Device and method for providing strain measurements of insulated pipes
This disclosure provides methods and apparatuses to monitor strain in a steel pipe with reduced or eliminated disruption of the insulative and anti-corrosive layers or coatings that cover the pipe. The methods and apparatuses can include an attachment scheme that is less intrusive and less sensitive to dilation of the insulation layer on the pipe than previous strain monitoring solutions. Additionally, methods and apparatuses can reduce corrosion by virtue of the reduction in the number and volume of metallic components.
1. A method of attaching a sensor to a pipe, the method comprising:
aligning at least two bases along an axis parallel to a length of insulated pipe;
bonding the bases to insulation extending around and covering an entire outer surface of the pipe, without clamps to thereby prevent damage to the insulation;
placing a sensor assembly into the bases; and
securing the sensor assembly into the bases so that the sensor assembly does not move within the bases.
2. The method of claim 1 wherein the bonding step is accomplished by welding the bases using a plastic weld.
3. The method of claim 2 wherein the welding step is accomplished without significant degradation of the insulation.
4. The method of claim 2 wherein the insulation and the at least two bases are made of polypropylene.
5. The method of claim 4 wherein the at least two bases are made of homopolymer polypropylene.
6. The method of claim 2 wherein the at least two bases are made of a material matching the insulation covering the outer surface of the pipe.
7. The method of claim 6 wherein the at least two bases are constructed so that the bases will fail under impact stress before the stress damages the pipe's insulation.
8. The method of claim 2 wherein the welding is accomplished by hot gas hand welding.
9. The method of claim 2 wherein the steps of claim 2 are repeated for multiple sensor assemblies positioned at different locations around a circumference of the pipe.
10. The method of claim 1 wherein no permanent bands are used to aid in the bonding of the bases.
11. A strain gauge assembly comprising:
a length of pipe including one or more layers of polypropylene insulation extending completely around the outer surface of the length of pipe;
at least one attachment base welded to the outer layer of insulation without clamping mechanisms that extend completely around the outer surface of the insulation, to thereby prevent damage to the insulation;
a displacement sensor attached to the at least one attachment base, so that the displacement sensor is immobile with respect to the at least one attachment base and registers displacement proportional to the bending of the length of pipe.
12. The strain gauge assembly of claim 11 further comprising a second attachment base welded to the outer layer of insulation, wherein the displacement sensor is attached to the second attachment base at an end substantially opposed to an attachment point of the displacement sensor to the at least one attachment base.
13. The strain gauge assembly of claim 11 further comprising at least a second displacement sensor attached to a different portion of the outer layer of insulation by at least one attachment base, wherein the displacement sensor and the second displacement sensor are able to register displacement proportional to the bending of the length of pipe in different planes.
14. The strain gauge assembly of claim 11 further comprising a protective casing substantially enclosing the displacement sensor within a cavity of the casing.
15. The strain gauge assembly of claim 11 wherein the attachment base is welded to the outer layer of insulation by a plastic weld.
16. The strain gauge assembly of claim 11 wherein the at least one attachment base is made of a material substantially similar to the outer layer of insulation.
17. The strain gauge assembly of claim 16 wherein the at least one attachment base is made of a material identical to the outer layer of insulation.
18. A device for attaching a strain gauge to a length of pipe with insulation extending completely around, comprising:
a first base having a cavity adapted to accept a first portion of a strain gauge, the base adapted to be welded to insulation on a pipe;
a first restraining member adapted to hold the first portion of a strain gauge immobilized within the cavity of the first base;
a second base having a second cavity adapted to accept a second portion of the strain gauge, the base adapted to be welded to the insulation without clamping mechanisms to thereby inhibit damage to the insulation; and
a second restraining member adapted to hold the second portion of the strain gauge immobilized within the second cavity of the second base,
wherein any movement of the first portion of the strain gauge with respect to the second portion of the strain gauge is indicative of strain on the underlying pipe.
19. The device of claim 18 wherein the first and second bases comprise a plastic material and are adapted to be welded to the insulation using a plastic weld.
20. The device of claim 18 wherein the first and second restraining members include a corrosion-resistant material.
21. The device of claim 20 wherein the first and second restraining members each include a plastic piece adapted to hold the respective portions of the strain gauge in the cavities of the respective first and second bases, and wherein the first and second bases are each adapted to accept at least one fastener for holding the respective plastic pieces and strain gauge portions in place.
22. The device of claim 18 wherein the first and second restraining members include a corrosion-resistant coating.
23. The device of claim 18 further comprising a protective casing substantially enclosing the strain gauge to thereby reduce impact damage to the strain gauge.
24. The device of claim 23 wherein the casing is waterproof.
25. The device of claim 1 further comprising a protective casing substantially enclosing the strain gauge to thereby reduce impact damage to the strain gauge.
26. The device of claim 25 wherein the casing is waterproof.