High temperature ultrasonic probe and pulse-echo probe mounting fixture for testing and blind alignment on steam pipes
A high temperature ultrasonic probe and a mounting fixture for attaching and aligning the probe to a steam pipe using blind alignment. The high temperature ultrasonic probe includes a piezoelectric transducer having a high temperature. The probe provides both transmitting and receiving functionality. The mounting fixture allows the high temperature ultrasonic probe to be accurately aligned to the bottom external surface of the steam pipe so that the presence of liquid water in the steam pipe can be monitored. The mounting fixture with a mounted high temperature ultrasonic probe are used to conduct health monitoring of steam pipes and to track the height of condensed water through the wall in real-time.
1. A monitoring system for determining the height of fluid in a pipe, comprising:
an ultrasonic probe, wherein the ultrasonic probe includes
a piezoelectric transducer element configured to receive and transmit ultrasonic waves,
electrical input terminals configured to receive a driving signal to said piezoelectric transducer element,
electrical output terminals configured to provide a response signal from said piezoelectric transducer element; and
a probe alignment system, configured to align the ultrasonic probe to an exterior wall of the pipe.
2. The monitoring system of claim 1 , wherein the piezoelectric transducer element has a Curie temperature of at least 350° C.
3. The monitoring system of claim 1 , wherein the piezoelectric transducer element has a dielectric loss tangent (tan δ) of 0.02 or less.
4. The monitoring system of claim 1 , wherein the piezoelectric transducer element has an electromechanical coupling factor in thickness dimension (Kt) of at least 0.45.
5. The monitoring system of claim 1 , wherein the ultrasonic probe further comprises a backing.
6. The monitoring system of claim 5 , wherein the backing is a selected one of air, a high impedance polymer or a low impedance polymer.
7. The monitoring system of claim 1 , wherein the ultrasonic probe further comprises a preload flexure, configured to coordinate with the probe alignment system to maintain a preload offset.
8. The monitoring system of claim 1 , wherein the ultrasonic probe further comprises:
a housing,
a preload flexure, configured to coordinate with the probe alignment system to maintain a preload offset
a protection layer, and
a backing,
wherein
the housing is a cylindrical housing having a front face configured to mount against the exterior surface of the pipe, and a rear face facing away from the pipe,
the preload flexure is disposed in the housing at the front surface,
the piezoelectric element is a round disc, disposed in the preload flexure, with an inner surface attached to the backing, and an outer surface attached to the protective layer.
9. The monitoring system of claim 8 , wherein
the housing contains a corrosion resistant stainless steel,
the piezoelectric element is fastened to the housing with an alumina adhesive paste, and
the input electrical terminals and the output electrical terminals are a coaxial cable, soldered onto the piezoelectric element.
10. The monitoring system of claim 1 , wherein the probe alignment system comprises:
a transducer alignment fixture configured to align and determine the axis of the ultrasonic probe relative to the surface of the pipe when the ultrasonic probe is inserted into the transducer alignment fixture and mounted to the pipe, and
a fastening system to secure the transducer alignment fixture to the pipe.
11. The monitoring system of claim 10 , wherein
the transducer alignment fixture includes:
a frame,
a probe alignment guide, connected to the frame by way of a plurality of flexures,
a connection mechanism, configured to connect the frame to the fastening system; and
the fastening system includes:
a strap, wherein the strap wraps around the pipe and is configured to connect to the transducer alignment fixture via the connection mechanism of the frame.
12. The monitoring system of claim 11 , wherein the plurality of flexures are configured to maintain the axis of the ultrasonic probe with respect to the transducer alignment fixture and keep the ultrasonic probe in contact with said steam pipe.
13. The monitoring system of claim 11 , wherein the plurality of flexures are parallel to each other.
14. The monitoring system of claim 11 , wherein the transducer alignment fixture further comprises at least one alignment bolt, the alignment bolts being connected to the surface of the frame, configured to align the transducer alignment fixture relative to the pipe.
15. The monitoring system of claim 14 , wherein said at least one alignment bolt has a sharp end, and connects to the frame at a surface of the frame facing the pipe.
16. The monitoring system of claim 14 , wherein said at least one alignment bolt has a cone shape, and connects to the frame at a surface of the frame facing the pipe.
17. The monitoring system of claim 14 , wherein said at least one alignment bolt has a position that is capable of being independently adjusted to align the transducer alignment fixture relative to a local preferred direction.
18. The monitoring system of claim 17 , wherein the local preferred direction is a local vertical direction.
19. The monitoring system of claim 17 , wherein the local preferred direction is normal to a surface of the pipe and a surface of water condensation within the pipe.
20. The monitoring system of claim 11 , wherein the connection mechanism is a selected one of a pin joint, a ball joint or a sliding ball joint.
21. The monitoring system of claim 11 , wherein the fastening system further includes a tension t-bolt with a spring connected to the strap, configured to maintain tension through the strap.