support the piston in the cylinder bore, keeping it in the ideal position.

Gland Seals

Attached to the piston is a rod that transfers the power generated in the hydraulic process. The hydraulic gland assembly threads onto the front cap of the hydraulic cylinder tube and supports the rod as it moves back and forth, transferring the power. Like the piston and the cylinder bore, the clearances between the gland and the rod are very close. The inner diameter of the gland also has a machined groove, which contains the gland seal that prevents hydraulic fluid from leaking through (remember, lost fluid equals lost pressure). As with the piston, there are also wear rings that support the rod and limit lateral movement. In many cases, there is also an exterior seal, called a scraper seal, that is part of the gland assembly and scrapes or cleans debris from the exposed rod surface as it retracts back into the hydraulic cylinder.

Selecting the Right Hydraulic Seal Kit

One of the tasks in replacing seals is determining that you have the best hydraulic seal kit available for your particular cylinder. Once you have determined that the seals in your hydraulic system need replacing, you should consult the owner’s manual to verify the specifications of the seals. Here are some things to look for as you evaluate your options:

Meets OEM Specifications

The original equipment manufacturer will often have hydraulic seal kits and gland kits available. Engineers designed the hydraulic system for a specific purpose, including the seals. The replacement seals need to meet the exact specifications as the factory-specified ones. Ensure that the components in the hydraulic seal kit meet those specifications, especially if the kit is not from the OEM. Failure to use OEM-approved hydraulic seal kits could also jeopardize any warranties in effect.

Dimensions

The components in hydraulic cylinders are machined to critical tolerances. In order for the seals to perform as intended, they must also meet these critical tolerances. Many hydraulic cylinder seals are so exact that they are machined using CNC spindles.

Material Compatibility

There are many materials used for hydraulic seal kits that can operate in temperatures ranging from -128° - 260°C. Be sure to match the material with your application. Be careful to also ensure that the replacement seal material is compatible with the hydraulic fluid in the system.

Components Included in The Kit

Disassembly of a hydraulic cylinder is a challenging task. If you must replace a seal, it is prudent to replace them all—primary seals, secondary seals, wear rings, wiper seals, scraper seals, and anything else. Ensure that the hydraulic seal kit you purchase is as complete as possible.

Seal Profile

Depending on their application, seals have different profiles, including U-seals, O-rings, V-rings, and others. Ensure profiles in the hydraulic seal kit match those specified by the OEM.

Do You Always Purchase Hydraulic Seal Kits from The OEM?

Sometimes this is not possible. Your hydraulic system may be custom designed or is a discontinued but still functional model. Many specialty seal manufacturers can provide the hydraulic seal kits you require as long as you can give them the correct specifications and dimensions.

Searching for an OEM-approved seal replacement kit for your hydraulic cylinder? Find out how CRC Distribution can help.

Tips on Installing New Replacement Seals

Just as important as using the correct seal replacement kit, it is also essential to install the seals correctly. Here are some guidelines:

• Cleanliness. Ensure all work areas, tools, and replacement rings are free of dirt, debris, or dust. Any of these contaminants, trapped in the ring groove or gland, can cause problems during operation. Always use clean, lint-free cloths.
• Lubrication. A lubricant is a handy tool for aiding installation, allowing seals to go on easier. Ensure the lubricant is compatible with the seal material. Wipe away any excess lubricant as part of your clean-up.
• Heat. Soaking the seal in hot lubricant will soften it and make it more pliable and easier to install. Be sure to use a lubricant that is compatible with the seal material. It’s also important not to exceed the temperature limits of the material. Do not place a seal in a microwave oven in an attempt to make it more pliable. This can render the seal unusable.
• Tool selection. Use tools carefully, and protect against creasing or nicking seals during installation. Consider using a cloth installation strap to help pull the seal over the piston and into the seal groove. This installation ensures you don’t inadvertently score the piston or cylinder bore. Measurements should be taken with a micrometer or other precision device before and after installation.
• Double check. Double check all your work. Fittings should be snug. Take care to reassemble all parts correctly and torque fasteners to factory specifications. It’s also a good idea to purchase extra hydraulic seal kits for emergencies.
  
  

Always Use Caution When Working on Hydraulic Cylinders

Hydraulic cylinders can vary greatly in size. Some are large and heavy enough that repair facilities must use larger overhead crane assemblies to safely move them around the shop floor. The end caps on these cylinders are often torqued to 50,000 ft./lbs.

CRC Distribution carries workbenches and other tools designed specifically for hydraulic cylinder repair. This equipment helps make it easy, safe, and efficient to work on even large cylinder assemblies.

Work With a Trusted Source for Seals

Ensure that your source is a reputable firm that can supply you with the correct hydraulic seal kit and valuable information on how to install the seals correctly. CRC Distribution has been serving the hydraulic industry in North America for more than 25 years. We carry a complete line of seals and seal replacement kits. We also maintain the technology, materials, and knowledge to manufacture replacement seals for all your hydraulic machinery, systems, and needs.

Contact CRC Distribution about the best seal replacement kit for your hydraulic cylinder.