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Reducing Noise in the Manufacturing Industry

Problem

Noise is undesired sound which, in extreme cases at high sound pressure, can have injurious effects.  Hydraulic drives and controls are characterized by extremely high levels of force, measured against the volume and weight of the components.  Where large amounts of power are converted in a small area, the result can be high, damaging sound levels.  Hydraulic system noise and leakage are still two of the most fundamental problems for modern hydraulic systems. Though many manufactures have come up with solutions, providing a simple cost effective resolution has still been an issue in the industry. Many hydraulic systems are still above 85 dB(A), which is the manufacturing factory average sound level of machines. Systems & Machines running above 85 dBA continuously for 8 hours or more exceed human exposure limits and could have lasting consequences to anyone in contact.

Solution

The threshold between pleasant sound and unpleasant sound equals noise.  The goal is to reduce or eliminate this damaging noise to ensure a safe workplace.  In noise abatement, it is important to know the physical basics of sound propagation. The basics pertain to:

  • Sound generation
  • Sound transmission
  • Sound projection

This list also echoes the priorities for abatement.  If one can prevent a large amount of sound energy from being created, the other measures become unnecessary.  Other important factors are the strength of the sound, how long it remains in effect, and the chronology.

There are two forms of noise protection measures: Primary & Secondary

Primary noise protection is more cost-effective, always addresses the sources of the sound themselves, and incorporates all the measures used to reduce the sound emissions or sound generation.  The right component selection, such as internal gear pumps, is the first step towards noise reduction.  The added investment becomes relative as soon as you take an overall view of the costs.  Actions taken after the fact are always expensive!  When selecting pumps for example, noise radiation should be taken into consideration along with the usual criteria of pressure, flow, fixed or variable displacement, etc.  An estimate of the emissions of the hydraulic system can be made for pumps from the values obtained in the sound chamber. Other examples would be the use of elastic pump mounts or assembly block construction, which are preferable to assembly wall (front panel) construction.  The use of control blocks makes the entire system stiffer, less prone to vibrate, and keeps the dimensions of the radiating surfaces small. 

Secondary noise protection has to do with reducing the radiation and conduction of the sound energy.  Barriers, absorption materials or enclosures around hydraulic systems are used when low-noise components are insufficient to achieve the desired results.  There is considerable potential for noise reduction in the area of secondary measures.  The extra effort required in planning, design, assembly and testing does however entail corresponding costs.  Primary and secondary sound protection measures can be eliminated if there is a separate hydraulic pit or the hydraulic power unit is in a room which does not always have persons occupying it.     

Shrouding and dampening of materials has been done successfully by many manufactures and is an effective approach, however, usually at a premium cost. Hydrotech continues to work on systems that reduce noise below 75 dBA within a cost effective budget.  Industry leader and our supplier Bosch Rexroth is doing amazing things when it comes to product innovation that incorporates noise reduction.  No costly, noise-reducing secondary measures are necessary when you involve these new products and innovative integration from the beginning. 

Just recently, Bosch Rexroth has used Soundguard soundproofing to drop noise levels from each of two ladle turners built at their Kings Park Hydraulics and Automation division for a copper smelter in Peru.  Soundbarrier is a range of Soundguard composites comprising of two foam layers and one barrier layer. The inner foam layer isolates or “decouples” the barrier layer from the structure. The outer foam layer absorbs airborne sound waves and the high mass of the flexible barrier exhausts the energy of the vibrations. Creative approaches like this are just one of many ways businesses in the manufacturing industry are reducing noise.

Even by selecting low-noise components and carrying out preventative design and installation measures, the desire or required levels still may not be attained.  In fact, they may even still exceed the regulatory limit.  Noise reducing measures for hydraulic systems are very complex, since numerous work and control elements work are in sync with each other, and often are attached to sound-reflecting fixtures and walls.  These mounting elements can act like loudspeakers and result in a significant increase in sound level.  Experience shows that the airborne sound level of a complete system lies around 6-12 dB (A) above that of the value for the pump obtained in an acoustic chamber.  These increased values also depend on the size of the power unit, i.e., on the size of the sound reflecting surfaces and on the corresponding secondary measures for noise abatement.        

Hydrotech is here to help with any noise related problems that you may have.  Our innovative engineers with decades of experience can customize a power unit and aid with installation in a way that would effectively reduce noise in your plant.  We have technical experts that can assist you in the right component selection that enable you to take the appropriate steps towards reducing noise from the beginning.  In the end, it will be more cost-effective for you to allow Hydrotech to aid you in the process and allow us to help you with any problem that may be of concern.  The reduction of noise can bring about many benefits to a company as a whole.  Not only is it required by state and national standards, but it will increase the moral of an employee to the extent that he will work harder for your company.