Workers at the German-owned manufacturing plant Liebherr Container Cranes in Killarney have begun a series of one-day strikes in protest at changes over the company's pension scheme.
The 450 workers at the plant have also introduced a complete ban on overtime.
The issue relates to a decision taken by the company in 2004 to close a defined benefit pensions scheme for new employees and to introduce instead a defined contributions scheme "of lesser value and on less favourable terms," according to Siptu branch secretary Donal Tobin.
Workers want the defined benefit scheme re-opened for all.
Speaking to ireland.comthis afternoon, Mr Tobin said talks on the matter had been ongoing since 2004 "without success".
"We had a meeting with management at the Labour Relations Commission last week but we failed to resolve the issues. We remain open to negotiation," he said.