Disputes over employment of clerks at the Norfold & Western Railway have been simmering for at least three years, fuled by the introduction of computers to replace individuals.

Based in Roanoke, N&W is the nation's ninth largest railroad. A major transporter of coal, N&W operates over more than 7,000 miles of track through 14 states and Canada. Its lines run west from Buffalo and Norfolk to Chicago, St. Louis, Omaha and Kansas City, providing connections with other railroads.

Unlike most rail operations in the Northeast and Midwest, however, N&W is not in weak financial condition. In fact, it long has been one of the most profitable transportation companies in America.

Last year, on revenues of more than $1.2 billion, N&W earned more than $103 million - and that was a year during which profits were depressed by an annually cold winter, the coal strike and heavy losses by the firm's Delaware & Hudson Railway subsidiary.

In tackling N&W over work rules and job security, the Brotherhood of Railway and Airline Clerks also took on the rail firm's feisty president and chief executive, John P. Fishwick.

Fishwick, a Harvard Law School graduate and rail industry maverick, has made clear on several occasions since 1975 his view that the remaining profitable railroads will end up in Penn Central-like bankruptcies if managements do not cut employment levels.

In the last six years, N&W has cut its payroll by about 15 percent and increased by at third the gross tonnage shiped per man hour. In August 1975, N&W imported a Chicago consulting firm to study worker productivity at the Roanoke headquarters. The move set off a series of conflicts with the union, resulting in a wildcat walkout the following February.

As computers eat up many N&W's clerks, the union has sought to gain jurisdiction over other jobs and to expand membership to include positions that N&W considers management or supervisory. BRAC also wants from N&W what some other roads provide - job security for members whose jobs are abolished. N&W said it has agreed to protect employes from layoffs caused by general business conditions - such as the coal strike or extreme weather.