SPX Corp. (SPW) is diverse enough, both in its products and services, as well as its roster of international customers, that it should easily weather a global economic downturn.

That’s why Frank Ingarra Jr., co-portfolio manager of the Hennessy Funds, said the company’s stock is expected to remain one of those included in the Hennessy Focus 30 fund, which readjusts its portfolio annually.

Ingarra said Charlotte, N.C.,-based SPX Corp. provides products and technical assistance

to an array of countries either just now building or in the process of repairing their infrastructures. The latter category includes the U.S. Even if its business slows down in the U.S. or in Europe due to tough economic times, customers in Asia can pick up the slack, Ingarra said.

Stocks that remain in the Hennessy Focus 30 fund for two consecutive years are something of a rarity. That’s because the fund, with $267 million in assets, adheres strictly to a formula from which the fund managers never deviate.

The formula requires mid-sized-capitalization stocks with a market cap below $10 billion (SPX has a market cap of $6.1 billion), and whose stock prices are growing in a fashion Goldilocks would approve – neither too fast nor too slow.

Ingarra said companies included in the Hennessy Focus 30 whose stock prices rise sharply are jettisoned from the fund when it readjusts each year because the stocks are deemed too expensive by the formula used to build the fund’s portfolio.  Factors not taken into account by the formula include revenue growth and a company’s  management team, according to Ingarra.

“We’re disciplined; we’re not emotional,” he said. “We stick to a very disciplined approach. When emotion enters the conversation, someone always loses.”

Nevertheless, Ingarra said SPX’s revenue growth in recent years was “nice to see.” Second-quarter revenues increased 29% to $1.56 billion, up from $1.21 billion a year earlier.

Founded in 1912 in Michigan as an automobile-components supplier, the company now provides products and services for a wide array of industries, including food and beverages, transportation, gas and oil production, agriculture, and pharmaceuticals and biotechnology. SPX, according to its Web site, has locations in more than 35 countries and employs more than 17,000 people, and makes everything from cooling systems for power plants and entertainment venues to specialized tools for making wind turbines.

Having diversified its operations a decade ago, the company now finds itself poised to take advantage of industrial growth in emerging countries such as China and India.