Standard Operating Procedure (SOP) for LPG Cylinder Replacement on Dual-Fuel Forklifts

1. Purpose and Scope

This Standard Operating Procedure (SOP) establishes the standardized workflow for replacing liquefied petroleum gas (LPG) cylinders on dual-fuel forklifts, ensuring operator safety, equipment integrity, and operational environment security. This procedure applies to all internal combustion counterbalanced forklifts equipped with LPG/gasoline dual-fuel systems, covering the entire process from pre-replacement preparation, replacement operations, post-installation inspection, to emergency response procedures.

2. Pre-Operation Preparation

2.1 Personnel Qualification Requirements

Operators must hold a valid forklift operator's license and special equipment operator certification

Must have completed specialized LPG cylinder replacement safety training and passed the qualification examination

Must be familiar with the structure and operating principles of the dual-fuel forklift LPG system

2.2 Work Environment Verification

Inspection Item Standard Requirement Verification Method

Ventilation conditions Outdoors or well-ventilated area Visual confirmation

Open flames/heat sources No open flames, heat sources, or ignition sources within 10 meters Visual confirmation

Ground conditions Level, firm, no low-lying water accumulation Visual confirmation

Firefighting equipment Dry powder fire extinguisher (≥4 kg) available On-site inspection

Warning signs "No Smoking or Open Flames" warning sign posted Visual confirmation

Environmental Safety Requirements: Cylinder refueling or replacement must be conducted outdoors in a well-ventilated, safe location. Open flames, heat sources, ignition sources, and low-lying areas (to prevent LPG accumulation) are strictly prohibited within the surrounding area.

2.3 Personal Protective Equipment (PPE)

Cut-resistant and puncture-resistant gloves (leather or rubber material): Prevent cuts from metal edges of cylinder valves and piping, and avoid low-temperature frostbite—when the cylinder valve is opened, liquid inside vaporizes and absorbs substantial heat, causing the valve and gas pipe to cool rapidly; contact may cause frostbite or even skin adhesion

Safety shoes (impact-resistant, puncture-resistant)

Safety goggles

High-visibility vest

2.4 Tools and Materials Preparation

Soapy water or electronic leak detector

Wrench (size matching cylinder fitting)

New cylinder (inspected and qualified, within validity period)

Record form (cylinder replacement log)

3. Standard Cylinder Replacement Workflow

3.1 Phase 1: Forklift Stabilization and System Shutdown

Step 3.1.1 — Forklift Positioning

Drive the forklift to the designated cylinder replacement area

Come to a complete stop, lower forks to the ground

Apply the parking brake, shift transmission to neutral

Turn off the ignition switch, shut down the engine

Operator dismounts from the operator's seat

Step 3.1.2 — Close Cylinder Manual Valve

Put on protective gloves

Rotate the manual valve (red valve) on the cylinder clockwise until fully closed

Note: The valve closing direction is clockwise, opposite to conventional water faucets

Step 3.1.3 — Residual Fuel Purge

Rotate the fuel selector switch to the NEUTRAL/OFF position

Restart the engine (using only residual LPG in the piping)

Allow the engine to idle until residual fuel in the piping is consumed and the engine stalls automatically

Purpose: Purge residual LPG from the low-pressure piping to prevent leakage during disassembly

Technical Note: This step is critical for cylinder replacement safety. If the residual LPG at 3.5–5 PSI in the low-pressure piping is not purged, fuel will spray out when the quick-connect fitting is disconnected, creating a combustible gas cloud.

3.2 Phase 2: Old Cylinder Removal

Step 3.2.1 — Confirm System Depressurization

Observe the pressure gauge (if equipped) and confirm the reading is zero

Gently touch the low-pressure piping fitting and confirm no gas flow sound

Step 3.2.2 — Disconnect Quick-Connect Fitting

The cylinder overflow valve outlet is equipped with a quick-connect fitting; both male and female fittings contain internal check valves

Rotate and separate the quick-connect fitting

Note: Due to the check valves, neither end will leak substantially, but a small amount of residual gas may escape (this is normal)

Secure the female fitting to the male fitting on the bracket to prevent the hose from swinging freely and causing accidents

Step 3.2.3 — Remove Cylinder Retaining Device

Loosen the cylinder bracket retaining strap/latch

Carefully remove the cylinder from the bracket

Strictly Prohibited: Impacting, dropping, or rolling cylinders on the ground

Step 3.2.4 — Old Cylinder Disposal

Place the old cylinder in an upright position

Move to the designated empty cylinder temporary storage area

Ensure the valve protection cap is intact

Record the old cylinder serial number and estimate remaining quantity

3.3 Phase 3: New Cylinder Installation

Step 3.3.1 — New Cylinder Inspection

表格

Inspection Item Acceptance Criteria Non-Conforming Disposition

Inspection validity period Within validity period Reject and return to supplier

Cylinder exterior No obvious dents, scratches, or corrosion Reject

Valve assembly Operates normally, no damage, no leakage Reject

Safety relief valve Outlet not blocked, protection cap intact Clean or replace

Liquid level gauge Displays normally Record initial liquid level

Cylinder Usage Requirements: Must select a formal supply station; never use cylinders that have exceeded their inspection period. Cylinder contents must not be completely used up; a residual amount of not less than 0.5% of the specified filling quantity must remain.

Step 3.3.2 — Cylinder Positioning and Installation

Position and install the cylinder according to the orientation arrow (pointing upward) on the cylinder end face

Carefully place the cylinder into the forklift rear bracket

Ensure the cylinder valve is oriented in a direction convenient for operation

The cylinder outlet direction must never be pointed toward personnel

Step 3.3.3 — Connect Quick-Connect Fitting

Align the female fitting on the low-pressure piping with the male fitting on the cylinder valve

Tighten the connection to ensure sealing

Check that the O-ring/sealing gasket is intact

Step 3.3.4 — Secure Cylinder

Tighten the cylinder bracket retaining strap/latch

Confirm the cylinder is installed securely with no movement

The bracket must be firmly installed to prevent cylinder displacement during travel

3.4 Phase 4: Leak Detection and System Startup

Step 3.4.1 — Open Cylinder Valve

Slowly open the cylinder manual valve in the counterclockwise direction

Observe whether there are abnormal sounds at the valve and fitting

Confirm the valve is fully open (typically 1.5–2 turns)

Step 3.4.2 — Leak Detection

Method 1: Soapy Water Leak Test

Use a soft brush to apply soapy water to the following locations:

Cylinder valve to cylinder body connection

Quick-connect fitting connection

Low-pressure piping joints

Regulator/vaporizer interfaces

Observe for 15–30 seconds

Acceptance Criteria: Appearance of bubbles indicates leakage

Method 2: Electronic Leak Detector Method

Use a portable combustible gas detector

Slowly move the probe close to each connection point

Acceptance Criteria: Instrument alarm indicates leakage

Step 3.4.3 — Leak Remediation

If leakage is detected:

Immediately close the cylinder valve

Maintain ventilation to disperse accumulated gas

Strictly prohibit switching any electrical equipment

Inspect and re-tighten the leaking fitting

Replace damaged sealing components

Re-perform leak detection until qualified

Step 3.4.4 — System Startup Verification

Confirm the fuel selector switch is in the LPG position

Rotate the ignition switch to the ON position

Start the engine (do not press the accelerator)

Observe engine operating conditions:

Stable idle

No abnormal noise, no abnormal vibration

Normal exhaust (no black smoke, no unusual odor)

Check that the pressure gauge reading is normal (3.5–5 PSI)

Warm up the engine for 2–3 minutes (especially in cold weather) to ensure coolant warms up and flows into the vaporizer

4. Special Considerations for Dual-Fuel Systems

4.1 Fuel Switching Backup

When the LPG in the cylinder is nearly depleted, the operator will noticeably feel reduced engine power. At this time:

The dual-fuel system can be immediately switched to gasoline mode to continue operation

Switching method: Rotate the fuel selector switch directly to the GAS (gasoline) position

No need to pause at the intermediate position

4.2 Gasoline System Maintenance

When dual-fuel forklifts primarily use LPG as fuel, the gasoline system may experience the following issues from long-term idleness:

Fuel line embrittlement

Carburetor clogging

Fuel pump failure

Maintenance Requirements: Keep at least 1/4 fuel in the gasoline tank; it is recommended to burn approximately 10 kg of gasoline monthly to ensure the gasoline system does not malfunction due to extended idleness.

5. Safety Prohibitions and Emergency Response

5.1 Absolute Prohibitions

表格

No. Prohibited Behavior Consequence

1 Replacing cylinders while the forklift is moving or the engine is running Fuel leakage causing fire/explosion

2 Replacing cylinders indoors or in poorly ventilated areas LPG accumulation causing asphyxiation/explosion

3 Impacting, dropping, or rolling cylinders on the ground Cylinder damage, valve breakage, leakage

4 Using cylinders that have exceeded inspection period or are damaged Cylinder rupture, serious accident

5 Pointing cylinder valve outlet toward personnel Unexpected valve opening causing personnel injury

6 Using non-explosion-proof tools or generating sparks Igniting leaked LPG

7 Unauthorized disassembly or adjustment of safety relief valve Loss of overpressure protection function

5.2 Emergency Response Procedures

Scenario 1: Cylinder Leakage

Immediately close the cylinder valve (rotate clockwise to tighten)

Evacuate surrounding personnel and establish a cordoned area

Open ventilation equipment or provide natural ventilation

Strictly prohibit switching any electrical equipment

Go to a safe outdoor area and call emergency services

Scenario 2: Cylinder Fire

If the valve is intact: Cover the valve with a wet towel and close it

If the valve is damaged: Quickly evacuate to a safe outdoor area

Call 119 (fire department); do not attempt self-remediation

Scenario 3: Personnel Frostbite

Immediately move away from the low-temperature source

Soak the frostbitten area in warm water below 40°C

Do not rub or apply heat

Seek medical treatment

6. Documentation and Archiving

Each cylinder replacement must be recorded on the "LPG Cylinder Replacement Log," including:

Record Item Filling Requirement

Replacement date/time Accurate to the minute

Forklift number Consistent with equipment registry

Old cylinder number Cylinder body stamped number

New cylinder number Cylinder body stamped number

New cylinder inspection validity period Year/month/day

New cylinder initial liquid level Gauge reading or weight

Leak detection result Pass/Fail, detection method

Operator signature Handwritten signature

Supervisor signature If applicable

Records must be retained for no less than 3 years for audit purposes.

7. Training and Assessment

7.1 Training Content

LPG physical properties and hazards

Dual-fuel forklift LPG system structure

All operational procedures in this SOP

Leak detection methods

Emergency response procedures

7.2 Assessment Requirements

Theoretical examination: ≥80 points to pass

Practical assessment: Independently complete the full cylinder replacement process without violations

Refresher training cycle: At least annually