EVALUATION OF SPRAY NOZZLE WEAR UNDER FIELD CONDITIONSABSTRACT
This study aimed to evaluate the impact of wear on different models of hydraulic ceramic spray nozzles focusing on changes in flow rate and the droplet size distribution in applications by medium-scale farmers in the agricultural region of Mato Grosso do Sul. Additionally, the study assessed the adequacy of nozzle replacement practices in accordance with recommended guidelines. Seven hydraulic ceramic nozzle models —JA3, AD/D 11002, BD 11002, JCI 80025, AXI 11003, CVI 110025, and AVI 11002—were tested. Nominal flow rates for each nozzle model were measured following ISO 10625 standardization criteria. The evaluated parameters included nominal flow rate, volumetric median diameter (VMD), relative span, and the percentage of the volume composed of droplets smaller than 100 µm (P<100). Prolonged use of hydraulic spray nozzles resulted in increased flow rates and modifications to droplet population characteristics, especially in the variation of the volume percentage of droplets smaller than 100 µm, which are more susceptible to drift. Although wear affected the volumetric median diameter, the change was not substantial enough to alter the droplet size classification.
application technology; volumetric median diameter; application rate; application quality; spray nozzles
INTRODUCTION
The application of phytosanitary products, predominantly via hydraulic spraying, remains the most widely employed technique for crop protection. Hydraulic spray nozzles play a crucial role in ensuring application quality; however, damaged or worn nozzles can increase the spray mixture flow rate, thus disrupting the intaltering the intended application rate and negatively impacting the original relative span and volumetric median diameter, compared to new hydraulic nozzles (Baio et al., 2022). Regardless of nozzle material, increased field usage leads to wear on the nozzle orifice, resulting in altered flow rates (Cunha et al., 2008).
Significant uncertainty remains regarding the optimal timing for replacing hydraulic spray nozzles on agricultural equipment. In practice, nozzle replacement by farmers is typically based on the number of crop cycles, with limited technical consideration of flow rate variations related to usage duration and the physical properties of the spray mixture. The operational lifespan of agricultural hydraulic spray nozzles is influenced by factors including the material composition, operating pressure during applications, water quality and particulate content in the spray mixture, the pesticide formulation, maintenance practices, and usage frequency (Kluza et al., 2019).
Plastic polymer is the most commonly used material in hydraulic nozzle manufacturing due to its chemical stability, low cost, and adequate lifespan (Denisov et al., 2022), which has also prompted interest in its potential for 3D printing. The primary materials used in nozzle production include ceramic, stainless steel, plastic, and brass. Ceramic nozzles are considered the most durable, even under higher hydraulic pressures, while plastic polymer nozzles provide the best cost-effectiveness in terms of the cost-to-lifespan ratio within comparable technological models (Milanowski et al., 2022).
The droplet spectrum produced by a hydraulic nozzle is influenced by several design factors, including the configuration of the nozzle’s internal chambers, the shape of the exit orifice, the spray angle, and, in certain instances, the operating speed, as these parameters significantly affect spray quality (Çetin et al., 2019). Wear-induced alterations to these componentes impact the droplet population, resulting in increased costs for producers, as an enlarged orifice size correlates with a heightened nozzle flow rate. This increase in flow rate indicates that nozzle wear has gone beyond the acceptable limits, which can be easily identified through direct measurements when the flow rate exhibits a coefficient of variation exceeding 10% (Martini et al., 2017). Although some nozzle manufacturers advise replacing worn nozzles when the flow rate increases by 10% from the initial measurement, many farmers continue to use these nozzles for extended periods. This practice results in elevated flow rates and increased pesticide waste (Singh & Bhatt, 2018).
From this perspective, are producers following the recommended guidelines for the replacement of hydraulic nozzles and the identification of wear based on flow rate increases? The objective of this study was to evaluate the effects of wear on various models of ceramic hydraulic spray nozzles concerning flow rate and droplet population generated after replacement by medium-scale farmers in the agricultural region of the Mato Grosso do Sul. Additionally, the study assessed the adequacy of nozzle replacements in accordance with established recommendations following substitution.
MATERIAL AND METHODS
Seven treatments (nozzle models) from three different agricultural properties located in the state of Mato Grosso do Sul (Figure 1) were employed across three different agricultural production regions. The nozzles were sampled after their replacement with new units, following the internal criteria of each property (all replaced based on the number of crop cycles, rather than technical criteria for replacement due to increased nozzle flow rate). The hours of use for the sampled nozzles were monitored using the hour meter of each self-propelled sprayer. The treatments HC1 (empty cone), DF (dual fan anti-drift), and PO (pre-orifice fan) were collected from an agricultural property located in Rio Verde, Mato Grosso, MS, which uses a Montana Parruda 2025-H sprayer. The treatments AI1 and AI2 (both air-induction flat fan nozzles) were collected from an agricultural property located in Maracaju, MS, which uses a self-propelled sprayer model Jacto Uniport 3030. The treatments HC2 (empty cone) and SF (extended use flat fan) were collected from an agricultural property located in Costa Rica, MS, which has a Jacto Uniport 2000 self-propelled sprayer. The rural properties from which the sampled nozzles originated have areas of 350, 800, and 1,700 hectares, classifying them as medium-sized according to rural property standards (Federal Law No. 8,629/1993, Article 4). These properties have implemented a crop succession of soybean (Glycine max) and second-crop corn (Zea mays) over recent harvests, reflecting practices common to many agricultural properties in the state.
Location of the sample-supplying properties in three agricultural regions of the state of Mato Grosso do Sul, Brazil.
The hydraulic nozzles were employed for the application of different agrochemicals and formulations under actual field conditions throughout their usage period on the farms. The formulations included concentrated suspension (SC); soluble concentrate (SL); oil dispersion (OD); dispersible granules (WG); with oil consistently used as an adjuvant. The cultivation of soybean and corn currently requires at least five or six spray applications throughout their respective growth cycles. Moreover, it is common in ground applications to use mixtures of agrochemicals, which can modify the physical characteristics of the spray mixtures (Tavares & Cunha, 2023). However, these minor changes do not significantly affect the droplet size variation (size change class) or the nozzle flow rate. Consequently, the physical characterization of the spray mixtures for each application conducted under field conditions was not considered. The water used in the mixtures was consistently sourced from artesian wells in the area. Seven different nozzle models were evaluated (Table 1), all constructed from ceramic material. The experiment was conducted using a completely randomized design with ten repetitions.
Flow rate assessments and droplet population characterization were conducted in the Application Technology Laboratory at the Federal University of Mato Grosso do Sul (UFMS). The nominal flow rate of the spray nozzles was measured and compared to reference flow rates in accordance with ISO 10625 standardization guidelines. The flow evaluation involved weighing the volume of water collected over one minute (in grams), using a Shimadzu BL-3200H analytical balance. The hydraulic circuit was maintained at the nominal pressure of 300 kPa, monitored by a pressure gauge installed near the nozzle. For each sample, three flow measurements were recorded, with values expressed in L min⁻1. The evaluations were conducted using a stationary sprayer powered by a Micron battery (Combat model).
Droplet population characteristics were assessment using the Spraytec (Malvern Spraytec Real Time Droplet Sizing System), a particle measurement device with a 10 mm laser beam diameter, 200 mm focal length lens, 670 nm laser wavelength, and an extended optical bridge. The spray nozzle was positioned 0.5 m above the optical beam. Alignment of the optical beam was verified initially to ensure correct positioning within the detection system; the background system (second plane) was monitored for the light deviation in the optical path and potential window contamination by particles. The device was calibrated prior to each reading. Based on manufacturer calibration, the device provides 3% accuracy and 1% precision when using the standard grid.
The droplet population spectrum was directly measured in real-time using the particle measurement device, which quantified the volumetric median diameter (VMD), the relative span (Span) of the droplet spectrum, and the percentage of volume comprising droplets smaller than 100 µm (P<100). Classification of the spray nozzles based on the droplet spectrum was conducted in accordance with the ASAE S-572 standard.
Box plots were generated to illustrate the dispersion of sampled values for each variable, comparing these values against reference values from a new nozzle. Pearson correlations among the evaluated variables were estimated, with a correlation network applied to graphically represent the results. In this network, node (line) proximity was proportional to the absolute value of the correlation, and a threshold of |rij| ≥ 0.60 was applied, emphasizing only correlations meeting this criterion. Positive correlations were highlighted in green, while negative correlations were indicated in red. Subsequently, a canonical variable analysis was conducted to assess the similarity between the variables and each nozzle model evaluated. All analyses were performed using RBio software (Bhering & Teodoro, 2021).
RESULTS AND DISCUSSION
Flow rate increased for all nozzles (Figure 2), with percentage diferences calculated between the reference value and the observed averages: 8.9% for nozzle HC1, 6.7% for nozzle DF, 8.0% for nozzle PO, 5.4% for nozzle HC2, 7.0% for nozzle SF, 6.6% for nozzle AI1, and 3.1% for nozzle AI2. Thus, the recommendation by some authors (Singh & Bhatt, 2018) to replace worn nozzles when the flow rate rises by 10% from the initial value may be insuficiente, as averaging sampled values can mask data variability and range. Following this recommendation (Singh & Bhatt, 2018), none of the sampled nozzle models would require replacement. However, two nozzle models exhibited substantial flow variation in the sampled data, as indicated by the coefficient of variation (CV): 13.4% for nozzle HC1 (hollow cone) and 10.5% for nozzle PO (pre-orifice). Continued use of these two nozzle models in the respective sprayers would likely lead to uneven application across the spray area, resulting in potential misdosing of pesticides (Baio et al., 2022). Thus, in these cases, the decision by farmers to replace these nozzles was justified. However, if the replacement decision were based solely on the average flow rate variation (Singh & Bhatt, 2018), replacement would not be warranted, even though these two models exhibit high CV values (>10%). On the other hand, if the criterion were based exclusively on a CV threshold of greater than 10% for flow rate variation (Martini et al., 2017), it is possible that uniform wear accross nozzles could result in an overall increase in flow rate, with minimal variation among sampled values. This scenario could potentially extending the use of a worn nozzle in the field, despite the uniformity masking significant wear. This situation can be illustrated by data from the DF nozzle (double flat fan), which showed a 6.7% increase in flow rate variation (almost reaching the threshold for replacement based on exceeding the appropriate flow rate), while displaying a coefficient of variation (CV) of only 3.3% among sampled values. This result suggests that applying both criteria together would be more effective: replacement would be recommended either when the average flow rate exceeds 10% of a new nozzle`s flow rate or when the CV among sampled values exceeds the same 10% threshold.
Box plot of the flow rate variation for the evaluated nozzle models. Values indicated by “*” represent the reference values of a new nozzle. The value represented by “x̅” is the mean for each treatment.
Overall, among the seven nozzle models sampled, farmers prematurely replaced five of these models (DF, HC2, SF, AI1, and AI2), leading to an unnecessary increase in production costs. On the other hand, farmers often replace spray nozzles before the start of the growing season to avoid interrupting any critical spraying during the cultivation period. The nozzle exhibiting the most significant wear in the field was the HC1 (hollow cone), likely due to its operation at hydraulic pressures 2 to 3 times higher than those of flat-fan nozzles. Kohl & DeBoer (1984) investigated water application patterns as a function of pressure and nozzle diameter, finding that water discharge from emitters depends on the pressure applied to the spray mixture. This pressure provides the force to push water through the nozzle or emitter, and for a standard nozzle or emitter, discharge rate rises as pressure increase (Barker et al., 2024).
Nozzles with adequate flow rates ensure greater uniformity in pesticide application, effectively targeting desired biotic organisms, reducing costs associated with inaccurate applications, and mitigating environmental contamination risks (Kluza et al., 2019). When nozzles orifices experience wear, resulting in deviations from the appropriate flow rate, variations may occur in working pressure and in the uniformity of the overall droplet population (Singh & Bhatt, 2018).
It is important to emphasize that technical recommendations based solely on flow variability do not fully capture application quality, as they overlook other critical indicators of droplet population characteristics. Advanced application technology requires a more comprehensive evaluation, particularly concerning droplet size distribution and its influence on application efficacy and environmental safety. Thus, further studies are warranted to examine nozzle wear in relation to additional droplet population characteristics, especially the proportion of very fine droplets in the spray volume (Baio et al., 2022). An increased proportion of fine droplets can exacerbate drift losses and raise environmental contamination risks near the application site. For instance, studies report that while 2% of droplets with a diameter of 1.5 mm were lost due to wind drift and evaporation, only 1% of droplets at 2.5 mm diameter experienced similar losses (Molle et al., 2012). Droplet size is inversely related to evaporation rates, as smaller droplets evaporate more quickly than larger ones (Al-agele et al., 2022).
An increase in the volumetric median diameter (VMD) of the droplet population was observed for all sampled nozzle models (Figure 3). The DF (dual fan), AI1, and AI2 (air induction) nozzles exhibited the greatest variability in VMD; however, this variation did not result in a change in the droplet size classification. The PO (pre-orifice) nozzle showed the highest average variation, with a difference of 25.2% between the measured VMD of the replaced nozzle and that of the new one. The measured VMDs classified the droplet sizes into the following categories: HC1 as fine, DF as medium, PO as fine, HC2 as fine, SF as medium, and the AI1 and AI2 nozzles as very coarse. Thus, the wear of nozzles under field conditions does not significantly alter the original droplet size classification. The appropriate choice of droplet size is essential in agricultural applications, as it influences the efficacy of pesticide contact with the target organism and, consequently, the effectiveness of pest control measures (Pan et al., 2019).
Box plot of the variation in VMD (volumetric median diameter) of the evaluated nozzle models. Values marked with “*” are references from the new nozzle. The value represented by “x̅” is the mean of each treatment.
The relative amplitude (Span) is an index that represents the homogeneity of the droplet size spectrum, considering the VMD in relation to the droplet sizes Dv10 and Dv90. These values indicate that ten or ninety percent (respectively) of the volume of the sprayed solution consists of droplets smaller than the specified diameters. Na increase in the span index reflects a corresponding increase in the heterogeneity of the generated droplet spectrum; therefore, values close to or less than 1 are preferred (Cunha et al., 2008). With the exception of the AI1 (air induction) nozzle, all other hydraulic nozzles exhibited an increase in Span compared to the reference value obtained from the new nozzle. The SF nozzle (expanded use spray) displayed the greatest variation, with a Span increase of 22.6%, followed by the DF nozzle at 20.1% and the HC2 nozzle at 19.5%.
Box plot of the variation in relative amplitude (Span) of the evaluated nozzle models. Values marked with “*” are the reference for the new nozzle. The value represented by “x̅” is the average for each treatment.
The DF (dual fan), HC2 (empty cone), and AI1 and AI2 (air induction) nozzles demonstrated an increase in the measured percentage of volume composed of droplets smaller than 100 µm. The largest increase was observed in the DF nozzle, which exhibited a variation of 31.5%. In contrast, the HC1 (empty cone), PO (pre-orifice), and SF (extended use fan) nozzles showed a decrease in their P<100 values, with the PO nozzle recording the largest negative variation at 10.3%. The increase in P<100 values suggests a hightened potential for smaller droplets to drift, thereby posing a greater risk to the environment. According to Cunha et al. (2008), it is recommended that the P<100 variable remain below 15% to achieve applications with a reduced risk of drift.
Box plot of the variation in the percentage of volume composed of droplets smaller than 100 µm (P<100) from the evaluated nozzle models. Values represented with “*” are the reference for the new nozzle. The value represented by “x̅” is the mean of each treatment.
The analysis of the Pearson correlation network (Figure 6) shows a strong positive correlation between the usage time (USO) and Span variable, as well as between P<100 and Span. Therefore, as the usage time of the nozzle increases, both correlated variables also exhibit na upward trend. The strenght of this correlation is represented by the thicker green lines, indicating a positive relationship (Bhering & Teodoro, 2021). Additionaly, the analysis demonstrates that, as expected, an increase in usage time correspond to an increase in nozzle flow rate, while the DMV decreases, when considering all nozzles in a joint analysis.
Pearson correlation network between the variables Nozzle Flow Rate, DMV, Relative Amplitude (Span), Percentage of Volume of Droplets Smaller than 100 µm (P<100), and Usage Time (USO).
The analysis of canonical variables (Figure 7) helps in the interpretation of the data by simultaneously examining all measured input and response variables. For the results to be considered significant, the cumulative percentage of the first two canonical components (reflecting the total values along the x and y axes) must exceed 75% (Bhering & Teodoro, 2021). The eigenvectors for P<100 and Flow Rate exhibited a strong correlation with the nozzle types DF, PO, and HC1, indicating that these nozzles demonstrated a more pronounced direct relationship with these variables. In contrast, the air induction nozzles (AI1 and AI2) showed reduced data variability and a lower degree of significant correlation with the measured variables. Notably, usage time exerted a greater influence on the variation of P<100 and Flow Rate than on the variation of Span and DMV.
Canonical variable analysis between flow rate, volumetric median diameter (VMD), percentage of volume composed of droplets smaller than 100 µm (P<100), usage time (USO), and Span of the seven evaluated spray nozzle models.
The results obtained and the collected samples indicate that farmers could achieve a reduction in production costs by extending the operational lifespan of their nozzles. Therefore, it is important to conduct annual flow rate measurements of the nozzles used in the pre-harvest period. This practice would enable a comprehensive evaluation of nozzle’s continued viability prior to the beginning of the harvest.
CONCLUSIONS
Farmers operating medium-sized agricultural properties in the region of Mato Grosso do Sul are prematurely replacing hydraulic nozzles made from ceramic materials. It is more appropriate to apply a combined approach for nozzle replacement criteria; specifically, nozzles should be replaced when the average flow rate variation exceeds 10% compared to that of a new nozzle, or when the coefficient of variation (CV) of the sampled data also exceeds 10%.
Extended use of hydraulic spray nozzles results in an increase in flow rate, but it also influences the characteristics of the droplet population, particularly concerning the variation in the percentage of volume composed of droplets smaller than 100 µm, which are more susceptible to drift. However, even though there are changes in the volumetric median diameter, the alteration is not significant enough to change the droplet size classification.
ACKNOWLEDGMENTS
Fundação de Apoio ao Desenvolvimento do Ensino, Ciência e Tecnologia do Estado de Mato Grosso do Sul - FUNDECT
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Edited by
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Area Editor:
Edna Maria Bonfim-Silva
