A fin tube that leaks in service does not fail quietly. It contaminates the product stream, forces an unplanned shutdown, and in a fired heater it can escalate into a tube rupture. The inspection regime behind every heat exchanger tube therefore matters as much as the material grade itself. At Yuhong, two tests sit at its centre: eddy current examination and hydrostatic testing.

Eddy current testing detects discontinuities in the tube wall without cutting the tube. A probe is passed through the bore while an alternating current induces eddy currents in the wall; any change in wall thickness, crack, lap, or inclusion disturbs the field and is recorded. The applicable standard depends on the tube grade — the single most common specification error in this field, which is why the standard-by-grade reference appears below.

Where E426 is applied to ferritic or duplex grades it is by project agreement and must be stated as such in the inspection and test plan. A sound programme adds full-length scanning, drilled-hole reference standards, automatic alarms with manual re-verification, and segregation of rejected lengths. Eddy current testing finds defects hydrostatic testing cannot see — a pinhole that holds pressure today may leak after a few thermal cycles.

Hydrostatic testing proves pressure integrity directly: each tube or bundle is filled with water, pressurised to 1.5 times the design pressure, held for a defined period, and examined for leakage, permanent deformation, and pressure drop. Two details decide whether the test is meaningful:

1. Water quality and chloride control — for stainless and duplex tubes, the test water must be controlled for chloride content and drained and dried promptly afterwards. Residual chlorides left in a super duplex tube can initiate pitting long before the equipment ever sees service.
2. Recorded evidence — pressure, hold time, water temperature, and the inspector's signature must be recorded for every test so the result is traceable years later.

Every shipment is accompanied by mill test certificates, PMI reports, eddy current records, hydrostatic test certificates, and dimensional inspection reports, plus third-party inspection where the purchase order requires it. Since 1990 this documentation discipline has supported export to more than 85 countries, with most orders coming from repeat customers.

Buyers only see whether the exchanger is still tight after three years. Specifying the correct eddy current standard for the actual tube grade — and hydrostatic testing explicitly — is the cheapest insurance available on a heat exchanger purchase.

Yuhong supplies a written inspection and test plan (ITP) with the quotation for any tube order, naming the exact eddy current standard, probe type, reference standard, and pressure test parameters.

No. ASTM E426 is written for austenitic stainless steel and similar non-magnetic alloys. For ferritic and martensitic grades the applicable eddy current requirements are found in the product standard's supplementary requirements, typically ASTM A450 / A1016, or in the project specification. Any use of E426 on those grades is by project agreement.

Typically 1.5 times the design pressure, held for a defined period under recorded conditions, with the test water controlled for chloride content and the tube drained and dried immediately afterwards.

Yes, but the magnetic ferrite phase changes the probe response, so probe frequency and reference standards must be adjusted and the method agreed as part of the inspection and test plan.