Hydraulic Articles | Hose and Fittings Source

How to Reduce Noise Emission

I got a HUGE response from sending out the cheat sheets, many people printing them off for quick reference for when they need them.

I’m glad they were helpful!

How to reduce noise emission from hydraulic machines

It is to be noted that in many industrialized nations, there are rules and regulations that restrict noise levels in the factories and workplace. The regular activities in the industrial areas using hydraulic machines and the resulting high noise emission of hydraulic components means that it is warning the machine operator to do something to reduce the noise of the machine in the working area. To do that you should know, “what exactly is the cause of the noise?”

Three Main Causes

Fluid Borne Noise

Structure Borne Noise

Air Borne Noise

The dominant cause of noise in hydraulic systems is the pump. The hydraulic pump produces fluid-borne noise and structure-borne noise into the system and radiates air-borne noise. All hydraulic pumps have a fixed number of pumping chambers, which operate in a continuous cycle like as opening closing of fluid inflow. The continuous process leads to a corresponding sequence of pressure pulsations, which cause the fluid-borne noise. This results in the downstream components to vibrate. The structure-borne noise is produced by exciting vibration in any component. The transfer of fluid and structure induced vibration to the nearby air mass results in air-borne noise.

How to reduce fluid-borne noise?

While the main cause of fluid-borne noise is pressure pulsation, it can be reduced through hydraulic pump design, though the problem cannot be fully eliminated. In large hydraulic systems or noise-sensitive applications, the fluid-borne noise emission can be reduced by the installing a silencer. The most simple form of silencer is the reflection silencer. This is widely used in hydraulic systems and it reduces sound waves by inducing a second sound wave of the same amplitude and frequency at a 180-degree phase angle to the first.

How To reduce structure-borne noise?

The structure-borne noise is caused by the vibrating mass of the power unit (this includes the hydraulic pump and its prime mover). This can be reduced through the elimination of sound bridges between the the power unit and valves and the power unit and tank. This is normally attained by using flexible connections like rubber mounting blocks and flexible hoses. In some cases it is necessary to introduce additional mass, the force of which reduces the transmission of vibration at bridging points.

How to reduce air-borne noise?

The force of noise radiation from an object is proportional to its area. This force is inversely proportional to its mass. Hence to reduce air borne noise, you can reducing an object’s surface area or increase its mass. For example, build the hydraulic reservoir from thicker plate. The magnitude of air-borne noise created directly from the hydraulic pump can be reduced by mounting the pump inside the tank. If the noise from hydraulic system remains outside the required level even after all the above noise reduction measures have been tried, encapsulation or screening must be considered.

Hydraulic Fluid Energy Storage

Another cause of noise in hydraulic systems is due to the storage and subsequent release of energy in the hydraulic fluid. Hydraulic fluid is not perfectly rigid. When the fluid is compressed, it results in energy storage. However if this compression is not properly controlled, the stored energy dissipates instantaneously. This sudden release of energy moves the fluid very fast, and this creates noise. So while handling hydraulic system, it is necessary to control the energy storage in hydraulic fluid.

Hydraulic Symbols Cheat Sheet Continued

Click on the links below to get cheat sheets 5 and 6 of hydraulic symbols. Print them off and use them for reference.

Cheat sheets 5 and 6 are lists of hydraulic symbols like valve hydraulic symbol, solenoid valve symbol, directional valve symbol, servo valve symbol, electric motor symbol, lubricator hydraulic symbol, gauge hydraulic symbol, indicator hydraulic symbol, thermometer hydraulic symbol, thermostat hydraulic symbol, silencer hydraulic symbol, cooler hydraulic symbol, filter hydraulic symbol, heater hydraulic symbol, level gauge hydraulic symbol, flow meter hydraulic symbol, etc.

Click on the links below to see the Working Line-Pressure/Return Hydraulic symbols, Hydraulic Cylinder Symbols, Hydraulic Motors Symbols etc.

Sheet 5
Sheet 6

Craig Cook

Hydraulic Symbol Cheat Sheets – Part 2

Click on the links below to get cheat sheets 3 and 4 of hydraulic symbols. Print these hydraulics cheat sheets off and use them for reference.

Cheats sheets part 3 and 4 are hydraulic symbols or schematic symbols of hydraulic valves, valves control hydraulic symbols, electric motor hydraulic symbols, reservoir hydraulic symbols, directional valve hydraulic symbols, filter, electro hydraulic servo symbols etc.

Click on the links below to see the Working Line-Pressure/Return Hydraulic symbols, Hydraulic Cylinder Symbols, Hydraulic Motors Symbols etc.

Sheet 3
Sheet 4

Craig Cook

Hydraulic Symbols

Click on the links below to get 2 cheat sheets of hydraulic symbols. Print them off and use them for reference.

These cheat sheets have a list of common hydraulic symbols and hydraulic schematic diagrams which are useful for reading, understanding and interpreting hydraulic schematics and circuit drawings. Click on the links below to see the Working Line-Pressure/Return Hydraulic symbols, Hydraulic Cylinder Symbols, Hydraulic Motors Symbols etc.

Next week I’ll put together another list of symbols you can print off and use as reference.

Sheet 1

Sheet 2

Craig Cook

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