Most people in the material handling industry know that the cost to design, specify, and construct a typical concrete industrial floor for a moderate size distribution center or warehouse can easily reach $1 million or more. However, the building owner or end user, concerned with limiting costs, may overlook the money-saving role of a floor with superior flatness and levelness. Here we look at the main reasons why Superflat floors are important to reducing daily operational costs, specific ways a Superflat floor saves money, and how to make floors Superflat.
According to Concrete Construction Magazine, there are two basic floor categories: random traffic and defined traffic. Superflat floors are related to defined traffic: for example, very-narrow-aisle warehouses where forklifts travel 6 ft wide aisles between storage racks with the aid of rack-mounted rails or a wire guidance system embedded in the floor. For these forklifts to perform as intended, defined-traffic floors must be extraordinarily flat and level, or superflat.
Why Is a Superflat Floor Important?
What most do not know is that a “Superflat” floor can potentially save its end user literally millions of dollars over the life of the building. This is because a Superflat floor can help reduce vehicle and equipment maintenance costs, less-than-optimum inventory turns, inventory damage, and healthcare costs due to increased worker injury from unstable lift trucks on bumpy floors -- according to the Office of Safety and Health Administration (OSHA), lift truck operators over the course of time may suffer from back, neck, hand, and arm pain caused by excessive vibrations or excessive physical forces from bumpy floors while operating lift trucks.
How Superflat Floors Save Money
Reduced maintenance costs: A concrete floor with a rough surface prohibits the rapid movement of cargo. When a concrete floor has bumps, dips, or joint problems, lift truck operators must constantly judge the surface and adjust their speed according to the floor’s immediate condition. Many times lift truck operators will drive the vehicle backward to better spot floor defects so that they can swerve to avoid them, or slow to crawl-speed in order to negotiate the defect to keep from losing cargo.
Superflat floors allow full speed lift truck operation with no need for the driver to negotiate around a bad area. Superflat concrete floors also reduce the need for lift truck electrical and mechanical repairs and for replacement parts such as wheels, and permit overall longer battery life.
Cargo placement/retrieval: Another way a Superflat floor saves money is in cargo placement and retrieval from storage racks. Seemingly minor variations in floor flatness and levelness can significantly amplify problems with cargo placement and retrieval as mast height increases. Because vibration from an uneven floor increases the “fishing rod effect” on lift truck masts and lift truck operators tend to have more trouble placing forks high up when the floor is bumpy, the operator must use extreme caution picking or placing high-reach cargo on a poor condition floor. The higher the mast height, the more pronounced the lean from uneven floors and the more likely that the lift truck may strike the storage racks.
In addition, the operator must lower the load in order to reduce mast sway when moving to another location in the aisle, thus wasting valuable time. With a Superflat floor, the time to pick or place cargo is greatly reduced. The mast will not sway as much and there is no need to lower the load to move to the next location.
Warranty issues: Many lift truck manufacturers today will not warranty new lift trucks unless the floor meets certain flatness and levelness specifications. Warranty repair costs are much higher with an inferior floor. Many industrial lift trucks also do not have a suspension system or pneumatic tires. A slope defect -- a small bump of only 0.06 (1/16) in. -- will cause one or more wheels to become airborne at speed and thus cause frame stress-cracking from the continuous dynamic cyclic flexing of the frame members.
This sudden change in floor flatness also causes significant mast deflection and runs the risk of rack-to-lift truck conflicts. Vibration from rough surfaces not only cause flexure and deflection of lift truck structural materials, but can also affect wheels, axles, hydraulic seals, bearings, and other key components. After the warranty period ends, a Superflat floor will continue to reduce or eliminate many maintenance problems associated with bumpy floors for years to come.
How Can I Get My Floors Superflat?
There are two ways to get a Superflat floor: construct a new floor or grind the existing floor. The decision on which method to choose depends on a few basic considerations:
For new construction, the proper forming, placement, and finishing of a Superflat floor is the most common approach nowadays. But for the operational distribution center or warehouse, grinding existing floors to Superflat tolerances is a very cost effective remedy that will return the investment in all of the ways listed earlier.
For an existing operation, grinding is definitely a consideration, even if the end user is not the building owner. The cost to grind varies depending upon the type of grinding needed, but the results are well worth the effort. Both the building owner and end user can share in the cost to grind and share in the benefit. The end user gets the immediate benefit of faster operations and the building owner gets future benefit from increased income because the building can be advertised as a Superflat warehouse for the next tenant.
Estimated Cost Savings of Superflat Floors
A typical distribution center/warehouse aisle is approximately 300 ft long. Proper calculation of lost productivity from non-Superflat floors should be done on a case-by-case basis; however, some fundamental mathematics reveal interesting, if not startling, results.
For instance, let us assume an average lift truck travels at full speed of approximately 6.5 miles per hour, or about 9.5 ft per second. The required time to traverse from one end of the 300 ft aisle to the other is approximately 31.5 seconds at full speed. Empirical data taken from Profilograph® floor measurements of existing floors indicate an average of approximately 10% of the aisle, or about 12 areas of varying lengths, need remedial grinding to meet the floor flatness specification needed for the installed racks, based upon the aisle width and rack height above the floor. Also, assume that the lift truck driver has a load and must slow down significantly for each defective area -- about 1.5 seconds lost to deceleration and acceleration per defect. In this scenario, the lift truck wastes about 18 seconds in a typical 300 ft aisle.
Next, assume that the cost per hour to operate the distribution center/warehouse is around $100 per hour per lift truck ($15/hour + benefits + taxes + insurance + overhead + burden, etc.). Multiply 18 seconds by $0.28 per second ($100 per hour divided by 3,600 seconds per hour) to get $0.50 per run.
Now consider the total possible number of runs in each 8 hour shift for one lift truck (about 729 runs), multiplied by the lost money per run ($0.50), multiplied by the number of shifts per working day (3 shifts), by the number of days per week, by the number of days per year, and the result is startling. Each lift truck loses about $1,000 worth of productivity per 3 shift day. Multiply $1,000 by 365 to equal an approximate third of a million dollars annually per lift truck. How many lift trucks does a typical operation use?
Recommendations
Building owners and end users should give serious consideration to the benefits of having their floors Superflat. Although some confusion may arise when trying to determine Superflat floor specifications, the time spent with a qualified concrete consulting company before work begins on the project is well worth the effort.
Initial investments of time and money to ensure a superior floor will be returned many times over through increased throughput, increased vehicle operating time, increased productivity, and decreased maintenance costs for vehicles, pallets, racks, and operator fatigue. Superflat floors are an important consideration in calculating cost savings of distribution center and warehouse daily operations.