Precision Requirements for Liquid Egg Metering Filling

Precision control for liquid egg metering filling is more difficult than for single liquids like water or oil because egg liquid is a natural raw material whose viscosity fluctuates with temperature, storage time, and egg source batch. The viscosity of whole egg, egg white, and egg yolk differs greatly: egg white is nearly gelatinous at low temperatures, while egg yolk is thicker, and the shear force of the filling valve further alters flowability. If buyers produce multiple egg liquid products, they should ask the equipment supplier to explain the corresponding adjustment methods for different viscosity ranges, such as changing the valve core, adjusting the stroke, or changing the pump speed, rather than using a single setting for all products. In practice, the drift after 2 to 4 hours of continuous operation often reflects true precision better than data from the first 10 minutes after startup, and this is the time period that must be observed during trial runs.

Buyers should define acceptable precision using two indicators: "per-unit weight tolerance" and "batch weight coefficient of variation (CV)", rather than looking only at the average. Per-unit weight tolerance determines whether each product falls within the labeled specification, usually expressed as a percentage or in grams; batch CV reflects the consistency of the entire batch, and a reasonable range common in the food industry should be confirmed based on the actual specification. When defining indicators, the end product must be considered: if the finished product is chawanmushi, the per-unit egg liquid amount directly affects texture and appearance, so the tolerance must be stricter; if the finished product is a pre-mixed baking egg liquid package, the tolerance can be looser but the CV must remain stable. It is recommended that buyers include these two indicators in the RFQ during the inquiry stage, allowing the equipment supplier to plan the filling valve and control system accordingly, and avoiding disputes over differing definitions of "precision" during acceptance.

Different filling valve types differ in precision performance in terms of "tolerance to viscosity changes" and "the impact of shear force on egg liquid". Common valve types include piston, gear pump, peristaltic, and pneumatic types, each suited to different viscosity ranges and production line paces. Piston valves offer high precision but are sensitive to viscosity fluctuations, making them suitable for whole egg liquid with stable viscosity; gear pump valves can handle thicker egg yolk liquid, but at high speeds, gear clearance can affect repeatability; peristaltic valves have low shear force and are suitable for egg white products that are sensitive to structure damage, but hose life is a maintenance cost. Buyers should, based on the egg liquid characteristics of their main products, ask the equipment supplier to explain the applicable range of the selected valve type, and during trial runs, test with both the thickest and thinnest egg liquids to observe precision drift, rather than only looking at favorable data from the middle range.

The filling station is often the rhythm bottleneck of the entire line. When planning the line, buyers should evaluate the filling station as a rhythm bottleneck and ask the equipment supplier to provide a "filling accuracy curve at different line speeds" rather than data at a single speed. In practice, the texture and appearance of steamed egg custard are highly sensitive to the liquid egg weight per piece. The trade-off between speed and accuracy must be decided during the trial run stage, as later adjustments are costly.

For the trial run and acceptance test, buyers should prepare "actual production liquid egg samples" and "measuring tools that can record individual piece weights," rather than letting the equipment supplier test with water or substitute liquids. The samples should cover the whole egg liquid, egg white liquid, and egg yolk liquid used in the main products, as well as a temperature range (chilled eggs at 4°C and room temperature eggs at 20°C, one batch each), because the same equipment may show significantly different accuracy at different temperatures. For measuring tools, an electronic scale with an accuracy of 0.1 g or better is recommended, and a statistical method that continuously samples more than 100 pieces should be prepared to calculate the CV value. The trial run process should include: sampling after the machine has stabilized, sampling again after 2 hours of continuous operation, and a final sampling before shutdown. Comparing these three sets of data will reveal drift trends. If buyers do not prepare these samples and tools, the trial run results cannot be used as a basis for acceptance, and the risk of subsequent disputes is high.

When accuracy problems occur, it is usually a problem at the "interface" between the equipment and the raw material, not the responsibility of a single party. Common equipment-side causes include filling valve wear, pump aging, sensor drift, and control parameters not being updated when the product changes. Common raw material-side causes include liquid egg temperature changes, batch viscosity differences, and excessive air content (air introduced during the egg breaking process). If buyers find accuracy anomalies after acceptance, they should first establish "accuracy records for the last 10 batches" and "corresponding raw material viscosity records," and then ask the equipment supplier and the liquid egg supplier to conduct a joint diagnosis, rather than asking the equipment supplier to improve alone. In practice, most disputes arise because both parties have not recorded these data synchronously, making it impossible to clarify responsibility afterwards. It is recommended that buyers specify in the contract the "data traceability method for accuracy anomalies" and the "joint diagnosis mechanism" to clearly define the responsibility interface.

When writing precision requirements into an RFQ, buyers should use specific figures and contextual descriptions rather than simply stating "high precision." A recommended RFQ should include: product name (e.g., chawanmushi, pre-mixed egg liquid pack), target weight per unit, allowable tolerance, expected line speed (units per minute or per hour), type of egg liquid used (whole egg / egg white / egg yolk), and temperature range. It should also specify the acceptance method: number of consecutive samples, measuring tool accuracy, and pass criteria (per-unit tolerance and CV value). If the buyer has multiple products, the precision requirement differences between the main product and secondary products should be listed so the equipment supplier can plan the adjustment flexibility of the filling system accordingly. The more specific the RFQ, the closer the supplier's quotation and configuration will match actual needs, and the fewer disputes there will be during subsequent trial runs and acceptance. This type of precision definition document is especially necessary for whole-plant planning and turnkey projects, serving as the basis for subsequent full-line acceptance.