Shift working - How can I protect ourselves from Industrial Dispute?

We have some single man post in shift working with reviler system. Due to 4 persons , 3 days in week a spare post occurs. i.e. 3 days double man power instead of single. Now management trying to shift the spare person in place of person who applied for leave.
Due to this mental harassment occurs to staff. How can I protect ourselves from Industrial Dispute ? Please Guide

First analyse manpower position.
If at all you want to make such changes, discretely sound out the union.
Be well prepared with why you have to change and how manpower gets more effectively used.
Talk to the concerned staff also and explain the need for this change in friendly manner and then go ahead.

While reiterating Mr.Nathrao's suggestion to settle the issue amicably, so far as an industrial dispute is concerned, it is employer's prerogative to deploy his staff at the point of need unless he violates any provision of law(working hours,rest intervals or holidays etc) or any settlement like prohibiting the employer from so deploying without the consent of the workman concerned. So check your action for any breach.
B.Saikumar
HR & Labour relations Advisor
Navi Mumbai

sir how can I make Industrial Dispute ?

It appears you want to raise an Industrial dispute on the posting of spare man power in place of regular manpower in the shift. It is the prerogative of the management to post manpower depending on the contingencies. There is no legally valid reason to object to this arrangement, however an emotive issue could be raised that by posting the spare manpower in place of regular manpower a customary privilege is withdrawn and your earnings by way of OT is adversely affected.