Why Do Bags Fail During Filling?

Bag failures during filling usually result from a mismatch between packaging strength, valve dimensions, airflow, machine pressure, and product behavior. Identifying the exact failure location is more effective than simply adding another paper layer or reducing production speed.

The Failure Location Provides the First Clue

A split close to the valve suggests different causes from an opening at the pasted bottom. Operators should retain damaged bags and mark where the failure first appeared.

Common failure patterns include:

• Torn valve sleeves during bag placement

• Open pasted ends under filling pressure

• Cracks along folds or corners

• Powder passing through ventilation holes

• Sidewall punctures after discharge

• Bags falling from the filling nozzle

Photographs, machine settings, and the time of failure help the manufacturer separate a packaging defect from an equipment or handling problem.

Valve Mismatch Creates Local Stress

The valve of paper valve bags must fit the filling nozzle without excessive force. An undersized sleeve can stretch or tear during placement. An oversized valve may move on the spout, leak powder, or release before the target weight is reached.

Automatic applicators are especially sensitive to valve position, opening shape, paper stiffness, and dimensional tolerances. Small variations that cause little trouble during manual placement may create frequent rejection on a high-speed line.

Valve length also matters. The nozzle needs sufficient insertion to support the bag, but the sleeve must still close correctly after discharge.

Trapped Air Can Burst a Suitable Bag

Powder carries air into the package. When paper permeability or venting is insufficient, pressure builds inside the bag. The package inflates, stresses the seams, and may open at its weakest point.

Excessive ventilation creates the opposite problem by allowing fine material to escape. Airflow should be adjusted through paper selection, inter-ply channels, micro-perforations, or valve design according to powder fineness and filling pressure.

Signs of poor air release include slow filling, rounded bags, unstable weight readings, and strong pressure around the valve immediately after discharge.

Material and Adhesive Must Match the Process

Hot cement, abrasive minerals, and heavy powders place different demands on paper and bonding. Kraft strength, grammage, ply count, adhesive type, and curing quality influence resistance to impact and internal pressure.

A bag may also fail because it was stored incorrectly before filling. Excessive humidity can soften paper, while very dry conditions may reduce flexibility around folds. Empty bags should remain protected and be used according to recommended storage conditions.

Reproduce the Problem Through Controlled Testing

To investigate bag failure during filling, run samples with the same product, target weight, nozzle, feed pressure, and production speed. Change only one parameter at a time so the result can be traced.

Measure failure rate, filling time, dust level, and final bag shape. Filled samples should then undergo normal drops and conveyor handling.

A capable filling bag supplier will need failed samples, machine drawings, powder data, current bag construction, and operating records. Share this evidence to obtain a targeted correction, revised samples, and a quotation for stable production supply.