SIPTU members have served notice of strike action at Zenith Energy Bantry Bay Terminals Limited, located on Whiddy Island in Co Cork.
The strike action is due to commence on Tuesday 13 December, in a dispute over redundancies at the energy company.
SIPTU says the company has taken a decision to lay off maintenance workers with long service while planning to employ contractors on an ongoing basis to do their work.
"Strike action is always a last resort but it is now obvious that the compulsory redundancies that Zenith Energy are seeking are not necessary," said SIPTU Sector Organiser, Willie Noone.
Efforts by the Workplace Relations Commission to resolve the dispute have been unsuccessful.
"SIPTU representatives have asked that the issues in dispute be the subject of a Labour Court hearing and for the immediate withdrawal of the redundancy notices," Mr Noone said.
"As there has been no positive response from the company, our members have been left with no option other than to serve strike notice," he added.
Zenith Energy said the notice of industrial action follows the rejection by SIPTU members of a WRC proposal to restructure Zenith Energy operations at the Bantry Bay Terminal.
"The WRC proposal was reached after more than seven months of negotiation both at local level and with the assistance of the WRC," the company said in a statement
"Both Zenith and SIPTU negotiating teams had recommended the proposals for acceptance," the company added.
Zenith said that there are 31 permanent employees at the Whiddy Island terminal and that it is implementing five redundancies as part of the restructuring process.
"Zenith Energy can confirm that Bantry Bay Terminal will remain operational and the company will ensure, at all times, the continued safety of personnel, the environment and the community in which they operate," the company said.