Patent Description:
To measure gas flow through a pipeline, ultrasonic gas flow meters are placed along a section of pipe. The meter is located between a front end treatment and a backend treatment. While certain details of the end treatments may vary between pipelines, all include elbows. By way of an example, in one design a front end treatment or elbow diverts the main pipeline flow toward the flow meter and reduces swirl using a flow conditioner placed <NUM> pipeline diameters ahead of the flow meter. The conditioner provides a bullet-nosed gas flow profile into the meter. A backend treatment or elbow located at least <NUM> pipeline diameters after the meter brings the now-measured gas flow back in line with the main pipeline. The backend elbow, along with a blind flange located opposite the main pipeline, helps attenuate ultrasonic waves generated by downstream equipment such as a control valve and prevents those waves from traveling back to the flow meter and interfering with flow measurement.

The use of elbows at the front and back end of the flow meter section widens the footprint of the section. Therefore, a wide skid must be built to support the section and special permits must be obtained to transport the skid to the job site. A need exists for an ultrasonic attenuation treatment that can eliminate the use of elbows.

<CIT> and <CIT> to McClintock, the content of which is incorporated by reference herein, disclose an in-line ultrasonic attenuation end treatment for use with an ultrasonic gas flow meter. The end treatment makes use eccentric reducers at each end and a series of plates arranged perpendicular or at an angle to the midline of the longitudinally extending pipe located between the reducers. Embodiments of the present disclosure do not require the eccentric reducers nor make use of plates as the baffle.

<CIT> discloses an in-line ultrasonic attenuator having first and second helices joined one to the other in the same or opposite directions where the first and second helices have a reciprocal offset of <NUM>° and perform an evolution with an angular amplitude of less than <NUM>°, for example of about <NUM>°, to ensure that the helices have angles of rotation and a number of evolutions which ensure extremely limited head loss of the flow of air.

An in-line ultrasonic attenuator of this disclosure includes a longitudinally extending pipe having a first end, a second end, and a constant inside diameter extending an entire distance between the first and second ends. The first and second ends may be flanged ends. Instead of plates, the attenuator includes at least one helical baffle, or a first and a second helical baffle arranged in series with one another, coaxial to the longitudinal center line of the longitudinally extending pipe. The first helical baffle has a first twist rotation and the second helical baffle has a second twist rotation opposite that of the first twist, each twist rotation being at least <NUM>°; wherein each of the first and second helical baffles include a plurality of bars (<NUM>), each bar of the plurality having a length equal to that of the constant inside diameter of the longitudinally extending pipe and being oriented at a different angular orientation than a corresponding adjacent bar of the plurality. The twist rotation may be up to <NUM>°. When in an intended use, no elbows are required at the front or back end of a measurement skid of which the attenuator is a part.

Each helical baffle provides the equivalent of a blind flange. The pipe wall-facing surface of each baffle can be corrugated rather than smooth to provide more reflection points (and therefore attenuation surfaces).

In embodiments of a method for attenuating ultrasonic waves downstream of an ultrasonic gas flow meter, the method includes providing an in-line ultrasonic attenuator of this disclosure. The attenuator may be included as part of a measurement skid. When in an intended use, the method further includes attenuating the ultrasonic waves of the meter with the in-line ultrasonic attenuator and passing a natural gas flow along a pipe wall-facing side of the first and second helical baffles.

Referring now to the drawing figures, embodiments of an in-line ultrasonic attenuator <NUM> of this disclosure includes a longitudinally extending pipe <NUM> having a first and a second end <NUM>, <NUM>, with a first and a second helical baffle <NUM>, <NUM> located between the two ends <NUM>, <NUM> and arranged coaxial to the longitudinal centerline <NUM> of the pipe <NUM>. Each end <NUM>, <NUM> may be a flanged end. The flanged end may have a serrated raised face and be sized and arranged for connection to the measurement section or measurement skid of a pipeline.

The longitudinally extending pipe <NUM> may include two pipe sections <NUM>, <NUM> welded together, with the first helical baffle <NUM> housed within the first pipe section <NUM> and the second helical baffle <NUM> housed in the second pipe section <NUM>. In embodiments, from flange <NUM> to flange <NUM> the attenuator <NUM> has a constant inside diameter. The helical baffle <NUM>, <NUM> may be offset from the pipe end <NUM>, <NUM> an amount effective so that welding of the pipe section <NUM>, <NUM> to the flanged end <NUM>, <NUM> and to the other pipe section <NUM>, <NUM> may occur.

The length of each helical baffle <NUM>, <NUM> therefore is typically less than that of the pipe section <NUM>, <NUM>. By way of a non-limiting example, in an attenuator <NUM> comprised of two <NUM>-inch (<NUM>) pipe sections <NUM>, <NUM>, each helical baffle <NUM>, <NUM> can be offset one-half inch (<NUM>) from each end <NUM>, <NUM>, each baffle <NUM>, <NUM> being about <NUM> inches (~ <NUM>) in length. The length of pipe, as well as diameter of pipe, that may be used for attenuator <NUM> is application-specific. The pipe size may be in a range of <NUM> inches to <NUM> inches (<NUM> to <NUM>).

Each helical baffle <NUM>, <NUM> has a twist opposite that of the other, with one of the helical baffles <NUM>, <NUM> having a right-hand twist and the other helical baffle <NUM>, <NUM> having a left hand twist. The amount of twist is at least <NUM>°. This amount of twist equates to one blind flange.

In some embodiments, each helical baffle <NUM>, <NUM> has a twist greater than <NUM>°, for example, <NUM>° or <NUM>° of twist. In other embodiments, the twist is in a range of <NUM>° to <NUM>°. In yet other embodiments the twist is in a range <NUM>° to <NUM>°, there being discrete values and subranges within the larger ranges being recited here.

There may be a single pair of baffles <NUM>, <NUM> or two or more pairs of baffles <NUM>, <NUM> arranged along the length of the attenuator <NUM>. However, a single pair of helical baffles <NUM>, <NUM> provides the equivalent of two blind flanges. In some embodiments, a helical baffle <NUM> or <NUM> may be extended to include both twist orientations, one twist being located in a first half of the baffle and the other being located in the second half.

The helical baffle <NUM>, <NUM> may be constructed of a plurality bars <NUM> that are square in cross section, each bar <NUM> having a length sized equal to the inside diameter of the longitudinally extending pipe <NUM> and through which a center hole <NUM> has been drilled to receive a rod <NUM>. Each bar <NUM> is twisted or angled a predetermined number of degrees about the rod <NUM> relative to an adjacent bar <NUM> and welded in place. There is an amount of overlap between the adjacent bars <NUM> such that, in an end view of the baffle <NUM>, <NUM>, there is no gap between the adjacent bars <NUM>. There is, however, a step back between adjacent bars <NUM>.

The ends <NUM> of the bars <NUM> form a corrugated surface along the outside (pipe wall-facing side <NUM>) of the helical baffle <NUM>, <NUM>. The helical baffle <NUM>, <NUM> appears square-shaped toward the end <NUM> and more triangular-shaped toward the center (rod <NUM>).

Other methods of constructing the helical baffles <NUM>, <NUM> may be used, including but not limited to twisting a flat piece of steel. However, providing a corrugated reflective surface rather than a smooth reflective surface creates more reflection points (and therefore improved attenuation performance). The helical baffle <NUM>, <NUM> may be 3D-printed in part or in whole.

In embodiments, the attenuator <NUM> makes use of line pipe, that is, the same size pipe as that used by the ultrasonic gas flow meter. As already mentioned, the pipe size may be in a range of <NUM> inches to <NUM> inches (<NUM> to <NUM>). Compared to prior art attenuators, embodiments of this disclosure reduce manufacturing costs by two-thirds or more in part because line pipe can be used. Prior art attenuators require larger size pipe than that used by the ultrasonic gas flow meter and therefore reducers for connection. The attenuator <NUM> can be in-line with the meter and not require any reducers, nor the elbows and bends of the prior art. This, in turn, reduces the overall footprint of the measurement skid which attenuator <NUM> may be a part.

By way of a non-limiting example, and using a <NUM> inch (<NUM>) pipe, a left- and right-hand helical baffle <NUM>, <NUM>, each extending <NUM> inches (~<NUM>) in length (axial direction), were formed by <NUM>, <NUM>/<NUM>-inch (<NUM>) square bars <NUM>, each <NUM> inches (<NUM>) long (radial direction) for <NUM>° of twist, each bar <NUM> being angled relative to its adjacent bar <NUM> by about <NUM>-<NUM>/<NUM>°. The square bars <NUM> could be angled relative to the adjacent bar <NUM> by about <NUM>-<NUM>/<NUM>° to provide <NUM>° of twist. However, the angle cannot be so great that a cross-sectional gap forms between the adjacent bars <NUM>.

Note that in the above example, half the circumference of the pipe is about <NUM> inches (~<NUM>). Given each bar <NUM> provides <NUM>/<NUM> inch (<NUM>) of arc, approximately <NUM> bars <NUM> would be needed to cover half the circumference on each side of the pipe. This number may be used as a starting point for determining the total bars <NUM> required and the amount of angle between adjacent bars <NUM> required to provide at least <NUM>° of twist. If <NUM>/<NUM> inch (<NUM>) bars <NUM> were used, <NUM> bars <NUM> would be required since the number should be rounded up to the nearest whole integer. The <NUM> bars <NUM> could each be angled relative to the adjacent bar <NUM> by about <NUM>-<NUM>/<NUM>° for <NUM>° of twist. In practice, the bars <NUM> might be angled by <NUM>°, providing <NUM>° of twist.

Using a <NUM> inch (<NUM>) pipe as another example, half the circumference of the pipe is about <NUM> inches (<NUM>). If <NUM>/<NUM> inch (<NUM>) bars <NUM> used, then <NUM> bars are required, each angled about <NUM>° relative to one another for <NUM>° of twist. A <NUM>° angle would provide <NUM>° of twist. If <NUM>/<NUM> inch (<NUM>) bars are used, then <NUM> bars <NUM> are required, each angled relative to one another by <NUM>°. From a practical perspective, <NUM> bars might be used with adjacent bars <NUM> angled <NUM>° relative to one another to provide <NUM>° of twist, <NUM> bars might be used and angled <NUM>°, which would provide about <NUM>° of twist. If <NUM>/<NUM> inch (<NUM>) bar was used, then <NUM> bars <NUM> would be needed to provide <NUM>° of twist.

As the diameter of pipe changes, so does the length of the bars <NUM>, the length being in the radial direction. The number of bars <NUM> needed is a function of the pipe ID, width of the bars <NUM>, and the predetermined amount of twist. Another consideration is the angle that can be held during construction of the baffle <NUM>, <NUM>. In embodiments, the bars <NUM> may be in a range of <NUM>/<NUM>" to <NUM>/<NUM>" (<NUM> to <NUM>), the width providing the arc angle (e.g. a <NUM>/<NUM>" bar provides <NUM>/<NUM>" arc angle (<NUM>)). Generally, speaking as pipe diameter increases, the width of the bars <NUM> should increase to help reduce the number of bars <NUM> required to achieve, for example, a <NUM>° of twist.

In general there are Bi total bars <NUM>, where i is an integer from <NUM> to n, B<NUM> being the first bar <NUM> and Bn being the last bar <NUM>. The first bar B<NUM> is typically oriented vertically or horizontally. The angular orientation of adjacent bars Bi, Bi+<NUM> are different from one another. Where there is <NUM>° of twist, the last bar Bn is oriented at the same vertical or horizontal orientation as bar B<NUM>.

Other than the first bar B<NUM>, each adjacent bar Bi+<NUM> is set rearward of its preceding bar B<NUM>. For bars B<NUM> to Bn-<NUM>, at least a portion of the front face <NUM> of bar Bi is in contact with a portion of the rear face <NUM> of bar Bi-<NUM> and a portion of the rear face <NUM> of bar Bi is in contact with a portion of the front face of bar Bi+<NUM>.

A helical baffle <NUM>, <NUM> of this disclosure provides minimal reduction in pipe cross-section. Because the front faces <NUM> are stepped back from one another, it is only the width of the first bar B<NUM> that reduces the cross section. In embodiments, cross section is reduced <NUM>% or less. A <NUM>% reduction in cross-section presents no detectable impact to gas flow rate through the attenuator <NUM>. Essentially, the helical baffle <NUM> or <NUM> presents a stretched out blind flange, with only a small portion of each bar B<NUM> to Bn presenting itself to the flow.

The helical baffles <NUM>, <NUM> prevent ultrasonic waves generated by downstream equipment from traveling back to the flow meter and interfering with flow measurement. However, the baffles <NUM>, <NUM> create sufficient open cross-section to provide adequate product flow through the attenuator without excessive pressure drop across the attenuator. For example, in tests conducted by the inventor, and using a <NUM> inch (<NUM>) diameter pipe, no detectable pressure drop occurred until gas flow was at <NUM> psi (~<NUM> kpa), at which point a pressure drop of less than <NUM> psi was detected. Because most ultrasonic gas flow meters max out at around <NUM> psi to <NUM> psi (~<NUM> kpa to <NUM> kpa), the baffles <NUM>, <NUM> present no pressure drop across the attenuator <NUM>.

Claim 1:
An in-line ultrasonic attenuator (<NUM>) comprising:
a longitudinally extending pipe (<NUM>) having a first end (<NUM>), a second end (<NUM>), and a constant inside diameter extending an entire distance between the first and second ends;
a first and a second helical baffle (<NUM>, <NUM>) housed between the first and second ends and arranged in series with one another coaxial to the longitudinally extending pipe;
the first helical baffle having first twist rotation and the second helical baffle having a second twist rotation opposite that of the first twist rotation, each twist rotation being at least <NUM>°;
wherein each of the first and second helical baffles include a plurality of bars (<NUM>), each bar of the plurality having a length equal to that of the constant inside diameter of the longitudinally extending pipe and being oriented at a different angular orientation than a corresponding adjacent bar of the plurality.