Should CECA rates be used for the productive time on site or the time actually whilst on site during working hours?
I assume that this relates to a compensation event quotation and the use of Equipment, whereby you have stated the use of CECA rates in Contract Data Part 2, with a corresponding percentage adjustment.
If an item of Equipment has an hourly hire rate stated, then the cost assessment would depend on whether it was used solely for the scope of the compensation event or is also used for other works on Site, which are not a compensation event.
Where solely for the use of a compensation event, then I would use the time on Site during working hours. If the Equipment is used for other works on Site as well, then the compensation event assessment should be for the period of productive working time that relates to the compensation event only, although an assessment of mobilisation, standing time and de-mobilisation may be included, such as setting up at a specific location, standing time whilst other associated works are completed and moving back to a secure area afterwards.