Technics

Mexican Fuel Quality
Pipeline Permeation
Chan Receives Honor
Uncovering Corrosion

Mexican Fuel Quality

SwRI analysts have produced the first comprehensive report on the quality of Mexico’s gasoline and diesel fuels — the first performed by an independent organization.

“Auto manufacturers look at fuel as an important component in helping to meet emissions standards. The Mexico Fuel Quality Report can provide information that will help design an engine, fuel system, or related components,” says Gerry Estrada, assistant director of the Petroleum Products Research Department in the SwRI Automotive Products and Emissions Research Division.

“A lot of people assume gasoline is just gasoline. People don’t always look at components or how the fuel is formulated,” he says. “Controlling emissions is a major concern today. What you burn in the engine eventually emerges from the tailpipe.”

In March and April 1999, the Institute collected 181 gasoline samples of regular and premium, the two grades available in Mexico, plus 91 diesel samples from 16 cities — Acapulco, Cancún, Guadalajara, Juarez, León, Mazatlán, Mérida, Mexicali, Mexico City, Monterrey, Querétaro, Tampico, Tijuana, Toluca, Torreón, and Veracruz. SwRI worked with Petroleos Mexicanos, the national oil company of Mexico, to ensure that the refineries and various areas of distribution were represented.

“Some people carry assumptions about the quality of Mexico’s fuel,” Estrada says. “We found that their fuel is not any better or worse than U.S. fuels. The fuel met their specifications for production about 98 to 99 percent of the time. Mexico has established strict sulfur requirements because sulfur is a big pollutant that the country is trying to remove from fuels. Our studies found they were actually maintaining a low level of sulfur throughout the country.”

Interest in Mexico’s fuel quality stemmed from several major automotive manufacturers who produce cars in Mexico for sale in that country, the United States, and South America. Estrada says automobiles manufactured in Mexico contain local fuel when they roll off the assembly line, and manufacturers wanted to ensure that the fuel meets their specifications. Others who may benefit from this report include manufacturers of automotive parts and additives, as well as regulatory agencies on both sides of the border because of the high amount of trade and traffic between Mexico and the United States.

The Mexico Fuel Quality Report is available for $3,750.

For additional information, contact Estrada at (210) 522-3006 or gestrada@swri.org.

Pipeline Permeation

The Institute’s permeation research facility has performed the first known permeation study on a tubular product that transports natural gas.

“SwRI is one of the first organizations to branch outside of using permeation studies on fuel tanks and other components used by the automotive industry,” says Mike Luna, a program manager in the Fire Technology Department. “I think we will start seeing more tubular products being tested for permeation. This could actually affect a wide range of industries — from water pipelines to various types of gas pipelines and anything in between.”

For this first study, SwRI is evaluating the permeation of natural gas in an underground pipeline. The concern is that if gas permeates through pipewall and accumulates outside the pipe, the gas has the possibility of igniting.

“The study will evaluate permeation at certain pressures and temperatures. The material for this pipeline is a composite, which is not typically used in natural gas pipelines,” says Luna. “Because this type of research has not been previously performed, we developed a new test protocol and procedure to study pipeline permeation.”

The Institute’s 2,000-square-foot permeation facility evaluates fuel system components for hydrocarbon emissions using two mini-SHED (Sealed Housing Evaporative Determination) facilities equipped with a gas chromatograph and a flame ionization detector. The SHEDs consist of a cylindrical aluminum chamber, which allows for heating and cooling at temperatures from –30°F to 180°F. Some chambers have a tendency for the hydrocarbons to become trapped in their seams and corners, causing hydrocarbon “hangups” that can falsify results. The SwRI SHEDs allow for more accurate results because their cylindrical shape reduces hydrocarbon hangup.

Contact Badders at (210) 522-3971 or bbadders@swri.org.

Chan Receives Honor

Dr. Kwai S. Chan, an Institute scientist in the SwRI Mechanical and Materials Engineering Division, has received the 2001 Champion H. Mathewson Medal from TMS (The Minerals, Metals, and Materials Society).

The award, established in honor of Dr. Champion H. Mathewson, president of the American Institute of Mining, Metallurgical, and Petroleum Engineers (AIME) in 1943, is given for a paper or series of closely related papers with at least one common author that represents a notable contribution to metallurgical or materials science.

Chan received the award for his papers “Evidence of Void Nucleation and Growth on Planar Slip Bands in a Nb-Cr-Ti Alloy,” “Effects of Ti Addition on Cleavage Fracture in Nb-Cr-Ti Solid-Solution Alloys,” and “The Fatigue and Fracture Resistance of a Nb-Cr-Ti-Al Alloy.” The award will be presented to Chan in February 2001 during the 130th TMS Annual Meeting.

A specialist in the mechanical behavior of materials, his current research interests are flow and fracture, micromechanical modeling of materials behavior, and development of life-prediction methodology.

Chan also earned awards with previous contributions to the technical literature. He was honored four times as a young author, receiving the ASM (American Society for Metals) International Marcus A. Grossman Young Author Award in 1986 and 1994, the Rossiter W. Raymond Memorial Award in 1990 from AIME, and the Alfred Noble Prize in 1991 from the American Society of Civil Engineers.

Contact Chan at (210) 522-2053 or kchan@swri.org.

Uncovering Corrosion

The cylindrically guided wave technique has been modified by SwRI engineers to detect and characterize borated water corrosion in the all-thread bolts used by the nuclear power industry in heat exchanger flanges. Detecting corrosion on these bolts before now was only possible by visually inspecting for discoloration. Suspect bolts were then physically removed for a closer inspection — at great expense.

“In the nuclear power industry, heat exchanger flanges are clamped together with nuts on each end of an all-thread bolt,” says Dr. Glenn M. Light, director of the SwRI Nondestructive Evaluation Science and Technology Department. “When used this way, most of the bolt is hidden by the heat exchanger flange, and it is difficult to inspect for corrosion.”

The cylindrically guided wave technique (CGWT), a zero-degree longitudinal wave method that allows ultrasonic energy to be injected into metal samples, measures changes in the characteristics of the ultrasonic energy propagation that signal the presence of corrosion and cracks.

Most types of corrosion leave rough, jagged surfaces, which destroy the mode conversion signals that make CGWT effective. In this application, however, the water running through the heat exchanger tubes is borated (mixed with borax or boric acid) to adjust the pH level which, in turn, minimizes corrosion. In the event of a flange leak, this borated water can flow over the threads of the bolt and corrosion eventually occurs, resulting in a loss of bolt material. This corrosion is unique because as the borated water corrodes the all-thread material it leaves a very smooth, almost polished surface. This smooth surface allows the ultrasonic mode-converted signals to form and produces the information needed to assess damage.

SwRI developed the technique under sponsorship from the Southern Nuclear Operating Company of Alabama.

This method can detect and characterize borated water corrosion levels on the order of 10 percent of the bolt diameter, in bolts approximately 20 inches long and 1.5 inches in diameter. The ultrasonic data are monitored using an oscilloscope. By comparing the location of the end of the bolt signal and the time differences between the subsequent signals observed on the oscilloscope, the remaining diameter and amount of corrosion damage can be determined.

“We developed this technique about 20 years ago for inspecting any bolt except all-thread,” says Light. “Borated water corrosion presents unique circumstances that enable inspectors to use CGWT in a slightly different manner than has been used previously.”

Contact Light at (210) 522-2218 or glight@swri.org.

Published in the Fall/Winter 2000 issue of Technology Today®, published by Southwest Research Institute. For more information, contact Maria Martinez.

Fall/Winter 2000 Technology Today
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