Question 1

What are the most common causes of hydraulic system failure?

Accepted Answer

There are many reasons that could cause a hydraulic system to break down, many of which are preventable if carefully monitored. Here we take a look at some of the signs and symptoms of hydraulic failure.

Fluid contamination

One of the main reasons hydraulic systems fail is due to fluid contamination. Whatever the type of fluid being used, if it becomes contaminated with any dust, dirt, or moisture, this can reduce the pumps ability to control system pressures. This in turn, can lead to overheating or a build-up in the system that causes the parts to seize and fail.

Always ensure that the different components and fluids are clean and fit for purpose before use, to prevent failure from occurring.

Poor or irregular maintenance

Servicing is vital to keep a system running smoothly. It is important to ensure that the system’s oil and filters are changed appropriately. Poor or irregular maintenance could cause the system to become contaminated, increasing wear on the pump and associated equipment.

The suction hose between the tank and pump also needs to be in good condition and replaced if any sign of wear.

It is good practice to inspect a hydraulic unit regularly, checking the oil levels, cleaning up any spillages and reporting any defects immediately.

Misuse and human error

It is imperative that proper instruction and training is given to anyone that is using an application operated by a hydraulic system. Faulty installation, using incompatible parts or improper usage are all major factors that can cause failure.

Environmental & operating factors

Temperature and working conditions all have an impact on the system.

The power unit needs be housed or operated in a well-ventilated area, so that the oil coolers are kept free from dust and contamination.

Is the application operating in high temperatures? If so, close attention will need to be given to the type of fluid used and specialist seals will need to be installed, in all applications. Always avoid using mineral based oils in high temperature applications, these are refined from crude oil and have a flash point, which means that they will ignite at a certain temperature.

If the application is operating in cold environments, a tank heater may need to be installed, in order to maintain the fluid viscosity. Hydraulic fluid that is too thick or too thin can cause damage to the system.

Aggressive working conditions can also put strain on a system, leaving it vulnerable to failure. External shocks and vibration can cause surging and cavitation between the tank and the inlet of the pump. This can be avoided by properly mounting the power unit on special anti-vibration units.

The hydraulic tank also needs to be mounted higher than the pump and kept as close together as possible.

No matter what the application, hydraulic system failure is inevitable at some point. However, issues can be avoided if you ensure that you regularly follow all maintenance procedures and make certain that the appropriate components are installed or replaced correctly. If you are unsure of anything, don’t be afraid to call on your industry peers or hydraulic professionals for their help and advice.

Question 2

How Do Hydraulic Seals Work?

Accepted Answer

Seals are essential to fluid power engineering, as they prevent a fluid or gas from passing between the different components of a hydraulic cylinder.

Dynamic (used when parts are in motion) or static (fixed application), different types of seals, each have their own role to play, in ensuring a cylinder runs as smoothly as possible.

Our quick guide below shows the main types of seals that you would find in a cylinder and describes how they operate.

Wiper Seals

Wiper seals or Scraper seals are designed in a way to keep external contaminants out of a hydraulic system, by cleaning the rod in the cylinder on each cycle.

Rod Seals

Also known as Gland seals, Headbush or Neck Seals, Rod seals act as a pressure barrier to maintain and regulate the operating fluid in a cylinder. They can seal the pressure from one side (single-acting) or from both sides (double-acting). Rod seals are key in preventing corrosion.

Static Seals

These are used to create a seal between fixed components. The full range of static seals include o-rings, back-up rings, flange seals, bonded washers and OP seals.

Piston Seals

Piston seals are important for controlling the motion of a cylinder. It creates a barrier for dynamic pressure between the piston and the cylinder, preventing fluid from passing the piston and allowing the cylinder to extend and retract.

Guide Rings

Guide rings also known as bearing rings, stop metal-to-metal contact between two dynamic cylinder components. This is crucial in the prevention of damage to the two moving surfaces.

The right seal for the job

When selecting the best seals for your hydraulic ram, both at OEM or repair stage, it’s important to consider the parameters of the application and the operating conditions.

High pressure, medium used, extreme temperatures, aggressive chemicals, working environment and legislation standards will all have an impact on the chosen material of seal.

Over time however, it is expected that hydraulic seals will eventually need replacing, this can be down to general wear and tear, improper installation or exposure to extreme elements.

Most replacement seals, for most applications can be found off the shelf and seal kits for well known applications can be picked up easily.

If you require any further advice regarding seals and their applications, the team of experts at FPE Seals can help you source what you need.

Can’t find what you’re looking for? We can also custom-manufacture a full range of seals, in a full range of materials to meet your exact requirements.

Contact us today

Question 3

What is a Hydraulic Ram and How Does It Work?

Accepted Answer

A hydraulic ram is a cylinder with a movable rod that can move a mass, or an obstruction as so required.

In principle, a hydraulic ram works by an external fluid being pumped into either side of a cylinder simultaneously, this creates a high pressure and low-pressure side within the cylinder depending on the load that it is trying to move.

Here we explore some of your commonly asked questions surrounding hydraulic rams, what they’re used for, how hydraulic devices work, and how hydraulic rams work.

How does a hydraulic device work?

Hydraulic devices use fluid that is moved by an external pump driven by a power unit. Hydraulic devices are designed around the principle that liquids are always considered to be incompressible. This means that when a force is applied at one point, the liquid will transfer an equal force at another point.

Most common hydraulic devices work by using a hydraulic pump, a reservoir for fluid storge to the pump. Mechanical energy is converted to hydraulic energy, moving the liquid through a system. Valves are used to regulate the flow of the liquid and control the pressure of the device. A hydraulic cylinder then converts the hydraulic energy back into mechanical energy.

There are a variety of hydraulic devices, including hydraulic rams, but most will use these components in their operation.

How do hydraulic rams work?

Hydraulic rams consist of several components:

• Cylinder
• Piston
• Neck Gland
• Rod
• Cylinder Ports
• End Caps

The area between the piston and the gland (rod side) is called the Annular side, & the area between the piston & the end cap is called the Full-Bore side.

Pumping fluid into the cylinder port on the Annular side of the cylinder will result in the rod being retracted, giving you a closed centre. Reverse the flow into the opposite port on the Full-Bore side and the piston will then extend the rod out of the cylinder (open centres), at the same time pushing the oil from the Annular side (low pressure) back to tank.

What is a hydraulic ram used for?

Today, hydraulic rams are used all over and have a variety of uses, from heavy plant and mining machinery such as excavators and diggers, agricultural equipment, to food & beverage and packaging machinery, deep sea, marine and automotive applications, to hand tools, fairground amusements and even zoo doors...the list goes on and on.

FPE Seals is a manufacturer and distributor of hydraulic cylinder parts and seal kits for devices including hydraulic rams. Shop online or contact us and find out how our cylinder parts can help improve your hydraulic systems.

Question 4

Seal Failure: Common Causes and Cures

Accepted Answer

In the world of machinery, repair and maintenance is a simple fact of life. So, it should come as no surprise that when it comes to sealing products being used for hydraulic and pneumatic applications, wear and tear is inevitable

Even when you have diligently installed the most robust product, in the best kind of material, certain factors will always lead to seals eventually having to be replaced.

Thankfully in most cases, problems can be identified early, before any serious operational damage can occur, and seals are easily reinstated.

Here we take a look at typical seal failure, the likely causes, and what can be done to rectify the problem.

Hardening

Hardening of the dynamic face has caused glazing and cracks.

Cause: Heat generated by high speed.

Cure: Slow stoke speed or use an alternative seal device.

The whole seal has gone hard and elasticity is lost.

Cause: High fluid temperature, deterioration of fluid or problem with the compatibility of the seal to the fluid.

Cure: Lower the oil temperature, renew fluid or change to a different seal compound.

Wear

The dynamic face of the seal is worn to a glossy mirror-like finish.

Cause: Insufficient lubrication

Cure: Check oil viscosity or use an alternative seal device.

Wear on dynamic lip of seal is egg-shaped.

Cause: Rod or piston bore is not concentric

Cure: Hone to within seal specifications or replace the worn rod or cylinder tube.

Signs of abnormal wear on one side of the dynamic lip.

Cause: Worn bearing or wear ring. Excessive lateral load.

Cure: Replace bearings. Increase bearing area.

Scarring

Cut or dent on the lip.

Cause: Storage on a nail or peg. Improper installation tool

Cure: Store flat in a plastic bag in a closed cardboard box. Installation tools should not have sharp edges.

Scratched on the dynamic side.

Cause: Scars on the rod or bore or foreign material in fluid

Cure: Hone, polish and deburr metal parts or flush the system.

Swelling

Material is soft and misshaped.

Cause: Absorption of fluid. Fluid and seal are incompatible or the there is water in the system.

Cure: Change the seal compound or system fluid. Or flush the system.

Deterioration

Cracks and loss of elasticity. The material easily crumbles.

Cause: High fluid temperature. Exposure to ozone or sunlight.

Cure: Lower oil temperature. Store seals away from sunlight and arc welding area.

Grooving

Axial cuts on the dynamic side.

Cause: Metal chips or other foreign material in system. Imploding air bubbles.

Cure: Flush System. Bleed air from the system.

Extrusion

Extruded material on the dynamic side of heel

Cause: Gap between mating surfaces is too wide, worn bearings or extreme pressure.

Cure: Employ a back ring, replace the bearings or use an alternative seal.

Extruded material on the static side of the seal.

Cause: Uneven support surface or undersized back-up ring.

Cure: Machine surface. Correct back up size.

Fracturing

Chunks of material torn from the dynamic side.

Cause: Excessive back pressure.

Cure: Check relief valves.

Pressure side of seal burned and broken.

Cause: Explosion of residual air at high pressure. ‘Dieseling’

Cure: Bleed air from the system.

Long cracks in the “V” portion of the seal.

Cause: Frequent high pressure shocks or spikes. Low temperature start-up.

Cure: Use alternative style seal. Warm system before applying pressure.

Breaking off of entire dynamic side.

Cause: Deterioration of material and/or fluid.

Cure: Use alternative material or seal. Flush system.

Replacement seals and seals kits, for most applications can be found off the shelf and despatched to you quickly.

If you require any further advice regarding seals and their application, the team of experts at FPE Seals can help you source what you need.

Can’t find what you’re looking for? We can also custom-manufacture a full range of seals, in a full range of materials to meet your exact requirements.

Contact us today

Question 5

Trouble Shooting Common Cylinder Creep

Accepted Answer

Cylinder drift is a common problem that can occur with hydraulic systems of all types.

Tim Bone, FPE Seals Cylinder Parts Manager

This is something that FPE Seals Cylinder Parts Manager Tim Bone knows only too well and is often offering our customer advice on how to troubleshoot the problem. Here he explains more on how you can get to the root cause of your creeping cylinder.

What is causing a hydraulic cylinder to creep faster than expected?

Often the cylinder on a hydraulic application can creep. The popular assumption for this, is that the problem is due to oil passing over a worn piston seal.

However, Tim explains, “Often customers tell me that even when they have resealed the cylinder several times, it still weeps down.

“In many cases, the more likely cause is that the oil is passing across the spoil, rather than the problem being with the seals.

“A simple way to test this, is to lower the load onto the ground so that the cylinder is not under tension, isolate the power source i.e. the hydraulic unit and relax the pressure in the system.

“You can then remove the hose, from the cylinder port that the direction of the rod is moving in (i.e. if the rod is extending, then remove the hose from the annular side, if the rod is retracting then remove it from the bore side). Place a high-pressure ball valve in the line, attaching the hose to the opposite side of the ball valve.

“Make sure that all connecting joints are tight and leak-proof and clean up any spillages.

“Move the lever of the ball valve to open position. Restart the hydraulic power source and operate the valve block (levers), placing load onto the cylinder concerned.

“If the cylinder shows signs of dropping again, move the lever of the ball valve to the closed position.

“If the cylinder stops creeping, this proves that the fault is in the main valve block, as generally the only seals in a valve block are the ones at each end of the spool, to stop oil from leaking externally.

“Hydraulic spools in valve blocks are a machined precision fit, over time the spools can wear across the surfaces causing oil to pass between the internal galleries. Fitting a standard pilot operated check valve or over centre valve can stop this from happening.

“If the cylinder continues to creep, then the problem is with the internal seals of the cylinder. Once identified these seals can be easily replaced.”

Replacement seals for most applications can be picked up off the shelf. FPE Seals stock and supply a full range of seals, including piston seals for all engineered applications.

If you require any further advice regarding seals and their application, the team of experts at FPE Seals can help you source what you need.

Contact us today.

Question 6

What are hydraulic seals made of?

Accepted Answer

Hydraulic seals are non-metallic rings used in fluid power engineering, that prevent a fluid or gas from passing between different components of a cylinder, used in industrial applications.

Just as seals come in all shapes and sizes, for a multitude of applications, they also come in a variety of materials.

Most hydraulic seals use polymeric materials such a polyurethane, elastomers, rubber or polytetrafluroroethylene (PTFE).

The selected material of the seal will depend on the end use. Operating conditions such as high pressure, fluid compatibility, extreme temperatures, aggressive chemicals, working environment and legislation standards all impact on the chosen material.

Below are just some examples of common polymeric materials used to fabricate seals, utilised due to their hardwearing properties:

Polyurethane
Blue polyurethane (Food and Drug Association (FDA) compliant)
Nitrile
Viton/FKM
Silicone
Polyacetal (POM)
PTFE (in its virgin state or can be filled with either glass, bronze or carbon)
Ultra-high-molecular-weight polyethylene (UHMWPE)
Nylon
Polyether ether ketone (PEEK)
Polyester
Tufnol/Phenolic
AFLAS
NORSOK MATL (Oil & Gas industry compliant)

When choosing the right type of seal, to ensure the safe and optimum performance of a machine, seal material plays a big factor.

Not sure what you are need? Get in touch with our knowledgeable team here at FPE Seals, who will discuss your requirements based on your application, and help you find the right seal for the job.

Question 7

Why is it important to bleed the air from a hydraulic system?

Accepted Answer

Air that enters a hydraulic system can cause many problems that could subsequently lead to system failure. Here we discuss how you can spot and prevent these potential problems and why it is so important that air is bled from a system as soon as it is detected.

Hydraulic pumps are not designed to pump air, essentially because when compressed, air generates heat. When air contaminates a hydraulic fluid, usually via the pump’s inlet, aeration, cavitation, or foaming can occur.

Aeration is bad news, as it degrades the hydraulic fluid causing damage to the components of the system due to loss of lubrication, resulting in overheating and burning of the seals. Overheating is particularly dangerous as dieseling can occur when the hydraulic cylinder oil mixes with the air, causing an explosion under compression.

Cavitation, brought on by the rapid changes of pressure in the fluid, causes small vapour-filled bubbles to contaminate the system, which implode when compressed. Ultimately this leads to metal erosion, which harms the system’s components and contaminates the fluid.

Air can also cause foaming in the tank, causing the equipment to operate erratically, as the pump takes large gulps of air along with the oil.

When to bleed a hydraulic system

Abnormal noise is often a tell-tale sign that there is trapped air in a hydraulic system. As air circulates through the system it compresses and decompresses, creating a banging or knocking noise.

This is why abnormal noise must always be checked out and careful inspection given to the condition of the system’s fluid, components and seals, to identify any signs of trapped air or contamination.

It is also important that displacement hydraulic cylinders are bled before installation, as any air trapped in the system would work like a gas shock absorber. For this reason, displacement cylinders have a breather at the top, to disperse any air.

And lastly, when testing a new hydraulic cylinder, it is important to check for potential air contamination, as this can result in blowing the dirt wiper and the hydraulic seal out of its housing extruding past the rod.

All things considered, if spotted early and dealt with quickly, bleeding trapped air in a system, will prevent any long-term damage or operational downtime.

Question 8

How Are Hydraulic Seals Made?

Accepted Answer

Hydraulic and Pneumatic Seals for engineered machinery can be designed and manufactured in a variety of materials, shapes and sizes.

Selecting the right material

Most hydraulic seals are made from polymeric materials, more commonly polyurethane, polytetrafluoroethylene (PTFE), elastomers and rubber. Although, other materials can be used for more specialist seals.

It's important to select a material that best suits a seal's end use. For instance, the seal's operating conditions such as pressure, fluid compatibility, extreme temperatures, working environment and legislation standards, will all have an impact when deciding on which material to use.

Manufacturing process

During the manufacturing process, a Computerised Numerical Control (CNC) lathe machine is used to create the seal. These can be programmed with standard and customised seal profiles. Taking the digitalised data of the profile, the CNC lathe then works to cut the shapes of the seal from the selected material.

Take a look at our short video to see how seals are manufactured at FPE Seals.

Question 9

What is a Rod Seal?

Accepted Answer

Rod Seals, also known as Gland Seals, Headbush or Neck Seals are an integral part of any hydraulic or pneumatic cylinder system. Essentially, they are designed to seal between a cylinder’s rod and gland.

The Rod Seal acts as a pressure barrier to maintain and regulate the operating fluid when a cylinder is in dynamic motion, and so plays a key role in preventing leakage and corrosion.

They do this by sealing the pressure from one side (single-acting) or from both sides (double-acting) and work together with a Wiper Seal to protect the system from external contaminants.

For more heavy duty applications, a Buffer Seal can be used alongside a Rod Seal to provide even further resilience.

Rod Seals come in a variety of sizes, styles and materials, to meet the parameters of the cylinder’s application and operating conditions.

High pressure, extreme temperatures, fluid compatibility, working environment and legislation standards will all have an impact on the chosen material of seal.

The range of Rod Seals include;

Grooved Rod Seals – A single-acting seal with an anti-extrusion ring on the internal diameter.

Rod Composite Seals – Energised by an o-ring, to provide low friction, non-stick/non-slip hard-wearing sealing.

Rotary Rod Seals – used to seal a rotating shaft.

Rubber & Fabric Seals – when this type of material best suits the application.

T-Seals – T-shaped seal with two back up rings to help prevent extrusion.

Vee-Packing (Chevron) Seals – multiple-lipped seals packed together in groups of three or five, used in medium to heavy duty applications.

If you require any further advice regarding Rod Seals and their applications, then our knowledgeable team at FPE Seals would be happy to help.

We stock, source and supply a fully range of Rod Seals. Can’t find what you’re looking for? We can also manufacture the seals to your specification, in a full range of materials to meet your exact requirements.

Contact us today

Question 10

What Causes Hydraulics to Run Slow?

Accepted Answer

When it comes to a hydraulic system, a common complaint can be that it is operating slowly or less effectively than before. There are many reasons why this can occur, but this is mainly down to an issue with fluid flow and faulty or failing parts. Here we discuss the critical role that individual components play in hydraulics and why it may be that these components are causing the system to slow down.

Hydraulic Tank/Reservoir – to avoid any issues a good tank or reservoir should always come fitted with a filler breather, suction strainer, site glass, removeable inspection/service plate and drain plug.

Suction Strainer – this is designed to remove any foreign bodies that may have contaminated the tank. Filters must be checked and cleaned on a regular basis. If they become blocked, they will restrict the flow of the hydraulic fluid entering the inlet side of the pump, causing the system to slow down and ultimately causing damage to the pump.

Filler Breather – this should also be checked regularly, to make sure that the cage is intact and free from foreign bodies. Check the breather cap and if required, clean using an appropriate solvent, to avoid the breather element from becoming clogged. If blocked, this can cause the tank to vacuum, which will lead to a restricted flow of oil to the pump.

Suction Hose – a short piece of hose is fitted between the outlet of the tank and the inlet of the pump. Over time, the rubber hose can degrade, becoming porous, and even delaminate internally, causing a restriction of fluid flow into the pump.

Hydraulic Pump – modern day pumps are extremely complex pieces of engineering and usually will not tolerate any form of contamination. Any foreign bodies in a pump can cause severe damage to its integral moving parts, resulting in low pressure and restricted flow. Any problems can be identified with a good quality flow meter.

Power Unit – one component that definitely needs to be checked for any problems is the power unit that is driving the hydraulic pump. This can be an electric motor or either a combustion engine. These can be checked by loading the pump with a flow meter. The tone of the power source should alter slightly under load but not die. If the flow drops and the power source stays the same, it may be worth checking the drive coupling between the output shaft and the input shaft of the unit.

System Relief Valves – these are prone to overheating and will change colour when the incorrect pressure rating is too high. This can cause damage to the seating face in the cartridge, causing oil flow to pass over the seat of the relief valve and return back to the tank via the tank line. A faulty or dirty relief valve can also have the same effect if set to low, the valve will run continuously open, losing flow and causing heat.

Directional/Proportional Control Valves – these can be fitted with additional or external valves that can be easily altered or damaged causing them to pass oil across and dumping it back to the tank. Always remember, any fluid will always take the easiest route away from the tank. The smallest imperfection on a seat, that cannot be felt but can be seen, will allow oil to pass.

Hydraulic Cylinder – just because there are no external signs of leakage does not mean to say that the internal piston seals of the cylinder are not worn or damaged. Although, usually there are identifying signs that the piston seals are worn. For instance, the cylinder may be dropping or have no lifting force.

In general, if your hydraulic system is running slowly when the fluid warms up, then this is due to the oil thinning and therefore able to pass easily across worn or damaged surfaces. Carrying out a simple flow test with a flow meter will help eliminate any of the key factors mentioned above.

Question 11

What is a Wiper Seal?

Accepted Answer

Wiper Seals, also known as Scraper Seals or Dust Seals are primarily designed to prevent contaminants from getting into a hydraulic system.

This is usually achieved by the seal having a wiping lip that essentially cleans away any dust, dirt or moisture from the rod of a cylinder on each cycle. This type of sealing is crucial, as contaminants can potentially cause damage to the other components of the hydraulic system, and cause the system to fail.

The wiping lip always has a smaller diameter than the rod it is sealing. This provides a tight fit around the rod, to prevent any dirt getting in, when in both a static and dynamic position, while still permitting a reciprocating ram rod to pass through the inner bore of the seal.

Wiper Seals come in range of different styles, size and materials, to best suit the application and operating conditions of a fluid power system.

Some Wiper Seals have secondary functions, this may include having a harder scraping lip to remove stubborn contaminants such as bonded dirt, frost or ice, or a secondary lip used to capture any oil that may have bypassed the main seal. These are commonly known as Double Lipped Wiper Seals.

In the case of a Flexible Wiper Seal, the seal is usually held in by its shoulder.

A Metal Cased Wiper Seal relies on the outer metal case having an interference fit to hold it in the housing. It will therefore measure slightly larger on the outside diameter.

If you require any further guidance on Wiper Seals, then our knowledgeable team at FPE Seals would be happy to help.

We stock and supply a fully range of Wiper Seals. If you can’t find what you’re looking for, we can also manufacture the seals to your specification, in a full range of materials to meet your exact requirements.

Contact us today

Question 12

Why Are Hydraulic Cylinders Cushioned?

Accepted Answer

Cushioning, or soft start as it is sometimes referred to, is used to slow down a hydraulic cylinder, by reducing the speed of a piston at the end of its stroke, or before it meets the end cap. This method is generally used in double-acting cylinders, for heavy duty applications that use a lot of kinetic energy.

Cushioning is commonly fitted to both the rod side and full-bore side of a cylinder, to bring the final movement of the rod to a stop. This prevents the piston from slapping against the back of the gland and the end cap of the cylinder when opening and closing.

The ultimate purpose of using a cushioning method is to avoid damage to the piston, which could occur when a high oil volume is applied to a hydraulic cylinder.

Other advantages of using a cushioning method are that it extends the life of the cylinder by reducing the impact of vibrations, as well as reduces any excessive audible noises.

How does hydraulic cylinder cushioning work?

Hydraulic cylinders operate by pumping a medium into the cylinder causing the piston to extend or retract to the end of its stroke.

A cushioning device works on the principle of forcing a small amount of the cylinder fluid through or over a smaller diameter / orifice which is usually present to the front or rear of the piston, as it comes to the end of its travel.

The cushioning device therefore restricts the flow of fluid to the back of the neck gland or base of the cylinder, which ultimately slows down the stroke of the cylinder as the fluid cannot go anywhere else, apart from through the tolerance aperture of the gland, resulting in slowing down the stroke to a stationary finish.

It is always best to decide whether to fit a cushioning device at the initial design and build stage of cylinder, as retro fitting can be a very costly.

Should you want any further advice on cylinder design and cushioning components, please contact our knowledgeable and helpful team today.

View our range of Non-Adjustable Cushioning Glands, Pistons and End Caps.

Question 13

Why Do Hydraulic Cylinders Fail?

Accepted Answer

Hydraulic cylinders come in all shapes and sizes and are used in a variety of applications. The reasons why a cylinder can fail will depend on their application but in general, most problems are usually down to either physical damage or seal deterioration.

If a cylinder is misused or has been physical damaged in some way, it can become a pressure intensifier, which causes harm to the different components, from misalignment, to the piston being pulled from the rod, to the drastic results of the cylinder splitting its full length.

All cylinders are pressure-rated based on their application. Most are designed to work at 250bar, which normally applies to the extrusion tolerance of the seals used in the cylinder’s different components.

Seals will wear slowly over time, this cannot be prevented but is easily solved by spotting any problems early and replacing the worn seals, without causing any major issues to the hydraulic system.

However, excessive pressure, heat, misuse, and poor fluid condition will cause seals to deteriorate rapidly. For example, the seals can harden, crack, or extrude.

How to prevent cylinder failure

Areas to typically look out for cylinder failure is between the rod and the gland, the gland itself, the cylinder and around the welded parts.

All cylinders should be checked externally on a regular basis. Especially at the mounting points, steel pipes and hydraulic hose fitting. Anything that is loose should be rectified immediately. Make sure that there is sufficient lubrication and look out for any areas of excessive wear. Worn areas should be addressed without delay.

Particularly, check all external mechanical stops, as any damage can result in the piston or gland being pulled from its threads.

Inspect the condition of the chromed rod that moves back and forth in the cylinder. Any external dents, rust, scrapes or bends could lead to severe damage to the other integral components of the cylinder.

Always check the fluid levels of your hydraulic system, change the filter regularly and keep fluids free from contamination. This will prevent seal failure and damage to the cylinder bore.

Overall, cylinder failure can easily be prevented with careful use, regular inspection, and servicing, ultimately reducing the need for costly repairs and downtime.

If you would like any advice on sourcing replacement metal parts or seals for your hydraulic ram, please contact our helpful and knowledgeable team today.

Contact Us

Question 14

What is a Piston Seal?

Accepted Answer

Piston Seals essentially provide a seal between a piston and cylinder bore.

The seal prevents leakage of hydraulic fluid or air, sealing dynamic pressure from one or both sides of a ram, to allow the cylinder to extend and retract.

Piston Seals are dynamic by nature and come in a range of different styles, sizes, and materials. The type of seal needed will be dependent on the design of the cylinder, the application, the medium used, and its operating conditions.

Single-acting Piston Seals contain the pressure and prevent leakage on one side of the piston only. Therefore, the seal moves the piston along the cylinder in a single action.

Double-acting Piston Seals contain the pressure and prevent leakage from both sides of the piston. This drives the hydraulic or pneumatic ram both in and out, or stops it in a controlled position. Typically, double-acting seals have a symmetrical profile, with identical sealing functions on both sides.

Back up rings and guide rings are also commonly used alongside piston seals, to reinforce the seal and ensure that it stays in the correct position.

If you require any further advice on selecting the right Piston Seal for you, our knowledgeable team would be happy to help.

FPE Seals stock and supply a comprehensive range of Piston Seals, Piston Rings and Cylinder Parts.

If you are are unable to find what you are looking for on our web store, please let us know. Our inhouse manufacturing team can create seals to specification, in a wide range of materials to best meet your requirements.

Contact us today

Question 15

Why Is My Excavator So Slow?

Accepted Answer

Tim Bone, Cylinder Parts Manager, FPE Seals explains some of the reasons why an excavator can be operating slowly.

“Modern day excavators come in many shapes and sizes, with most now fitted with more than one hydraulic pump, along with various system relief valves, service relief valves and priority valves to make the excavator run more smoothly.

Generally, there are two main hydraulic pumps, one for each of the track motors and possibly a smaller displacement pump for the pilot circuit. Reasons as to why an excavator is running slowly, can be down to the two main hydraulic pumps, as it is these that are primarily designed to power the main function of the excavator.

An excavator’s load is spread equally across both pumps. On its return, flow it is diverted through a loading valve or regeneration valve, combining both flows and giving the extra power needed to the required cylinder, resulting in a better tear out force.

Check the power

An excavator’s two power supplies, the engine and the hydraulic pumps, are driven through a flexible drive coupling. The first signs of a problem will show when an excavator tracks to one side or some of the functions are slow, while others are working normally. If all the functions are slow then this might be a sign that the power unit has a fault, or the drive coupling is worn and slipping.

First check the power unit. Is the engine struggling? Do the revs of the engine increase under load or do they die off as though the engine is struggling to increase its power band?

Basically, if the engine is not running correctly or in need of a service, then it cannot provide the necessary power for the hydraulic pumps to supply the flow to run the system.

Engines need to be serviced regularly. Diesel filters need to be kept clean and free from contamination. Remove and replace the air filter if this has got very dirty.

Secondly, check the flexible drive coupling. This could be worn, shattered or even slipping on the drive shaft. Drive couplings wear out as the rubber segment that gives it the flexibility take a lot of stress. Also check the hydraulic fluid levels, if the suction strainer is blocked this can cause cavitation and starvation to the pumps.

Process of elimination

Finding a fault on any machine is time consuming, but using a process of elimination component by component will make a diagnosis easier. Try not to think that the problem is a major component, in the majority of cases it is often something very simple like an O-ring or a damaged seat of a valve.”

FPE Seals provide hydraulic seals and cylinder parts for excavators, contact our knowledgeable team today who will help find you what you need.

Question 16

The History of Hydraulics:  Then to Now

Accepted Answer

Hydraulics is the technology and applied science, that uses fluid for power.

The first hydraulic systems date back thousands of years, with irrigation and water clocks being used by ancient Greeks and Egyptians, as early as 600 BC.

The Persian Empire, Roman Empire, ancient Greek, Chinese and Arabic societies that followed, each brought their own early innovations of hydraulic machinery, such as watermills, water wheels, water turbines, mining equipment, and the first known steam engine (known as an Aeolipile).

DID YOU KNOW?

The word "hydraulics" originates from the ancient Greek word "hydraulikos" meaning water (hydor) pipe (aulos).

Hydraulic technology has come a long way since then and can be found being used in a wide variety of applications every day, across the world.

Pascal's Law

Pivotal in setting the foundations for all modern hydraulics, was gifted French mathematician, physicist, and philosopher Blaise Pascal.

In 1640's, while studying hydrodynamics, he discovered a mathematical equation, known as 'Pascal's Law', which pronounced the principle of transmission of fluid pressure.

Pascal's law realised that pressure on a fluid in a confined area, remains constant in all directions and that this force could be harnessed.

Bernoulli's Principle

Nearly a 100 years later in 1738, Swiss mathematician and physicist Daniel Bernoulli put Pascal's fluid power discovery to use by pressurising water in pumps and mills using Bernoulli's principle.

First Hydraulic Press & the Industrial Revolution

Engineers soon began experimenting with functions of the principle described in Pascal's Law. One such engineer was Englishman Joseph Bramah, who in 1795 patented a design for a hydraulic press, paving the way for the industrial revolution.

The press used a hydraulic cylinder to harness fluid power to generate a compressive force, which then was used to produce mechanical force. This was used to automate all types of manufacturing and heavy-lifting equipment, such as printing presses, cranes, and machines that involved cutting, stamping, and crushing.

From water to other fluids

While water was the first hydraulic fluid ever used, engineers soon discovered that there were better options out there, to best suit specific applications.

Oil was regarded as a better alternative for pumps and motors, as compared to water it was non-corrosive, lubricated the components, and could handle high temperature and pressure better.

Nowadays, there are a whole host of different fluids being used in hydraulics systems. Hydraulic fluids are selected based on their compatibility with the operating conditions of the application, considering qualities such as the fluid's density, viscosity, and response to heat and pressure.

Modern day hydraulics

Fast forward to modern day, hydraulic systems are used all over, in a variety of ways. From heavy plant and mining machinery, to agricultural equipment and manufacturing facilities, through to deep sea, marine and automotive applications, to hand tools and household appliances, the list goes on and on.

Innovation in the field of hydraulics continues, with new hydraulic systems and equipment being designed and tested every day.

If you need any advice regarding your hydraulic cylinder design, or help to source the seals and metal parts needed, please contact FPE Seals knowledgeable team, who would be happy to help.

Helpzone

How to

How to: Measure Hydraulic and Pneumatic Seals

How to: Assemble a Hydraulic Cylinder

How Seals Are Made

How to: Fit a Gland Seal

How to: Fit OP Seals to a Cushioning Gland

How to: Fit a Composite Piston Seal

How to: Fit a 5-piece Piston Seal

How to: Order & Register Online

Frequently Asked Questions

Helpzone

How to

How to: Measure Hydraulic and Pneumatic Seals

How to: Assemble a Hydraulic Cylinder

How Seals Are Made

How to: Fit a Gland Seal

How to: Fit OP Seals to a Cushioning Gland

How to: Fit a Composite Piston Seal

How to: Fit a 5-piece Piston Seal

How to: Order & Register Online

Frequently Asked Questions

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