This industrial port, with its squat red brick and gray limestone buildings, is supposed to be closed "tighter than a drum" because of a national strike by truck drivers. According to a London newspaper headline, Hull is "a city under siege."

In fact, the tall cranes along King George Dock are loading and unloading freighters. Supermarkets in town are filled with food and shoppers. Mills making feeds for East Yorkshire's pigs and poultry are producing about 60 percent of their normal output. Neither animals nor humans have starved. Factories, too, are still turning out some share of their production.

That is one side of the picture. The other is that strategically placed truck driver pickets have virtually stopped freight from moving in and out of the huge sheds that line the dock. They are running out of space and could be filled completely in another week or two.

Supermarket owners say their warehouses are emptying. Already there is no salt, sugar or cornflakes in most stores. Factories not involved in the strike have had to lay off about 5,000 workers for lack of supplies, a large number in a city of 280,000. Those laid off are geting about $38 in unemployment compensation compared to a normal take-home pay of about $140 a week.

In sum, the "city under siege" is not a disaster area, but its life has been made difficult. National fallout however, could turn out to be more drastic. Prime Minister James Callaghan's Labor government has been forced to compromise its economic strategy, raising the politically damaging prospect of a new round of high inflation rates and providing an opening for the Conservative opposition in forthcoming elections.

"There are no nice strikes," says David Cairns crisply. He is the shrewd, articulate general secretary of the Transport and General Workers Union or T and G in this part of the world

His headquarters is Bevin House, named for the former T and G leader who became Britain's postwar foreign secretary. There, Cairns and the strike committees listen to businessmen appeal for removal of pickets to let vital supplies through. Cairns radiates confidence, sure his truck drivers will soon win what they want, a 2 percent pay increase.

He has reason to be confident. The last big barrier broke a few days ago, when the government set aside its anti-inflationary standards and agreed that trucking companies could pass on any pay gain through higher rates to customers.

Cairns vigorously denies it, but the victory could be Pyrrhic. It means the end -- at least for this year -- of serious efforts to restrain wage demands.

Cairns and the drivers want that.

But it also means that Britain is almost surely headed once again into another bout of double-figure inflation, wiping out the buying power of some or all of the pay increase.

Cairns and the drivers do not want that.

Finally, it gives Margaret Thatcher, the Conservative Party leader, a powerful boost toward her ambition to dislodge Callaghan in the election, which must take place this year.

Cairns readily acknowledges this would be a "political disaster of the first order" from his standpoint and that of his members. But his first duty is "to try to have a good settlement."

"If there are political implications, that's not of our making," he adds.

The tactic Cairns and his men employ is outlawed in the United States. It is a secondary boycott, placing pickets outside factories, warehouses and depots with which the union has no wage dispute.Drivers do not like to force fellow workers onto the dole.But as Harry Williamson, a burly auto hauler here, says, "They ask us not to cross their picket lines. We don't."

The shutdown is far from complete because hundreds of deals are worked out with the T and G to let food and other vital supplies move freely. Reckitt and Colman, a big drug and food concern still had 1,700 of its 2,500 employees at work by the end of the week, thanks to such a deal. Another arrangement kept the shelves of the Grandview Supermarket full, although warehouses were emptying.

Nobody knows for certain howmany drivers are striking. The number across the country may be 100,000 of 500,000. The rest work for company owned fleets, the national trucking company or for family concerns. They are not involved in the quarrel.

The basic rates for driving the biggest trucks here are $2.65 an hour. The trucking companies have offered a boost to $3.00 but the union demands $3.25.

This, however, is not the whole story.The men get a guarantee of about 10 extra hours a week at overtime rates. This lifts average pay to about $145.

They seek the big boost for two reasons: Common Market safety regulations will force down the overtime hours they now work and strip away much of the premium pay. The drivers are not a bit impressed by the argument that pay curbs have slashed British inflation from a terrifying 30 percent to a tolerable 8 percent. They thought they had been promised an end to rising prices.

Back in London, there is widespread agreement that this strike will confront Parliament with irresistible demands to curb union strength and especially the secondary boycott weapon. William Rodgers, the Labor government's transport minister, says firmly, "There must be some rules and some restraint."

But there is sharp disagreement over whether incomes policy, the sort of pay restraint the Carter administration is attempting, can be revived. Rodgers says, almost testily, "If this shows anything, it shows free collective bargaining does not work." He predicts union chiefs will now come to the government in a more congenial frame of mind.

But Sir John Mathven, head of the Confederation of British Industry and chief spokesman for business, insists that incomes policy is a proven failure. Instead, he would rely on enlightened self-interest, a new version of Adam Smith's invisible hand.

"People have some understanding," he says smoothly "People have a fear of inflation."