DESC:FIELD OF THE INVENTION:

The present invention relates to a multi-sensory external reformer tube crawler unit that captures the outer diametrical profile and sub surface data of reformer tubes in hydrogen generation furnaces. More specifically, the present invention covers the outer diametrical growth of a tube, which is an indicator of creep damage, while the sub surface data provides information about the tube wall condition.

BACKGROUND OF THE INVENTION:

Hydrogen reformer tubes are predominantly used in the refining and petrochemicals industry for the production of hydrogen. Hydrogen is generated within the tubes by the catalytic reaction of hydrocarbons and steam. Due to the high operating temperature of hydrogen reformer furnaces and the large temperature variations, these tubes experience internal stresses leading to creep damage within the tube walls. Over time, the damage mechanisms degrade the structural condition of the tubes eventually leading to rupture. If there is a sudden rupture, there is a likelihood of an unscheduled shutdown of the hydrogen generation unit.

Furnace operators incur a large amount of capital to replace each tube while the retubing cost can be extremely high. An accepted practice is to conduct a periodic metallurgical examination of the tubes and utilize the tubes close to the end of their design life. Early retirement of serviceable tubes is a loss since new tubes have to be purchased while late removal of faulty tubes can impact operations due to sudden failure and affect more reformer tubes. In case of tube rupture in a furnace, the operators would be forced to take unplanned furnace shutdowns leading to disruption in other units of the plant. It was shown by Ray et al that overheating during operation leads to the deterioration of the tubes and can result in tube failure. Performing a condition-based assessment, using non-destructive evaluation (NDE) technologies will save capital and maintenance costs due to better understanding of the true condition of the assessed tubes.

In order to predict the tube life accurately, it is vitally important to determine the level of damage in the reformer tubes. Rather than removing tubes for sectioning and metallurgical examination at every plant shutdown, it is much more convenient to use non-destructive evaluation (NDE) technologies on a regular basis to screen tubes for discontinuities.

Commercial automated solutions using multiple NDE technologies to inspect hydrogen reformer tubes are available in the market. The inspection device, LEO-SCAN, developed by Magnetische Pruefanlagen GmbH contains eddy current and diametrical measurement probes. The inspection system developed by H-Scan International, mentioned by Brian Shannon and Carl Jaske, utilizes multiple NDE techniques including ultrasonic, eddy current and profilometry, to assess the condition of a reformer tube. A solution by TCR Advanced Engineering [7] has IR sensors to capture diametrical growth and ultrasonic sensors to inspect reformer tubes (https://www.tcradvanced.com/artis.html). R. Roberts [8] presented a combined approach using an internal (LOTIS) and an external tube crawler (MANTIS), developed by Quest Global, for reformer tube inspections. International Pat. No. 2005067422 (2005) to Quest Trutec, Lp describes the laser technology used in LOTIS to inspect the interior of a reformer tube. US Pat. No. 20040114793 to Quest Integrity USA, LLC further explains how the laser data in LOTIS is processed and filtered to compute the tube damage incurred by mechanisms such as creep.

In all of these solutions except LOTIS, the outer diametrical growth of a tube is measured. The principal rationale behind this NDE technique is that, as creep damage occurs within the reformer tube, the tube bulges. Swaminathan et al. [9] conducted failure studies and remaining life assessment of service exposed reformer tubes. By analysing the microstructure of the tube material, they determined that failure can be caused by localized overheating, leading to creep damage. They also observed that there was significant expansion of outer diameter of the tubes at the failed regions. The correlation between creep strain and tube outer diameter expansion was also observed and validated by B. Singh [10].

A review was conducted by Sposito et al. [11] comparing various NDE techniques developed for assessing damages caused by creep mechanism. They concluded that ultrasonic techniques produce satisfactory results once microcracks start developing and the signal output quality from eddy current testing (ECT) depends on multiple factors. Alvarez-Arenas, Riera-Franco de Sarabia and Gallego-Juarez [12] evaluated creep damage in steel samples based on ultrasonic velocity and attenuation measurements. They determined that the ultrasonic scattering effects increase as the degree of creep damage increases. Garcia Martin, Gomez-Gil, Vasquez-Sanchez [13] discusses variables in ECT such as lift-off, skin and edge effect that affect inspections and presents various ECT configurations used.

Electromagnetic acoustic transducers (EMAT) are transducers that generate and receive ultrasonic waves using electromagnetic mechanisms to detect and characterize surface and sub-surface defects. It is a non-contact technique, meaning it does not use a couplant unlike conventional ultrasonic testing (UT). Based on the literature, shown by Clough, Fleming and Dixon [14], Ribicini et al. [15] and Hirao & Ogi [16] [17], a permanent periodic magnet configuration generates shear horizontal (SH) waves in an electrically conductive material. Hirao and Ogi [17] generated SH circumferential ultrasonic guided wave using PPM EMAT to detect defects on the outer surface of a tube. The authors determined that SH0 and SH1 mode travelled around the tube and responded to surface defects.

OBJECTIVES OF THE PRESENT INVENTION:

To overcome some of the problems and shortcoming of the prior art a need exists for new and improved condition-based assessment, using non-destructive evaluation (NDE) technologies, that will save capital and maintenance costs due to better understanding of the true condition of the assessed reformer tubes. The present invention provides an alternative to existing solutions available in the market.

It is a primary objective of the invention to provide a multi-sensory system which incorporates metrology, ultrasonic propagation and electromagnetic mechanisms to inspect reformer tubes.

It is yet another objective of the present invention to provide a crawler structure with compact design, which uses two sets of four wheels, with one set at the top and another set at bottom of the unit in order to ensure that the crawler moves in a straight-line during inspection.

Further, the object of this invention to provide Electromagnetic Acoustic Transducers (EMAT) technology for reformer tube inspections and by using the pitch catch configuration, the EMAT probes send ultrasonic guided waves along the circumference of the reformer tube without using a couplant.

It is further objective of the invention to provide a plurality of reflective laser sensors which capture the distance from the laser to the tube surface.

It is yet another objective of the invention to provide a low frequency eddy current probe to be located on one side of the system.

It is yet another objective of the invention to provide a method of determination of the outer diameter of the reformer tube.

Summary of the present invention:

This summary is provided to introduce a selection of concepts, in a simplified format, that are further described in the detailed description of the invention. This summary is neither intended to identify key or essential inventive concepts of the invention and nor is it intended to determine the scope of the invention.
In one of the embodiments, the invention provides a system for inspecting reformer tubes comprising;
- a crawler structure consisting of two sets of wheels with four wheels at the top and four wheels at the bottom of the crawler, wherein the wheels are placed at an angle to grip and guide the crawler along a straight axis;
- There are two DC motors. One motor is adapted to power two wheels at the bottom and the other motor is adapted to power two wheels at the top of the crawler structure;
-the motors transmit the power to the wheels using a bevel gear transmission mechanism
- plurality of reflective laser sensors which capture the distance from the laser sensors to the tube surface;
- two EMAT probes using a pitch catch configuration, wherein one probe is a transmitter and the second probe is a receiver, wherein the EMAT probe scans along the tube circumference and at a given vertical location. ;
- a low frequency eddy current probe located on one side of the system along the same vertical axis as the laser sensors to capture the eddy current data; and
- a rotary encoder fixed onto the shaft of one of the wheels adapted to capture the distance travelled by the crawler while moving up or down the tubes.
In another of the embodiments, the invention provides a crawler structure compact design which uses two sets of four wheels, one set at the top and another set at bottom of the unit in order to ensure that the crawler moves in a straight-line during inspection.

In another of the embodiments provides EMAT technology for reformer tube inspections. Using the pitch catch configuration, the EMAT probes send ultrasonic guided waves along the circumference of the reformer tube without using a couplant.

In another of the embodiments, the invention provides reflective laser sensors for determining the outer diameter for reformer tube.

In another of the embodiments, the invention provides a rotary encoder fixed onto the shaft of one of the wheels in order to capture the distance travelled by the crawler when moving up or down the reformer and the distance data from the encoder are more accurate due to the minimal lateral motion.

In another of the embodiments, the invention provides a method to compute the outer diameter (OD) of a reformer tube.

To further clarify the advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which is illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail with the accompanying drawings.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

These and other features, aspect, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein the device and process described in the present invention are explained in more detail with reference to the following drawings:

Figure 1 illustrates a design of the system for inspecting reformer tube crawler unit showing the gearbox transmission (bevel gears) to connect the wheels and DC motors.
Figure 2 illustrates a design of the system for inspecting reformer tube crawler unit showing the position of the DC motors, EMAT probes, laser sensors and eddy current probe.
Figure 3 illustrates a Data acquisition system used by the tube crawler to capture the laser data.
Figure 4 illustrates a response of laser sensor for Tube 1.
Figure 5 illustrates a response of laser sensor for Tube 2.
Figure 6 illustrate a typical response of EMAT probe.

DETAILED DESCRIPTION OF THE INVENTION
For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skilled in the art to which this invention belongs. The system, methods, and examples provided herein are illustrative only and not intended to be limiting.

The term “some” as used herein is defined as “none, or one, or more than one, or all.” Accordingly, the terms “none,” “one,” “more than one,” “more than one, but not all” or “all” would all fall under the definition of “some.” The term “some embodiments” may refer to no embodiments or to one embodiment or to several embodiments or to all embodiments. Accordingly, the term “some embodiments” is defined as meaning “no embodiment, or one embodiment, or more than one embodiment, or all embodiments.”

The terminology and structure employed herein is for describing, teaching and illuminating some embodiments and their specific features and elements and does not limit, restrict or reduce the spirit and scope of the claims or their equivalents.

More specifically, any terms used herein such as but not limited to “includes,” “comprises,” “has,” “consists,” and grammatical variants thereof do NOT specify an exact limitation or restriction and certainly do NOT exclude the possible addition of one or more features or elements, unless otherwise stated, and furthermore must NOT be taken to exclude the possible removal of one or more of the listed features and elements, unless otherwise stated with the limiting language “MUST comprise” or “NEEDS TO include.”

Whether or not a certain feature or element was limited to being used only once, either way, it may still be referred to as “one or more features” or “one or more elements” or “at least one feature” or “at least one element.” Furthermore, the use of the terms “one or more” or “at least one” feature or element do NOT preclude there being none of that feature or element, unless otherwise specified by limiting language such as “there NEEDS to be one or more . . . ” or “one or more element is REQUIRED.”

Unless otherwise defined, all terms, and especially any technical and/or scientific terms, used herein may be taken to have the same meaning as commonly understood by one having ordinary skills in the art.

Reference is made herein to some “embodiments.” It should be understood that an embodiment is an example of a possible implementation of any features and/or elements presented in the attached claims. Some embodiments have been described for the purpose of illuminating one or more of the potential ways in which the specific features and/or elements of the attached claims fulfil the requirements of uniqueness, utility and non-obviousness.

Use of the phrases and/or terms such as but not limited to “a first embodiment,” “a further embodiment,” “an alternate embodiment,” “one embodiment,” “an embodiment,” “multiple embodiments,” “some embodiments,” “other embodiments,” “further embodiment”, “furthermore embodiment”, “additional embodiment” or variants thereof do NOT necessarily refer to the same embodiments. Unless otherwise specified, one or more particular features and/or elements described in connection with one or more embodiments may be found in one embodiment, or may be found in more than one embodiment, or may be found in all embodiments, or may be found in no embodiments. Although one or more features and/or elements may be described herein in the context of only a single embodiment, or alternatively in the context of more than one embodiment, or further alternatively in the context of all embodiments, the features and/or elements may instead be provided separately or in any appropriate combination or not at all. Conversely, any features and/or elements described in the context of separate embodiments may alternatively be realized as existing together in the context of a single embodiment.

Any particular and all details set forth herein are used in the context of some embodiments and therefore should NOT be necessarily taken as limiting factors to the attached claims. The attached claims and their legal equivalents can be realized in the context of embodiments other than the ones used as illustrative examples in the description below.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

While the invention is susceptible to various modifications and/or alternative adaptations, specific embodiment thereof has been shown by way of examples and will be described in detail below. However, it should be understood, that it is not intended to limit the invention to the particular structural arrangement disclosed, but on the contrary, the invention is to cover all modifications, structural adaptations and alternative falling within the spirit and the scope of the invention as defined herein.

According to the main embodiment, the present invention covers the multi-sensory system which incorporates metrology, ultrasonic propagation and electromagnetic mechanisms to inspect reformer tubes.

Figure 1 and Figure 2 show the design and the components of the system/unit for inspecting reformer tube (B) that may include crawler unit/structure (10) according to an embodiment of the present invention. The system is adapted to utilize a non-contact ultrasonic NDE technique to inspect reformer tubes instead of conventional ultrasonic techniques which use a couplant to transmit ultrasonic waves into a specimen.

According to the main embodiment, the system for inspecting reformer tube (A) crawler unit/structure (10) consists of two sets of four wheels (2). The crawler may be adapted to include four wheels at the top and four wheels at the bottom of the crawler (10), wherein the wheels are placed at an angle. This angulation of the wheels provides grip and guide the crawler (10) along a straight axis of the reformer tube (A).

The crawler (10) structural body is compact and optimized since the payload is small. The design of the crawler altogether has eight rubber wheels, with four at the top and four at the bottom. The wheels are placed at an angle to grip and guide the crawler along a straight axis, and they are mechanically supported with springs to adjust for diametrical variations.

The structural body of the crawler (10) is designed so that the unit wraps around the reformer tube (A) meaning it is one single component. There is also one point of attachment which requires the operator to use only one dowel pin to fasten the system around the tube (A). Two knobs are adjusted to further compress the springs supporting the wheels, firmly fixing the unit onto the reformer tube.

Figure 1 shows the two views (front and side view) of the crawler structure (10). The power required for the propulsion of the crawler is supplied by two DC motors (1a, 1b). On the top side, one DC motor (1a) is powering two (2a) of the top four wheels using a bevel gear transmission mechanism (4a). Similarly, another DC motor (1b) is powering two (2b) of the bottom four wheels using another bevel gear transmission mechanism (4b) as shown in Figure 1. The unit altogether has eight wheels, four on each side (top & bottom) as shown in Figure 1. The wheel configuration used in this setup significantly reduces the horizontal spinning movement and ensures that the crawler travels straight along the vertical axis. Since the crawler travels in a straight line, this invention does not need guide rails. The crawler structure (10) is a single piece which wraps around the tube and the operator attaches the unit onto the tube using a dowel pin.

The system may include two EMAT probes (3a,3b) to electromagnetically generate ultrasonic circumferential guided waves within the reformer tube (A). In addition, the EMAT probes (3a, 3b) scanning coverage at a given vertical location includes the entire tube circumference.

The system may include a plurality of reflective laser sensors (5a, 5b) which capture the distance from the laser to the tube (A) surface. A rotary encoder is also fixed onto the shaft of one of the wheels of the crawler (10) in order to capture the distance travelled by the crawler (10) when moving up or down the reformer tube (A). The EMAT probes use a pitch catch configuration, where one probe is the transmitter while the second probe is the receiver (see Figure 2).

The crawler (10) of the system may further include a low frequency eddy current probe (6) located on one side of the crawler (10), along the same vertical axis as the laser sensor. One low frequency eddy current probe (6) is placed above one of the laser sensors (5a,5b), as shown in Figure 2.

The data from the laser sensors and rotary encoder were acquired using a data acquisition unit (DAQ). The information collected by the DAQ was then sent to a laptop which presents the data in a readable format using a Software program (see Figure 3). The operator enters the initial outer diameter (OD) of the tubes, on purchase, and the reference OD for each tube in the software program. The reference OD of each tube is usually measured at the starting position of the tube crawler for each scan. Based on these parameters, the program shows the percentage variation of the inspected tube’s outer diameter with respect to the position of the crawler.

The EMATs on the crawler are two commercial PPM (periodic permanent magnet) EMAT probes, each containing three racetrack coils and a wavelength in the range of 2 mm to 40 mm. Based on the material’s ultrasonic shear velocity, the probe frequency is determined in order to send electrical pulses to the EMATs at this frequency. Apulser receiver unit is used to allow the operator to set parameter to send electrical pulses into the racetrack coils. Both the EMAT transmitter and receiver are connected to the pulser receiver unit. In addition, this unit also acts as an oscilloscope allowing the user to view the signal output from the receiver and acquire the data. A typical response of EMAT sensor is visualized as in Figure 6.

The eddy current probe is directly connected to a DAQ device, which constantly sends data to a system which runs the eddy current software.

Method steps for calculating the % variation of outer diameter (%OD) of reformer tube.

The reformer tube crawler unit uses two laser sensors to capture the outer diameter (OD) variation of tubes.

Two reflective laser sensors (Sensor 1 and Sensor 2 in Figure 3) capture the distance from the laser to the tube outer surface (L1 and L2). A rotary encoder is also fixed onto the shaft of one of the wheels in order to capture the distance travelled by the crawler when moving up or down the reformer tube. The data acquired from the laser sensors and rotary encoder is acquired using a data acquisition unit (DAQ). The information collected by the DAQ is sent to a computer which presents the data in a readable format using a software program.

According to the further embodiment, the present invention covers the method to compute the outer diameter (OD) of a reformer tube comprising the steps of:
Entering the OD of the tubes when initially installed and the OD at the point where the crawler is attached into system program.
Program calculates the sensor to sensor (SS) distance based on the data entered.
Program receives the analog output signals (L1 and L2) from two reflective lasers and computes the OD of the reformer tube.
Generates a 2D graphical display showing the percentage variation of outer diameter of reformer tube with respect to the distance data collected by the encoder.

The typical experimental data of laser sensors captured during field trial of the developed tool / technology in various refineries is given below.

The step by step procedure for calculating the % variation of outer diameter (%OD) is as below:

Note down the initial outer diameter (IOD) of the tubes, (i.e. tube diameter on purchase of tubes) from past records of the tube
Mark the reference position on the tube. It is at the marked at bottom of the tube.
Physically measure the reference outer diameter (ROD) for tube using a pi tape at reference position
Enter the IOD and ROD into the software program. The program uses these parameters, to calculate the percentage variation of the inspected tube’s outer diameter with respect to the position of the crawler.
At the reference position, the SS distance is calculated by the program using the sensor values (L1 and L2) collected by the two laser sensors see Equation (1) and Figure (3).

The formula used for calculating SS is as given below:
SS=ROD + L1 + L2 (At the reference point) …………………….(1)

The SS distance is fixed during the scan of total length of tube since the position of the laser sensors do not change.

vi. Based on the SS distance, the outer diameter (OD) is calculated using following formula

OD= SS - L1 - L2…………………………….(2)

vii. Now, OD variation (%OD) is calculated from the changing sensor values (L1 and L2) collected by the two laser sensors and initial outer diameter as shown in Equation (3).

%OD=[SS-L1 -L2 -IOD]/IOD*100 % …………………………….(2)

Calculation Example 1 (e.g. tube no. 1)
Initial outer diameter (IOD) on purchase = 136 mm
Reference Outer diameter (ROD) measured = 137.5 mm

Calculation at reference position of tube no. 1
ROD and IOD entered into program
L1 = 50 mm
L2 = 54.1 mm
Calculated SS Distance = 241.6 mm
Measured OD = 137.5 mm
%OD = 1.10%

Calculation at another point on same tube i.e. tube no. 1
SS Distance = 241.6 mm
L1 = 49.1 mm
L2 = 54.2 mm
Calculated OD = 138.3 mm
%OD = 1.69 %

Calculation Example 2 (e.g. tube no. 2)
Initial outer diameter (IOD) on purchase = 136 mm
Reference OD (ROD) measured = 138.9 mm

Calculation at reference point of tube no. 2
ROD and IOD entered into program
L1 = 50.32 mm
L2 = 50.14 mm
Calculated SS Distance = 239.36 mm
Measured OD = 138.9 mm
%OD = 2.13%

Calculation at another point of the same tube i.e. tube no. 2
SS Distance = 239.36 mm
L1 = 48.35 mm
L2 = 52.38 mm
Calculated OD = 138.63 mm
%OD = 1.93 %

The examples of the calculation for Tube 1 and Tube 2 are illustrated in Figure 4 and Figure 5.

Technical advantages of the invention:
The present invention has the following advantage over the prior arts:
more portable compared to existing solutions such as LEO-SCAN, H-Scan and ARTiS, which are more bulky and tougher to setup.
The overall weight of the unit, with the multiple sensors, is around 6-12 kilograms due to the relatively small payload and the compact design of the wheel support system.
Simplified design compared to other systems since water supply, or a water tank is not required for the ultrasonic inspection and the scanning area coverage of the EMAT system is greater than conventional ultrasonic techniques.
Wheel support system ensures that the crawler does not deviate from its path and has minimal lateral motion.

While specific language has been used to describe the present subject matter, any limitations arising on account thereto, are not intended. As would be apparent to a person in the art, various working modifications may be made to the system and method in order to implement the inventive concept as taught herein.
,CLAIMS:We Claim:
1. A system for inspecting reformer tubes (B) comprising;
- a crawler (10) structure consisting of two sets of wheels (2) with four wheels at the top and four wheels at the bottom of the crawler (10), wherein the wheels are placed at an angle to grip and guide the crawler (10) along a straight axis;
-two DC motors (1a, 1b) wherein one motor is adapted to power two wheels at the bottom and the other motor is adapted to power two wheels at the top of the crawler structure;
- plurality of reflective laser sensors (5a, 5b) which capture the distance from the laser sensors to the tube surface;
-two EMAT probes (3a, 3b) using a pitch catch configuration, wherein one probe is a transmitter and the second probe is a receiver, wherein the EMAT probe scans along the tube circumference and at a given vertical location
- a low frequency eddy current probe (6) located on one side of the system along the same vertical axis as the laser sensors (5a, 5b) adapted to capture the eddy current data; and
- a rotary encoder fixed onto the shaft of one of the wheels adapted to capture the distance travelled by the crawler when moving up or down the tubes.
2. The system as claimed in claim 1, wherein the wheels are mechanically supported with springs to adjust for diametrical variations.
3. The system as claimed in claim 1, wherein the crawler structure (10) is single piece and compact.
4.The system as claimed in claim 1, wherein the overall weight of the system is 6-12 kilograms.
4. The system as claimed in claim 1, wherein the power from the DC motors (1a, 1b). is transmitted, using a bevel gear transmission system (4), to the two of the four top wheels and also to the two of the four bottom wheels.
5. The system as claimed in claim 1, wherein the crawler structure has one point of attachment to the reformer tube using a dowel pin.
6. The system as claimed in claim 1, wherein the EMAT probes (3a, 3b) contains three racetrack coils and a wavelength of 2 mm to 40 mm.