FIELD OF INVENTION
The present invention relates to a device to reduce Noise levels emanating
during operation of a Boiler Feed Pump assembly.
BACKGROUND OF THE INVENTION
A Boiler Feed Pump (BFP) is provided to increase the head of a flowing fluid by
enhancing its pressure component. It is operated by a moving rotor which is
made to rotate by a prime-mover, which in turn is driven by a power source
(generator). In this process, there is a possibility of viable pressure differences
which leads to Flow Induced Vibration (FIV's). FIVs degrade the performance of
the whole equipment by excess vibrations. The vibrating surfaces of a structure
excite the surrounding medium, in most cases air, causing pressure disturbances
which are experienced as noise. This phenomenon is known as noise radiation.
Where noise is a problem, rotating machinery such as electric motors or gear
boxes are generally identified is the cause. The vibration source in these types of
machinery being electromagnetic forces, the meshing of gears or mechanical
vibrations caused by imbalance of the rotating parts, the resulting vibrations are
transmitted from the rotating parts to the surrounding structure, which in the
end radiates noise.
The transfer and radiation of noise can be reduced by reconfigurating the
structure components of the application, for example, the BFP. The transfer of
noise can also be reduced by decoupling the components in such a way that the
noise path is interrupted. This can be achieved by adding noise reducing
treatments to the structure such as elastic elements, masses, local shielding or
damping layers.
Allowable noise levels in any type of industry for time exposure are as follows:
Allowable Noise exposure is based on Noise Dose according to international
standards[1]
Noise Dose is expressed as a percentage of the allowable limit. How high it goes
depends on both noise intensity and time of exposure to noise.
Louder (More dBA) = More Noise Dose
Longer (More Time = More Noise Dose
Absolute Quite =. 0% Noise Dose
85 dBA for 8 Hrs = 50% Noise Dose
90 dBA for 8 Hrs = 100% Noise Dose
95 dBA for 8 Hrs = 200% Noise Dose
95 dBA for 12 Hrs = 300% Noise Dose
If the existing level is more than the permissible theoretical value, it results into
problems like fatigue, sleep interference, decreased work performance, hearing
loss along with certain health problems, having cardiovascular effects, to
workforce. Apart from this, it has far reaching effects on the equipment Energy
Efficiency.
From the above data, it can analyzed that even 95 dBA for 8 Hrs is considered as
200% deteriorating effects.
OBJECTS OF INVENTION
It is therefore an object of the invention to propose a device to reduce Noise
level emanating during operation of Boiler Feed Pump assembly, which
eliminates the disadvantages of prior art.
Another object of the invention is to propose to reduce a device Noise level
emanating during operation of Boiler Feed Pump assembly, which constitutes an
eco-friendly composite provided at the noise-emanating areas of the BFP.
A further object of the invention is to propose a device to reduce Noise levels
emanating during operation of a Boiler Feed Pump assembly, which acts as an
attenuating shield.
SUMMARY OF THE INVENTION
A device to reduce noise level emanating during operation of a boiler feed pump
assembly, the boiler feed pump increasing the head of a flowing fluid by
enhancing the pressure component of the fluid, the assembly comprising an
electric motor coupled to a boiler feed pump via a hydraulic coupling, the motor
being operably connected to a booster pump, the device comprising a cylindrical
hollow enclosure disposed between an inlet side of the boiler feed pump and a
rear end of the hydraulic coupling; and a visco-plastic material sealably disposed
between the inlet of the pump, and the cylindrical hollow enclosure to form an
acoustic attenuating shield.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 - shows a generic view of a boiler feed pump (BFP) assembly
Figure 2 - shows a treated structure of a BFP assembly with sound
producing data according to the invention
Figure 3 - shows a prior art sound-protecting enclosure of a BFP.
DETAIL DESCRIPTION OF THE INVENTION
Figure 1 shows a BFP assembly comprising an electric motor (3) coupled to the
boiler feed pump (BFP), (1) via a hydraulic coupling (2). The motor (3) is
operably connected to a booster pump (4). Figure 3 shows a BFP of prior art
enclosed in a sound proof chamber. The pump (1) is mounted on a MDF base (5)
which is supported by a concrete slab (6) casted on the floor (7) of the shop.
One each resilient mat (8,9) is disposed between the MDF base (5) and the
concrete slab (6), and between the floor (7) and the concrete slab (6). Finally,
the pump (3) is surrounded by a MDF enclosure (9) having an internal cover (10)
made of sound absorbing foam. Figure 2 shows that between the hydraulic
coupling (2), and the boiler pump (1), an acoustic attenuating shield (11,12) is
provided which consists of a cylindrical hollow enclosure 912) and is sealed with
a visco-elastic material (11). The enclosure (12) is interposed between an inlet
side (13) of the pump (1), and a rear end (14) of the hydraulic coupling (2).
Figure-2 additionally shows the sound permissible level (SPL(A)) emanating from
various components of BFP assembly having 500MW pump, the values expressed
in db. It can be seen from the values that more that 105 dBA is being observed,
and that the exposure time is around 8 hrs in lasting area.
As shown in figure 2, to reduce SPL, or inturn PEL, to some allowable or
tolerable values, the present invention provides alternative technical solutions in
the form of attenuating shield. They are as follows:
1. Applying JUTE composite around the inlet area of the pump:
In this process alkali treated Jute-felt[11] is applied and wrapped around
the inlet of the pump including other noise emitting areas. This will act as
an alternating shield and reduce the noise levels considerably.
2. Applying Visco-elastic material with cladding (I/O:
In this method, a visco-elastic material is kept in between two thermally
insulated sheet metals to form an attenuating shield. These layers must
be applied around the inlet pipe or other noise emitting areas.
This requires two thermally insulated sheet metals one each fixed at inlet
of the BFP and rear end of the hydraulic coupling. This could additionally
prevent (by high temperatures) the damage of the visco-elastic material
{VEM-Visco-elastic material is a good dampening material}
3. Provision of enclosure
According to the invention, an acoustic attenuating shield (11,12) is
provided to reduce the noise. The invention teaches covering the sound
emanating source with a cylindrical hollow enclosure (12) and sealing it
with a layer of Visco-Elastic Material (11) between them. This shield is
flexible enough to be adjusted to any type of aerodynamic equipment or
turbo-driven system.
According to the invention, when the NOISE-SPL LOG Addition formula namely,
SPLtotai=10.logio (S1001SPLj) is applied, where T implies particular noise SPL
value, the Resultant SPLtotai=112.24 dBA is found (Considering three values
(108,109,104 dBA) for the pump alone.
From the Noise Dose tables (TABLE-1), it can be seen that taking 90 dBA as 100
Permissible exposure level (PEL) for 8 Hrs, and taking 112 dBA, the PEL comes
out to be 2111 which is like having 2011% more effect in terms of performance
parameters when the inventive process is implemented.
TABLE - 1
When determining the Permissible Exposure Limit (PEL) of Noise Dose, the
invention makes use of only the portion of the Table including noise levels of 90
dBA and higher. When determining the Action Level (AL) of Noise Dose, use is
made of the entire table. It may be noted that using a Sound Level Meter (SLM)
and Table-1 to estimate noise dose should be still considered to be an
approximation of actual noise dose. Accordingly, 2 dBA is added to the
measurements by the SLM to allow for calibration or sampling errors.
Refereces:
1. MSHA STATE GRANT PROGRAM FOR MICHIGAN-REPORT
2. http://www.mine-safety.mtu.edu/noise/03noise basics.htm
3. JUTE AS AN ECO-FRIENDLY NOISE CONTROL MATERIAL - A CASE
STUDY, S. Fatima and A.R. Mohanty, Department of Mechanical
Engineering, Indian Institute of Technology, Kharagpur
WE CLAIM
1. A device to reduce noise level emanating during operation of a boiler feed
pump assembly, the boiler feed pump increasing the head of a flowing
fluid by enhancing the pressure component of the fluid, the assembly
comprising an electric motor (3) coupled to a boiler feed pump (1) via a
hydraulic coupling (2), the motor (3) being operably connected to a
booster pump (4), the device comprising a cylindrical hollow enclosure
(12) disposed between an inlet (13) side of the boiler feed pump (1) and
a rear end (14) of the hydraulic coupling (2); and a visco-plastic material
(11) sealably disposed between the inlet (13) of the pump (1), and the
cylindrical hollow enclosure (12) to form an acoustic attenuating shield.
2. The device as claimed in claim 1, wherein the attenuating shield
comprises visco elastic material interposed between two thermally
insulated sheet metals one each affixed at the inlet of the pump and the
rear end of the hydraulic coupling.
3. The device as claimed in claim 1, wherein the attenuating shield
comprises an alkali-treated jute-felt wrappingly disposed at the inlet of the
pump.
4. A device to reduce noise level emanating during operation of a boiler feed
pump assembly, as substantially described and illustrated herein with
reference to the accompanying drawings.

The present invention relates to a device to reduce noise level emanating during
operation of a boiler feed pump assembly, the boiler feed pump increasing the
head of a flowing fluid by enhancing the pressure component of the fluid, the
assembly comprising an electric motor (3) coupled to a boiler feed pump (1) via
a hydraulic coupling (2), the motor (3) being operably connected to a booster
pump (4), the device comprising a cylindrical hollow enclosure (12) disposed
between an inlet (13) side of the boiler feed pump (1) and a rear end (14) of the
hydraulic coupling (2); and a visco-plastic material (11) sealably disposed
between the inlet (13) of the pump (1), and the cylindrical hollow enclosure (12)
to form an acoustic attenuating shield.