Manufacturing Process of UL Fire Doors-Shanghai Xunzhong Industry Co.,LTD

.Door Core Material: Fire-resistant insulation materials (e. g. , mineral wool, ceramic fiber, fire-rated gypsum board, or honeycomb fire-resistant structures) must be UL-certified and comply with ASTM E84 fire ratings (20/45/60/90/120/180inutes). Shanghai Xunzhong had pass all the UL Certification from 20mins to 180mins

.Door Frame & Leaf Metal:

 Steel doors use galvanized steel sheets (thickness ≥18-20 gauge), while wood doors use fire-retardant-treated lumber (e. g. , flame-retardant soaked or fire-rated plywood).

.Hardware: Hinges, locks, and closers must be UL-listed fire-rated hardware (e. g. , at least 3 hinges made of stainless steel or high-temperature-resistant alloy).

. Door leaf fabrication

Steel Doors:

1.Cutting & Stamping: Laser-cut steel sheets, pre-punching holes for locks and peepholes.

2.Bending & Forming: Use a press brake to bend edges for reinforcement, then fill with fire-resistant core material and bond under high pressure.

3.Welding & Grinding: Weld corners for airtightness and grind seams smooth.

4.Wood Doors:

Layered Pressing: Fire-retardant wood and fire-rated plywood are laminated with a fire-resistant core.

Edge Reinforcement: Steel or aluminum edges are added to enhance fire integrity.

. Door Frame fabrication

Steel Frame: Formed from cold-rolled steel, welded at corners, and filled with intumescent strips (expands under heat to seal gaps).

Wood Frame: Fire-rated veneer on the surface, with fire-resistant gaskets embedded inside.

Fire-Rated Glass Installation (If Applicable)

Use UL-certified fire-rated glass (e. g. , ceramic or gel-filled laminated glass), sealed with fire-resistant gaskets. The glass area must not exceed the maximum allowed per NFPA

5. Assembly & Testing

Hardware Installation: Install UL-compliant fire locks, closers (ensuring self-closing function), and hinges (heat-resistant to prevent failure).

Gap Control: Clearance between door leaf and frame ≤3mm (to prevent flame penetration). Optional automatic drop-down seals at the bottom.

Fire Testing: Submit to UL labs for fire endurance tests (e. g. , UL 10C furnace test) to verify ratings (20/60/90 minutes, etc. ).

6. Surface treatment

Coating: Steel doors receive high-temperature-resistant paint (electrostatic powder coating) in customer-specified colors.

Veneering: Wood doors may be covered with fire-rated wood veneer or PVC finishes.

7. Quality Inspection & Labeling

Checks: Dimensional tolerances, hardware functionality, sealing performance, and label integrity.

Permanent Marking: Label fire rating (e. g. , "20-Minute Fire Rating"), UL certification number, and manufacturer details on the door top edge.

8. Packaging & Shipping

Wrap doors in moisture-proof materials to prevent damage. Include factory test reports and installation manuals.

Key standard reference

NFPA 80: Standard for Fire Doors Installation and Maintenance

UL 10C: Fire Test of Door Assemblies (Dynamic)

ASTM E119: Fire Tests of Building Construction

Contact me if you have a fire door request

E-mail:anne@ulfiredoormfg. com

F-Telephone: +8615903871355