# Measurement and Analysis of Industrial Forklifts Vibration Levels for Unit Load Testing Purposes
###### Abstract  
Forklifts are one of the most common types of material handling equipment used in warehouses and distribution centers. Vibration generated by forklifts may have an effect on the performance of unit loads and product damage rates. Historical research projects have focused predominantly on the measurement of vibration for over-the-road transportation. Thus, there is still a lack of understanding of the level of vibration caused by forklifts. The goal of this study was to understand how the vibration that is experienced by unit loads while being transported by forklifts is affected by factors such as speed, road condition, unit load weight, type of forklift, and sensor location. For this study, power spectral density (PSD) measurements were collected using a Lansmont Saver 9X30 data logger. Vibration levels were measured for three different industrial forklifts on two different surface types. The forklifts were driven at two different speeds while carrying two different unit load weights. For all of these conditions, the vibration levels were measured at the forklift carriage, at the back of the fork time heel, and at the fork time tips. The results obtained show that the highest vibrational intensity occurred at 3-4 Hz, while the highest overall Grms value observed was 0.145 G\({}^{2}\)/Hz (between 1-200 Hz). An increase in the forklift speed caused an increase in vibration intensity. In contrast, an increase in the unit load weight carried by the forklift caused a decrease in vibration intensity. Among the three forklifts studied, the gas-powered forklift had the highest vibration intensity, and all forklifts, when driven on asphalt, experienced more vibration. v 202  
contents, the breaking of solid/liquid suspensions, static charge buildup, or bottle-closure cap back-off, causing leak of fluids and powdered products [4]. In most of the studies conducted, vibration data are often collected in a time-domain, where the horizontal axis is the time. However, it is difficult to describe the characteristics of the motion or use it as a control target for the random vibration test system. Thus, the power spectral density (PSD) plots are used for data analysis instead. PSD plots chart the average intensity of the vibration against the frequency of the vibration [2]. This form is called frequency-domain representation, where the horizonal axis is frequency. Random vibration PSD plots are also specified in terms of their \"overall Grms\". This root-mean-square (RMS) calculation is used to average the PSD plots to obtain a number which gives the intensity, in G, over the frequency spectrum of interest. Many studies have been conducted previously to study the vibration levels produced by different modes of transport in multiple countries, such as heavy trailer-truck and rail cars [5; 6; 7; 8; 9], and medium and small trucks [10; 11; 12]. Some of the previous studies measured the effect of distribution circumstances on vibration as a function of road conditions, truck speeds, suspension systems, or payloads [13; 14; 15; 16]. In addition, these studies revealed that intensity of vibration in transportation is related to various factors such as speed and driving performance, road conditions and quality, load conditions, and truck suspension systems. Materials and products are also moved around within warehouses. Warehousing is becoming a critical activity in trade enterprises in order to outperform competitors in productivity, lead time, and customer service [17]. The most common type of material handling equipment in a warehouse is the forklift [18; 19]. Forklifts play an important role in the global distribution of packaged products. Moreover, they have a major impact in the economic growth of the industry. There are more than 540,000 powered industrial truck operators currently employed in the United States alone, operating in all 50 states, and working in more than 300 different industries. According to the needs of the user, forklifts can come in a variety of designs, sizes, engine types, and load capacities.