- Problem Definition.
As a part from Field Development Program (FDP) it recommends introducing to upgrade the oil shipping facility. In this project two Oil transfer pumps to be installed in B station to increase the shipping capacity from 20,000 ppd to 50,000 ppd. In the below table a summary of project activities:
Table 1 Project activities summary
During Construction stage, to get a true evaluation of the project results Non Productive Time (NPT) Appraisal is preformed. The as-planned of this project (in bar chart format for clarity) is 53 days as shown in Figure 1.
Figure 1 As-planned schedule.
As per contract, standby rate count when NPT happened in this stage. Lost time is recorded to show management a reason for low production in a particular day or lower line efficiency.
- Identify the Feasible Alternative.
NPT is monitored and will calculate by work sampling method. Work sampling is a method that evaluates the amount of productive and non-productive time (NPT) assigned in recording’s stage.
Figure 2 Sample Work sheet for NPT records
- Development of the Outcome for Alternative.
The as-built schedule, which includes all delays that occurred during construction of the project, had total project duration of 83 days.
Figure 3 As-built schedule.
Work Sampling has three main uses:
a. Activity and Delay Sampling: To measure the activities and delays of workers or machines (e.g. to measure the percentage of the day that a person is working or not working).
b. Performance Sampling: To measure working time and nonworking time of a person on a manual task, and to establish a performance index or performance level for the person during his or her working time.
c. Work Measurement: To establish a time standard for an operation.
A= Absolute accuracy
Z= Number of slandered deviation
P= Observed percentage
N= Total number of work sampling observation made
Input Information to find N:
A= 5%, Z=2, P= 50%
Therefore, N= 256 observation.
For 83 days duration of the project the work sampling required is 3 observations per day.
- Selection of Criteria.
The criteria for improvement selection are based on the activity that have greatest of non-productive time.
Table 2 results of productivity and NPT%
- Analysis and Comparison of the Alternative.
Figure 4 Summary of NPT items
- Selection of the Preferred Alternative.
Table 3 Action mitigation plan to each NPT item
- Performance Monitoring and the Post Evaluation of Result
The attention of management personnel should be focused on the sources and causes of delays. A major problem at present is that several methods that measure and monitor productivity on construction sites are unable to direct attention to the cause of the delay. The breakdown of nonproductive time into two factors, the idle and waiting times, is therefore very important in order to direct the attention of management to the root causes of the nonproductive time.
1. John Christian,Daniel Hachey. Effects Of Delay Times On Production Rates In Construction,1995.
2. Taufik. 2014. W18_ TMA_Non Productive Time (NPT) Appraisal. Retrieve from
3. AACE International Recommended Practice (2004). Recommended Practice No. 22R-01 : Direct Labor Productivity Measurement – As Applied in Construction and Major Maintenance. AACE International.