Frequently asked questions

It is a corrugated steel sheath that creates a void in concrete through which prestressing tendons are placed and later grouted. The corrugation is intended to provide mechanical interaction with the surrounding concrete and the grout. EN 523 addresses uncoated cylindrical steel strip sheaths and their couplers used for this purpose.

Round ducts are cylindrical sheaths. Flat ducts are formed profiles used where structural depth or tendon layout makes a round section impractical. DUSO flat sizes are produced from defined round diameters (for example round 60/65 → flat 72/21), so coupler and process selection still refer to the round origin.

Diameter follows the tendon system, strand count, grouting requirements and the project specification — typically defined by the post-tensioning designer or system holder. Select a published DUSO size that matches that specification, or send the tendon datasheet with your RFQ. This website does not replace structural design.

Published production thicknesses are 0.40 / 0.45 mm, 0.50 mm and 0.60 mm. Not every diameter is produced in every thickness; use the technical tables.

They are different steel strip thicknesses used to form the sheath. Thicker strip generally increases unit weight (see kg/m columns) and changes handling and forming behaviour. Required thickness is a project specification item and may relate to the standard category specified for the sheath. Do not infer load or leak-tightness performance from thickness alone.

EN 523:2003 is the European standard “Steel strip sheaths for prestressing tendons — Terminology, requirements, quality control.” It applies to uncoated cylindrical corrugated steel sheaths and couplers made from interlocked or welded strip, with nominal internal diameter up to 130 mm. Categories described in public summaries include Category 1 (normal) and Category 2 (rigid). Seals between sheath and coupler are outside its scope.

EN 524 is the series of test methods referenced for steel strip sheaths for prestressing tendons. EN 523 points to EN 524 for measurements such as dimensions and the mechanical / leaktightness tests applicable to the classified sheath. Exact test selection belongs in the project quality plan.

Material (mill) certificates and production/quality documents can be supplied as defined in the order. Certificate types and numbers are not listed as marketing claims on this site. Request the document set you need in the RFQ.

Non-standard diameters can be evaluated against tooling, strip and programme. Send the required internal/external dimensions and thickness. Capability is confirmed only after engineering review — not assumed from the published matrix.

Cut lengths are produced to order. Machine maximum length is 12 m; truck transport often prefers about 6.5 m in practice. Advise transport limits, site handling and coupler needs when requesting lengths. Use 1 coupler per end-to-end joint.

Published equivalents: 66/22 ← 48/53; 68/22 ← 50/55; 78/22 ← 55/60; 72/21 ← 60/65; 83/24 ← 60/65; 88/29 ← 65/70; 94/28 ← 70/75. Additional flat notes appear in the round datasheet (72/21 and 97/25 equivalents).

The kg/m values in the tables are manufacturer data for the listed thickness and dimension combinations. Use them for take-off and logistics. They are not independent laboratory certifications.

Couplers are matched to the connected duct diameter (round and, where listed, flat equivalents). Quantity rule: 1 coupler per end-to-end joint. Confirm fit, seal and installation method from the project specification and EN 523 coupler rules when that standard is invoked.

Yes. This is a core DUSO offering: production machines are shipped to site, configured, installed and operated with training and optional supervisor support.

A configured production unit (round and/or flat), power supply meeting the machine requirements, handling space, steel coil supply, and trained operators. Exact footprint and utilities are confirmed during project analysis.

Machines can be prepared for international shipment. Incoterms, packing and installation country are defined in the machine RFQ.

Yes. Steel strip can be supplied from Türkiye subject to the project specification and schedule.

Local steel may be used if it meets the technical requirements defined for the duct programme. Suitability is assessed before production, not assumed.

Incoming steel is identified and verified before release to production. Material certificates are reviewed when they form part of the order documentation.

Typical sequence: incoming verification, production control, dimension verification, surface control, final inspection, packaging inspection and shipment documentation. Acceptance limits are those of the order quality plan.

Manufacturer-stated capacities: 3,000 metres/day for EN 523 Class 1 production and 2,500 metres/day for EN 524 Class 2 production. Actual output on a given order depends on size mix, thickness and shift pattern.

Ducts are identified, bundled and stored under appropriate conditions until shipment, then prepared for the agreed transport mode including container loading where applicable.

Export packing and worldwide delivery are part of the commercial offer. Export destinations include Russia, Denmark, Italy, Iraq, Kuwait, Israel and France; destination and terms are confirmed per quotation.

Yes. DUSO supplies production machinery as capital equipment, including mobile/on-site configurations.

Installation and commissioning can be included when specified in the machine quotation. They are not automatic unless contracted.

Yes. Operator training is offered for factory and on-site installations. Scope and duration are defined per contract.

Yes. Supervisor support can cover mobilisation, start-up and early production. It is scoped in the on-site or machine agreement.

Spare and wear parts are quoted against machine identity. Keep the machine code and, if possible, part references when ordering.

For ducts: type (round/flat), duct diameter, steel thickness, cut length, quantity (pcs), delivery date and destination. For machines: type, required production range, installation country, and whether installation/training are required. For on-site production: project country, expected volume, duration and local steel availability. Drawings (PDF/DWG/DXF) and spreadsheets can be uploaded with the RFQ.