Ultrasonic check valve inspection

The disclosed method includes the steps of positioning an ultrasonic transmitter (50, 52) on the exterior body portion (54) of the valve (14), oriented so that the transmitted ultrasonic wave intercepts the path (46) of the closure member (30) at least at one location, and positioning an ultrasonic receiver on the body portion oriented to detect reflected ultrasonic waves when the closure member passes through such location. The valve body (20) is filled with water and the closure member is caused to move along the path. The transmitter and receiver are operated to generate an output signal trace (64) commensurate with the magnitude of the ultrasonic wave reflected from the closure member at the targeted locations along the path.

BACKGROUND OF THE INVENTION 
The present invention pertains to valve inspection, and more particularly, 
to an in-line inspection technique that provides a simple, non-intrusive 
verification of check valve operability without valve disassembly. 
Conventionally, in process industries such as power plants and the like, 
the operability of check valves is verified during planned outages, by 
disassembling the valve, inspecting the valve components, and then 
reassembling the valve. Particularly in nuclear power plants, this 
conventional procedure has many disadvantages. The major disadvantage is 
that the valve to be inspected is itself often radioactive, or it contains 
residues of radioactive fluid. The typical time required for conventional 
verification is on the order of several hours, during which the 
maintenance worker may be exposed to, or must be protected from, 
radiation. In addition, there exists some risk that the valve will not be 
correctly reassembled, which could adversely affect valve performance. 
Thus, the need exists for a reliable, non-intrusive, in-line check valve 
inspection technique for verifying valve operability. 
SUMMARY OF THE INVENTION 
The present invention satisfies this need in accordance with a method in 
which one or more ultrasonic transducers are positioned on the valve body, 
to generate output traces that can confirm whether the closure member in 
the valve can be caused to move as expected. 
More particularly, the invention includes the steps of positioning an 
ultrasonic transmitter on the exterior body portion of the valve, oriented 
so that the transmitted ultrasonic wave intercepts the path of the closure 
member at least at one location, and positioning an ultrasonic receiver on 
the body portion oriented to detect reflected ultrasonic waves when the 
closure member passes through such location along the path. The valve body 
is filled with water and the closure member is caused to move along the 
path. The transmitter and receiver are operated to generate an output 
signal trace commensurate with the magnitude of the ultrasonic wave 
reflected from the closure member at the targeted locations along the 
path. 
The invention is especially well-suited for verifying the range of motion 
of the closure member on check valves, which normally do not include 
position indicators. In a swing-type check valve, two transmitters and 
associated receivers are preferably used, oriented at right angles to each 
other. One is positioned next to the valve seat, transverse to the flow 
direction, and the other is positioned on the valve surface closest to the 
fully open position of the closure member, facing the valve seat. 
Once an ultrasound technician has been trained to use the technique of the 
present invention, only about one-half hour is require to verify operation 
of a typical check valve. Also, since the valve is not disassembled, the 
maintenance and operability uncertainty associated with proper valve 
reassembly is eliminated.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 schematically illustrates a portion of a process 10 including a 
fluid line 12 in which are located a check valve 14, the operation of 
which is to be verified, a pump 16 and a control valve 18. 
FIG. 2 illustrates in section the internals of a typical check valve 14. A 
valve body 20 includes an inlet 22 and an outlet 24 which are aligned 
about a flow axis 26. At the interior end of the inlet 22 a ring valve 
seat 28 is provided for interacting with a closure member 30 in one of two 
modes. When the valve is open for flow in the permitted flow direction, 
the closure member 30 must be spaced away from the seat 28, thereby 
permitting full flow through the valve. In the event a reverse flow begins 
through the valve, the closure member 30 must seal against the valve seat 
28 to prevent reverse flow through the inlet 22. 
The closure member 30 includes a disk portion 32 adapted for sealing 
engagement with the seat 28. The disk 32 is carried by swing arm 34 which 
is pivoted at 36 to a yoke 38. The yoke is rigidly supported at the lower 
portion of valve bonnet 40. When flow in the permitted direction is 
initiated, the arm 34 swings upward until the land surface 42 thereof 
contacts the valve housing interior at the convex juncture 44 of the 
bonnet 40 and body portion 20. The disk 32 thus has an arc path of motion 
indicated at 46 between a fully closed position and the fully open 
position shown in phantom. 
One of the causes of check valve misoperation is the sudden, high pressure 
initiation of flow in the permitted direction through the valve. The force 
with which the closure member 30 swings away and contacts the convex 
surface 44 is so great that the arm 34 or pivot 36 are bent or otherwise 
damaged with the closure member 30 sticking in the upward position or 
having only limited freedom of movement. It is this type of anomaly which 
the present invention is intended to identify. 
According to the present invention, at least a pair of ultrasonic 
transmitters and receivers are attached to the exterior of the valve body 
as part of the verification procedure to be more fully described below. In 
the preferred embodiment, a first transmitter/receiver pair 50 is 
positioned adjacent disk 32 when the disk 32 is in the fully closed 
position (FIGS. 1 and 2). The wave transmitted from the transducer 50 is 
in a direction generally transverse to the permitted flow direction 
through the inlet 22. A second transducer pair 52 is attached to the valve 
exterior and oriented so that the transmitted wave is generally parallel 
to the path of motion 46 of the disk 32, in a direction perpendicular to 
the transmitted wave of the first transducer 50. In the illustrated 
embodiment, the second transmitter is located in the concave portion of 
the juncture 44, which coincides with the closest surface of the valve 
relative to the fully open position of the disk 32. 
Preferably, the transducers are of a type commonly available, in which the 
transmitter and receiver are embodied in a single housing but this is not 
necessary. Suitable transducers include a 2.25 MHz dual contact transducer 
and 45 degree angle beam transducer with Lucite wedge connected to an 
ultrasonic pulser receiver model EPOCH-2000 compact field unit available 
from the Parametrics Company of Boston, Mass. 
It should be appreciated that before the transducer can be attached to the 
valve exterior, any insulation or other obstructions must be removed from 
the exterior surface of the valve. The transducers must be in direct 
contact with the valve body to ensure proper transmission of sound waves 
through the valve. For similar reasons, the valve must be filled with a 
liquid, preferably water, that is a satisfactory medium for transmitting 
sound waves at typical ultrasonic frequencies. The liquid may in many 
situations be the process liquid available in line 12, or a separate, 
auxiliary test line with water (not shown) can be utilized during the 
verification procedure. The procedure requires that the person performing 
the test be able to apply actuating pressure sufficient to selectively 
move the disk 32 between the full open and full closed position, 
preferably with the ability to maintain the disk stationary in an 
intermediate position. This control can be provided by flow control valve 
18, or a similar device utilized in connection with an auxiliary test 
line. 
In a first embodiment of the invention, the first transducer 50 is located 
at a stationary position as shown in FIG. 1 on the near wall 54 (the 
portion that is above the plane of the paper and thus is not shown in FIG. 
2). The second transducer 52 need not be present. With the first 
embodiment, verification is made that the disk 32 is freely movable 
between a closed position adjacent the valve seat 28 and an open position 
spaced away from the valve seat. It should be understood that this 
verification is only a gross indicator that the arm is free to swing 
through at least most of the path 46. The verification does not 
necessarily show that the valve closure member is operable between the 
fully closed and fully open limits of the path 46. 
FIG. 3 shows a signal trace 56, generated by the first transducer 50 in 
accordance with the first embodiment. The vertical axis 58 corresponds to 
reflected wave amplitude and the horizontal axis 60 is the time delay 
between the transmittal of the wave and the receipt of the reflected wave. 
When the closure member 30 is at the valve seat 28, the first transducer 
50 generates a trace 56 in which the initial reflection 62 is due to the 
valve near wall 54 on which the transducer is mounted. The peak 64 
represents the wave reflected from the disk 32. Other, smaller peaks are 
reflections from other structures within the body and are to be ignored. 
The peak at 66 represents the wave reflected from the back wall 68 on the 
other side of the valve body (FIG. 2). The technician operating the 
equipment can more easily interpret the traces by having a drawing of the 
valve interior, but it is within the ordinary skill of ultrasound 
technicians to set up and operate the equipment and interpret the traces 
in accordance with the teachings herein. 
In FIG. 3b, it may be seen that the peak 64a associated with the disk 32 in 
FIG. 3a is absent, indicating that the disk moved a substantial distance 
along the path 46 and is spaced a significant distance away from the valve 
seat 28. The technician can observe the transition between the conditions 
illustrated in FIGS. 3a and 3b by controlling the flow rate through the 
valve 14 in small increments between zero and the flow rate for which the 
valve was designed to open fully. 
If a particular valve is tested annually or on a regular schedule, the 
traces can be saved and compared from inspection to inspection, to 
identify discrepancies after taking into account differences in test 
equipment and other uncertainties. Also, a given valve type would have a 
characteristic trace in the open and closed conditions which may be 
utilized to interpret the traces for a particular valve of that type 
installed in the field. 
In a second embodiment, the second, stationary transducer 52 alone could be 
used for obtaining traces of the reflection of the disk 32 as the disk is 
moved between a fully opened and a fully closed position using the valve 
18 or other flow control device upstream of the check valve 14. FIGS. 
4a-4f represent traces from a second transducer mounted as shown in FIG. 
2. 
In FIG. 4a the initial reflection 70 is visible as a thick reflection at a 
time delay of about one unit and the disk reflection 72a is observed at 
approximately 31/2 time units. With the valve in the 90% open position as 
shown in FIG. 4b, the spike 72b due to reflection of the disk has moved to 
about 41/2 time units. Similarly, as the disk is moved from the fully open 
to the fully closed position (FIGS. 4a-f), the disk reflection 72a through 
72f is delayed longer and longer so that, when the valve is open less than 
10%, the reflected delay 72f is at approximately seven time units. As 
mentioned above, the traces are continuously visible on the operator's 
oscilloscope so that the movement of the disk spike 72 would be 
unmistakeable. 
In a third embodiment of the invention, both transducers 50, 52 are 
utilized. The first transducer 50 is positioned initially as in the first 
embodiment adjacent the valve seat on the valve body surface and the 
second transducer is positioned on the exterior surface closest to the 
fully open position of the disk. In this embodiment, however, the first 
transducer 50 is moved along the body parallel to the arc of path 46 of 
disk 32 in increments corresponding to incremental positions of the disk 
32 along path 46. The incremental positions of the disk 32 are controlled 
by the valve 18. 
By correlating the trace between the first and second transducers in this 
embodiment, a more complete and reliable analysis can be made of the limit 
positions of the disk resulting from the maximum and minimum flow rates 
produced through the valve by means of the pump 16 and control valve 18. 
The operator can thus more easily distinguish between an operable valve 
and defective valve in which the disk is free to move but with only 
limited movement. Also, since it is important that the check valve disk 32 
not "flutter", it is desirable that it have only two modes of operation, 
i.e. fully closed or fully open. By using the present invention, it may be 
determined with reasonable accuracy what flow rate will move the disk into 
the fully opened position. 
Although the present invention as described above cannot unequivocally 
verify that the check valve will not experience small leaks when a high 
back pressure is applied from the outlet 24 to the inlet 22, it will 
satisfactorily identify problems which would lead to a significant 
backflow. It should also be understood that other combinations of 
stationary and movable transducers are also within the scope of the 
invention.