Internal Diameter Of Pipe Research Articles

Estimating Water Flow in Drainage Pipes

Drainage pipe effluent is frequently analyzed to determine the water composition to address nutrient or contaminant transport. The total effluent volume must be known in order to determine the total nutrient or contaminant discharge. These estimates of total effluent volumes may be accomplished with flow meters; however, equipment and labor costs may be prohibitive and a qualitative method may be a practical alternative. This manuscript outlines a mathematical approach for employing Manning's formula; in which, the cross-sectional area and wetted perimeter of partially filled conduits are determined using measurements of the pipe internal diameter, the maximum depth of water in the pipe, and the coefficient of roughness. Field observations indicate that the method is a qualitative estimate of water effluent and is accurate for field approximations; however, field calibration is warranted.

Horizontal pneumatic conveying from a fluidized bed

In this paper the feasibility of feeding a horizontal pneumatic conveying line directly from a fluidized bed is explored by investigating the relationships governing the solids mass flow rate in such a pipe as a function of both pressure drop and pipe length. Three different materials were fluidized by air and discharged though a 25 mm internal diameter pipe. Materials used were turnip seeds of mean diameter 1.5 mm, carbon steel shot of mean diameter 0.73 mm and plastic pellets of mean diameter 3.76 mm. Several pipe lengths were used, from 0.75 to 1.77 m. The experiments showed that it is feasible to feed directly from a fluidized bed to a horizontal pneumatic conveying line. The flow regime in the pipe was that of dense phase conveying also called slug flow. The data collected show that there is a clear relationship between the pressure drop down the conveying line and the discharge rate of solids from the line. The discharge rate is also dependent on the pipe length. In previous studies of pneumatic conveying, the solids and gas mass flow rates have been independently set, which cannot be done if the conveying line is fed from a fluidized bed. For a pipe fed from a fluidized bed, the solid and gas mass ratio are coupled and this was modelled using the theory for air-augmented granular discharge through an orifice in a hopper or silo of Nedderman et al. [1983. The effect of interstitial air pressure gradients on the discharge from bins. Powder Technology 35, 69–81], but as modified by Thorpe [1984. Air-augmented flow of granular materials through orifices. Ph.D. Thesis, University of Cambridge] for horizontal discharge. This was then combined with a modification of the theory of Konrad [1981. Ph.D. Dissertation, University of Cambridge] to give a prediction of the total pressure drop and the gas and solid mass flow rates. This combined model for dense-phase conveying from a fluidized bed was found to give an excellent fit to the data using the standard values for the constants in every equation. The predictions of the combined model also agree well with the experiments of Konrad [1981. Ph.D. Dissertation, University of Cambridge] for discharge from a hopper into a horizontal conveying line.

Upward vertical two-phase flow local flow regime identification using neural network techniques

Traditionally, the flow regimes in two-phase flow are considered in a global sense. However, a local flow regime is required to understand and model the interfacial structures present in the flow. In this work, a new approach has been used to identify both global and local flow regimes in a two-phase upward flow in a 50.8 mm internal diameter pipe under adiabatic conditions. In the present method, the bubble chord length distributions, which are measured simultaneously with three double-sensor conductivity probes, have been used to feed a self-organized neural network. The global flow regime identification results show a reasonable agreement with the visual observation for all the flow conditions. Nonetheless, only the local flow regimes measured at the center of the pipe agree with the global ones. The local flow regime combinations found are analyzed using the flow map information, cross-correlations between the probe signals, and previous correlations. In this way, it is possible to identify eight different global flow regime configurations.

Effect of inclination on circumferential film thickness variation in annular gas/liquid flow

Time-varying, circumferentially local liquid film thickness data have been collected on a 38 mm internal diameter pipe at inclinations of 0 ∘ , 30 ∘ , 45 ∘ , 60 ∘ and 85 ∘ from the horizontal using flush-mounted and parallel wire conductance probes. Analysis of these data permits time-averaged thicknesses, probability density functions, and power spectral densities to be determined. Results show that the distribution of the liquid film is not symmetrical with thicker films on the lower part of the pipe, which are dominated by large disturbance waves. Moreover, as the inclination angle deviates from horizontal, the film thickness distribution becomes systematically less asymmetric. The probability density functions show a strong narrow peak where the liquid film is less disturbed by the presence of waves. The power spectra show that a large portion of wave energy at the bottom is carried by waves of frequency ⩽ 12 Hz . There is no influence of liquid velocity on the shape of the spectra. However, the dominant frequency appears to decrease with increasing liquid flow rate. The frequency of the disturbance waves at the bottom decreases with increasing inclination. Moreover, the spectra tend to flatten out with increasing inclination, due to the more uniform distribution of energy among waves of a broad frequency range.

Compression Behavior of Nonslender Cylindrical Steel Members with Small and Large-Scale Geometric Imperfections

The compression behavior of cylindrical steel members is affected by geometric imperfections resulting from manufacturing, handling, and damage during installation and service. This paper summarizes the full-scale laboratory tests and the finite element simulations to quantify the effects of both small-scale global and large-scale local geometric imperfections on the compression behavior of nonslender cylindrical steel members. Systematic measurements of the small- and large-scale imperfections on 300-mm internal diameter pipe specimens with 6.17-mm wall thickness were used to characterize the imperfections for nonlinear finite element simulations of axial compression. Excellent agreement is shown between the analytical results and the detailed force, deformation, and strain measurements on the test specimens loaded well beyond their peak loads. The analytical and experimental results are summarized for the load reduction effects of the global imperfections as a function of the amplitude, expressed as a percentage of the wall thickness, and the various patterns of the local surface imperfections. Recommendations are made with respect to the imperfection effects on the compression load capacity, methods of modeling the imperfections, and the implications with respect to the design, inspection, and the serviceability decisions in the field.

Two-phase upward flow 90� bend pressure loss model

Based on experimental pressure loss data during air-water flow in vertical 90° Plexiglass bends with an internal pipe diameter of 30 mm and a curvature radius of 120, 180, 240 and 300 mm a prediction model in the style of a two-phase flow multiplier is proposed. The underlying single-phase liquid flow pressure loss is calculated on the basis of the model by K.H. Beij, resp., D.S. Miller. The scatter of the logarithmic ratios made of the experimental and the predicted values amounts to about 25 % and is substantially lower than that obtained with selected models recommended in the literature. The new model includes physically consistent the usual design parameters and the limits of single-phase gas as well as liquid flow. Reasonable extrapolations with respect to bend dimensions, fluids and (subcritical) flow parameters should be possible.

Liquid re-circulation in turbulent vertical pipe flow behind a cylindrical bluff body and a ventilated cavity attached to a sparger

The turbulent flow field ( Re = 60024 ) in the wake of a cylindrical bluff body in a 0.105 m internal diameter pipe with an area blockage ratio of 82% in turbulent single-phase flow was studied using laser Doppler velocimetry (LDV). The results for the time-averaged velocity showed a toroidal vortex below the bluff body. The axial location below the bluff body where both the time-averaged radial and axial velocity components were zero (eye of the vortex) was found at approximately 0.72 D . The end of the re-circulation region as defined by a stagnation point on the centreline of the pipe was found at an axial location below the bluff body of approximately 1.3 D . These two locations did not change when altering the liquid superficial velocity confirming that the geometry (i.e., size) of the toroidal vortex is not dependent on the superficial liquid velocity or the speed of the vortex. Similar measurements using LDV were taken in the wake of a ventilated cavity in a vertical 0.105 m internal diameter pipe, with an area blockage ratio of 80%. The flow beneath the cavity was turbulent two-phase bubbly flow and the liquid-only flow ahead of the cavity was turbulent ( Re = 45618 ) . The cavity was attached to a (central) sparger, which is a scale-up of the design used by Bacon (1995). The average gas void fraction in the wake of the cavity was 7%. The results for the time-averaged velocity confirmed the formation of a toroidal vortex remarkably similar to the vortex formed below the bluff body. The eye of the vortex and the end of the re-circulation region were found at an axial location below the ventilated cavity of 0.78 and 1.35 D , respectively, i.e., almost identical to the results for the bluff body. The LDV results of the cylindrical bluff body and the ventilated cavity were compared with the fully predictive model of the velocity distribution in the vortex proposed by Thorpe et al. (2001) and good agreement was found in both cases. The model also agreed well with the data of van Hout et al. (2002) for a Taylor bubble rising in stagnant liquid in a 0.025 m internal diameter pipe. The CFX simulations of Thorpe et al. (2001) carried out for a 0.050 m internal diameter pipe, agreed well with the experimental data of the cylindrical bluff body, the ventilated cavity and the data obtained by van Hout et al. (2002) when correlating the results in the appropriate dimensionless form. Our analysis showed that the maximum axial re-circulation velocity in the centre of the vortex ring was directly proportional to the mean velocity in the annulus at the base of the cylindrical bluff body, the ventilated cavity or the Taylor bubble. The proportionality constant for all cases was found to be approximately 0.38 confirming the value proposed by Thorpe et al. (2001).

Synthesis and Characterization of Hexagonally Ordered Carbon Nanopipes

CMK-5 ordered mesoporous carbons that consist of two-dimensional (2-D) hexagonal arrays of pipes were synthesized using furfuryl alcohol as a carbon source and SBA-15 aluminosilicate of 2-D hexagonal structure as a template. External and internal pipe diameters were varied concomitantly by using SBA-15 templates with different pore diameters. The internal pipe diameter was also adjustable by changing conditions of the deposition of the carbon film on the walls of the template. It was shown that, under the typical synthesis conditions, furfuryl alcohol is fully polymerized inside SBA-15 pores. The internal pores of the pipes are generated during pyrolysis of the furfuryl alcohol under vacuum conditions. These pores are quite uniform in diameter, although there was evidence for the presence of constrictions in them, which may be related to the internal surface roughness or corrugation. The thickness of the carbon layer on the walls of the SBA-15 template was estimated as a difference between the pore radius...

Passive acoustic method of measuring the effective internal diameter of a pipe containing flowing fluids

Changes in the internal diameter of a fluid handling pipes are measured by measuring the vibrational characteristics by a non-invasive, passive acoustic technique. Deviations from the normal vibrational characteristics are sensed and used to determine changes of increase or decrease in the pipe's internal diameter.

Using positron emission particle tracking (PEPT) to study nearly neutrally buoyant particles in high solid fraction pipe flow

Positron emission particle tracking (PEPT) allows the flow path of a tracer particle to be followed in opaque flows. It has been used here to study particle trajectories and velocity profiles of a single radioactively labelled tracer particle in high solid fraction, solid–liquid pipe flow. Experiments studied 5 and 10 mm almost spherical alginate particles, of specific gravity 1.02 in a 45 mm internal diameter pipe positioned either vertically or horizontally. Solid delivery concentrations from 20% to 40% v/v were investigated in carrier fluids of 120–500 mPa s mean apparent viscosity, with mean mixture velocities of 20–125 mm/s. Different flow patterns were identified and studied including concentric and capsule flow. A slow-moving annular region of particles near the pipe wall was measured when high viscous carrier fluids and/or small particles were used. The asymmetry of the horizontal velocity profiles was found to depend strongly on the solid concentration and the particle Reynolds number. Results are especially relevant to food and bioproduct flows but show the relevance of the technique to the study of solids conveying.

New developments in surface roughness measurements, characterization, and modeling fluid flow in pipe

The purpose of this paper is to present petroleum and chemical engineers with a simple means of measuring or estimating the absolute surface roughness, ϵ, and relative roughness, ϵ/ D, for internally coated pipes. Our research thrust is to develop new relative roughness charts along with corresponding mathematical equations for internally coated pipes. An integral part of the frictional pressure drop due to fluid flow in pipes involves the determination of absolute surface roughness and relative roughness. An accurate determination of the pressure drop due to fluid flow in oil and gas wells is required for optimizing oil and gas production design calculations. Some of these calculations include developing tubing programs to maximize well deliverability, wellbore flow performance, sizing surface flow lines, and designing artificial lift installations. Previous multiphase fluid flow laboratory and field tests, during the past 50 years, provided correlations for calculating pressure gradients in tubulars [Chem. Eng. Prog. 45(1) (1949) 39; Hetsroni, G., 1982. Handbook of Multiphase Systems, Hemisphere/McGraw Hill, 1174 pp.; Brown, K.E., 1984. The Technology of Artificial Methods, vol. 4, Penn Well Publishing, Tulsa, OK, 447 pp.; Tengesdal, J.O., 1998. Predictions of Flow Patterns, Pressure Drop, and Liquid Holdup in Vertical Upward Two-Phase Flow. MSc Thesis, The University of Tulsa, Tulsa, OK; Farshad, F., Garber, J.D., Polaki, V., 2000. Comprehensive model for predicting corrosion rates in gas wells containing CO2. Soc. Pet. Eng. Prod. Facil. 15(3), 183–190]. All the multiphase fluid flow correlations, used in production operations to calculate these pressure gradients and flow regimes, stem from the general energy balance equation and involves the determination of friction pressure losses. Still today, these friction losses only are being evaluated by practicing engineers using the Darcy–Weisbach equation, which involves the Moody friction factor, f [Szilas, A.P., 1975. Production and Transport of Oil and Gas. Elsevier Sci. Publ., Amsterdam, p. 630; Economides, M.J., Hill, D.A., Ehlig-Economides, C., 1994. Petroleum Production Systems, Prentice Hall, Englewood Cliffs, NJ, 611 pp.]. Moody [Trans. AME 66 (1944) 671] prepared a relative roughness chart for a number of common piping materials. This initial relative roughness correlation was based on experiments on pipes artificially roughened with sand grains. At that time, internally coated pipes were not invented. Hence, Moody did not provide the relative roughness for internally coated pipes. In addition, Moody did not perform a regression analysis of the data to generate functional forms of equations by relating roughness, ϵ/ D, as a function of internal pipe diameter, D. Currently, internally coated pipes are being utilized worldwide in oil field production systems. Consequently, new absolute surface roughness and relative roughness values of internally coated pipes are needed to properly model the hydrodynamics [Brown, K.E., 1984. The Technology of Artificial Methods, vol. 4, Penn Well Publishing, Tulsa, OK, 447 pp.]. The new relative roughness plots developed for internally coated pipes are presented and show that the correlation fits between the commercial steel and drawn tubing in the Moody chart.

Velocity and Concentration Distributions in Sheet Flow above Plane Beds

This paper reports the results of experiments on particle-water flow over plane-topped stationary beds. The particles used were silica sands having d50 of 0.30 and 0.56 mm and Bakelite particles having d50 of 1.05 mm. The facility was a recirculating loop with pipe of 105-mm internal diameter. Data comprised measurements of hydraulic gradient, volumetric discharge, temperature, concentration profiles, velocity profiles, and delivered concentrations. The thickness of the sheet-flow layer is found to vary in proportion to the shear stress. The velocity at the top of the layer is found to be ∼9.4 times the shear velocity, and a simple relation expresses the velocity gradient at this height. The Richardson number at the top of the sheet flow averages ∼0.035, decreasing with increasing ratio of particle fall velocity to shear velocity.

COARSE PARTICLE WALL FRICTION IN VERTICAL SLURRY FLOWS

ABSTRACT Experiments have been conducted using spherical glass particles transported in a recirculating flow loop with internal pipe diameter of 40.9 mm by water and by ethylene glycol solutions. Particle diameters were 1.8 and 4.6 mm and the solids concentrations ranged from 9% to 38% by volume. Pressure gradients have been interpreted in terms of a particle friction factor which depends upon factors first identified by R.A. Bagnold in experiments conducted by shearing neutrally buoyant suspensions in a concentric cylinder viscometer.

Large bubbles attached to spargers in downwards two-phase flow

Suitably formed gas injection geometries permit optimizing the volume of the bubbles created in oil production pipes without recourse to having to change the flow rates of gas. Unfortunately, little research attention has been dedicated to such a study, which may affect the gas lift method of EOR. To address this knowledge gap and to gain more understanding about the coalescence and entrainment processes of the stationary Taylor bubble, an experimental investigation in a bubble drop-down facility using an air–water system was carried out using advanced instrumentation, wire mesh sensor (WMS) and high-speed video photography. The experiments were performed in a 67 mm internal diameter pipe on a stationary Taylor bubble in a downward liquid flow using three different gas injection geometries. Taylor bubble length, the gas and liquid flow rates approaching the stationary bubble were varied. Also, the wake length below, the stationary bubble was measured at different conditions, of gas and liquid superficial velocities and comparisons were made with existing data. A high-speed camera was used to obtain video images of the flow to validate the measurements taken on the wake lengths. Also, the WMS was placed at two different positions, below the gas injection point to obtain time and cross-sectionally resolved information about the spatial distribution of the flowing phases. This information was used to produce time-averaged void fraction, bubble size distribution and contour plots of the two-phase flow structure. Probability density function (PDF) of void fraction of the wake section of the stationary bubbles showed that the flows are in the bubbly flow region whereas the PDF of void fraction for the entire slug unit depicted a typical twin-peaked slug flow. The results of the measurement of Taylor bubble lengths and the corresponding wake of the bubble lengths showed a good match against current published works. The results revealed that the bubble wake length depends on both the nature of the fluid and the pipe diameter, while on the contrary, the bubble length mainly depends on the gas superficial velocity.

Ultrasonic Inspection of Adhesive Bonded Coupler Joints in GRP Piping Systems

Ultrasonic measurements have been performed with two typical GRP pipe materials, and it was found that the attenuation increased approximately linearly with frequency, thus implying that low frequency transducers should be used for inspection. By combining measurements from two transducers located at opposite sides of flooded pipes, quantitative measurements of propagation times through the GRP pipe wall were obtained without prior knowledge of wall thickness, internal pipe-diameter, and sound velocity of the liquid in the pipe. C-scan imaging of GRP pipes was performed by measuring the ultrasonic attenuation through the pipe wall by a pulse-echo method from the outside, with the opposite inner pipe-wall acting as reflector for the signal. The quality of the resulting images was comparable to the quality of images obtained by the conventional through transmission technique.

Emulsions For Short Distance Transportation Of Heavy Crude Oil: Pipeloop Test Results

Abstract The effects of temperature and sand content on the flow resistance of high concentration heavy oil in water emulsions have been studied experimentally. The flows were laminar in a recirculating flow test loop with pipe diameter 53 mm. The effect of temperature could be explained through changes in the viscosity of the brine used to prepare the emulsions. Sand concentrations in the flow experiments were limited to 3% (mass) of the produced oil. Sand in the oil either increased or decreased the flow resistance depending upon the amount of water present initially in the oil. The sand flowed in a distinct layer at the bottom of the pipe and the velocity necessary to transport the sand was strongly dependent on emulsion effective viscosity. Velocity distribution measurements and a finite element simulation showed that a region of low viscosity forms at the pipe wall as a result of oil droplet migration into the flow. Introduction Crude petroleum is a multiphase mixture of oil, water sand and gas whose flow properties are known to be complex. For these mixtures, the resistance to flow depends strongly on the nature of the nature of the continuous phase. With no gas phase present the flow resistance can be minimized by using a surfactant to ensure that an oil in water emulsion forms. Heavy oil producers in the Lindbergh. A1betta, area have examined emulsion technology to improve the performance of oilfield pipeline gathering systems(1,2) Widespread use of flow lines would reduce truck traffic and minimize the proliferation of surface facilities. Emulsions for short distance flow lines must be easy to prepare using produced water, a minimal amount of chemical additive and simple mixing equipment. These emulsions need not be particularly durable but the oil and water must separate readily once the emulsion enters the treating facility. Unlike long distance emulsion pipelines, these short distance gathering systems may have to cope with substantial amounts of produced sand and highly variable flow rates. This investigation considered the effects of temperature and sand content on the flow resistance of high concentration heavy oil emulsions. The emulsions were prepared with moderate shear using fairly low surfactant concentrations in an attempt to simulate flow in gathering system pipelines. Sand transport by fluids in turbulent flow is comparatively well understood, but little is known about laminar flows. Because high concentration oil in water emulsions have high viscosities, laminar flow is likely to occur and the test program was restricted to this case. Emulsion Flows The resistance to flow of a single phase or multiphase mixture in a pipeline is expressed in terms of the frictional pressure gradient (ΔP/L) (kPa/m). For single phase fluids (ΔP/L) is a linear function of the viscosity µ as long as the flow is laminar. Equation 1 (available in full paper) where V is the bulk velocity and D is the pipe internal diameter. The viscosity can be measured conveniently in a variety of viscometers which do not involve pipe or tube flow.

Computer-Assisted Tomography: From Qualitative Visualization To Quantitative Core Analysis

Abstract The effects of temperature and sand content on the flow resistance of high concentration heavy oil in water emulsions have been studied experimentally. The flows were laminar in a recirculating flow test loop with pipe diameter 53 mm. The effect of temperature could be explained through changes in the viscosity of the brine used to prepare the emulsions. Sand concentrations in the flow experiments were limited to 3% (mass) of the produced oil. Sand in the oil either increased or decreased the flow resistance depending upon the amount of water present initially in the oil. The sand flowed in a distinct layer at the bottom of the pipe and the velocity necessary to transport the sand was strongly dependent on emulsion effective viscosity. Velocity distribution measurements and a finite element simulation showed that a region of low viscosity forms at the pipe wall as a result of oil droplet migration into the flow. Introduction Crude petroleum is a multiphase mixture of oil, water sand and gas whose flow properties are known to be complex. For these mixtures, the resistance to flow depends strongly on the nature of the nature of the continuous phase. With no gas phase present the flow resistance can be minimized by using a surfactant to ensure that an oil in water emulsion forms. Heavy oil producers in the Lindbergh. A1betta, area have examined emulsion technology to improve the performance of oilfield pipeline gathering systems(1,2) Widespread use of flow lines would reduce truck traffic and minimize the proliferation of surface facilities. Emulsions for short distance flow lines must be easy to prepare using produced water, a minimal amount of chemical additive and simple mixing equipment. These emulsions need not be particularly durable but the oil and water must separate readily once the emulsion enters the treating facility. Unlike long distance emulsion pipelines, these short distance gathering systems may have to cope with substantial amounts of produced sand and highly variable flow rates. This investigation considered the effects of temperature and sand content on the flow resistance of high concentration heavy oil emulsions. The emulsions were prepared with moderate shear using fairly low surfactant concentrations in an attempt to simulate flow in gathering system pipelines. Sand transport by fluids in turbulent flow is comparatively well understood, but little is known about laminar flows. Because high concentration oil in water emulsions have high viscosities, laminar flow is likely to occur and the test program was restricted to this case. Emulsion Flows The resistance to flow of a single phase or multiphase mixture in a pipeline is expressed in terms of the frictional pressure gradient (ΔP/L) (kPa/m). For single phase fluids (ΔP/L) is a linear function of the viscosity µ as long as the flow is laminar. Equation 1 (available in full paper) where V is the bulk velocity and D is the pipe internal diameter. The viscosity can be measured conveniently in a variety of viscometers which do not involve pipe or tube flow.

Glass reinforced plastic pipe bend subjected to vacuum and flexure

Tests were carried out on a right-angled GRP pipe bend constructed from E-glass and polyester resin by hand lay-up. The glass was in the form of chopped strand mat and the content was 1.2 kg m −2. The internal pipe diameter and the mean bend radius were nominally 250 mm. Straight lengths of pipe were attached to the bend for experimental purposes. Electrical resistance strain gauges and displacement transducers were used extensively to obtain measurements when the bend was subjected to vacuum only, in-plane flexure with and without vacuum and out-of-plane flexure with and without vacuum. Derived stress distributions and displacements were compared with theoretical estimates. The pipe bend under vacuum was finally tested to fracture when subjected to inplane flexure (tending to reduce the bend radius). It was clear that in designing GRP bends of certain geometries, vacuum alone and vacuum combined with flexure should be taken into consideration in applications where it is possible for vacuum to occur.

Testing the wall thickness and internal diameters of thin-walled pipes

Testing the wall thickness and internal diameters of thin-walled pipes

New Electronic Casing Caliper Log Introduced For Corrosion Detection

Abstract The electronic casing caliper is a new tool that measures the internal diameter of pipe in a well and records the curve at the surface. Rune with the casing inspection tool, the caliper log determines whether metal loss or casing damage has occurred internally or externally. A number of field examples are presented with suggested interpretations. Introduction The electronic casing caliper log has been introduced to complement the casing inspection log. Since the casing inspection log measures wall thickness it soon became evident that a companion tool was necessary to run simultaneously with the casing inspection log and record inside pipe diameter. An attempt was made to run a finger-type caliper device but this was found to be unsatisfactory. This paper describes operation of the tool and relates interpretation procedure as determined by laboratory and field examples. Principle of Operation The electronic casing caliper log (Fig. 1) uses a non-contacting tool which measures and records the inside diameter of pipe. casing or tubing. The measuring system is extremely sensitive and small variations of inside diameter are capable of being detected. The electronic casing caliper tool can be run separately or simultaneously with the casing inspection tool and is unaffected by borehole fluid. The tool uses an electronic principle to measure the inside diameter of metal pipe and the reading obtained is a measure of the average inside diameter of the pipe over a length of 1 or 2 in., depending on tool size. Successful logs can be recorded through scale, paraffin or cement adhering to the inner surface of the pipe. The log is particularly sensitive in locating vertical splits or cracks because of an interruption of electrical continuity along the inner surface of the pipe. Holes as small as 3/4-in. Diameter for casing sizes and 1/2-in. diameter for tubing sizes are detectable by laboratory and field investigation. Calibration is performed with casing sleeves which are precision bored to exact inside diameters. A two-point calibration insures accurate and repeatable logs. The curve itself is linear and is presented with a scale of 0.025 in./ 1/4-in. division. All sizes of electronic casing caliper tools are approximately 10 ft in length, temperature rated to 350F and pressure rated to 18,000 psi. Construction and operation of the tools are such that satisfactory results can be obtained with any type of well fluid, Table 1 indicates sizes of electronic casing caliper tools and casing inspection tools currently available to the oil and gas industry. Equipment The down-hole tool is illustrated in Fig. 1. Centralizing springs are used at the top and bottom of the tool to minimize wear on the tool housing. It may be run individually or simultaneously with the casing inspection tool which measures casing wall thickness. The surface recording equipment includes a conventional strip chart recorder in the logging unit. The log are normally recorded on a scale of 5 in./100 ft. Interpretation Fig. 2 is a typical simultaneous electronic casing caliper log and casing inspection log of 7-in., 23-lb casing. The wall thickness as measured by the casing inspection tool is shown on the right. Casing collars are indicated at 3,527 and 3,570 ft. JPT P. 933ˆ