Spout Insertion Accuracy, Not Fill Speed, Sets the Leak Rate

Two Spout Configurations

For inserted spout lines, the flange weld (ultrasonic or heat) must center on the pouch hole. Misalignment thins one side of the weld and that is where it lets go.

The Fill-Seal Sequence

1. Pouch picked from magazine, opened.
2. Spout inserted (or already present) and flange welded to the wall.
3. Nozzle descends into the spout; liquid filled (by volume or weight).
4. Spout wiped, cap applied and torqued.
5. Leak/visual check before discharge.

Liquid on the spout thread before capping is the other leak source — a wipe or blown-air clean at the spout is mandatory for viscous product.

Field Data: A Thai Juice Line

A Bangkok producer of 200 ml mango juice in spout pouch ran 50 pouches/min with 3.3% flange-leak rejects (spout off-center by 0.8–1.5 mm) and 1.0% cap-thread liquid. Storage was ambient SEA, wet-handled.

We added a vision-aligned spout inserter, switched flange weld to servo heat with feedback, and a blown-air spout wipe before capping. Outcome:

Off-center by 1 mm = leak: The flange weld is a ring; shift it and one side is half-thickness. Vision alignment of the spout is what holds the leak rate, not filler speed.

Selection Errors

• No spout alignment. You weld off-center and leak on the shelf; filler speed is irrelevant.
• No spout wipe. Liquid on the thread caps a leak; viscous product especially.
• Wrong flange weld for film. Heat vs ultrasonic depends on laminate; mismatch and the weld is weak.

Compliance by Region

European Union

EU food 10/2011 for laminate and ink; CE machinery. Recyclable mono-material spout+pouch pushes design changes — confirm compatibility.

United States

FDA food contact; UL electrical. Legible net-weight and flavor label.

Southeast Asia

Halal where relevant; hot, wet handling demands a strong flange weld and cap torque.

Middle East

GCC/SASO conformity, Arabic label. High-barrier laminate for summer; tamper-evident cap.

Procurement Traps

• Quoting fill speed without spout-alignment spec — you buy leaks.
• Omitting the spout wipe; thread liquid caps a reject.
• No leak test (vacuum or dye) in the scope.

Frequently Asked Questions

Pre-applied or inserted spout?

Pre-applied is leak-safer but less flexible on spout style; inserted is flexible but needs precise alignment. Match to your SKU range.

Why do my pouches leak at the spout?

Usually off-center flange weld or liquid on the thread. Vision alignment + spout wipe fix both.

Heat or ultrasonic flange weld?

Depends on laminate — heat for standard, ultrasonic for some mono-materials. Mismatch weakens the weld.

Do I need a leak test?

Yes — vacuum or dye on every lot; a weak flange weld is invisible until the shelf.

Written by Helen Xu | Chief Industrial Application Engineer

Helen Xu is a Chief Industrial Application Engineer with 9 years of specialized experience in packaging machinery and liquid filling machine design, equipment model selection, and full production line process optimization. He focuses on delivering customized packaging & filling solutions for pharmaceutical, food, and chemical manufacturing industries, with mature practical expertise in GMP compliance, ISO 9001 quality management standards, and turnkey large-scale filling & packaging production line integration.