Use Check Sheets To Identify The Causes of Downtime
A true case study demonstrates how organizing information can help solve problems
by Davis R. Bothe
Downtime--the period of time when a machine, computer or any other piece of equipment breaks down and needs repairs--is rarely considered a good thing.
For example, an East Coast shipyard has large overhead cranes that are often inoperable, causing much downtime. The downtime results in regular work slippages, delaying the completion of a major project and costing a lot of money because the shipyard is assessed a huge penalty for every day it fails to meet its deadline. The more downtime, the more money the shipyard loses.
In an attempt to reduce or eliminate downtime, organizations must identify the problems causing the downtime in the first place. After all, you can't solve a problem if you don't know what's causing it. But where do you begin when you have no idea what the root cause of the problem is? A check sheet is a great way to reduce the possibilities and cover all the bases.
Determining the problem
Let's return to the shipyard, where a production supervisor named Betsy has been assigned to solve the problem of the inoperable cranes. She begins by having a discussion with maintenance personnel. During this meeting, Betsy learns that the main reasons for crane downtime are problems with the cranes' onboard computers. To determine which of the shipyard's five cranes has suffered the greatest number of computer glitches, Betsy decides to design a check sheet (see Figure 1).
Reviewing every maintenance report involving computer trouble that was written during the past four months, she uses the check sheet to tally how many problems each crane experienced. When she's done, Betsy realizes that all five encountered about the same number of computer problems over the four month period.
The stratified check sheet
Having noticed that the maintenance reports also specify on which shift the computer malfunction occurred, she decides to incorporate this second factor into her analysis by creating a stratified check sheet--a check sheet that divides or stratifies information into categories (see Figure 2). Betsy assigns a different crane to each of five rows in this matrix, while a different shift is listed in each of three columns.
When the computer problems for each crane are now cross tabulated by shift on this revised form, she learns that the majority of problems (68 of 72) happened on the third shift, which runs from 11 p.m. to 7 a.m.
Armed with this new clue, Betsy concentrates her investigation on the 11 p.m. to 7 a.m. time frame and discovers that the local power company performs tests and maintenance operations only at this time. While sharing this revelation with shipyard electricians, she learns these activities could cause interruptions to the electrical power supplied to the cranes. Such a power outage could potentially disrupt, or even wipe out, the memory of a crane's computer, resulting in a malfunction.
Based on these findings, Betsy connects an uninterruptible power supply unit to every crane's computer.
Because she installed the power supply units, Betsy reduced crane downtime by more than 90% and helped the shipyard complete its project on time.
While this particular shipyard learned the value of check sheets firsthand, anyone can use this data collection tool. Regardless of which industry you are in, check sheets are an effective way to organize information, determine the causes of a problem and solve it--eliminating downtime.
DAVIS R. BOTHE is the director of quality improvement at the Inter- national Quality Institute in Cedarburg, WI. He has a master's degree in business administration from the University of Wisconsin-Milwaukee. Bothe is an ASQ Fellow and a certified quality engineer and reliability engineer.