The sequential closing function of double leaf fire doors is a difficult point in acceptance. This function relies on the collaborative work of the door closer and sequencer. The specific detection steps are as follows:

1. Single machine test: First, close one door and observe whether the other door can automatically close under the action of the sequencer;

2. Linkage test: Simultaneously open both doors and check if they are closed in the "left first, right second" or design sequence after release;

3. Extreme test: Release the door leaf when it is opened to 90 ° and simulate the closing performance in emergency situations.

According to GB12955-2008 "Fire Doors", double doors must be equipped with sequencers, and the closing time difference should be controlled within 3-5 seconds.