A gleaming 36-foot-long turbine stamped "USSR 4" sits on a loading dock at a factory here with no place to go.

It and 46 others being built by the AEG-Kanis company cannot be shipped to the Soviet Union for use in the mammoth pipeline bringing natural gas from Siberia to Western Europe as long as U.S. trade sanctions against the Soviet Union for its role in the imposition of martial law in Poland remain in force.

The sanctions have presented Horst Kerlen, director of the vast red-brick Ruhr factory employing more than 1,000 workers, and other plant directors across West Germany with multimillion-dollar problems that engineering school never prepared them for.

Kerlen and his workers find themselves caught up in superpower politics involving not only governments in Moscow, Washington, and Western Europe, but also bankers and industrialists across this continent.

Last Sept. 28, AEG-Kanis signed a $300 million contract with the Soviet Union to sell 47 turbines for the pipeline. Armed with this impressive business deal Kerlen ordered millions of dollars worth of components from General Electric in Schenectady, N.Y.

But on Dec. 29, two weeks after Poland imposed martial law with the Kremlin's strong backing, President Reagan imposed trade sanctions on the Soviet Union. The pipeline is a major target of the sanctions, which prohibit the reexport of the U.S.-built GE rotor used inside "USSR 4." Kerlen now has applied to the U.S. Commerce Department for special approval to ship the turbines to the Soviet Union.

His problem points up the practical difficulties faced by the Reagan administration as it attempts to rally allied support for a strategy that would squeeze the Soviet economy by denying it Western credit and technology and force the Kremlin to shift money and resources away from military development.

But in Europe this approach is often seen as based on poor information, counterproductive designs, insensitivity to local problems and lack of appreciation of some countries' traditional economic interlocks with Eastern Europe.

The attack on European trade with the East strikes at powerful vested interests including banks, heavy industry and energy companies that influence the politics of Bonn, Paris and London in favor of continued trade with the Communists.

During interviews last week, all of the major West German companies involved in the Siberian pipeline project made clear that they intend to fulfill their contracts with the Soviet Union regardless of Reagan's final decision on sanctions.

A spokesman for the West German utility Ruhrgas, which negotiated the latest Soviet purchase agreement, predicted that the Soviets will be able to meet their contractual obligations to deliver more gas in 1984 even if U.S. sanctions force delays in the completion of the Siberian pipeline.

At Kanis, Kerlen stressed that if the U.S. sanctions continue, his company would attempt to meet its contract to deliver the turbines by buying comparable rotors manufactured by Alsthom-Atlantique, a French company licensed by GE to produce the same kind of rotors without the restrictions on their sale.

"We are bound by the export regulations of the U.S. government, and we will abide by them," said Kerlen. But at the same time, he said, "We have a contract with the Russians, and we have to fulfill it."

Buying the rotors in France, however, could delay the completion of the pipeline, since the French company has a two-year backlog of orders.

In playing down the importance of trade with the Soviet Bloc, industrialists here point out that only 2 percent of West German exports go to the Soviet Union.

Moreover, West German officials object to being singled out for their involvement in the pipeline deal, noting that British, French and Italian companies also have major contracts to supply equipment and that British and French banks also are providing credits at subsidized rates.

An official of the huge Ruhr steel combine Mannesmann, stressing the historical nature of trade with the Soviets, noted last week that his company had been selling pipe there for 90 years "without a single loss."

U.S. officials, however, argue that West Germany lost sight of the strategic dimensions of this trade and the role it plays in strengthening a country involved in suppressing Polish freedoms.

A 25-year Soviet-West German economic agreement, signed by Chancellor Helmut Schmidt in 1978, commits Bonn to industrial and financial cooperation across a broad front, including cooperation in the field of energy, joint development in production of certain types of equipment, extraction and processing of certain types of raw materials, cooperation in banking and insurance and "the granting of medium- and long-term credits . . . on as favorable terms as possible."

Although West German officials describe the agreement as very general, they have told American officials repeatedly that the commitments contained in it make it difficult for Bonn to join U.S. trade sanctions against the Soviets.

The existence of the 25-year agreement has raised questions in Washington about the future role of West Germany in Soviet pipeline projects and energy development plans that go far beyond what is involved in the current deal.

These include a second natural gas pipeline to run alongside the 3,600-mile line for which equipment and financing already has been arranged, and four other pipelines that eventually will supply industrial centers in the Soviet Union and Eastern Europe. These projects, costing more than $25 billion according to some Western estimates, would lay the foundation for Soviet energy independence well beyond the year 2000.

It is evident here in the country's industrial heart that the Reagan administration's concerns have not deterred West Germany's government or industry from pressing ahead with Soviet trade.

In January, less than a month after Reagan banned the export of U.S. oil and gas equipment to the Soviet Union, Mannesmann signed a new contract with Moscow to ship 1.2 billion tons of large diameter pipe.

This month Bonn's Ministry of Economics confirmed that the government insurance company Hermes has approved $517 million of export credit guarantees for the Soviets since the start of the year.

Meanwhile work continues in the cavernous metalworking shops of AEG-Kanis, as Kerlen awaits U.S. action on his application to ship the turbines.

The Soviet turbine orders account for about half of the Essen factory's workload. If the orders were canceled it would not mean immediate financial disaster, since 85 percent of the contract is covered by insurance provided by Hermes. But it would expose the company to lawsuits, force layoffs and possibly reopen discussions at Kanis' parent company, AEG-Telefunken, on whether to close the plant.

West German Economics Minister Otto Lambsdorff met with officials of General Electric and senior U.S. policy-makers to discuss the problem when he visited the United States in January.

Officials in Bonn insist that their determination to proceed is not a sign that the country is turning away from the United States, but a move to develop energy sources outside of the Middle East and help the German economy through the recession. They say both objectives keep West Germany economically healthy and indirectly strengthen the Western alliance.

German industry, which excels in producing heavy-duty equipment and steel for export, has always been drawn naturally to the Soviet Union with its vast mineral resources and need for equipment and engineering to develop these resources.

The controversy over the pipeline deal is colored by the fact that the central actors also include West Germany's largest banks, steel companies and utilities, all of which have close connections to the political establishment in Bonn as well as closely knit ties to each other.

Mannesmann, which has exported 8 million tons of pipe to the Soviet Union since 1970, has an equity interest in Ruhrgas, the major importer of Soviet gas under an agreement signed Nov. 21. The interlocking network of banks and companies is strongly opposed to the policy of "economic warfare" being promoted by some members of the Reagan administration.

In the case of West Germany, Deutsche Bank, Mannesmann and Ruhrgas (two-thirds of which is owned by international oil companies) have been playing a role in Soviet energy development since 1970. These companies view the new Siberian line as a natural continuation of West German involvement rather than as a threatening new trend toward dependence on the Soviet Union, as some in the Reagan administration view it.

By the same token, the Bonn government has provided the backup support for the German-Soviet energy deals from the beginning in the form of bilateral agreements and credit guarantees.

Ultimately, however, the future of East-West trade seems likely to depend more on politics than on the technicalities of finance.

Senior officials in the Reagan administration, while wanting to find ways to keep economic pressure on the Soviet Union and its economy, fear that too much pressure could add to strains with West Germany and other allies.

At AEG-Kanis, director Kerlen says he is concerned about signs of an anti-American mood among his workers.

"Our employes like the United States, and they don't like what has happened in Poland," he said. "But lately they have been asking why they should be the ones to suffer. If this goes on there could be a change of mood."