Caliper

Caliper is measured in micrometers. There are three main ways to measure caliper  

The accuracy of this method depends on the application and is between 1 and 0.5 microns. The relative accuracy, which is needed to measure the shape of a cross profile, can be better than 0.25 microns. 

Air bearing caliper measurement The sensors are mounted onto flat measurement plates with a diameter of roughly 60 mm. Those plates are drilled, with pressurized air coming out of the tiny holes. The plates are pressed towards the paper from both sides. The distance of the plates from the paper is controlled by the air flow. The distance between the plates is measured using an electromagnetic field. 

The thickness of the paper is calculated by subtracting the thickness of the air bearings from the distance of the sensor plates. As the thickness of the air bearings is not known precisely, this method is mainly used as a relative measurement to detect MD and CD profile variations of very sensitive papers, where a contacting measurement is not applicable. But also the relative accuracy is much less than the accuracy of the contacting sensor. 

Optical caHper measurement Due to the deficiencies of the air bearing sensor and the need for a precise noncontacting caHper measurement, most sensor manufacturers currently push the development of optical noncontacting measurement methods. They consist of three sensors  

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Permeable intervals can be identified from a number of logging tool measurements, the most basic of which is the caliper tool. The caliper tool is used to measure the borehole diameter which, in a gauge hole, is a function of the bit size and the mudcake thickness. Mudcake will only build up across permeable sections of the borehole where mud filtrate has invaded the formation and mud solids (which are too big to enter the formation pore system) plate out on the borehole wall. Therefore the presence of mudcake implies permeability. 

In this experiment students measure the length of a pestle using a wooden meter stick, a stainless-steel ruler, and a vernier caliper. The data collected in this experiment provide an opportunity to discuss significant figures and sources of error. Statistical analysis includes the Q-test, f-test, and F-test. 

Methods for (a) to (c) are electromagnetic or use eddy currents. The method for (d) is a mechanical system similar to the caliper pig, in which the probe runs over the inner wall of the pipe over pits, shallow pits and penetration holes. 

There are two categories of equipment which determine the selection of equipment general-purpose and special-to-type equipment. It should not be necessary to specify all the general-purpose equipment needed to perform basic measurements, which would be expected to be known by appropriately trained personnel. You should not need to tell an inspector or tester which micrometer, vernier caliper, voltmeter, or oscilloscope to use. These are the tools of the trade and they should select the tool which is capable of measuring the particular parameters with the accuracy and precision required. However, you will need to tell them which device to use if the measurement requires unusual equipment or the environmental conditions prevailing require that only equipment be selected that will operate in such an environment. In such cases the particular devices to be used should be specified in the test or inspection procedures. In order to demonstrate that you selected the appropriate device at some later date, you should consider recording the actual device used in the record of results. With mechanical devices this is not normally necessary because wear should be detected well in advance of there being a problem by periodic calibration. 

Dickenmesser, m. thickness gage, caliper. Ilickfarbe, /, thick color, body color, dickflussig, a. thickly liquid, viscous, viscid, DIckflussigkeit,/. viscosity thick liquid, dickgrell, a, (of pig iron) dead-white,... 

Fein-messen, n. precision measurement, -mes-ser, m. micrometer vernier, -messgerat, n. precision measuring instrument, -messlehre, /. micrometer caliper or gage, -mess-... 

Hohlimg, /. cavity, hoUew, excavation. Hohl-vene, /. (Anat.) vena cava, -walze, /. hollow cylinder or roll, -welle, /. hollow shaft, -zahn, m. (Bot.) hemp nettle, -ziegel, m. hollow brick (or tile), -zirkel, m. inside calipers, -zylinder, m. hollow cylinder. 

Lehre,/. teaching, instruction, doctrine, theory, science, -ology lesson apprenticeship pattern gage balance centering, lehren, v.t. teach, instruct gage, caliper. — ge-lehrt, p.a. learned, lehrenhaltlg, a. true to gage. 

Rachen-lehre, /. calipers, -reizstoff, m. throat irritant. 

Taster, m. calipers key feeler, antenna. -zirkel, m. gaging calipers. 

Tast-gefuhl, n., -sum, m. sense of touch. Tastung, /. touching, etc. (see tasten). Tast-versuch, m. tentative experiment, preliminary experiment, -zirkel, m. calipers, tat, pret. (of tun) did, made, put. 

To determine strength ot worn links, measure with calipers. Link capacity is that of weakest eye. Consult manufacturer for rating. 

Thickness is measured at bottom of lower eye wilh calipers... 

Caliper for wear and MAINTENANCE check for crocks (both ends)... 

Diameter of Ropes and Tolerance Limits. The diameter of a wire rope shall be tbe diameter of a circumscribing circle and shall be measured at least 5 ft (1.52 m) from properly seized end with a suitable caliper (see Figure 4-65). The diameter tolerance of wire rope shall be... 

A problem with the early MWD mud pulse systems was the very slow rate of data transmission. Several minutes were needed to transmit one set of directional data. Anadrill working with a Mobil patent [100] developed in the early 1980s a continuous wave system with a much faster data rate. It became possible to transmit many more drilling data, and also to transmit logging data making LWD possible. Today, as many as 16 parameters can be transmitted in 16 s. The dream of the early pioneers has been more than fulfilled since azimuth, inclination, tool face, downhole weight-on-bit, downhole torque, shocks, caliper, resistivity, gamma ray, neutron, density, Pe, sonic and more can be transmitted in realtime to the rig floor and the main office. 

A typical set of logs recorded while drilling is shown in Figure 4-280. The wireline caliper is shown in the gamma ray track. Displayed on this attachment are gamma ray, R curve, Pe curve, neutron and density curve. The delta-rho curve is the quality curve check for the density log. 

Statistical methods are used to measure the density variation as the tool rotates, the stand-off can be estimated and the density corrected. A density caliper can be computed that works for cavings of 2 in. (5 cm) or less when the tool rotates at a speed ranging from 6 to 150 rpm. 

Figure 4-284 shows a typical MWD density log compared to a wireline density log. The calipers are also shown. At 1620 ft, the wireline caliper detects a much larger caving because it was run several days later. 

We need the porosity. R is given by R in the lower sand. We also need R. Ultrasonic Caliper and Sonic Log while Drilling... 

In the ultrasonic caliper sub, two ultrasonic sensors are mounted 180° apart on stabilizer blades as shown in Figure 4-288. 

Figure 4-288. MWD ultrasonic caliper (a) sensor in the stabilizer blades (b) schematic of the echoes. (Courtesy Anadrill [113].J...

The caliper is used to correct the density and neutron porosity measurements for borehole effects and also can be used as a borehole stability indicator. Figure 4-289 shows an example of comparison between the MWD ultrasonic caliper and the four-arm wireline caliper run five days later. 

Figure 4-289. Comparison of MWD ultrasonic caliper logs with the 4-arm wireline caliper logs run five days later. (Courtesy Anadrill [ 3].)...

Each length of pipe shall be measured for conformance to wall thickness requirements. The wall thickness at any place shall not be less than the tabulated thickness minus the permissible undertolerance specified in Table 4-146. Wall thickness measurements shall be made with a mechanical caliper or with a properly calibrated nondestructive testing device of appropriate accuracy. In... 

A caliper survey prior to pulling a worn string of tubing will provide a quick means of segregating badly worn lengths for removal. 

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