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Xin Rui Da Fasteners
Xin Rui Da Fasteners
Engineering proof

Case Studies | Xin Rui Da Fasteners

Real challenges, engineering solutions, measurable results.

Steel Structure — High-Strength Bolts Under-Torqued on Site
Steel Structure Contractor

Steel Structure — High-Strength Bolts Under-Torqued on Site

▸ Condition
10.9 grade M20 HRSG bolt assemblies in a slip-critical connection. Untested impact wrenches on site; third-party audit found scattered torque values and under-tightened joints.
▸ Diagnosis
Uncalibrated torque tools drifted up to ±25%; inconsistent nut lubrication pushed the torque factor K between 0.13 and 0.25; no final-torque verification step on the crew.
▸ Solution
Calibrated digital torque wrenches with a snugging–final–check routine, single-lot nuts held to K = 0.110–0.150, torque-factor test report and batch traceability shipped with every delivery.
Key Result
98% first-pass rate on the final-torque audit, torque scatter cut to ±5%. Three further packages awarded; 4.2 million sets supplied.
More delivery records
Offshore Platform — Pitting on Cooling-Water Flange Bolts
Offshore Equipment Builder

Offshore Platform — Pitting on Cooling-Water Flange Bolts

A2-70 (304) hex bolts M16×70 on seawater cooling lines in the splash zone showed rust staining and pitting after 14 months, with weeping at the flange face.

Upsized to A4-80 (316) DIN933 bolts with 316 washers, MoS₂ anti-seize, Ra ≤ 3.2 flange face control and a 720 h salt-spray plus PREN report.

36 months with no pitting or weeping; inspection interval stretched from annual to every three years. A4-80 is now the client's offshore standard.
Commercial Vehicle — Wheel Flange Nuts Backing Off
Axle Manufacturer

Commercial Vehicle — Wheel Flange Nuts Backing Off

DIN6923 grade 8 flange nuts M12×1.5 backed off 1–2 turns on some wheels after roughly 8,000 km of road testing, triggering imbalance warnings.

Serration-face flange nuts with friction coefficient held to ±8% per lot, torque-plus-angle servo tightening with per-wheel records, and a DIN 65151 (Junkers) qualification report.

Zero back-off over 500,000 km of road testing; residual preload in Junkers testing rose from 32% to 91%. Approved supplier list, 1.2 million nuts per year.
Hydrotreater Line — B7 Studs Relaxing at 320°C
Refinery EPC Contractor

Hydrotreater Line — B7 Studs Relaxing at 320°C

DIN975 / ASME B7 studs M27×320 on a 320°C steam line leaked at the gasket after about one year, forcing hot-tightening campaigns.

Switched to ASTM A193 B16 studs with 2H nuts, bolt tensioner for target stress, 200 h stress-relaxation curve at 320°C, high-temp anti-seize and spiral-wound gasket selection.

No leakage through a full 26-month run; hot-tightening eliminated. The solution is now written into the client's flange joint standard.
Dairy Filling Line — Rust on Stainless Screws
Food & Beverage Machinery Builder

Dairy Filling Line — Rust on Stainless Screws

M8 DIN912 socket screws showed rust blooms at the head fillet after three months under alternating acid/alkali CIP and high-pressure washdown; flagged in HACCP audit.

A4-80 (316) DIN912 with full nitric passivation and magnetic check, dedicated non-ferrous tooling and segregation, enlarged head fillet with Ra ≤ 0.8 to avoid liquid traps.

18 months of CIP service with no corrosion and a clean HACCP re-audit. Sole-source supply of all hygienic fasteners on the line.
Wind Tower — 10.9 Stud Fracture at Mid-Flange
Wind Farm Operator

Wind Tower — 10.9 Stud Fracture at Mid-Flange

On a 1.5 MW turbine, 3 of the 10.9 grade M30 tower flange studs had fractured and 7 showed indications after six years; remaining torque readings were low across the joint.

Replacement studs baked within 8 h of galvanising (200°C × 8 h) with baking records, ultrasonic axial-load acceptance instead of torque alone, flange flatness re-measured and shimmed, and a three-stage re-torque schedule over one year.

Preload scatter reduced from ±28% to ±6%; no new indications after two years of inspection. The testing plus re-torque protocol was rolled out across 12 of the client's wind farms.
01
Requirement review

Confirm material, dimensions, and technical details of the duty.

02
Sampling & trial

Fast prototypes validate performance and dimensions before batch production.

03
Batch delivery

Strict production and inspection, on-time delivery, stable supply.

Engineering Solutions

Common Bolt Failures — Our Solutions

Thirty years of field and export experience. For every common failure mode we have a proven, documented solution.

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