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D3089-97 – Standard Test Method Technical Guide
📏 Scope and Significance
This standard practice covers the rapid determination of the A-D dimension for aerosol valve dip tubes with 1-in. (25.4-mm) mounting cups. The A-D dimension is defined as the centerline distance from the top plane of the valve mounting cup curl to the far end of the dip tube. Values are stated in inch-pound units, with SI conversions provided for reference only.
Correct dip tube length is crucial for ensuring complete product discharge and preventing operational issues. It helps avoid tube jamming during gassing, excessive cup protrusion that may cause production problems, and bottom sealing against flat can bases that restricts product entry. Additionally, dip tubes that extend fully to the bottom without excessive distortion can retain connection to the valve body tailpiece, especially when the aerosol content causes plastic swelling.
| 🟦 Influencing Factor | 📏 Description |
|---|---|
| Tube Curvature | Varies between tubes, affecting alignment |
| Valve Cup & Gasket Thickness | Changes the top reference plane |
| Pedestal Elevation | Altered by crimping and hot-tanking |
| Product Swelling | Swelling or shrinking of dip tube plastic |
⚙️ Apparatus and Procedure
The apparatus consists of a gage with three machined parts, a scale graduated in 1/32 in. glued to the scale block, and optionally a foam pad base. The reference plane must be at zero on the scale for accurate measurement.
To measure, hold the gage (as shown in Figs. 2-6) on a flat surface or in hand. Insert the valve with the actuator/stem end toward the higher end of the device. Push the slide bar firmly to the left to seat the mounting cup against the base end. Then, read the scale at the end of the dip tube to obtain the A-D dimension.
💡 Measurement Tip: Consistent firm pressure when seating the cup reduces operator variability and improves repeatability.
📊 Precision and Reporting
Report all relevant valve details, including lot number, date received, supplier, and intended product. Specify the A-D dimension to the nearest 1/32 in. (0.80 mm). Precision studies have shown variability due to operator technique and gage accuracy, and no formal precision statement is available due to limited repeatability and reproducibility data.
| 📐 Parameter | 🎯 Specification |
|---|---|
| Mounting Cup Size | 1 in. (25.4 mm) |
| Scale Graduation | 1/32 in. (0.80 mm) |
| Measurement Precision | Nearest 1/32 in. |
⚠️ Caution: Attempts to develop a precision statement have not been successful; thus, data on precision cannot be given. Operators should be aware of potential subjective influences.
❓ Frequently Asked Questions
🔍 What is the A-D dimension?
The A-D dimension is the centerline distance from the top plane of the valve mounting cup curl to the far end of the dip tube.
💡 Why is choosing the correct dip tube length important?
It ensures complete product discharge, prevents tube jamming, and avoids issues like excessive cup protrusion or sealing against the can base.
⚡ What factors influence the A-D dimension?
Factors include tube curvature, valve cup and gasket thickness, pedestal elevation changes from crimping, and product swelling or shrinking.
📌 How is the measurement taken?
Using a gage, the valve is inserted with the actuator end higher, the slide bar is pushed to seat the cup, and the reading is taken at the dip tube end to the nearest 1/32 in.