He decided to go and see for himself. He had to look on a map to see where Temse was (it's on the river Scheldt upstream of Antwerp, close to Sint-Niklaas), and then set off from Brussels full of curiosity about the place where they made ships as long as a street and as tall as an apartment block.

When he got there, the occupying workers didn't let him in. But he returned, made friends with them and started to learn the story of the shipyard. Over the next four years this developed into As Long as Shipbuilders Keep Singing, an examination of the ship-building industry in Temse that was coming to an end before his eyes. Completed in 1999, the three-part film, which is four hours in total, is now being revived, with screenings this month around Flanders and the release of a DVD.

Looking back, Vromman sees his lack of knowledge at the beginning of the project as an advantage. "Innocence is a good position to start with," he says. "It's like a child who sees an amusement park for the first time, and for me the amusement park was the beauty of the ships."

While not from a working class background, he has a long-standing fascination with industry. "I always like to visit factories, whether it’s a car production line or a glassworks. It's always an aesthetic experience, apart from all the social and other aspects. Without this aesthetic experience I would never have got through the [Boel] story."

As well as exploring the conflict in 1995, Vromman's film goes back to the origins of the business in 1829, when Antwerp shipwright Bernard Boel set up a workshop on the banks of the Scheldt to build river boats. As the business was handed down from father to son, the Boels went from being artisan workers to overseers and then owners. The shipyards expanded, the materials changed from wood to iron to steel, the vessels from inland boats to ocean-going ships.

But in parallel, the owners diversified, so that the shipyards were just one of their business interests. When competition from Asia became too intense, the shipyard was allowed to go under. The government took over with a Dutch business partner, but the reprieve was shortlived.

The last members of the family firm, Philippe Saverys and his son Nicolaas, feature in the film, explaining their position and the pressures of the increasingly globalised industry. Vromman admits that he was intimidated by the prospect of talking to them, let alone to the politicians, who he interviewed about government support for the shipyards. He only noticed later that this came through in the images, which are more polished than those of the workers.

"It's strange. You feel obliged to put on a technical performance when you talk to a minister, but you improvise when you talk to a worker," Vromman recalls. "All these things speak to the viewer. This kind of static frame for the minister, this supple, direct way of filming people on the shop floor give an emotion to the film – an emotion that is beyond my control."

As a mark of Shipbuilders’ subjectivity, Vromman also included himself in the film, not just carrying out interviews but bumbling around in his apartment and trying to get to grips with charts and papers. "I had to show my small position in front of this big question."

Meanwhile there were aspects of the story that were important to him, but which were not about facts and figures or the struggle between the workers and the owners. So throughout the film, which already contains a good deal of singing from the workers and performances by their brass band, he adds his own lyrical reflections on subjects as diverse as hats and helmets, abandoned bicycles and the magazine pin-ups on workshop walls.

"It's like the chorus in Greek tragedy," he explains. "There are some elements that you can't say with a voice-over, things that you feel while you are there. You have to find a form to express these feelings. I also needed to include my love of making images, not just telling a thematic story."

Shipbuilders is being released now with the support of the unions, even though they don't come out of it particularly well. One of the film's themes is the long-running and sometimes bitter argument between the charismatic shipyard activists, some of whom had entrenched positions, and the more pragmatic union leaders working at the national level.

Revisiting the conflict is hardly a case of nostalgia. "For a lot of people it was a failure, including the people leading the social struggle. It is always difficult to look back at defeat," Vromman says. "But, on the other hand, there is some pride that this memory is being preserved."

He feels a little odd that this film rather than one of his more creative works should be singled out for attention. "But I also feel proud because it is the work of a documentary maker to make something that has historical value. If you see now where we are with the memory of this industry, it is perhaps the only museum that it has. And an industry also has the right to be commemorated."

28 May, 20.00
Film Plateau
Paddenhoek 3, Ghent
with director Jan Vromman
29 May, 16.00
Cinema Zuid
Lakenstraat 14, Antwerp
31 May, 19.00
Cinema Rits
Dansaertstraat 70, Brussels

All screenings of As Long as Shipbuilders Keep Singing include introductions and debates. The film is also available on DVD with English, French and Dutch subtitles
www.scheepsbouwerszingen.be