Duty gap

Dear Sir,

I have a doubt.

In a continuous process factory (24 hours x 365 days), working in three ‘8 hourly’ shifts namely A, B & C. The workmen are assigned duties in various shifts on daily basis with one off day in a week. While assigning the duties one in each day whether a gap more than an ‘8 hourly’ shift is mandatory? 

Thanks & regards,

Dr A Sur