Process and Quality Control of Oil Cylinder for 4TG-FC Series (202mm Bore) Front Top dump Truck

After the parameters are confirmed, the next question every customer asks is: what happens after the order is placed, and how is quality guaranteed? This article walks through the main manufacturing steps and control points of the 4TG-FC series 4-stage hinge-mounted front-top cylinder, from raw material to finished shipment.

Raw Material Control

The barrel is made of standard-compliant seamless steel tube, and the piston rod uses high-quality quenched-and-tempered steel, ensuring base strength and wear resistance.

All incoming blanks undergo material re-inspection and internal defect ultrasonic testing before being released to production, eliminating material risks at the source.

Key point: This model has a 202 mm bore and a 5390 mm stroke. As a large-bore, long-stroke product, it places extremely high demands on raw-material straightness, wall-thickness uniformity and internal soundness, so the material selection stage is controlled very strictly.

Key Machining Processes

• Barrel inner-bore machining: Each stage barrel is precision-bored on dedicated equipment to guarantee inner-wall smoothness and dimensional accuracy, providing a good working surface for the seals.
• Piston-rod machining: Each rod goes through rough turning, finish turning and grinding to meet cylindricity and surface-finish requirements. Long rods require extra attention to straightness control.
• Sleeve machining: This is a 4-stage telescopic structure; the clearance between successive sleeves must be tightly controlled to ensure smooth extension and reliable sealing. The more stages, the harder cumulative tolerance control becomes.
• Trunnion machining: Two pin diameters, 60 mm and 65 mm, are available, both precision-machined to fit the customer's frame pin bushings accurately.
• Protective sleeve machining: The 273 mm diameter outer sleeve must maintain roundness and straightness to effectively shield the inner barrels and rods from outside debris.
• Welding: Critical welds at the cylinder bottom, oil ports and trunnion brackets follow qualified welding procedures and are checked by liquid-penetrant and ultrasonic testing to rule out welding defects.

Surface Treatment (Anti-Corrosion and Wear Resistance)

• Every piston rod is hard-chrome plated for good wear resistance and rust protection in outdoor operating conditions.
• The outer barrel surface and protective sleeve are spray-painted with an anti-rust primer plus a finish coat to improve overall corrosion resistance.

Note: On long-stroke cylinders the exposed rod area is large, so plating quality is especially critical. We apply the plating to specification to prevent peeling over long service life.

Assembly

All components are cleaned before assembly to prevent iron chips, dust and other contaminants from entering the cylinder.

Seals are installed with dedicated tools to avoid scoring or twisting and to maintain sealing performance. Threaded joints are tightened to standard torque to prevent loosening or over-tightening.

Special attention: A 4-stage cylinder has many seal points; each stage seal must be confirmed in place and marked for traceability. During assembly of long-stroke cylinders, rod straightness must be respected — never force a rod into place, as this will damage the seals.

Factory Inspection Tests

Every cylinder must pass the following tests before shipment:

• Pressure test: Held at a test pressure above the rated pressure to verify the strength of each stage barrel and the welds.
• Leakage test: Internal and external leakage of each stage is checked separately to ensure every seal point is tight.
• Operation test: The cylinder runs through its full stroke under simulated working conditions to check that every stage extends smoothly, without abnormal noise or jamming, with particular attention to the transitions between stages. Long-stroke cylinders are also checked for stability at full extension.
• Synchronization check: The extension sequence and speed of each stage are verified against the design requirements.
• Visual inspection: Surface coating, markings and mounting dimensions are confirmed against the drawings.

Conclusion

From raw material to finished product, every 4TG-FC series front-top cylinder goes through standardized processes and multiple inspections. Large bore, long stroke and 4-stage telescoping demand high manufacturing precision and process control; we have the equipment capability and inspection methods to back that up. If you need detailed process documentation or inspection reports, please contact us at any time.

Frequently Asked Questions

What tests does each cylinder pass before shipment?

Every cylinder goes through a pressure-hold test above rated pressure, internal and external leakage checks at every stage, a full-stroke operation test, a synchronization check, and a visual and dimensional inspection against the drawings.

How is quality controlled on a long-stroke 4-stage cylinder?

Through strict incoming-material straightness and wall-thickness inspection, precision barrel honing, tightly controlled sleeve clearances, individual verification and marking of every seal point, and a full-stroke stability test at maximum extension.

Can I receive a factory inspection report for my order?

Yes. On request we provide inspection reports covering pressure, leakage and dimensional results. Please tell your sales contact before order confirmation so the report can be prepared and included with the shipment.