Thank you I will look for Timmerhaus.
Our textbook book is 'Chemical Engineering Design' by Sinnott, the labour section under costings is minimal, I've copied it in below.
Extract from Sinnott:
Labor Costs
The wages paid to plant operators and supervisors are a fixed cost of production, as
described in Section 6.2.4. Almost all plants are operated on a shift-work basis (even
batch plants), with typically 4.8 operators per shift position. This gives a four-shift
rotation with allowance for weekends, vacations, and holidays and some use of
overtime. Most plants require at least three shift positions: one operator in the
control room, one outside, and one in the tank farm or other feed/product shipping
and receiving area. Plants that use more mechanical equipment, particularly solidshandling
plants, typically require more shift positions. More shift positions are also
needed when handling highly toxic compounds. In some cases two or more smaller
plants may be grouped together with a common control room and tank farm to reduce
the number of operators needed. Very few plants run entirely unattended though,
with the exception of gas processing plants, which hold no inventories of feed or
product and are usually automated to allow a single control room operator to watch
over several plants.
Operator salaries vary by region and experience level. For initial estimates, an
average USGC salary of $50,000 per shift position per year, not including overhead,
can be used. Supervision and overhead costs are discussed in Section 6.2.4.