Page 19 - Industrial Process Plant Construction Estimating and Man Hour Analysis

xxxiv Introduction

TABLE 4 Illustration of portion of tracking report for erection of a fire water
system—cont’d

Phase code Percent Productivity
Cost code description Budget Actual complete (A/E)
000000 Fire water 260 257 100.00% 1.01
hydrant
000000 Extinguisher 80 82 100.00% 0.98
000000 Mobile 40 40 100.00% 1.00
foam unit
Direct craft 540 535 100.00% 1.01
man-hours

Estimating methods
Comparison method

The comparison logic is based on estimating similarities and differences for
proposed equipment installation and previously installed equipment for which
historical man-hour data are available.
Designate

MHc¼Historical man-hour (know man-hour estimate)
MH ə ¼Equipment quantity is increased
MH β ¼Equipment quantities are decreased

MHc<¼MH ə MH ə is directly proportional to MHc; MH β is a lower bound,
and logic is expanded to MH β <¼MHc<¼MH ə .
The estimate that is either above or below the known estimate must satisfy
the work scope and quantity takeoff. The less difference between the equipment
estimate and the original comparison estimate, the better the comparison.
The comparison method provides the opportunity to compare the proposed
estimate with the previous estimate. The estimate data must be current and need
tobeverifiedbymeasurement,projectcostreports,one-cyclerepetitivetimestudy,
and historical experience, and the data need to be revised continuously with the
many combinations of construction design and engineering, labor skill, material,
equipment, and procedures. The comparison method in this manual will be more
effective if maintained and revised by the contractor, engineer, and owner.

Estimating equipment by comparison
Determine scope of work for the proposed equipment installation and make a
detailed quantity takeoff.