Rotary metering device useful with abrasive fluids

The present invention is directed to an apparatus useful for measuring the flow of an abrasive fluid. The present invention comprises a rotary metering device particularly useful for the measurement of oil well production fluids including sand and other abrasive materials. The present invention comprises a rotary metering device for repetitively producing a measuring chamber by the shuttle movement of a plurality of symmetrically disposed blades through slots in a rotor body into and out of a fluid flow channel between the rotor body and its housing. The rotor body of the present invention includes slots having surfaces comprised of a highly wear resistant metal, preferably having a hardness between about 40 and about 70 on the Rockwell C hardness scale to increase the service life of the meter. In a more preferred embodiment, the surface of the cooperating blades is also comprised of a metal having a high wear resistance, also preferably between about 40 and about 70 on the Rockwell C hardness scale, but less than that of the cooperating slot surface.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention generally relates to an apparatus useful for 
measuring the flow of an abrasive fluid. The present invention comprises 
an apparatus and method of constructing the same particularly useful in 
the measurement of petroleum liquids flowing from a well head and 
contaminated with sand or other abrasive materials. 
2. Description of the Background 
The need for accurate, reliable and durable rotary metering devices for 
measuring the flow of fluids is well established. Those associated with 
the oil and gas industry are well aware that it is critical to 
continuously and accurately measure the flow of petroleum liquids from 
remote well sites. The devices used for these measurements must be 
accurate, reliable and durable. Further, because sand and other abrasive 
materials are often suspended within the produced fluids, these metering 
devices are prone to failure. The continuous and accurate operability of 
these devices is critical to the correct measurement of well production. 
Failure can prove exceedingly expensive in both inaccurate production 
totals and lost production time. Therefore, accurate, reliable and durable 
metering devices are a necessity. 
The most widely used metering devices employ rotary flow mechanisms based 
on those disclosed by R. S. Smith in U.S. Pats. Nos. 2,207,182 and 
2,263,145, the disclosures of which are incorporated herein by reference. 
Flowmeters based on these disclosures have been widely adopted throughout 
the oil and gas industry. The rotor and housing of these meters are 
typically manufactured from cast iron. Because it was desirable to have 
lightweight blade mechanisms with these meters, aluminum blades have 
typically been employed. However, these meters are prone to failure in oil 
fields producing fluids having high levels of sand or other abrasive 
materials. Sand and other abrasive materials carried by the well fluids 
have caused rapid deterioration of these meters resulting in inaccurate 
production totals and lost production. A particularly troublesome failure 
point is the rapid deterioration of the fit of the metering blades and the 
slots in the rotor through which the blades move. The tolerance at this 
interface is rather small and is particularly subject to rapid erosion 
when metering fluids containing high levels of sand or other abrasive 
materials. The presence of sand or other abrasive materials within the 
well fluids increases the rate at which this gap erodes, thus shortening 
the useful life of the meter. In fields producing particularly abrasive 
well fluids, these meters often provide satisfactory operation for only a 
few months before needing repair or replacement. This rapid deterioration 
results in inaccurate production totals, lost production and the necessity 
that the meter be repaired or replaced. These meters are typically 
repaired by replacing the rotor and/or blades with newly manufactured 
parts or by installing an entirely new meter. Accordingly, frequent repair 
or replacement is both time consuming and expensive. However, the more 
significant economic loss often results from the inaccurate metering of 
the production fluids and from the loss of production during the repair of 
the meter. 
Accordingly, there has been a long felt but unfulfilled need within the 
industry for an accurate, reliable and durable metering device, 
particularly for a long-lasting device useful for metering production 
fluids containing sand or other abrasive materials. 
SUMMARY OF THE INVENTION 
The present invention provides a new and improved apparatus useful for 
measuring the flow of abrasive fluids through a pipe. Further, the present 
invention provides in improved, long-lasting measuring device particulary 
useful in metering production fluids having high levels of sand or other 
abrasives from remote well sites. 
A rotary metering device in accord with the present invention comprises a 
cylindrical housing within which is mounted a cylindrical rotor body for 
rotation about an axis parallel to the axis of the housing. A flow channel 
through the housing between an inlet and an outlet port is defined by the 
exterior of the rotor body and the interior of the housing. The rotor body 
includes a plurality of slots through its cylindrical surface, the slots 
symmetrically disposed and parallel to the axis of the rotor body. The 
device comprises a plurality of blades mounted for shuttle movement 
transversely of the flow channel and through the slots. Finally, the 
device includes means for moving these blades through the slots into and 
out of the flow channel to repetitively produce a measuring chamber of 
predetermined volume within the flow channel. 
Increased meter life and durability is achieved by employing a metal of 
high wear resistance on the exposed surfaces of the slots formed by the 
rotor body. Preferably, this metal comprises only thin plating over the 
base material from which the rotor body is constructed. Greatly improved 
wear resistance is achieved by employing a metal having a Rockwell C 
hardness greater than 40, preferably between about 40 and about 70, as the 
metal forming the exposed surface of the slots. Metals of choice include 
nickel and chromium which are plated over a rotor body of a base metal by 
conventional electrochemical, electrolytic or electrodeless plating 
processes. Further improvement is achieved by heat treating the nickel 
plated surfaces by conventional heat treating techniques to further 
increase the hardness thereof. Still greater wear resistance is achieved 
by employing similar wear resistance metals for the corresponding surfaces 
of the moving blades. Again, the preferred metals are plated by 
conventional techniques onto a base material from which the blade assembly 
was constructed. A particularly advantageous device is produced when both 
the rotor body and blades are nickel plated and only the rotor body is 
heat treated. 
A metering device in accord with the present invention provides an 
accurate, reliable, durable, wear-resistant and long-lasting metering 
device particularly useful for the metering of abrasive fluids or fluids 
containing abrasive materials, e.g., production fluids containing sand or 
other abrasive materials. Meters in accord with the present invention have 
proven surprisingly durable and troublefree even when employed with 
abrasive, sand-bearing oils. These and other meritorious features and 
advantages of the present invention will be more fully appreciated from 
the following detailed description and claims.

While the invention will be described in connection with the presently 
preferred embodiment, it will be understood that it is not intended to 
limit the invention to this embodiment. On the contrary, it is intended to 
cover all alternatives, modifications and equivalents as may be included 
in the spirit of the invention as defined in the appended claims. 
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The present invention is directed to an apparatus for measuring the flow of 
fluid and is particularly useful for measuring the flow of abrasive 
liquids. Further, the present invention contemplates a method of producing 
such a device. 
The figures illustrate an apparatus which may be constructed in accord with 
the present invention. A rotary meter 10 may be constructed as illustrated 
with a double housing for safety. A meter 10 includes an outer housing 40 
of generally cylindrical shape having a flange 42 at one or both ends for 
sealing engagement with an end plate 44 also flanged 46 about its 
periphery. Bolts or other conventional fastening means (not shown) are 
fastened through a plurality of cooperating and symmetrically disposed 
bores 48 in the flanges 42 and 46. Sealing is achieved by any conventional 
means, e.g., an O-ring (not shown) in groove 49, between the fastened 
flanges. The outer housing further includes an inlet connection 50 and an 
outlet connection 52. Both connections include flanges 54 having 
symmetrically disposed bores 56 therethrough permitting the meter 10 to be 
disposed in a pipe string by any conventional sealing and fastening means. 
The actual rotary metering device is contained within a cylindrical housing 
20 disposed within safety housing 40. Cylindrical housing 20 has a flange 
22 at one or both ends for sealing engagement by conventional O-ring or 
other sealing means with end plates 24 using bolts or other conventional 
fastening devices (not shown) placed through bores 26 in the flanges 22. 
The cylindrical housing 20 includes an inlet port 30 and an outlet port 32 
in fluid communication with the inlet port 50 and the outlet port 52, 
respectively, of the outer housing 40. Disposed within the cylindrical 
housing 20 is a cylindrical rotor body 60 on conventional bearing means 
for rotation about an axis parallel to the axis of the housing 20. 
Preferably, the axes of the cylindrical rotor body 60 and the cylindrical 
housing 20 are coincident. Such a configuration, together with block 28 
produces a flow channel from the inlet port 30 to the outlet port 32 
defined by the exterior of the rotor body 60 and the interior of the 
housing 20. The cylindrical rotor body 60 is characterized by a plurality 
of symmetrically disposed slots 80 about its periphery. Preferably, four 
such slots 80 are disposed symmetrically and parallel to the axis of the 
cylindrical body 60. Disposed within the cylindrical body 20 and about an 
axle 82 are upper and lower blade assemblies 70, each comprising a pair of 
interconnected blades disposed relative to one another at 180.degree.. The 
blades 70a, 70b, 70c and 70d are sized for cooperation with the slots 80 
of the cylindrical rotor body 60. The blades are disposed to move through 
the slots 80 transversely of the flow channel to alternately completely 
block and be completely removed from the flow channel. Each blade makes 
one complete cycle during each revolution of the rotor body. The clearance 
between the exposed outer surface 66 of the cylindrical body 60 forming 
the slot 80 and the exposed side surface 76 of the blade 70 should be not 
more than about 0.003-0.007 inch for proper operation of the meter. The 
blade assemblies 70 include cam followers 88 mounted on axles 86 for 
cooperation with an eccentric cam 84 mounted on the main axle 82. For ease 
of understanding the operation of the rotor body 60 and blade assemblies 
70, a portion of this structure is illustrated in the partial assembly 
drawing in FIG. 2. 
The operation of the meter of the present invention is schematically and 
simply illustrated in FIGS. 3A, 3B and 3C. Liquid enters the flow channel 
produced between the housing 20 and the rotor body 60 through an inlet 
port 30. This entering liquid impinges upon fully extended blade 70b to 
cause rotation of the rotor body 60 and the blade assemblies 70 about the 
axle 82. Liquid which has previously entered the flow channel and is 
disposed between fully extended blades 70b and 70c is measured in 
measuring chamber 90. Further impingement of the entering fluid upon fully 
extendable blade 70b causes rotation of the rotor body 60 and blade 
assemblies 70 to the position as illustrated in FIG. 3B. This rotation 
causes the cam followers 88 moving about the eccentric cam 84 to begin the 
extend blade 70a into the flow channel from its initially fully retracted 
position while corresponding blade 70c, initially fully extended, begins 
to retract. Accordingly, the measuring chamber 90 is opened on the outlet 
side permitting the measured fluid to leave the device through outlet port 
32. Further impingement of fluid continues rotation of the rotor body 60 
and blade assembly 70 to the position illustrated in FIG. 3C where a new 
measuring chamber 90 has been formed between fully extended blades 70a and 
70b. The rotation of the rotor body 60 and consequent repetitive formation 
of the measurement chamber 90 and measurement of the fluid therein is 
recorded by a conventional digital recorder or other device (not shown) 
driven through gears 78 by rotation of the rotor body 60. 
Rotary meters constructed in accord with that illustrated and described 
will suffer wear at the exposed surfaces of the rotor body 60 forming the 
slots 80 and on the blade surfaces 76 of the blade assemblies 70. Shuttle 
movement of the blades 70 transversely of the flow channel and through the 
slots 80 produces wear on the adjacent surfaces of the blade and slot. 
This wear is particularly troublesome when measuring abrasive fluids, 
e.g., well fluids such as petroleum liquids containing sand and other 
abrasive materials. Accordingly, metering devices used in the oil field 
have particularly short lives. 
The above device is greatly and unexpectedly improved when the exposed 
surface of the slots 80 in the rotor body 60 are comprised of a metal of 
high wear resistance. Preferably, such a metal should have a wear 
resistance greater than 40 on the Rockwell C hardness scale and preferably 
between about 40 and about 70 on that scale. The metal of preference is 
nickel, although chromium is also satisfactory. Even more preferable is 
nickel which has been heat treated by conventional means to increase its 
hardness further. Because such metals are expensive, the prferred device 
employs a thin layer 64 of such a metal bonded by conventional means to 
the surface 62 of the rotor 60. These thin layers are typically not more 
than about 0.005 inch thick and may be produced by conventional 
electrochemical, electrolytic or electrodeless plating techniques. In a 
further improvement, the exposed surface 76 of the blade assembly 70 is 
also comprised of a material of high wear resistance, but prferably a 
material not as hard as that of the corresponding slot surface of the 
rotor body. In a most preferred embodiment, the surface 66 of the slot 80 
of the rotor body 60 is comprised of a thin, plated layer of heat treated 
nickel while the corresponding surface 76 of the blade 70 is comprised of 
a thin, plated layer 74 of nickel bonded to the blade surface 72 by 
conventional means. 
The foregoing description of the invention has been directed in primary 
part to a particular preferred embodiment in accord with the requirements 
of the patent statutes and for purposes of explanation and illustration. 
It will be apparent, however, to those skilled in the art that many 
modifications and changes in the specifically described apparatus may be 
made without departing from the scope and spirit of the invention. 
Although Applicant believes the disclosed apparatus provides the most 
advantageous use of the present invention, the invention is not restricted 
to the particular form of construction illustrated and described, but 
covers all modifications which may fall within the scope of the following 
claims. 
It is Applicant's intention in the following claims to cover such 
modifications and variations as may fall within the true spirit and scope 
of the invention.