The BU Type 12M Flame Spray Gun is one of the world’s most reliable and high-performance wire flame spray guns, designed for producing combustion flame-sprayed coatings using metal wires. This blog explains the complete details of the 12M Wire Flame Spray Gun—its design, working principle, features, operating method, safety instructions, and recommended maintenance, directly derived from the official Balaji Udyog manual.

1. Overview of the 12M Wire Flame Spray Gun

According to the manual, the 12M gun is a universal, forged-aluminum gas head system capable of spraying a variety of metallizing wires ranging from 3/16 inch down to 20 gauge. FLAME SPRAY GUN 12M MANUAL 2024…

The standard setup is designed to spray 1/8" wire, but hardware is available for all standard sizes.

The gun is compact and lightweight:

• Length: approx. 9 inches (229 mm)

• Weight: 5 lb (2.27 kg)
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2. Principle of Operation

The 12M gun operates using a compressed-air-driven turbine that powers the wire feed mechanism. The wire is fed through the gun into a fuel gas + oxygen flame, where it melts and is atomized by compressed air to produce a fine spray.
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How it works (manual-based explanation):

1. The turbine pulls the wire through the rear wire guide.

2. The wire enters the hot oxygen + fuel flame and melts.

3. Compressed air blasts the molten metal forward, creating a spray pattern.

4. Coating is deposited on the prepared surface.

This mechanism allows continuous, stable spraying with controlled speeds ranging from 1.5 ft/min up to 45 ft/min, depending on gear configuration. FLAME SPRAY GUN 12M MANUAL 2024…

3. Key Features of the 12M Flame Spray Gun

The manual highlights several engineering improvements that make the 12M superior:
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✔ O-Ring Sealed Nozzle System

Instead of lapped surfaces, O-rings provide tight sealing and easier maintenance.

✔ Improved Turbine & Lubrication System

• Grease seal to prevent leakage

• Built-in pump circulates lubricant for longer gear life

✔ Wire Grip & Feed Control

• Quick-action wire grip handle

• Independent wire-bite adjustment cap

• Hardened stainless-steel drive rolls for wear resistance

✔ High Resistance to Backfire

A redesigned siphon jet gas head provides:

• High spray rates

• Lower gas consumption

• Extreme resistance to backfire

✔ Easy Nozzle & Air Cap Change

Nozzle, air cap, front guide, and siphon plug come out as one unit for quick maintenance.

4. Operating Controls (As per Manual)

The gun has three main controls:
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1. Gas Head Valve

Controls fuel/oxygen flow to gas head and turbine.

2. Speed Control Ring

Adjusts wire feed speed.

3. Wire Grip Handle

Engages or releases drive rolls.

Additionally, a wire grip adjustment cap changes how hard the rollers bite into the wire.

5. Installation Requirements

Compressed Air Requirement

The 12M requires 30 CFM (0.85 m³/min) at 65 psi (4.5 bar).
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The manual recommends:

• Air after-cooler

• 3AC air cleaner

• 4A air control unit

• 2AF air flowmeter

These ensure clean, dry air for high-quality coatings.

Gas Requirements

The gun can use oxygen combined with:

• Acetylene

• Propane / LPG

• MPS gas

• Natural gas / manufactured gas
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Each fuel requires a specific nozzle + siphon plug combination as per manual charts.

6. Lighting & Spraying Procedure (Step-by-Step from Manual)

Before Lighting

1. Open gas head valve fully.

2. Adjust oxygen & fuel gas to Lighting Pressure as per spraying tables. FLAME SPRAY GUN 12M MANUAL 2024…

3. Set air pressure.

Lighting the Gun

Manual procedure:
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1. Open gas head valve fully.

2. Wait 3 seconds.

3. Close valve halfway to reach lighting stop.

4. Ignite with spark lighter.

5. Immediately reopen valve fully.

After Ignition

• Wait for turbine to reach speed.

• Start wire feed.

• Adjust wire feed speed until wire melts consistently without spatter.

Spray Distance

Maintain 5" to 8" (130–250 mm) distance from surface.
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7. Start-Stop Operation

During spraying, the operator can temporarily stop wire feed by lifting the wire grip handle.
The built-in snubber prevents wire from falling out of the gun.
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However:

⚠ Manual Warning:
Do not operate the gun with snubber locked out; flashback through wire guide may occur.

8. Changing Wire Sizes

The 12M supports wire sizes from 3/16" to 20 gauge, including the common 3.15 mm size.
Changing wire size requires:

• Matching Nozzle

• Matching Air Cap

• Correct Drive Rolls & Gears

• Correct Front/Rear Wire Guide
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The manual includes a Wire Guide & Drive Roll Selection Chart for correct combinations.

9. Avoiding Trouble (Manual Troubleshooting)

Backfire Causes

Manual lists key causes:
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• Damaged nozzle O-rings

• Dirt in nozzle jets

• Incorrect air cap

• Plugged siphon plug

• Incorrect gas pressures

• Obstructions in hoses

Backfire requires immediate shutdown.

Difficult Lighting Causes

• Dirty nozzle

• Blocked bleeder holes

• Dirty hoses

• Excess lubricant in gas head valve

Sticking Wire Causes

• Bent or kinked wire

• Dirty drive rolls

• Worn wire guide
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Overheating Prevention

As per manual:
Use correct pressures, maintain airflow, and avoid overspeeding wire feed.

10. Routine Maintenance Schedule

The manual includes a detailed periodic maintenance plan:
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Every 8 Hours

• Clean outside of gun

• Clean drive rolls

• Clean air cap

• Clean nozzle

Every 40 Hours

• Clean siphon plug

• Lubricate wire grip & hinge

Every 80–200 Hours

• Lubricate turbine bearings

• Clean screens & filters

• Lubricate speed control ring

Every 1000 Hours

• Complete overhaul

• Replace gear lubricants

These intervals ensure maximum lifespan and performance.

11. Construction & Parts Overview

The gun consists of:

1. Gas Head Assembly

2. Wire Drive Unit

3. Turbine & Speed Control Assembly

4. Gear Case & Transmission

5. Wire Grip Mechanism
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Each part is serviceable and replaceable using Balaji Udyog spare parts.

12. Why the 12M is Trusted Worldwide

Based on the manual’s engineering details, the 12M Gun offers:

• High coating efficiency

• Universal fuel compatibility

• Robust drive mechanism

• Minimal maintenance requirements

• Quick part replacement

• Long operational life

This makes it ideal for industries such as:

• Steel plants

• Automotive

• Valves & pumps

• Marine

• Mining

• Engineering repairs

Conclusion

The 12M Wire Flame Spray Gun is a precision-engineered tool designed to deliver high-performance metal coatings. When operated according to the manual—using correct pressures, clean air, proper nozzles, and routine maintenance—the gun provides exceptional performance and long life.

This blog is fully based on details from the official 12M Flame Spray Gun Operation & Maintenance Manual.
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