This article discusses how Six Sigma analysis in a chemical plant helped it keeping the technicians efficient and its machinery reliable. The focus of this project was the wrench time of the technicians—that is, the actual time they spend in the field carrying out their primary job. An initial survey, based on examination of work records, discovered that the wrench time of the technicians was about 20%. It was suggested that by improving wrench time, the company would control overtime expenses of the technicians and would also improve service to ensure reliable and smooth operation of the plant’s machines. A Six Sigma approach was employed to identify the issues responsible for the low wrench time and to identify the solution for improvement. The approach had five steps: define, measure, analyze, improve, and control. The approach was useful in the identification of the factors responsible for the problem. The major success of the project was the reliable operation of the plant, the objective for which the management had been striving.


The annual expenses of the machinery section of our urea plant were on the high side a couple of years ago.

Part of the increased expenditure was clear. The section had invested in expensive digital vibration analyzers to better monitor the plant's machinery. Nonetheless, management insisted that budgetary expenses be reduced as much as possible.

There was, however, one area that seemed prime for cost reduction. A team of three technicians, whose primary job was to monitor machinery in the field, had overrun its overtime budget by 200 percent in 2007.

The reason for that wasn’t immediately clear. So a project team applied a variety of Six Sigma techniques to find out why it happened and to identify steps that have remarkably improved the situation.

The plant, operated by Engro Chemical Pakistan Ltd., is a urea fertilizer complex located in the interior of the Sindh province of Pakistan. The complex has a production capacity of 1 million metric tons of urea on an annual basis.

The technicians are charged with taking diagnostic equipment to monitor the plant's machinery on a regular schedule and to report what they find so that equipment can be maintained on a timely basis.

The focus of the project became the wrench time of the employees—that is, the actual time they spend in the field carrying out their primary job. Wrench time excludes meetings, training sessions, and breaks. We reasoned that by improving wrench time we would control overtime expenses, and improve service to ensure reliable and smooth operation of the plant's machines.

I coordinated the project, which was sponsored by my section head and supported by my fellow-engineers.

The company is committed to a philosophy of condition-based monitoring of its machinery. The section responsible for the compliance with the condition-based monitoring philosophy includes a team of engineers and technicians.

The technicians in the machinery section are provided with tools for monitoring machines—vibration analyzer, stroboscope, sound analyzer, etc. The data they collect are reviewed by a team of engineers. Based on the engineers’ evaluation, any remedial work orders deemed necessary are delivered to the maintenance and production team for execution. Technicians have to visit different sub-facilities at the plant site, and each machine has to be given coverage on a schedule.

The section has three qualified and experienced fulltime technicians responsible for monitoring more than 300 machinery units, including steam turbines, gas turbines, compressors, pumps, electrical motors, and blowers at the plant.

An initial survey, based on examination of work records, discovered that the wrench time of the technicians was about 20 percent. That is, 20 percent of total working hours—eight hours a week—were spent in the field checking on machinery, and the remaining 80 percent of their time was taken up by other activities exclusive of field work.

The employees were interviewed in certain instances, and two observers were appointed to monitor and inquire about the daily routine of each technician.

A Six Sigma approach was employed to identify the issues responsible for the low wrench time and to identify the solution for improvement. The approach has five steps: define, measure, analyze, improve, and control. The definition of the problem was clear: “Wrench time of our employees is as low as 20 percent.” Through international benchmarking from several maintenance books, and other sources, the project team determined that wrench time of 60 percent is a good rate to make proper use of an employee's skill.

Furthermore, the low wrench time was accompanied by high overtime rates. The overtime pay for work by these employees in calendar 2006 and 2007 was much higher than in previous years.

To measure the problem, the daily activities of the employees were surveyed. The activities were divided under given heads—job planning and instruction, material and tool issuance and preparation, delays due to procedural requirements (including paperwork and filling out reports), tool availability, delay in job handover, keeping the work area neat and clean, personal breaks, and actual field work.

After compilation of the data, we estimated the exact wrench time of our employees at 22 percent, and the expense budget sheet indicated that the technicians reported more than 1,500 overtime hours in the 2007-2008 periods. The cost averaged more than 500,000 Pakistani rupees a year.

The breakdown of daily activities suggested that the employees spent more than six hours out of an eighthour general shift on personal breaks, waiting, tool preparation, training sessions, and housekeeping. The amount of hours spent on their basic work was far below acceptable limits.

To analyze the information, we developed a constant, noise, and X-variable (CNX) diagram to relate the factors responsible for the low wrench time of the employees. In this diagram, we identified the variable factors, on which corrective measures can be taken. Factors that affect wrench time but are the result of required procedures are considered constant. Factors that are independent or uneconomical to address are regarded as noise. Through this analysis we established the following as variable factors, which we can control to improve wrench time.




  • Data management: More than 300 machines at chemical units were being monitored without proper frequency. No proper route was developed for the technicians to visit machines, which were spread over an area of 10 acres.

  • Procedural requirements: Often the presence of a technician was mandatory for a specific test, but his active involvement lasted for minutes. The over-speed-trip test of a turbine, for example, is approximately a two-hour activity; however, the running duration of the turbine itself is only five minutes. We were unable to minimize the duration of procedural requirements because our administrative policies are aligned with safety standards, and we stood firm not to compromise safety standards.

  • Ineffective reporting: The employees took the monitoring signature, but often did not upload the results on the computer, and forgot to report.

  • Tool preparedness: The technicians often reported late to a plant site because they had been waiting at their office for their analyzer to get charged. Data upload and download also took time, and were additional causes of delay.

To improve the situation a route management plan was developed for monitoring machinery. Monitoring frequency of critical and semi-critical units was previously executed on a bimonthly basis. The frequency was redesigned and route management plans were developed for fortnightly, monthly, and bimonthly monitoring of equipment, based on criticality and mean time between failure. Through revised route management, we were able to ensure the active participation of our technicians in the field and achieve reliable operation of our plant as a consequence.

The lube oil program was revamped. The employees were assigned responsibilities with reference to lube oil sample collection, followed by the compilation of the lube oil sample reports on monthly basis.

The section's engineers, referring to the history of the various kinds of equipment, graphed the vibration trends of critical and semi-critical machinery, and alarm limits were defined. The development and compilation of the data base were the responsibility of the technicians.

The technicians were required to assist in repairs by observing and supporting the maintenance team, and to verify certain activities including installation of bearings, and seals during maintenance.

Technicians were rewarded through annual remuneration and appreciation letters for value-added observations and timely rectification measures. There have been instances when technicians reacted promptly to resolve high-vibration issues in machinery through support adjustment, process variation, oil change, etc.

Tool calibration and preparedness was another factor which severely affected the overall performance of the employees. Calibration frequency was redefined for all the critical tools, and was practiced religiously. The digital vibration analyzers often required charging. In the past, employees had refrained from visiting an area because the equipment was not charged, and so the reliability of the plant was at risk. Responsibilities were assigned to technicians, and a schedule for charging analyzers and tools was developed and implemented.

The punctuality of the employees was an important factor, and often employees were reporting late due to certain administrative issues, for instance, with the company's housing and medical sections. Those sections have agreed to schedule appointments according to the technicians’ work schedule. The services of the company's administration were requested to improve the social and personal issues of the employees, who have been living in company-provided accommodation.


The overall impact of the improvement project was positive, and wrench time increased to more than 55 percent. The employees were now spending more than four hours a day in the field. Personal breaks and tool-related issues were reduced to an average of about one hour a day, down from two and half hours. The rest of their time is taken by procedural requirements, such as training sessions, documentation, and reporting machine data.

In 2006, 2007, and the first part of 2008—before the implementation of the project—the overtime of our employees was more than 560,000 Pakistani rupees on an annual basis. Through this project we were able to reduce the overtime by 300,000 rupees, which is equivalent to 1,000 man-hours. Furthermore by focusing on tool preparedness, we saved 200,000 rupees by finding economical ways to deal with calibration, including calibrating our equipment against that of other local plants.

Through increased wrench time we were able to increase the surveillance by our employees at the plant site. Their vigilance assisted in the prompt identification of problems with machinery. The machines were attended prior to any catastrophic or unforeseen damage. The mean time between failure of critical and semi-critical machinery units increased, and the machinery units of the chemical site were operating well from a mechanical perspective. There was no plant shutdown from July 2008 to June 2009, except for certain electrical and instrument-related failures.

Reliable and smooth operation of the plant's machines avoided process interruptions, which could have caused production losses worth millions of rupees. We also developed a plan to operate stand-by units on a defined schedule. Thus the health of stand-by units was ensured and plant operation was made more reliable. The key to this reliability was improved wrench time.

The Six Sigma approach has been useful in the identification of the factors responsible for the problem. The major success of the project has been the reliable operation of the plant, the objective for which our entire management has been striving.

The monitoring operations have become so efficient that Engro has been able to offer the services of the technicians to other plants in the area, where they get to work with and observe technicians and engineers from other companies to diversify their experience. The sites include oil rigging facilities, chemical plants, and power plants, which all work in close collaboration. Services are offered as a courtesy, and availability is limited to a maximum period of one or two days.

This wrench time project was a pilot run by the company, and was initially applied at the section level on a small team. Results have encouraged the company to apply these techniques at the department level. Currently projects on wrench time have begun in the maintenance department and the instrumentation and electrical department.