By Yuhong Holding Group Co., Ltd · Technical Team · 11 Nov 2026

We have shipped a series of studded tube orders recently — different base tube grades, stud patterns and destinations. Each shipment is a reminder that passing final inspection is only half the job. The other half is delivering the tube to site in the condition it left the workshop: a tube arriving with bent studs, rusted weld-prep bevels or an illegible stamp has failed before installation began.

Studs are exposed, weld-prep ends unprotected, and markings can go illegible in transit. Shipping protection is part of the delivered quality.

After final inspection, every studded tube is stamped on the plain (unstudded) section of the base tube, or marked according to the customer's specified method. The stamp must be legible, but the indentation depth must not exceed 0.3 mm — deep stamping creates a stress raiser on a pressure part, and on thin-wall tube it can become a crack initiation site. The stamp carries the base tube material and the tube specification.

For austenitic base tubes the marking ink and paint must be selected carefully: metal salts and harmful metals — lead, zinc and copper in particular — must not be present. These elements trigger localized corrosion on austenitic stainless, and the marking itself becomes the corrosion site.

Before packing the whole tube is blown through with compressed air to remove loose scale, dust and debris from the bore and from between the studs. Both ends are then fitted with plastic caps. For austenitic tubes the caps must be chloride-free: standard plastic caps can carry chloride residues that initiate pitting in a moist transit environment.

The reason is specific: the bevel is the surface welded on site, and a rusted bevel means re-preparation before welding. Austenitic tubes stay uncoated because the coating itself contaminates the surface.

Studded tubes ship in groups, each group carried in a steel fixing frame. Two requirements govern the frame design:

• No tube-to-tube contact. Any two studded tubes in a bundle must not touch, because the studs are the first thing to deform under vibration or handling impact.
• Frame rigidity. The frame must stay tight through lifting, road transport and ocean transit; a frame that loosens under load lets tubes move, and the damage shows up as bent studs or deformed weld-prep ends.

The bundle tag carries what is needed to match the tube to the project without opening the case: contract and project numbers, specification and material, sequence and batch number, mill mark and gross weight.

• The marking method, stamp location and maximum indentation depth (0.3 mm).
• For austenitic tubes, prohibition of lead-, zinc- and copper-bearing marking materials, and mandatory chloride-free end caps.
• The rust-preventive treatment for carbon and low-alloy tubes, and its exclusion for austenitic tubes.
• The bundling method, rigid fixing frame and the no-contact rule between tubes.
• The tag content: contract and project numbers, specification, sequence and batch number, mill mark, gross weight.

None of these items adds engineering difficulty; they add traceability, weldability and stud integrity at site.