1. INTRODUCTION
Regularly roll testing the MicroPulse Directional Controller is critical to ensure that the directional sensors are performing within specifications. Various factors including temperature exposure, shock and vibration exposure, and time can affect the directional module’s accuracy. Every directional module needs regular calibration, but the interval between calibrations can vary depending on the conditions under which it has been operated. To track directional sensor performance and identify the need for re-calibration, roll tests should be performed at regular intervals. This document outlines the best practices for how to perform the roll tests and what considerations must be considered when performing a roll test.
2. Setup Requirements
A diagram showing the various sensor locations and connector configurations for the MicroPulse 3 and MicroPulse 3+ is shown below in Figure 1. Note the location of the magnetometers, which are susceptible to external interference.
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Figure 1: Sensor locations and connector configuration of the MicroPulse 3 and MicroPulse 3+.
2.1. Key Considerations Setting Up for a Roll Test
Note the following important considerations when setting up for a roll test:
- Ensure that the MDM-15S connector that mates to the MDM-15P on the uphole end of the MicroPulse is a non-magnetic MDM connector with an aluminum shell and that is retained by brass or titanium screws. The Min-e-Con MBR series of MDM connectors is recommended.
- Ensure that only non-magnetic hardware is used to attach to the Uphole end of the MicroPulse; specifically, only use BRASS or TITANIUM screws. Stainless-steel is magnetic and using any stainless-steel alloy screws on the uphole end of the MicroPulse can negatively affect the roll test performance!
- Use a non-magnetic roll test stand that is constructed out of all non-magnetic materials for performing the roll test. (e.g., aluminum, brass, bronze, titanium).
- Ensure that the MicroPulse is secured to the stand such that there is no wobble or slop in the mounting of the MicroPulse to the roll test stand.
- Mount the MicroPulse such that the magnetometers are centered about the pivot point of the stand (see Section 3 for additional details).
- Minimize any twist/torque on the chassis during assembly or roll testing, ensure that there is not significant drag as the tool is rotated, if there is significant resistance when rotating the tool, that can induce twist in the chassis and affect the roll test results.
3. Roll Test Stand Configuration
It is critical to mount the MicroPulse magnetometers about the center of rotation of the stand in both terms of inclination change and azimuth change. Figure 2 shows a non-magnetic roll test stand similar to the one used internally by Erdos Miller to calibrate the MicroPulse. Figure 3 shows the center of rotation on the roll test stand; Figure 4 and Figure 5 show a side view and a top view of the MicroPulse mounted on the rotation stand with the magnetometers mounted at the center of rotation of the stand.
Figure 2: Example of a non-magnetic roll test stand manufactured by Compass Americas.
Figure 3: Side view of the roll test stand shown in Figure 2, with the center of rotation marked.
Figure4: Side view of the roll test stand with the magnetometers centered about the center of rotation.
Figure 5: Figure 5: Top view of the roll test stand with the magnetometer centered about the center of rotation.
The distance from the end of the tool to the magnetometers on the various versions of MicroPulse is shown below in Figure 6.
Figure 6: Distance from the uphole end of the MicroPulse to the magnetometers on MicroPulse 2, 3/3+, and 4.
3.1. Stand Clearance Requirements
There should be a minimum of 10 feet of clearance from the center of rotation of roll test stand to any magnetic or potentially magnetic objects. There should also be a minimum of 4 feet of clearance above and below the center of rotation to any magnetic or potentially magnetic objects. More clearance to potentially magnetic objects is better, but there is a point of diminishing returns. The roll test stand should be in an area where there is not significant foot traffic or movement of large magnetic or potentially magnetic objects in the area. Rebar in the floor is a significant source of magnetic interference which is hard to avoid, but if possible locate the stand in a location that has minimal or no rebar. Also take care to take into consideration items above the roll test stand (e.g., HVAC ducting)
3.2. Mounting the MicroPulse to the Roll Test Stand
The MicroPulse can be roll tested in a pressure housing or in isolation. If roll testing the MicroPulse in isolation, it is best to retain the chassis by the o-ring grooves, ensuring that it is clamped securely to eliminate any slop or wobble. However, the clamping should not be overly tight as that can induce stress and twist on the chassis which may compromise roll test results. An example of fixturing to retain the MicroPulse on the roll test stand by its o-ring grooves is shown in Figure 7.
Figure 7: Example of fixture used to retain the MicroPulse by its o-ring grooves.
4. Roll Test Stand Location
Locating the roll test stand appropriately within your facility can significantly impact the quality of the roll tests and ensure that high quality roll test measurements are taken. There are two critical considerations to make: The uniformity of the magnetic field in the facility and the volume of space that the magnetometers sweep during a roll test. In theory, in a perfectly uniform magnetic field, the volume across which the magnetometers traverse becomes irrelevant. However, in practice, most roll test locations do not have a perfectly uniform magnetic field. The impact of this phenomenon on a roll test is dependent on the degree of nonuniformity in the magnetic field and on the volume through which the magnetometers travel during the roll test. Minimizing the travel volume will minimize the impact of a nonuniform field; conversely, a larger travel volume introduces greater susceptibility to a nonuniform field. Figure 8 shows the travel path of the magnetometers when they are not centered – magnetometers that are more centered will move through a smaller volume and be less susceptible to the impacts of sweeping through a nonuniform magnetic field.
Figure 8: Example of the volume (shown by the red circle) that the magnetometers will sweep through if the magnetometers are not centered about the axis of rotation.
4.1 Positioning the Roll Test Stand
To find the ideal location for the roll test stand within a given area perform the following procedure:
Figure 9: Example of a 5x5 grid.
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Set up a grid in 1 foot increments; for example, if a 5 foot by 5 foot area is available, set up a 5x5 grid marking the intersections of the grid as shown in Figure 9.
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Position the roll test stand over each intersection on the grid and perform a 4-point tumble positioning the stand in the four positions shown in Figure 10.
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Record the total magnetic field spread for each set of 4-point tumbles on the grid.
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Position the stand in the location with the lowest total magnetic field spread within the grid.
Figure 10: Positions for a 4-point tumble of the tool.
5. Shop Roll Test Points
The following settings are the minimum recommended positions for performing a shop roll test:
Table 1: Recommend shop roll test positions.
These are also the minimum number of positions for validating the tool performance using SuperiorQC’s CalCheck software, which is highly recommended for all shop roll tests in addition to the roll test report generated by Erdos Miller’s Eclipse Touch software or ToolHub Roll Test utility.
Author:
David Erdos - Product Line Manager
