TECHNICAL ARTICLE:

Introduction

Tubular Ultrasound LP, USA, has recently entered into an exclusive long-term technology agreement under which it will supply Delta Tubular International LP with ultrasonic tubular inspection systems and services. The initial technology provides for the complete end-to-end ultrasonic testing of plain-end oil country tubulars.

“We selected Tubular Ultrasound's UTFL system because of the company's reputation as the leader in ultrasonic technology,” said Steve Miller, General Sales Manager at Delta Tubular International. “The end-to-end UT inspection is a technological breakthrough in design that provides greater value for our customers by eliminating the necessity of SEA inspections.”

Delta Tubular, a wholly-owned division of publicly-traded Lone Star Technologies Inc (NYSE: LSS), is a leading provider of threading, inspection and logistic services to distributor end-users of oil country tubular goods (OCTG). Lone Star Technologies Inc is a holding company whose principal operating subsidiaries include Lone Star Steel Company which manufactures and markets oilfield casing, tubing, and line pipe, specialty tubular products, and flat-rolled steel products.

Photo 1: The Tubular Ultrasound UTFL test system is based
on the new full-digital Krautkramer electronics platform

Tubular Ultrasound LP, an affiliate of Energy Tubular LLP, designs, assembles and operates high-speed ultrasonic inspection systems used on oil country tubular goods (OCTG). Tubular Ultrasound has received three US Department of Energy Awards through the Energy Related Inventions Program (ERIP) in 1991, 1995 and 2000. Tubular Ultrasound engineered full-body test systems have been in operation for decades at major domestic seamless OCTG steel mills, as well as tubular processor locations. Prior-generation Tubular Ultrasound test systems are owned and operated by various third-party tubular inspection providers such as Tuboscope.

At the Heart: GE Krautkramer VIS Electronics Platform

In the agreement, Tubular Ultrasound provides one or more ultrasonic tubular inspection systems and related inspection services at Delta’s Houston location. There it will ultrasonically inspect OCTG tubulars according to either API or end-user customer specifications. Tubular Ultrasound has maintained and refined the same test system design philosophy for more than 20 years. The basic design concept of traversing a rotating tubular using a top-loaded transducer array is currently used to test more oilfield tubulars than any other method.

These test systems are the first to incorporate the new GE Krautkramer fully digital ultrasonic VIS electronics platform in the United States. Krautkramer VIS electronics are currently operating in six OCTG tube mills throughout Europe and South America.

The test system will accommodate Range I, II or III oil country tubular goods (OCTG) ranging in diameter from 41/2-24” OD (115-600mm), having wall thicknesses from 0.200-0.900” (5-23mm). Seamless or ERW products of all API grades are accepted. Depending upon tube diameter, 100 to 200 joints may be processed through the system, per shift.

Test System

The test system provides for the detection, marking, presentation and recording of the internal or external longitudinal transverse, or oblique two-dimensional flaws. Each system has a separate lamination/midwall/inclusion detection system, as well as a separate ID/OD pit detection system, both of which operate independently at selected sensitivity levels. Each flaw system gate is provided with alarm two thresholds, allowing for immediate disposition of certain material and permitting other lengths to be identified for prove-up evaluation.

Test Electronics Offer Vital Features

Each test system incorporates the new Krautkramer fully digital VIS ultrasonics platform, manufactured by General Electric Inspection technologies LLC. Krautkramer VIS electronics are currently operating at six OCTG tube mills in Europe and South America. Features of the test electronics include:

Dual Gain Control

Dual gain control provides two independent gain settings per channel for controlling main gain and the gain in one flaw gate. This feature is used to normalise the gain independently for both the ID and the OD flaw indication on each channel.

Phased Array Ready

The VIS electronics is designed for future expansion to phased array technology, as it becomes commercially available.

Thickness Monitoring

Any channel of the VIS can be selected to perform flaw, thickness or both flaw and thickness on different cycles. Unique to the test electronics are separate internal pit and mid-wall lamination test sub-systems.

The VIS User Interface

The VIS does not use a multiplexed system design, and can operate at true 20Khz pulse repetition frequencies. Each channel also has the ability to perform a different test on each cycle of each channel, at up to 20,000 tests per channel per second.

Data Recording Software

The data recording software displays up to 16 traces and allows multiple channels of ultrasonic data to be combined onto a single trace. The operator has the choice of viewing only the strip chart display, or combining the A-scan presentation.

Photo 2: 56 Separate test channels, 4 gates/channel, dual alarm thresholds

Test Head Assembly

The test head assembly contains and positions the ultrasonic transducer arrays. It is mounted on an overhead gantry, and indexes along the top surface of the rotating tubulars under examination. The test head assembly may be configured to a variety of throughput rates and flaw orientations. The test system is capable of detecting longitudinal, transverse, and up to four oblique angles of flaws, as well as performing wall thickness measurements. The test system operates at production rate helixes of between 0.750” and 3.50” (20-90mm) per revolution, at surface speeds of approximately 80”/second.

Photo 3: The traces can be programmed to show red/green (pass-fail)
or colour and amplitude as shown above

The test head assembly utilises the water column ultrasonic test method, whereby transducers are suspended in a water reservoir that indexes axially along the top of the tube. As this occurs, a complete helical ultrasonic inspection of the material is generated.

The water column test method was selected because it has several advantages over shoe, wheel, or bladder methods. Because water is the only interface between the ultrasonic transducer and the material under examination, the ultrasound can be focused, resulting in much better signal-to-noise ratios, along with lower gain levels of generally 30dB, for repeatable 5 per cent defect detection.

Photo 4: Actual inspection data presentation of one length of 13 5/8” OD OCTG material. Note separate data tracks for longitudinal ID and OD, transverse ID and OD, and in this instance 12º and 22º oblique ID and OD, left and right orientation. Also listed is a separate pit monitoring trace, and finally, an A-scan presentation of the wall thickness data. Red indications denote reject level indications, and are operator selectable

Special End Area (SEA)

The design of the Test Head Assembly allows for the inspections of plain-end material to be performed to within 0.250” (6 mm) of each tube end. This results in a complete end-to-end ultrasonic inspection of such material, eliminating the need fro a separate special end area (SEA) inspection in many instances.

Because these end inspections are now incorporated into the tube body inspection, they gain the advantages of being ultrasonic, automated, and archived in conjunction with the rest of the tube.

Operational Schedule

Final installation of the initial test system is being completed at the Delta Tubular International, Houston facility. End-user certifications and commercial inspections are scheduled to begin in July of this year.