Q. Will increasing the hydraulic pressure make the machine go faster?

A. Generally, no. Speed is a factor of flow. You need more flow to make things move faster (Rule 5). There is a possibility though, where increasing the relief valve pressure setting may increase the speed. Some flow may be being lost over the relief valve so therefore by increasing pressure the flow will be available for useful work. Extra caution is required in these situations so call an experienced hydraulic technician at Excel.


Q. Will putting a bigger (higher flow) pump on my machine give it more force?

A. No. A bigger pump will displace more fluid and make cylinders extend faster, but it is more pressure that will give you more force (Rule 6).

Q. My machine is getting hot, will fitting a heat exchanger help?

A. Yes. A heat exchanger is a device to reduce heat from a hydraulic system. However a better question would be, why is my system getting hot? Using the Excel rules, determination of the heat cause can be found. Better still get an overall appraisal of your hydraulic system. This will save more money than just installing a heat exchanger. Call Excel to help you with that.

Q. A new installation incorporating a large hydraulic cylinder makes a banging noise when in operation. What can we do to fix it?

A. Call Excel! As the cylinder has a large volume of oil within its body, under pressure this oil compresses. When the directional valve shifts to allow the cylinder's direction to change, this oil decompresses rapidly causing the bang. With expert fitting of additional valving this fluid can be decompressed and therefore do away with the destructive banging.

Q. One cylinder on my machine has no force, what could be the problem, given that every thing else hydraulic is operating normally?

A. Force is a function of pressure (Rule 6). You only experience pressure when there is a restriction to flow (Rule 1). Knowing that the fault is limited to only one cylinder and that a system requires a restriction to flow, a suggestion would be to start with the cylinder and its associated valve. The problem could be with cylinder seals, a pressure valve failing to allow easy passage of fluid or a directional valve not shifting. At EXCEL, our vans are equipped with an array of test equipment to make these tests and checks so much easier and more effective.

Q. Do EXCEL have the resources to successfully repair our hydraulic components?

A. Yes! But don't take our word for it. Our Smithfield NSW workshop is open typically longer than "normal" working hours. Come in and have a look a look at the clean bright working environment and check out the hydraulic test and data loggers.

Q. Can I repair my own small hydraulic cylinder?

A. Yes. However the standard the hydraulic component maintains will depend on the standard of the repair. To maximise a hydraulic component's effectiveness and longevity, you need experts. Excel are the experts. We have a standard series of checks and tests that are applied to all component repairs large or small. These checks are performed throughout the whole repair cylinder process. This enables Excel to provide a lifetime warranty on all repairs.

Q. What does an accumulator do?

A. An accumulator stores hydraulic fluid under pressure. This stored fluid can then be used for operations even when the pump is turned off.

Q. I have moved a three phase electrically powered hydraulic machine from one position to another and now it will not operate.  What is wrong?

A. Hydraulic pumps operate correctly with their drive shaft rotating in one direction only. Electric motors can easily rotate in either direction with the reversal of any two electrical phases. Three phase electrical outlet sockets have no commonality with phase rotations. Therefore, moving hydraulic equipment from one electrical outlet to another could cause the equipment to malfunction. With the equipment plugged into an alternative location, it is possible for the electric motor to rotate in an opposite direction. Rotating the pump backwards (sucking instead of blowing) causes the operational fault. The fix is an easy one for a certified electrician. Exchanging any two electrical phases will cause the pump to operate as designed.

Q. The hydraulic oil in my equipment has not been replaced for as long as I can remember, should I replace it immediately?

A. Hydraulic oil is to machines as blood is to humans. Here at Excel Hydraulics, experience has taught us that it is hugely worthwhile to have a simple oil analysis performed before replacing the fluid. Just as your doctor performs blood tests before ordering a complete transfusion, an oil test should be done before you decide to replace any oil. It is useful as a vital indicator of your machine's internal condition. For example, high particle counts indicate either the unchecked integration of contamination or failure of the filtration system. Metal levels help to identify unacceptable component wear. Water levels above 0.10% are detrimental to component wear. There are so many factors that throwing the fluid away without testing first is like "throwing the baby out with the bath water". Have the oil tested first, the results will then tell you if there are deeper issues to resolve. This simple process will save you both time and money.

Q. Pressure intensification, what is that?

A. Pressure intensification is to hydraulics as a lever is to a builder. 

 Q. Is hydraulic oil harmful to humans?

A. Hydraulic oil can be present in a couple of states: under pressure and in the drum. Lets answer the question looking at each state independently. Harm may occur if high-pressure oil is able to penetrate the skin. This would transpire in situations where a pin leak has formed and a jet of high-pressure oil sprays from this leak. Oil at atmospheric pressure is not deemed a hazardous product. If your were to swim in it there is a possibility of mild irritation to the skin. When swimming wear goggles as if you were to get it in your eyes you would need to irrigate with copious quantities of water to prevent irritation. But keep your mouth closed, as either 46 or 68 grade hydraulic oil is slightly toxic possibly causing some gastric irritation.

Q. I know what a hydraulic cylinder is however what is a hydraulic displacement cylinder?

A.  Displacement cylinders are hydraulic actuators that have one fluid port. Fluid entering this single port causes the rod to extend. Retraction of the cylinder only occurs when some external force is applied such as springs gravity or another external force. Construction is generally achieved by either sealing the fluid around the rod area or sealing the piston against the bore. There are advantages of each sealing technique. The rod sealing option provides better lubrication outcomes as both the piston and rod areas are constantly flushed with the hydraulic fluid. Rod sealing is generally a more cost-effective alternative, as the design is simpler. Sealing the piston against the bore however provides more force when equivalent pressures are applied to both designs due to the increased diameter associated with the piston. Applications of displacement cylinders are commonly found in numerous applications such as portable jacking rams, hydraulic car jacks and truck hoists to name a few.

Q. My hydraulic repair company informs me that the cause of my cylinder malfunction was due to failure with a check valve. What is a check valve?

A. One of the simplest hydraulic components is the check valve, a device designed to allow fluid to flow in one direction only. This is achieved with the aid of a seat, a ball or poppet and a spring. In the free flow direction the fluid lifts the ball of its seat against the tension of the fixed force spring. In the non-flow direction, also known as the checked direction, the fluid acts on the spring side of the ball. This forces the ball into the seat preventing the passage of fluid. For the electronics gurus, the check valve is the hydraulic equivalent of the electronic diode.

Q. Can you please explain the difference between a hand operated hydraulic Directional Control Valve with a detent option when compared to a spring center option?


A. Good question, however first we need a basic understanding of a typical hand controlled Directional Control Valve (DCV) operation. Let's assume this DCV has three positions, four ports, open center configuration and is connected to a double acting Hydraulic Cylinder. Flow is provided by a fixed displacement pump with inbuilt relief valve.


There are three possible control positions for this DCV scenario:

1.     Center

2.     Cylinder Extend

3.     Cylinder Retract


1. Center control position

Is where the DCV is in a neutral position; the hand leaver is neither pushed nor pulled, raised nor lowered. The cylinder is also neither extending nor retracting and generally remains in a fixed position (Dependant on the DCV's center configuration). The pump flow is being diverted back to tank under zero pressure. (Well not quite zero but pretty close)


2. Cylinder Extend

Is when the hand leaver is shifted in one direction, causing the cylinder to extend. The pump flow is now connected to extension port of the cylinder and the cylinder's retraction port is connected back to tank. If the cylinder continues to be extended in this way it will only stop moving when either the systems full designed load capacity is reached, or the cylinder's full mechanical stroke limit is found. In either case the system pressure will climb until the relief valve setting is achieved. All the pump flow will now pass through the relief valve and begin to heat up as it passes through.


3. Cylinder Retract

Is the opposite to the extend operation with the hand leaver shifted in the opposite direction. Instead of the pump flow being connected to the extend port of the cylinder, it's now connected to the retract port and the extension cylinder port now connected to tank. Again the cylinder's motion will only stop if either the systems pressure is reached or the cylinders full retraction stroke is achieved.


So back to the question:

What are the differences between a DCV with a spring center or detent option?


Spring centered option

This operation means that while ever the valve handle is released the DCV will always spring back to the center neutral control position. Advantages here are that the cylinder operation will always fail safe. Let go of the leaver and the DCV will always finds its neutral position. This option does however mean an operator needs to be continually present.


Detent option

A valve fitted with a detent option on the other hand will always be mechanically held, by a simple mechanism, in whatever position the leaver was last left in. The cylinder will continue to extend or retract depending on what position the lever remains in. This allows the operator to walk away and the cylinder will continue to either extend or retract without their presence. Downside of course is there are no failsafe measures.