Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02245069 1998-08-12
P10505 S/wil 27 July 1998
Applicant: Mueller-BBM GmbH
Robert-Koch-Strasse
8215~ Planegg
Ultr~onlc Attenuator
The invention relate~ to a ~evice for ultra~onic attenuation
for a piping or tubing through which a gaseous medium i~
flowing.
For mea~uring the flow-rate of a gaseou~ medium such a~ natural
gas in piping ultra~onic gas metere are employed to an ever-in-
creasing extent. The~e ultrasonic meters benefit fro~ the fact
that the ultraeonic pul~e3, which operate in a range from
roughly 60 to 200 kHz, propagate at a hig~er rate in the down-
~tream direction and at a lower rate in the upstream direction.
At these frequencie~ the acoustic waves have lengths o~ less
than 6 mm.
One problem in the application of an ultra~onic gas me~er con-
sists in the ~act that the u~eful sound i~ concealed by inter-
ferin~ noiee. Noi~e 80~rce~ ~uch as fittinge, compre~ore or
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fans, which supply the ~ound ~ithin a frequency range used by
the gas meter, account for the occurrence of ~uch interfering
noi~e. Accordingly there is the need for trouble-free operation
of an ultrasonic ga~ meter in piping that an ultra~onic at-
tenuator will be mounted ahead and down~trea~ of the ultrasonic
ga~ meter, which attenuates sound wave~ ha~ing wave length~ of
le~ than 6 mm. At the same time the aspect muqt al~o be duly
considered, on account of the ~hort sound wave lengths, that
avoidance of soiling ie an essential prerequisite for the func-
tional integr~ty of the ultra~onic attenuator a~ ~uch.
From application6 in other frequency range~ the pro~i~ion of
~ound-ab~orbing deflector~ in the for~ of a pipe manifold hav-
ing an absorbing lining i~ known. ~hat haq turned out a~ disad-
vantage in the applicat~on within the ultrasonic range, how-
ever, is a high risk of 60iling. r~loreover such a ~ound-attenu-
ating provislon requires extended fitting di~en~ions which re-
~ult i~ expen~ive solution~.
The invention i~ now ba~ed on the problem of making an effi-
cient ultrasonic attenuator device available for piping through
which a gaseou~ medium ic flowing, which presents a ~imple com-
pact ~tructure with a low 90iling rick.
In accordance with the invention thi~ problem i~ ~olved by the
features defined in Claim 1. Preferred feature~ defining expe-
dient improve~ents of the lnvention may be derived from the de-
pendent Claims.
The invention hence expediently prop~ec an ultra~onlc attenua-
tor device wherein, at a short fitting length, not only the
~oiling risk iB low but al~o the pressure 108e across the at-
tenuator may be kept s~all. The inventive device allow~ for
great reductions of the noise ievel.
The mutually parallel orienta~ion of the individual per~orated
plates along the flow direction contributes to the ~en~itivity
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in terms of fioiling. The device can be de~igned ~ith an
extraordinarily compact struc~ure including a tubular ca~e
which may be mounted, even sub~equently, in exi9ting pip~ng,
either directly or via a~sociated flanges. The device a~ such
preferably consist~ of corroeion-re~i~tant ~pecial ~teel~.
~he thickne6s of the perforated plate is comparatively non-
critical within the range between 60 and 200 kHz, and range~
appro~imately bet~een 0.5 and o mm, pre~erably between rou~hly
1 and 4 mm.
The perforated plate~ preferably present a uniform perforation
pattern with constant diameters of ~he perforatione amounting
to ~ 10 mm, preferably S 6 Inm; it E~hould be noted that 80iling
cannot be precluded in the case of s~aller hole diameters.
A~ far as the ~ize of the distance bet~een adjacent perforated
plate~ 1~ concerne~ this distance mu~t be presumed to be a
functlon of both the dl~ance from the associated ultrasonic
ga~ meter, on the one hand, and o~ the configuration of the
~ound ~ource a~d the length of the sound wave~, on the other
hand. The di~tance between adj acent perforated plate6 should
not amount to more than two timee the length of the ~ound waves
oE the ultra60nic meter, e.g. roughly 8 mm at a frequency of
1~0 kHz.
The length of the tubular case amounts to roughly 200 mm in or-
der to achieve an in~ertion loe~ of 20 dB. Shorter and longer
de~ign~ are, of course, possible, too, and it i~ equally poss~-
ble to couple several device~ in tandem arrangement, in w~ich
ca-~e, however, the orlentation of the per~orated plates of the
~ir-s~ device shouLd be normal on the exteneion of the pe~fo-
rated plate~ of the other dev$ce.
A~ far as .he diameter of the tubular ca~e i~ concerned ap-
proximate sizeY from 100 to loO0 mm are preferred, depending on
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the application, e.g. in nat~ral ga~ pipes and piping~ of any
type through ~hich gas i8 ~1Owing.
Regarding the three-dimen~ional orientation ~f the perforated
plate~ it i~ moreover expedient to di~pose them vertically in
the ca~e becau~e ~uch an arrangement i9 al~o accompanied by a
further reduction of the ~oiling ri~k.
The inventive concept, which provide~ for absorption by a com-
bination of a flo~ attenuation and a A/4-re~onator, allow~ for
a ~hort-length and hence compact device wherein the generation
of new ~ound waves in the devlce a~ such at the perforated
plate6 ifi expediently avoided in an e~ficient and reliable
manner by the provi~ion that the flow arri~es at the face of
the per~orated ~heet3 only rather than flowing through the
perforated area. This achieve~ also the advantageou~ aspect
that only a ~mall pressure los~ i~ created across the
ultrasonic attenuator device.
In the following, the invention will be explained in more de-
tail~ ~ith reference to the attached drawings. In the drawings:
Fig. 1 i~ a plan view of the face of one embodi~ent of an ul-
tra~onic attenuator device;
Fig. 2 show~ a sectional view taken along the line II - II ln
Fig. 1, and
Fig. ~ i6 a ~ectional plan view of another embodimen~ of the
inventive device in ccrre~pondence with Figure 1.
Figure 1 shows a device 10 for ultra~onic attenuation, which
compri~e~ a case 11 in the for~ of a hollow cylinder ha~ing a
diameter o~ roughly 200 mm in one embodiment and a length of
roughly 15~ mm according to Figure 2,. The ca~e 11 ls provided
with a flow inlet 12 and a flow outlet 13. The direction of
flow i~ indicated ~y the arrow~ A in Figure 2.
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In the case 11 numerous perforated plate~ or perforated sheets
14, re~pectively, are dispoeed in mutually parallel arrange-
ment, which e~tend between the zone of the flow inlet 12 and
the zone of the flow outlet 13 in parallel to each other. In
the illustrated em~odiment they are flush with the case 1~ at
the inlet and outlet sides.
The perforated ~heet~ 14 are dieposed in vertical arrangement
in the ca6e 11 and pre~ent a uniform perforation pattern with
hole~ ~5 of con~tant diametere of perforation, which are le~
than 6 mm in ~he illustrated embodiment.
The thickness d of the perforated plate~ 14 amounte to roughly
3 mm in ~he illu~trated e~bodiment.
The ~ize of the ~pacing a between adjacent per~orated p~ates 14
amounts to 4 mm, approximately.
The device con~i~t~ of a corrosion-re~istant ~teel. The
perforated sheet~ 14 are mounted in the hollow cylinder of the
ca~e 13 by welding, and the case 11 i~ then either in~erted
into and fa~tened in an existing pipe 20 or it i~ mounted via
lateral flange~, which are not illu~trated here, po~ibly in a
flared pipe ~ection so a~ to avoid an exce~ive pres~ure lo~.
In accorda..ce ~ith Figures 1 and 2 the inventive device 10 for
ultrasonic attenuation consi6t~ of an arrangement of perforated
disks 14 which are arranged in parallel with each other. The
liquid ~lows through the de~ice in parallel with the perforated
di~k~ 14. In this type of device sound noise components in the
audible range may be created from a certain flow rate onwards,
and hence result in an unde~irable noi~e nui~ance. The ef fi-
ciency of the device for ule~a~onic attenuation (level reduc-
tlon in the ultra~onic range) i8 not impaired,~hereby~however~
With reference to Fi~ure 3 now a modified embodiment o~ the in-
ventive device will be de~cribed. The inventive device accord-
ing to Figu-e 3 include~ perforated di~k~ or ~heet~ 14, re~pec-
- CA 02245069 1998-08-12
tively, which are di~po~ed in parallel with each other, as ha~
been described ~ith reference to Figure 1. S~pplementing the
embodiment accordlng to Figure 1, non-perforated disks ~2 are
inserted in addition to the perforated disks 14, which are in-
tegrated into the hollow cylinder of the ca~e 11. As i8 evident
from Figure 3, preferably one non-perforated disk 22 i8 pro-
vided to join every two or three perforated di~k~ 14 in the em-
bodiment illu8trated there, ~hich non-perforated disk i8 joined
again by another two or three perforated di~ks 14. The perfora-
tions in the perforated sheet~ 14 are identified - in corre-
~pondence with Figure 1- with reference numeral 15 in Figure 3.
All of the disks 14, 22 are arranged in parallel with each
other and in parallel with the axis of the ca3e ll. In the em-
bodiment illu~trated in Figure 3, etarting out from the left
end, first two perforated di~ks and then one non-perforated
di~k 22, finally three perforated diske 14, one non-perforated
di~k 22 and again two perforated di~ks 14 are di3po~ed. If ~ec-
e~ary, the ~tructure, i.e. the in~ertion of the non-perforated
disk~ 22, may be appropriately varied. The perforated ~heets
and the non-perforated ~heets (14, 22) are fa~tened oppo~ite to
the ca~e 11 li~e in the embodiment according to Figures 1 and
2.
With the device illustra_ed in Figure 3 ~ound noi~e component~
in the audible range ~ay be avoided, by contra~t to the device
according to Figures 1 and 2.
