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Acoustic Components
Recom Engineering Acoustic Components Store
 An ultrasonic cleaner is a cleaning device that uses ultrasound (usually from 15-400 kHz) to clean delicate items. They
are often employed for cleaning of jewellery, lenses and other optical parts, coins,
watches, dental and surgical instruments, fountain pens, industrial parts and electronic
equipment. In everyday use such devices may be found in use in most jewelry workshops,
watchmakers establishments, or in cellular phone repair workshops (where it could
be used for cleaning a phone that has been exposed to enough moisture to hinder
its operation). Design In an ultrasonic cleaner, the object to be cleaned is placed
in a chamber containing a suitable ultrasound conducting fluid (an aqueous or organic
solvent, depending on the application). In aqueous cleaners, the chemical added
is a surfactant which breaks down the surface tension of the water base. An ultrasound
generating transducer is built into the chamber, or may be lowered into the fluid.
It is electronically activated to produce ultrasonic waves in the fluid. The main
mechanism of cleaning action is by energy released from the creation and collapse
of microscopic cavitation bubbles, which break up and lift off dirt and contaminants
from the surface to be cleaned. The higher the frequency, the smaller the nodes
between the cavitation points which allows for more precise cleaning. The bubbles
created can be as hot as 10,000 degrees and 50,000 lbs per square inch, but are
so small that cleaning and removal of dirt is the main result[citation needed].
Uses Industrial ultrasonic cleaners are used in the automotive, sporting, printing,
marine, medical, pharmaceutical, electroplating, engineering and weapons industries.
Cleaners are also used to experimentally determine the elastic constants of many
anisotropic materials. Traditionally, ultrasonic waves can only be sent through
a material at angles normal to the materials surface. However, in water the angle
of incidence for a longidunal wave can be set, inducing both longitudinal and transverse
waves in the material. Then by measuring the time of flight for both waves, the
elastic constants can be determined. Devices for home and hobby use are readily
available, and may cost as little as US$20, as of January 2007. Suitable materials
for ultrasonic cleaning Ultrasonic transducers showing ~20 kHz and ~40 kHz stacks.
The active elements (near the top) are two rings of lead zirconate titanate, which
are bolted to an aluminium coupling horn. Ultrasonic transducers showing ~20 kHz
and ~40 kHz stacks. The active elements (near the top) are two rings of lead zirconate
titanate, which are bolted to an aluminium coupling horn. * Stainless Steel * Mild
Steel * Aluminium * Copper * Brass * Other alloys * Wood * Plastics and Rubber *
Cloth Ultrasonic transducers work by rapidly changing size when excited by an electrical
signal. This creates a compression wave in the liquid of the tank. These compression
waves actually ‘tear’ the liquid apart, leaving behind a ‘void’ or ‘partial vacuum
bubble’. When these ‘bubbles’ (and there are many millions of them in an active
ultrasonic tank) collapse, they collapse with enormous energy. When sufficient energy
is built up in the ‘bubble’ or cavitation, the cavitation collapses violently. The
transducers are usually composed of piezoelectric material (e.g. lead zirconate-titanate
or Barium Titanate), and occasionally are made of magnetostrictive material (e.g.
nickel or ferrite). The often harsh chemicals traditionally used as cleaners in
many industries can be reduced or eliminated with the introduction of ultrasonic
technology. Ultrasonics are also used in many medical and dental techniques and
industrial processes, as well as in industrial cleaning.
Acoustic cleaning is used wherever there is a build up of dry materials and particulates
which need to be cleaned regularly to ensure maximum efficiency and minimize maintenance
and down time. An acoustic cleaner works by generating powerful sound waves which
will vibrate the dry materials differently to each other and the surrounding structures.
History and Design An acoustic cleaner consists of 2 parts. * The wave generator
which takes the compressed air and applies it to a diaphragm (acoustics). The wave
generator is usually made from solid machined stainless steel. The diaphragm within
the generator is the only moving part within an acoustic cleaner and there is no
danger of sparking.The diaphragm is usually manufactured from special aerospace
grade titanium to ensure performance and longevity. * The bell, which is usually
made from spun 316 grade stainless steel. The bell is a resonance section or amplifier
and it will tune and direct the sound waves. An acoustic cleaner is powered by compressed
air with an operating range of between 4.8 to 6.2 bars or 70 to 90 psi. The resultant
sound pressure level will be around 150 dB. The overall length of the acoustic cleaner
will range from between 430 mm to over 3 metres long. There are generally 4 ways
to control the operation of an acoustic cleaner. * The most common is by a simple
timer. * SCADA. * PLC (programmable logic controller). * Manually by Ball valve.
An acoustic cleaner will typically sound for 10 seconds and then wait for a further
500 seconds before sounding again. This ratio for on/off is approximately proportional
to the working life of the diaphragm. Provided the operating environment is between
– 40 and 100 °C a diaphragm should last between 3 and 5 years. The wave generator
and the bell have a much longer life span and will often outlast the environment
in which they operate. The older bells which were made from cast iron were susceptible
to rusting in certain environments. The new bells made from 316 spun steel have
no problem with rust and are ideal for sterile environments such as found in the
food industry or in pharmaceutical plants. Acoustic cleaning began in the early
1970s with experiments using ship horns or air raid sirens. The first acoustic cleaners
were made from cast iron. From 1990 onwards the technology became commercially viable
and began to be used in dry processing, storage, transport, power generation and
manufacturing industries. The latest technology uses 316 spun stainless steel to
ensure optimum performance. Operation and performance The majority of acoustic cleaners
operate in the audio sonic range from 60 hertz up to 420 Hz. Occasionally there
is a requirement to operate in the infrasonic range below 40 Hz. This would apply
if there were strict noise control requirements, or there was limited plant access.
There are three scientific fields which converge in the understanding of Acoustic
Cleaning Technology. * Sound propagation. This relates to an understanding of the
nature of the sound waves, how they vary and how they will interact with the environment.
* Mathematics of the environment. Materials science, surface friction, distance
and areas familiar to a mechanical engineer. * Chemical engineering. The chemical
properties of the powder or substance to be debonded. Especially the auto adhesive
properties of the powder. An acoustic cleaner will create a series of very rapid
and powerful sound induced pressure fluctuations which are then transmitted into
the solid particles of ash, dust, granules or powder. This causes them to move at
differing speeds and debond from adjoining particles and the surface that they are
adhering to. Once they have been separated then the material will fall off due to
gravity or it will be carried away by the process gas or air stream. The key features
which determine whether or not an acoustic cleaner will be effective for any given
problem are the particle size range, the moisture content and the density of the
particles as well as how these characteristics will change with temperature and
time.. Typically particles between 20 micrometre and 5 mm with moisture content
below 8.5% are ideal. Upper temperature limits are dependent upon the melting point
of the particles and acoustic cleaners have been employed at temperatures above
1000 C to remove ash build up in boiler plants. It is important to match the operating
frequencies to the requirements. Higher frequencies can be directed more accurately
whilst lower frequencies will carry further, and are generally used for more demanding
requirements. A typical selection of frequencies available would be as follows:
* 420 Hz for a small acoustic cleaner which might be used to clear bridging at the
base of a silo. * 350 Hz will be more powerful and this frequency can be used to
unblock material build up in ID (induced draft) fans, filters, cyclones, mixers,
dryers and coolers. * 230 Hz. At this frequency the power involved is sufficient
to use in most electricity generation applications. * 75 Hz and 60 Hz. These are
generally the most powerful acoustic cleaners and are often used in large vessels
and silos. Health and safety. The introduction of acoustic cleaners has been a significant
improvement in many areas of health and safety. For instance in silo cleaning -
the previous solutions tended to be intrusive or destructive. Air cannons, soot
blowers, external vibrators, hammering or costly man entry are all superseded by
non invasive sonic horns. An acoustic cleaner requires no down time and will operate
during normal usage of the site. If we take the example of silo cleaning a little
further then there are two typical problems. Bridging This is when the silo blocks
at the outlet. Previously the problem was addressed by manual cleaning from underneath
the silo which in its turn introduced significant risk from falling material when
the blockage was cleared. An acoustic cleaner is able to operate from the top of
a silo through in situ material to clear the blockage at the base. Rat holing Compaction
on the side of a silo. This not only reduces the operating volume in a silo but
it also compromises quality control by disrupting the first in first out cycle.
Older material compacted on the side of a silo can also start to degrade and produce
dangerous gases. An acoustic cleaner will produce sound waves which will make the
compacted material resonate at a different rate to the surrounding environment resulting
in debonding and clearance. Advantages of Acoustic cleaners. * Repetitive use during
operations means that there are fewer unscheduled shut downs. * Improved material
flow by the elimination of hang-ups, blocking and bridging. * Minimisation of cross
contamination by ensuring complete emptying of the environment. * Improved cleaning
and reduction of health and safety risks. * Increased energy efficiency. Reducing
the build up on heat exchange surfaces results in lower energy usage. * Extended
plant life. Aggressive cleaning regimes are avoided. * Ease of operation. It is
easy to automate the horns either at regular intervals or to tie the sounding in
to changes in their environment such as pressure or flow rates. * Importantly they
prevent the material build up problem from occurring in the first place. These advantages
mean that the financial payback is often very quick. It is also possible to compare
acoustic cleaners directly to alternative solutions. * Air cannons. These are well
established but are expensive with limited coverage thus requiring multi unit purchase.
They are also noise intrusive and have a high compressed air consumption. * Vibrators.
These are easy to fit to an empty silo but can cause structural damage as well as
contributing to powder compaction. * Low friction linings. These are very quiet
but are expensive to install. Also they are prone to erosion and can then contaminate
the environment or product. * Inflatable pads and liners. Again these are easy to
install in an empty silo. They help side wall build up but have no impact on bridging.
They are also hard to maintain and can cause compaction. * Fluidisation through
a 1 way membrane. This can help already compacted material. However they are expensive
and difficult to install and maintain. They can also contribute to mechanical interlocking
and bridging. Specific applications for Acoustic cleaners * Boilers. Cleaning of
the heat transfer surfaces. * Electrostatic precipitators. Acoustic cleaners are
being used for cleaning hoppers, turning vanes, distribution plates, collecting
plates and electrode wires. * Super heaters, economisers and air heaters. * Duct
work. * Filters. Acoustic cleaners are used on reverse air, pulse jet and shaker
units. They are effective in reducing pressure drop across the collection surface
which will increase bag life and prevent hopper pluggage. Generally they can totally
replace the both reverse air fans and shaker units and significantly reduce the
compressed air requirement on pulse jet filters. * ID fans. Acoustic cleaning helps
to provide a uniform cleaning pattern even for inaccessible parts of the fan. This
maintains the balance of the fan. * Kiln inlet. Acoustic cleaners help to prevent
particulate build up at the kiln inlet and this will minimise nose ring formation.
* Mechanical pre Collectors. Acoustic cleaners help prevent build up around the
impellers and between the tubes. * Mills. Acoustic cleaners help maintain material
flow and also prevent blockages in the pre grind silos. They also help prevent material
build up in the downstream separators and fans. * Planetary Coolers. Acoustic cleaners
help prevent bridging and ensure complete evacuation. * Precipitator. Acoustic cleaners
help clean the turning vanes, distribution plates, collecting plates and electrode
wires. They can either assist or replace the mechanical rapping systems. They also
prevent particulate build up in the under hoppers which would otherwise result in
opacity spiking. * Pre heaters. Used in towers, gas risers, cyclones and fans. *
Ship cargo holds. Used both to clean and de aerate current loads. * Silos and hoppers.
To prevent bridging and rat holing. * Static cyclones. Acoustic cleaners will work
both within the cyclone and with the associated duct work.
If you are manufacturing acoustic components/ products and associated equipments please send
us an email sales@recomsys.net to include your products or services in recomsys.net
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Acoustic components for mobile phones, computers,
cars, medical instruments, hearing aids, cordless phones, MP3 players and game consoles.
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http://new.aacelectr.com/en/ |
AAC Acoustic Technologies (Shenzhen) Co., Ltd, Block A, 2/F, Building
8, Tianan Industrial Park,Nanyou, Dengliang Road, Nanshan, Shenzhen, China
Tel:86-755-26054538 26054502
Fax:86-755-26407627 E-mail:aaca@aacelectr.com
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Military and commercial sonar transducers, projectors
and hydrophones, underwater and hull-mounted telephones and diver hand-held sonars |
http://www.harrisacoustics.com/ |
Harris Acoustic Products, 141 Washington Street, East Walpole,
MA 02032-1155 Phone: 508 660 6000
Fax: 508 660 6061 |
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RPG Europe (acoustic grg products ltd)
have been manufacturing Acoustic Treatments for over 15 years for many applications
from Home Cinema to National Auditoriums. |
http://www.rpg-europe.co.uk/ |
Acoustic GRG Products Ltd/RPG
Europe, Lower Wall Road,West Hythe, Kent CT21 4NN tel 01303 230944
and 01303 230962
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