Acoustics – Sound-modifying means – Muffler – fluid conducting type
Reexamination Certificate
2002-07-24
2004-01-06
Hsieh, Shih-Yung (Department: 2837)
Acoustics
Sound-modifying means
Muffler, fluid conducting type
C181S264000, C181S265000, C181S278000, C181S281000, C181S267000
Reexamination Certificate
active
06672425
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to a noise abatement system for lowering air velocity in a closed system. Specifically, the invention describes a straight pipe module suppressor, with internal vanes, which reduces the velocity of air used in an industrial airblow cleaning operation.
2. Description of the Related Art
High pressure/high velocity air may be used to clean industrial piping. Reference to cleaning in this application is the process of removing loose and/or lightly adhered debris from piping. The piping to be cleaned may be that which is used in the operation of a power generating plant by providing steam to turbines, in a petrochemical plant to provide stock or product to a process or storage unit, or in any other environment using piping that is typically operated under high pressure and/or high temperature.
The piping to be cleaned may be new fabrication, which may nonetheless contain dirt, sand, loose bolts, used welding rods or other non-structural items or debris left from the fabrication process. Alternatively, the piping to be cleaned may already have been in service and in need of cleaning to remove built-up material (usually scaling) on the interior of the piping. Typically, cleaning of piping that has been in service is accomplished by first flushing the line with a chemical flush to loosen the mill scale, which is solubilized into a solution. The line is then rinsed, and the metal neutralized (washed) to remove the solution containing the chemical flush and the soluble scale particles. The remaining loose or lightly adhered insolubles left in the piping are then removed with the high-pressure air.
Debris from either new fabrication or scaling can damage downstream equipment, such as a turbine, processing unit or other equipment/systems. For example, high pressure impingement of debris on turbine blades operating at high speed could result in damage or catastrophic failure of the turbine.
In a typical pipe cleaning operation, the piping to be cleaned is connected at its upstream end to an air pressurization system, typically a pressure vessel and/or piping, and at its downstream end to a temporary bypass line. The temporary bypass line diverts the high pressure cleaning air away from downstream equipment.
In either use of high pressure air for cleaning piping (new or used), the air pressurization system is typically charged to a level sufficient to provide air pressure through the piping 1.2 times the normal operating pressure of the piping. This high pressure air passes through the piping and is discharged along with the debris out of the piping.
If the high pressure cleaning air, typically traveling at or above sonic speed through the piping, is released directly to the environment without velocity suppression, the noise is intolerable. It is not unusual for such a release to generate noise levels between 115 dB and 140 dB, which can cause hearing loss to those nearby and structural damage or nuisance several miles away. Further, high pressure air can penetrate the skin of a person exposed to the exhaust airflow. This air penetration through the skin can cause air embolisms in the blood vessels, which can be fatal. Thus an air velocity suppression/reduction system is needed in such environments.
Air velocity suppressors for high pressure/high velocity air used to clean piping air are found in the prior art. However, these silencers typically use a baffle system to reduce the velocity of the air. These create unwanted backpressure that reduces the velocity of the air upstream in the cleaning process, thus creating the requirement for higher initial air velocity.
Other air velocity
oise suppressors use a muffling device with a closed cap end, and direct all airflow laterally outward through release holes in the sides of the inner and outer pipes of the suppressor. This system is dangerous when used with high velocity/high pressure stream, since sudden blockage of the release holes, as from a large piece of debris, will cause immediate over-pressurization of the suppressor and likely explosion.
Air suppressor systems used in low velocity applications, such as mufflers used on internal combustion machines or small scale pneumatic silencers on leaf blowers and the like, are unacceptable in high pressure/high velocity air cleaning systems. These low velocity devices, even if scaled up, are unable to adequately reduce the volume and velocity of high-pressure air being exhausted from the system due to their structural and design limitations.
BRIEF SUMMARY OF THE INVENTION
Accordingly, the objectives of this invention are to provide, inter alia, a new and improved air suppression system that:
Does not create undue back pressure;
Does not pose a risk of sudden blockage;
Reduces high air velocity, including those about sonic speed;
Uses standard fabrication components; and
Is cost effective.
These objectives are addressed by the structure and use of the inventive device. A straight through pipe has air directing internal vanes attached to the interior wall of an inside tube. The walls of the inside tube are perforated to permit airflow separated from the main air stream to escape to a space between the inside tube and the outside tube. These vanes cause the high velocity air to rotate about its directional axis. Laminar resistance of the rotation causes a tail of air to form, moving away from the center or core of the exhaust stream and against the interior wall of the inside tube. The high velocity air being released into the inside tube has an exhaust
15
shape shown in
FIGS. 6 and 6A
, comprising a outer layer
19
and a core
17
. Outer layer
19
is formed as laminar resistance allows side air to move away from the center of exhaust
15
, while the faster air of core
17
speeds through the center of the inner tube
30
. By directing exhaust
15
to rotate about its linear axis, outer layer
19
is “chewed away” as its air is directed into velocity dampening areas between the inside tube
30
and the outside tube
20
of the invention. As outer layer
19
is removed, it is replaced by air from core
16
, thus decreasing the overall velocity of exhaust
15
.
Other objects of the invention will become apparent from time to time throughout the specification hereinafter disclosed.
REFERENCES:
patent: 1818469 (1931-08-01), Floyd
patent: 2403403 (1946-07-01), Sauer
patent: 3374857 (1968-03-01), Hutchins
patent: 4109753 (1978-08-01), Lyman
patent: 4325459 (1982-04-01), Martin
patent: 4966253 (1990-10-01), Stephens et al.
patent: 5058381 (1991-10-01), Christenson et al.
patent: 5058704 (1991-10-01), Yu
patent: 5962822 (1999-10-01), May
Bracewell & Patterson LLP
Hsieh Shih-Yung
Onyx Industrial Services, Inc.
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