FREQUENTLY
ASKED QUESTIONS
ON NIRAFON ACOUSTIC CLEANING SYSTEMS (NACS) |
| |
| Q1 |
What is
the principle of Acoustic Cleaning? |
| Ans |
Nirafon Acoustic
Cleaning Systems utilize the acoustic energy of low frequency
sound waves, which are generated in form of acoustic pressure
pulses. These pressure pulses weaken the bonds between the particles
themselves as well as between the particles and the surface.
This causes the bonds to break and the particles are dislodged
from the surface to which they were adhering. The dislodged
particles are carried away by air/ gas stream or by gravity. |
| |
|
| Q2 |
Can existing build-ups/
depositions which have become hard be cleaned by using NACS? |
| Ans |
Acoustic Cleaning
Technology is based on the Preventive Maintenance philosophy.
It is always recommended that before NACS is installed for any
application, the equipment surfaces facing deposition problems
be cleaned thoroughly so that NACS can work on clean surfaces
and prevent the dust particles to build up and develop into
a solid hard mass. It is difficult to remove already formed
hard/solid deposits by using NACS. However, it is possible to
remove existing accumulations of loose dust/ash by using NACS. |
| |
|
| Q3 |
Does it mean that if
NACS is installed on clean surface, there shall be no deposition
at all and the surface shall remain clean forever? |
| Ans |
The function
of NACS is to reduce the rate of deposition of dust/particulate
matter on the surface thus keeping the surface substantially
clean for a much longer period of time than without NACS. The
need of manual cleaning is reduced considerably, resulting in
a marked improvement in equipment availability. |
| |
|
| Q4 |
What is the sound pressure
level (SPL) that would be generated by the Acoustic Cleaning
Systems? What is the sound pressure level that would be heard
near the place where the Acoustic Horn is installed? |
| Ans |
A.
Under test conditions at our laboratory, the generated Sound
Pressure Level is more than 150dB(A).
Inside the equipment on which the NACS is installed, the sound
pressure level would be more than 130dB(A).
In vicinity of the Acoustic horn, outside the equipment on which
it is installed, the sound pressure level (SPL) is around 80dB(A)
depending upon the distance from the horn. In many cases, the
sound of the horn gets drowned in the background noise generated
by other equipment in the plant. |
| |
|
| Q5 |
Does the sound level
violate the Norms for Industrial Noise Pollution? |
| Ans |
The industrial
noise pollution norms classify noise as Continuous and Impact
Noise. For continuous noise, the rules specify the max no. of
hours a person can be subjected to a given Sound Pressure Level
(dB). Impact noise is intermittent in nature and the norms permit
exposure to a much higher Sound Pressure Level. Here, the norms
specify the no. of impulses /impacts that can be permitted for
a given SPL (dB).
The Acoustic Cleaning Systems sound in pulses which makes the
sound intermittent and the norms for Impact Noise are applicable.
The Sound Pressure Level in the vicinity of an Acoustic Horn
is much lower than the permissible SPL stated under the norms.
Hence Acoustic Cleaning Systems do not violate the Norms for
Industrial Noise Pollution at all. |
| |
|
| Q6 |
Does the sound create
vibrations and if so, would it not damage the equipment/structures
on which the NACS is installed? |
| Ans |
The Acoustic
horns have been so designed as to generate sound of frequency
ranges effective in vibrating/resonating the dust particles
but not the structures or the mother equipment on which the
horns are installed. In fact, the acoustic horns operate at
frequency ranges much higher than the range of natural frequencies
of structures/equipment thus eliminating the remotest chances
of their getting damaged by way of resonance. Thus Acoustic
Cleaning is a completely safe method. |
| |
|
| Q7 |
What does the total
hardware comprise of? |
| Ans |
The total system
hardware comprises of the Acoustic Horn, Air Handling Unit (AHU)
and the Electrical Control Unit (ECU). The Acoustic Horn generates
the sound by vibration of a diaphragm by means of compressed
air. The Air Handling Unit (AHU) filters and regulates the pressure
of the compressed air and allows it to flow to the Acoustic
Horn by opening of a solenoid valve. The Electrical Control
Unit (ECU) controls the operation of the solenoid valve in the
AHU as per desired time settings. |
| |
|
| Q8 |
What is the compressed
air requirement? |
| Ans |
Compressed air
at 5-6 kg/cm2 pressure is required to operate NACS. The consumption
per horn is approx.25-40 lit/sec (free air, depending upon the
model) when the horn sounds and 1-2lit/sec (free air) continuously
as Cooling & Rinsing Air. The compressed air flow has to
be sufficient to ensure minimum pressure drop during sounding.
It is recommended that air receiver /manifold of suitable capacity
be installed near the systems. |
| |
|
| Q9 |
What is the power requirement
for operating NACS? |
| Ans |
Since there
are no electrically driven moving parts, NACS has very low power
consumption. Solenoid valves (8-10W each) are required to be
operated intermittently using the ECU. The Power supply to the
ECU may be 220V AC/ 110V AC/24VDC as per client’s requirement. |
| |
|
| Q10 |
What is the quality
of compressed air required for operating NACS? |
| Ans |
The compressed
air should be free from dust, moisture and oil content. In case
there is high moisture content in the compressed air, the client
should provide air dryer or moisture trap to ensure moisture-free
air for NACS. In most cases, plant air is quite acceptable for
NACS operation, otherwise instrument air is used. |
| |
|
| Q11 |
Can the installation
be done while the plant is in operation ? |
| Ans |
Installation
of the system involves making cutouts on the body of the main
equipment which cannot be done while the plant in operation.
Also, thorough cleaning of the main equipment is required prior
to NACS installation for which shutdown is a must. For this
purpose, the installation program is made to suit client’s
shutdown schedule. |
| |
|
| Q12 |
Does the system have
any flexibility when it comes to the sounding pattern and frequency
of sounding? |
| Ans |
The sounding
pattern and the time settings for operation are decided based
on the demands of the application and can vary considerably
from application to application. Even for a given application,
in order to cater to changing demands, the operation of the
system is made flexible by keeping provision of changing the
settings in the ECU, such as duration of sounding, no. of sounding
pulses and the interval between the soundings. The pattern/sequence
of sounding of the horns can also be changed if required. |
| |
|
