Application Note Such Disturbances

Weighing Performance during Typhoons Improving Balance Stability ScinoPharm Taiwan Ltd. Environmental disturbances cause issues with balance stability around the world. Peak typhoon season in particular creates significant weighing challenges for users of sensitive balances - measurement issues that standard balance filters simply cannot compensate for. Rather than accept this adverse effect on weighing results, METTLER TOLEDO set out to find a solution that could be utilized during Application Note such disturbances. The result is reliable weighing performance in extreme weather conditions. A typhoon is a mature tropical cyclone that develops in the northwestern part of the Pacific Ocean between 180° and 100°E, commonly referred to as the Northwest Pacific Basin. This region includes all the territory north of the equator and west of the International Date Line, including the South China Sea, and it is the most active basin on Earth, accounting for almost one-third of the world's annual tropical cyclones. While no official “typhoon season” exists, storm activity in the Northwest Pacific Basin tends to be highest from August to October, a period which nearly corresponds to Atlantic hurricane season. Along with high storm frequency, the basin also features the most intense tropical storms on record. Features like warm sea temperatures, atmospheric instability, high humidity, air rotation, and low ver- tical wind shear combine to create these potentially deadly storms. Aside from the obvious danger of typhoon landfall, manufacturers in Pacific regions such as coastal China, Hong Kong, Japan, Taiwan, Vietnam, South Korea, and The Philippines—and, to a lesser extent, Southeast Asian nations such as Malaysia, Thailand and Singapore—have reported poor balance stability and difficult weighing operation during periods of typhoon activity. Category Sustained winds Typhoon ≥ 64 knots ≥ 118 km/h Severe Tropical Storm 48 - 63 knots 89 - 117 km/h Tropical Storm 34 - 47 knots 62 - 88 km/h Tropical Depression ≤ 33 knots ≤ 61 km/h Table 1: Tropical Cyclone Intensity Scale from Regional Specialized Meteorological Center (RSMC) Tokyo Application Note Periods of abnormal balance performance caused by the storms can be costly. Annually, typically 20 - 30 tropical cyclones in the Northwest Pacific Basin acquire tropical storm strength or greater (Table 1). During a normal peak season, this can mean days or even weeks of balance instability. These weighing difficulties can be parti- cularly serious for operators relying on high-resolution balances in regulated industries such as pharmaceuticals where even minute errors can affect the efficacy and safety of final products—and product irregularity can incur steep fines from regulators. Partnering for Advancement in Research To further investigate this phenomenon and develop measures to improve balance performance during strong weather disturbances, METTLER TOLEDO collaborated closely with ScinoPharm Taiwan Ltd., a leading process research and development company and manufacturer of active pharmaceutical ingredients (API). The initial hypothesis was based on wind and atmospheric pressure-induced vibrations of the buildings causing the balance instabilities, so the joint study involved measurement of a series of atmospheric parameters during recorded typhoon events, including pressure changes caused by both developing and mature storms. The end result of the study was development of a specific “Typhoon filter” that, despite resulting in a slightly lon- ger balance stabilization time, ultimately creates the repeatability required for even the most sensitive of weighing operations under tropical storm conditions. Here’s how they did it, and why it matters to balance users in tumultuous coastal regions around the world. Establishing the Cause of Instability To ensure sensitive weighing and robust data collection, a team of METTLER TOLEDO weighing experts created a special measurement box that contained four WSX205SDU/15 DualRange balances (Fig. 1). These high-preci- sion balances were chosen as they offer an impeccable repeatability down to 10 micrograms during "on-board" automated weighing, combined with a compact design destined for the installation in industrial devices. These features, along with the frequent usage of WXS205 balances in typhoon areas, made then ideally suited for the task. The measurement box also contained sensors which measured the humidity, atmospheric pressure, tem- perature, vibration, and differential pressure. Up to 1.8 gigabytes (GB) of raw data could be collected per day directly from the balance weighing cell and environment sensors by an onboard industrial PC. This raw data was used for offline analysis and testing of potential solutions, before deployment to the field. This approach meant that all potential improvements to filter settings could be tested for robustness before implementation. 2 Application Note METTLER TOLEDO Application Note Figure 1: Measurement box hardware layout The measurement box apparatus was placed in the Quality lab at ScinoPharm Taiwan, located on the upper floor of a two-story building in Shan-Hua, Tainan – at a latitude and longitude of 23°07’11.5” N and 120°16’55.7” E. During the 2013 season, a number of tropical events offered opportunities to study typhoon effects (Fig. 2). While all events that affected Taiwan are indicated by the red boxes in Fig. 2, this article will focus only on data collected during Typhoon Soulik (7-14 July 2013) and Typhoon Usagi (16-24 September 2013). Figure 2: Typhoon Events in Pacific during June-Dec 2013 3 Application Note METTLER TOLEDO The atmospheric data collected during these events showed several trends. As evidenced by Fig. 3, atmospheric pressure during each event decreased by an order of -20 mbar. Pressure variability also increased, as shown by the final standard deviation chart plotted against the dates of the typhoon events. Analysis of the collected data showed a strong correlation of the poor balance performance to the impact of typhoons, although it could not be concluded absolutely that this degradation in performance was solely pressure or vibration based. Typhoon Soulik Application Note Typhoon Usagi Typhoon Usagi Figure 3: Comparison of Atmospheric Pressure Fluctuations during Typhoons Soulik and Usagi During the typhoon, the balance weighing signal was severely disrupted. The biggest weighing signal change was plotted every hour for 10 days. This value is defined as the maximum minus minimum difference in weighing signal (in milligrams) over a period of 15 minutes at zero load, half load, and full load in respect to the weighing capacity of the balance. The standard deviation of the weighing signal over the same 15 minute period was also plotted for 10 days. Graphs displaying the fluctuation of the filtered weight signal during both events (Figs. 4 and 5) show the impact of the typhoon on the weighing signal. Deviations of up to 5 mg were recorded, which directly corres- pond to the passing by of the typhoon. 4 Application Note METTLER TOLEDO Typhoon Soulik Application Note Figure 4: Disruption of Weighing Signals during Typhoon Soulik Typhoon Usagi Figure 5: Disruption of Weighing Signals during Typhoon Usagi 5 Application Note METTLER TOLEDO Based on the nature of high-resolution balances and the type of weighing they facilitate, the results presented a real problem for balance users in the Pacific region. So, what was the next step? Mettler Toledo needed to find a solution that would stabilize the balances and provide repeatable, accurate filtering in the face of atmospheric changes and vibrations brought on by typhoon activity. Identifying the Optimal Solution Using continuous data collected before, during, and after typhoon events in an environment that historically reported abnormal balance operations, a series of approaches and optimizations led to a final, workable solu- Application Note tion for ScinoPharm Taiwan in 2014. The following steps were taken: Approach 1: Develop an algorithm to average filtered data collected over a fixed period of time. This method had already been successfully applied in several other dedicated applications, where large vari- ations in environmental conditions can cause an issue. Examples of this situation are weighing near manu- facturing equipment which emits low frequency vibrations; or weighing small samples on board a large ship. However, in this case, the solution proved impractical due to the use of dedicated commands, and the need for a terminal for implementation. For these reasons, an alternative approach was investigated. Approach 2: Develop a unique “typhoon filter.” Instead of averaging filtered values, the approach of applying a stronger filter at the outset was taken. The initial filter structure involved multiple stages dictated by successive smoothing of the weighing signal as indicated in Fig. 6. However, whilst this new approach proved more robust than the original averaging in relation to disturbances, it was less sensitive to load changes below a certain threshold. Figure 6: Initial Typhoon Filter Approach Refining Approach 2: Testing additional filtering stages. Based on the results of the initial filter and evaluating the improved repeatability against increased settling time (which decreases productivity), additional filtering stages were tested. The optimum filter parameters were care- fully established as an acceptable compromise between repeatability of weighing results and balance settling time. Fig 7 shows

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