The Built-In Inefficiency of Your Hydraulic Equipment

The ‘built-in’ inefficiency of every hydraulic system:

Compression of the oil.

A fluid’s compressibility is defined by its bulk modulus of elasticity – which is the opposite of compressibility. Meaning, as the bulk modulus of elasticity increases, compressibility decreases.

Bulk modulus is an inherent property of the oil and therefore an inherent inefficiency of a hydraulic system.

The fluid in the pipeline and actuator must be pressurized, and consequently compressed, before it will move a load.

Because this compression of the fluid requires work at the input – which cannot be converted to useful work at the output – it is lost work and therefore a contributing factor to the overall inefficiency of the hydraulic system.

The larger the actuator and the faster the response time, the higher the inefficiency attributable to bulk modulus.

And in high-performance, closed-loop electro-hydraulic systems, deforming oil volumes affect dynamic response, causing possible stability problems such as self-oscillation.

Unlike viscosity index, bulk modulus cannot be improved with additives. However,hydraulic equipment users can take steps to minimize the inefficiencies and potential control problems associated with compression of the fluid.

The first is to ensure hydraulic equipment doesn’t run hot.

Compressibility of the fluid increases with temperature. Mineral hydraulic oil is approximately 30 percent more compressible at 100°C than it is at 20°C.

Of course, there are many reasons why you should never allow hydraulic equipment to run hot – most of which we’ve already discussed. Reduced bulk modulus is another one.

The second is to prevent conditions that cause aeration.

Air is 10,000 times more compressible than oil. One percent of entrained air by volume can reduce the bulk modulus of oil by as much as 75 percent.

While controlling aeration is largely a design issue – for example, the amount of dwell time the oil has in the tank – proper maintenance also plays an important role.

Dissolved air comes out of solution as temperature increases, which is another reason to maintain appropriate and stable operating temperatures.

Also, oxidative degradation and water contamination inhibit the oil’s ability to release air, often resulting in an increase in entrained air and thus compressibility.

Craig Cook

4 Simple ways to make your hydraulic oil last longer

Oil has never really been cheap, but at today’s prices, you sure don’t want to be spending any more for it than you have to.

#1 Keep it in

The first and most obvious thing is to keep it in the hydraulic system. Those couple of slow leaks you’ve been putting off fixing are costing you more per day, week and month.

#2 Keep it cool

There’s a lot of good reasons to maintain appropriate and stable operating temperatures. Oil life extension is not the least of them.

According to Arrhenius’s Law, for every 10 degrees Celsius increase in temperature, the rate of reaction doubles.

The chemical reactions we’re concerned with in so far as hydraulic oil life is concerned are oxidation – due to the presence of air; and hydrolysis – due the presence of water.

So the hotter the oil, the faster the rate of these reactions – and exponentially so.

By way of illustration, if you pour some cooking oil into a glass, it’ll take days, even weeks before it darkens in color – a sign of oxidation.

But tip the same amount of cooking oil into a frying pan – which gives the oil a large contact area with air – then heat the begeezez out of it, and the oil will go black in a very short space of time.

#3 Keep it dry

Water too has a number of negative effects on the oil. In so far as oil life is concerned, it can chemically compromise (hydrolyze) the additive package. For example, the antiwear additive ZDDP is prone to instability in the presence of water.

#4 Keep it clean

Unless you’ve been living in a cave, you know when it comes to hydraulic oil: cleanliness is next to Godliness’.

But particle contamination also affects oil life. Certain wear metals act as catalysts which increase the rate of oxidation and hydrolysis.

Particles can also attach themselves to additives in the oil, resulting in additive depletion when these particles are captured in the system’s filters.

So to wring the most out of every drop of your hydraulic oil, keep it in; keep it cool; keep it dry and keep it clean.

And ONLY change it when base oil degradation or additive depletion demands it be changed.

Till next time.

Craig Cook

What’s the most common problem with hydraulics?

Overheating,

It’s a simple problem really. If you understand percentages – and I know you do, then overheating problems are easy to get a handle on.

You see, it’s a balancing act between the percentage of input power lost to heat and the percentage of heat dissipated by the system – mainly the heat exchanger.

Take a system with an input power of 100 kilowatts.

If it’s 80 percent efficient, it’s creating 20 kilowatts of heat load.

If the exchanger is dissipating 20 kilowatts of heat then a stable operating temperature will be maintained.

If the system starts to overheat, then either:

The system is no longer 80 percent efficient; or
The exchanger is no longer dissipating 20 kW of heat.

It’s that simple.

Craig Cook

How to Minimize Pressure Spikes on Your Hydrostatic Transmission

When a hydrostatic transmission is subject to a sudden increase in load, the motor stalls momentarily and system pressure increases until the increased load is overcome or the high pressure relief valve opens – whichever occurs first.

While the motor is stalled, there is no return flow from the outlet of the motor to the inlet of the pump. This means that the transmission pump will cavitate for as long as it takes to make up the volume of fluid required to develop the pressure needed to overcome the increased load (or the high-pressure relief valve).

How long the pump cavitates depends on the output of the charge pump, the magnitude of the pressure increase, its influence on the increase in volume of the pipe or hose, and the decrease in volume of the fluid.

This is called the ‘accumulator effect’.

One way to minimize stalling and pressure spikes and the resulting ‘accumulator effect’ in applications where the load on the transmission varies – in say drill rigs for example, is to install a flywheel between the hydraulic motor and reduction box.

The stored energy in the flywheel assists the hydrostatic drive to maintain speed and torque, and minimize the magnitude of pressure fluctuations resulting from sudden increases in load.

Craig Cook

How to get your vane pump pumping

Here is an issue I heard about that came up recently on getting a vane pump pumping:

“There is a 2 section vane pump with new cartridges. The problem is, 1 cartridge has no oil coming out when we crack open the hydraulic line going to the control valve. When we tighten the fitting the hose reacts as if it has pressure in it. When we crack it again – nothing.”

First off make sure the cartridge is the correct rotation.

If it is in the correct rotation then this is most likely a priming issue.

You see, unlike most other hydraulic pumps, vane pumps can be tricky to get pumping.

The vanes in a vane pump don’t have springs to hold the vanes in contact with the cam ring.

Centrifugal force is supposed to throw the vanes out against the cam-ring. But it doesn’t always work out that way.

A downstream resistance is sometimes necessary to create back-pressure to hydraulically actuate the vanes against the cam ring, so the pump primes.

The solution is usually simple enough. Ensure there’s a head of oil above the outlet port. If the valve bank is below the pump, then head can be achieved by routing the hose so that at some point, it extends a foot or so higher than the outlet port.

Till next time,

Craig Cook

How We Can Help You!

It has hit me that many of our customer may not know all the services we offer.

So here is a quick ‘low down’ in case I haven’t gone over everything that we can help you with.

With everyone watching their bottom line these days, we hope you’ll look to Power Components as THE source for all your fluid power repair needs.

We provide world-class service and unmatched value on everything from:
Pumps
Motors
Power units
Valves
Cylinders
Accumulators
And more..
We service many makes and models including Vickers, Parker, Rexroth, Oilgear and many others.

In addition, we are happy to work on all you OEM construction or Agricultural heavy equipment.

Something else in another category that we have not listed, not to worry, dedicated staff will do their best to make it like new again.

As a Power Components customer, you’ll also enjoy a one-year warranty on all repairs completed by our full-service hydraulic repair shop located inside our 58,000 square ft. Fort Wayne facility.

Our staff includes many of the same fluid power professionals you already know and rely on, with a combined 138 years of hydraulic expertise on our Power Components team.

Craig Cook

Coming on Location to Help You Out!

A monster machine that bends 10″ pipe

This machine is being built to bend 10″ round pipe. Tim “the tool guy” Allen from Home Improvement would be proud of this bad boy.

This is a project we did a couple years ago. We ran all the hydraulic piping, fittings, and hoses on the machine. The red arrows points out some of what we were helping them out with.

If you have a similar project like this one or need help trouble shooting a problem, let me know.

Craig Cook

Jigs and Fixtures to Improve Production

Check out this packing jig used for production

packing-production-jigs-and-fixtures-fort-wayne

This is a production jig we are building for a client to use to make the parts easier to grab and use during production. (the springs on the parts get tangled up if they are just put into a pile) We built more than 50 of the these jigs for them so far.

If you need any jigs or fixtures similar to this one give us a call.

Craig Cook

Our hydraulic testing beast

Say hello to our “beast”!

hydraulic-hose-fittings-test-bench

Okay so it isn’t exactly a beast BUT it is a huge bench that allows us to test every aspect of any hydraulic component.

When you have us repair or rebuild any hydraulic component, it goes through rigorous testing on our hydraulic test stand.

We use the test stand for:

Pumps
Cylinders
Valves
Motors (spin test)

Every repair goes through testing on this bench to make sure it meets and exceeds the needs your requirements.

If you need anything repaired feel free to give us a call at (260) 426-4673.

Till next time,
Craig Cook

Minimize the Chance of Tapered Threads From Leaking

Tapered thread connections can have a tendency to leak. If you have to use tapered thread connections, there are tricks to minimize them from leaking.

How to minimize the chance of your tapered thread connections from leaking.

First, don’t waste your time with thread tape – I only ever use it when there’s no thread sealing compound available. I’ve had best success with Loctite 567 and 577 (my favorite), which are pastes rather than liquids like some of the others.

If you’re re-sealing a joint, thorough cleaning of the old adaptor and port is essential. If you’re in your workshop, a brush wheel in a bench grinder does a great job on the threads of the adaptor. But the female threads in the port aren’t so easy.

Once you’ve removed all remnants of thread tape or sealant, the next step is to use the appropriate Loctite cleaner. Don’t skip this step – you’ll regret it.

Next, if you’re not able to wait the 6 hours or so for acceptable cure strength, apply the Activator 7649 and allow it to dry. If you have the luxury of leaving the joint overnight
before pressurizing it, you can skip this step.

Starting two threads back, apply a bead of paste around the entire circumference – completely filling the threads. Do the same with the female threads in the port.

Now torque the joint. I will go over proper torquing next week.

Craig Cook