Workers at Marine Terminals in Dublin Port have gone on strike over pay cuts.
SIPTU said the company is seeking to impose compulsory redundancies on staff and reduce pay and conditions for remaining employees.
Dublin Port said the strike is not having any adverse effect on its operations.
However, a spokesperson for the company has said the action by SIPTU workers is affecting operations at the terminal.
Transport arriving there cannot access Marine Terminals' facilities as a result of the picket.
The union represents approximately two-thirds of the 70 workers at the company.
This afternoon Marine Terminals said it had been granted a court injunction against those on the picket line.
Company spokesman, Alex Hamilton, said that the injunction has been displayed on the gates, which states that it is illegal for anyone on the picket line to prevent a vehicle or individual from entering or leaving the terminal.
Answering earlier union claims that Marine Terminals has put workers on half time while employing workers from Scotland and Northern Ireland, Mr Hamilton said that it has a contingency plan in place to ensure that the port continues to run smoothly.
He explained: 'We have been using other workers only when union members have failed to turn up for shifts, which unfortunately has been happening consistently.'
Mr Hamilton said that the company has been prepared to talk to unions throughout the dispute.
However, he said that the union is demanding redundancy payments of €150,000, double the company's offer.
He said that the union is also refusing to consider reducing the crane operator’s salary from €75,000 to €60,000 with changed shift patterns.
SIPTU says the action will continue until normal working conditions are restored.
Previous talks at the Labour Relations Commission ended without resolution.