Piping Man-hours Estimation. Rough estimation of the order of magnitude (ROM) in the piping. In this post and the following, we will estimate the number of work hours required to assemble the welded piping as shown in the figure using three calculation methods.
The three methods of calculation of man-hours of welding piping
- Man-hours Estimation. Rough estimation of the order of magnitude of man-hours (ROM)
- Work hours Estimation. Precise estimation to arrive at the most probable execution time.
- Work hours Estimation. Precise estimation of man-hours, with prefabricated execution.
Later we will make a comparison with the results.
Piping Man-Hours Estimation – Validity Requirements of the Calculation
First, we must determine the conditions under which this estimation is valid.
- Performance applies to carbon steel tubing and is designed in accordance with ASME B31.3.
- The quality control of the work is performed by means of hydraulic tests (when quality control is performed with NDT tests, more care must be taken in chamfering, quality control and welding).
- Times do not include manipulation, painting, isolation, supports, scaffolding.
- The performance of operators is not stimulated by payments per production or per task completed.
- Work is done in standard conditions.
The criteria that define the standard conditions in which these performances apply are:
- The site of the Works is isolated, and the execution of the Works is independent of any other plant in operation or any nearby activity affecting it.
- The consumption of man-hours per activity is that used by a typical work team composed of a helper, a Pipe fitter and a welder.
- The work is carried out in a moderate climate (i.e., average temperatures between 5 °C and 40 °C) and with winds of less than 30 km/hour.
- The area where the work is carried out is free of contamination.
- Work is performed in daylight.
- The work is carried out on a site with flat and dry ground.
- The maximum height of the working plane does not exceed 1.80 m above ground level.
- Minimum clearance height in covered areas = 2.60 m.
- Maximum transport distance from the storage or unloading area to the work site = 300 m.
- Operators’ entrance door is 200 m or less from the working area.
- We receive engineering goods and supplies in a timely manner based on the project schedule.
- Trained field personnel are available.
- Adequate construction equipment and tools are available.
- The project site must be at an elevation above sea level such that the altitude of the site does not require additional effort on the part of the workers.
- Does not include man-hours consumed for fabrication of accessories.
- Time consumed for work to correct design errors is not included.
- Pipe is NPS 4″ SCH40.
Piping Diagram—Man-hour estimation for steel piping
Estimating the order of magnitude (ROM) for piping man-hours in a rough manner
To achieve this estimation, we used the historical mean value for welding piping assembly, which is 0.70 man-hours per inch of field weld or its inverse of 1.43 inches (3.63 cm) per hour.
The person-hours required to perform the work indicated in the table below.
Piping Man-hours Estimation – Table for hours worked
Piping Man-hours Estimation – Calculate Man-hours.