Tender for Supply of Steel Pipes and Steel Fittings for the Southern Coal Group Company

Tender Name: Supply of steel pipes and steel fittings for the Southern Coal Group Company

Subject of Contract: Supply of various steel pipes and steel fittings for the Southern Coal Group Company

Lot 1: Black Flanged Steel Pipes and Steel Fittings

Product Definition and Application

This lot involves carbon steel pipes and matching flanged fittings without galvanization, commonly known as "black pipes" in the industry. Such materials are primarily used for conveying non-corrosive media in underground coal mine systems such as compressed air, drainage, and grouting. As they do not require zinc coating protection, they are suitable for dry or general environments without severe corrosion risks.

Technical Requirements for Steel Pipes

Material and Manufacturing Standards: Pipes must be made of non-alloy quality carbon structural steel, typically grades such as Q235B, Q355B, or higher. Their chemical composition and mechanical properties must comply with the technical requirements of EN 10255:2004+A1:2007 "Non-alloy steel tubes suitable for welding and threading". For seamless pipe requirements, EN 10216-1 standard shall be followed; for welded pipes, EN 10217-1 standard shall be followed.

Dimensions and Tolerances: The nominal diameter (DN) range, wall thickness (Sch40, Sch80, or specific millimeter values), and allowable deviations must strictly adhere to the specifications in Attachment 5 of the tender documents. Ovality and wall thickness unevenness must not exceed the standard specified values.

End Preparation: Both ends of the pipes shall be machined with flanged connection bevels as required. The bevel angle is typically 30-37.5°, with the root face dimensions conforming to welding process requirements. Pipe ends shall be flat and free of burrs, with perpendicularity deviation controlled within the allowable range.

Surface Condition: The surface shall be free of cracks, scabs, folds, rolling defects, and scratches exceeding the negative wall thickness tolerance. Before delivery, shot blasting or sandblasting treatment shall be performed to remove scale and rust, achieving Sa2 grade (near-white) cleanliness. Weldable rust-preventive primer or anti-rust oil shall be applied immediately for temporary protection.

Technical Requirements for Flanges and Fittings

Flange Type and Standard: Matching flanges shall be plate flanges (PL type) or slip-on flanges (SO type). Their dimensions, tolerances, and sealing face machining must comply with EN 1092-1 "Flanges and their joints - Circular flanges for pipes, valves, fittings and accessories, PN designated - Part 1: Steel flanges". The pressure rating (PN6, PN10, PN16, etc.) shall be determined according to the design drawings.

Material Compatibility: Flange material shall be compatible with the pipe material, typically using carbon steel of the same or higher strength, such as S235JR or S355JR.

Sealing Face: Raised face or flat face sealing surfaces shall be finely machined, free of radial scratches, with surface roughness meeting the standard (typically Ra 3.2-6.3μm) to ensure effective contact with the gasket.

Fasteners: Matching bolts and nuts shall comply with EN ISO 898-1 "Mechanical properties of fasteners made of carbon steel and alloy steel - Part 1: Bolts, screws and studs". Bolt strength grade is typically 8.8 or 10.9, with nuts of matching strength grade. The surface shall be treated with bluing, phosphating, or Dacromet anti-corrosion coating.

Fittings: In addition to flanges, this includes steel pipe fittings such as elbows, tees, and reducers. Their material and wall thickness shall be consistent with the main pipeline. Manufacturing standards refer to EN 10253-2 (butt-welding fittings) or EN 10241 (steel threaded pipe fittings).

Lot 2: Galvanized Flanged Steel Pipes and Steel Fittings

Product Definition and Application

This lot involves steel pipes and flanged fittings that have undergone hot-dip galvanizing. They are mainly used in systems requiring higher corrosion resistance, such as underground coal mine water supply, fire sprinkler systems, and emulsion fluid transportation. The zinc coating effectively isolates corrosive media, significantly extending the service life of the pipeline.

Technical Requirements for Pipe Base Material

Base Pipe Material and Manufacturing: The base pipe (black pipe before galvanizing) shall also meet the requirements of EN 10255 or other equivalent standards. The material shall have good galvanizability, with key elements such as carbon and silicon content controlled within a range suitable for hot-dip galvanizing to ensure coating quality.

Dimensional Requirements: The outer diameter and wall thickness tolerances of the base pipe shall allow space for the subsequent zinc coating, ensuring post-galvanizing dimensions still meet design requirements.

Hot-Dip Galvanizing Process and Coating Requirements

Galvanizing Standard: The hot-dip galvanizing process and coating quality must comply with EN 10240 "Internal and/or external protective coatings for steel tubes - Specification for hot dip galvanized coatings applied in automatic plants". This is the core European standard for hot-dip galvanizing of steel pipes.

Coating Appearance: The coating shall be continuous, complete, and smooth. In principle, defects such as bare spots, blisters, rough nodules, zinc dross, and dullness are not permitted. Slight local spangle unevenness is acceptable.

Coating Thickness: According to EN 10240, the average coating thickness shall meet the requirements (typically, for pipe wall thickness ≥3mm, the average coating thickness shall not be less than 55μm; for wall thickness <3mm, not less than 45μm). Corresponding regulations also exist for local minimum thickness.

Adhesion: The coating shall be firmly bonded to the base metal, verifiable through hammering or file tests. The coating shall not peel or flake off.

Post-Treatment: Passivation treatment (e.g., chromate passivation) shall be performed after galvanizing to enhance resistance to white rust, but attention must be paid to its potential impact on subsequent welding. If designed for field welding, the pipe ends may need to have a non-galvanized section reserved (approx. 10-15cm) or use methods like bevel machining after galvanizing followed by touch-up with zinc-rich paint.

Requirements for Galvanized Flanges and Fittings

Flanges and Fittings: The quality of the final galvanized coating on matching flanges, elbows, tees, and other fittings, whether they are galvanized as prefabricated parts or formed from galvanized steel plate, must also comply with the EN 10240 standard.

Thread Protection: For threaded fittings, excess zinc dross on the thread surface must be carefully cleaned after galvanizing. Thread gauges shall be used for inspection to ensure thread accuracy and assemblability, and anti-rust grease shall be applied for protection.

Fasteners: Matching bolts and nuts are typically galvanized or made of more corrosion-resistant stainless steel. If galvanized fasteners are used, attention must be paid to preventing hydrogen embrittlement risks and ensuring appropriate thread tolerance fit.

Lot 3: Steel Pipes and Flanged Steel Fittings for Backfill Mining

Product Definition and Application

This lot is specifically for coal mine backfill mining processes, which involve transporting backfill slurry—a mixture of gangue, fly ash, cementitious material, and water—via pipelines to underground goafs. Such pipelines endure severe abrasion from high-concentration, high-hardness solid particles and impact from high-pressure transportation, placing extremely high demands on material wear resistance and strength. They belong to the category of heavy-duty wear-resistant pipelines.

Technical Requirements for Base Pipe

Material and Strength: The base pipe shall be made of high-strength carbon structural steel or low-alloy high-strength steel, such as Q345B, Q390, or higher grades, to ensure it can withstand the high pressure (typically up to 4-10 MPa or even higher) generated by backfill pumps. Its chemical composition and mechanical properties shall meet the corresponding standards.

Dimensional Accuracy: To ensure consistency in subsequent wear-resistant lining or heat treatment processes, the requirements for wall thickness uniformity and ovality control of the steel pipes are stricter than those for ordinary pipes.

Core Requirements for Wear Resistance

Wear-Resistant Lining/Treatment Method: Depending on the abrasiveness of the backfill slurry, one or more of the following reinforcement measures shall be applied to the pipe's inner wall:

Inner Wall Hardening: Induction hardening or overall heat treatment of the pipe's inner wall to form a high-hardness martensite layer, improving wear resistance. The hardened layer depth shall reach 1.5-3mm, with inner wall hardness reaching HRC 40-55 or higher.

Bimetallic Composite Pipe: Using centrifugal casting or metallurgical bonding processes, the outer layer is carbon steel (providing strength) and the inner layer is high-chromium cast iron (Cr15-28%) or other high-wear-resistant alloys (providing wear resistance). The inner wear-resistant layer thickness shall be uniform, typically 3-8mm, with hardness up to HRC 55-65.

Ceramic Lining: Composite alumina ceramic layer applied to the pipe's inner wall using self-propagating high-temperature synthesis or bonding processes. The ceramic layer thickness is typically 3-10mm, with high hardness (above HRA 85) and excellent wear resistance, but attention must be paid to its impact resistance.

Bond Strength of Wear-Resistant Layer: Whether it is a hardened layer, metallurgically bonded layer, or ceramic lining, it must have sufficient bond strength to ensure it does not peel or flake off under long-term high-pressure and impact conditions. A bond strength test report shall be provided.

Special Requirements for Flanges and Fittings

Flange Type: Typically, replaceable flanges or loose flanges are used to allow for flange replacement only when the wear-resistant lining wears out, reducing maintenance costs. The connection between the flange and the pipe can be welding (attention must be paid to the heat-affected zone's impact on the wear-resistant layer) or mechanical locking.

Flange Material and Strength: The flange material strength shall match that of the pipe, ensuring the sealing and pressure-bearing capacity at the connection is not lower than that of the pipe body.

Sealing Design: Given the high-pressure transportation, the sealing structure must be reliable. Special groove designs are typically used in conjunction with high-performance sealing rings (e.g., polyurethane or nitrile rubber) to ensure leak-free joints under high pressure.

Wear-Resistant Treatment for Fittings: Elbows, tees, and other fittings are the most severely worn parts. Their wear-resistant treatment grade shall be no less than that of the straight pipe sections, or they shall employ reinforced designs such as thickened wear-resistant layers or replaceable liners.

Lot 4: Quick-Install Galvanized Steel Pipes with VICTAULIC-Type Couplings

Product Definition and Application

This lot involves galvanized steel pipes connected using grooved mechanical couplings (i.e., Victaulic-type couplings, also known as "grooved fittings" or "grooved pipe couplings"). This connection method eliminates the need for welding and secondary flange bolt tightening, achieving fast and reliable mechanical connections through rolled grooves and couplings. It is particularly suitable for temporary or semi-permanent pipeline systems in underground coal mines requiring rapid installation, disassembly, and frequent relocation, such as temporary drainage, local ventilation, and hydraulic support supply/return lines.

Requirements for Pipe Base Material and Galvanizing

Base Pipe Material: The steel pipe base material shall also comply with the EN 10255 standard, possessing good mechanical strength and ductility to withstand groove rolling without cracking or excessive deformation.

Hot-Dip Galvanizing: The galvanizing process and quality must comply with the EN 10240 standard. It should be noted that groove rolling is typically performed after the pipe is galvanized (or pre-rolled before galvanizing with subsequent coating repair). The quality of the zinc coating directly affects the corrosion resistance of the grooved interface.

Technical Requirements for Groove Machining

Groove Type: Based on the coupling type, grooves are typically divided into two types:

Rolled Groove: Formed at room temperature by squeezing with rollers using a dedicated grooving machine, without cutting metal. The groove bottom has a rounded transition, preserving the integrity of the zinc coating. Suitable for thin to medium wall thickness pipes.

Cut Groove: Machined by turning, which cuts metal and exposes the base material, with a square groove bottom. Suitable for thick-walled pipes or applications requiring strict axial restraint. After cutting, the exposed metal surface must be repaired with high-quality zinc-rich paint, and the corrosion protection level must not be lower than the original zinc coating requirement.

Groove Dimensional Accuracy: The groove width, depth, bottom diameter, and distance from the pipe end must strictly comply with ISO 6182-12 or the corresponding Victaulic coupling manufacturer's technical standards. Excessive dimensional deviation can lead to joint leakage and connection failure.

Groove Quality Inspection: After grooving, the pipe end shall remain round, and the groove bottom shall be smooth without cracks or burrs. Dimensional inspection and sealing performance sampling tests shall be conducted on the first piece and batch products.

Technical Requirements for Victaulic-Type Couplings

Coupling Material and Process: The coupling housing is typically made of malleable cast iron (complying with EN 10242 "Threaded pipe fittings in malleable cast iron") or ductile iron via precision casting, offering high strength and good toughness. The surface shall be treated with hot-dip galvanizing or electro-galvanizing, with the corrosion protection level meeting the requirements of the underground use environment.

Gasket Performance: The gasket is a key component of the grooved coupling. The material shall be selected based on the conveyed medium:

General Purpose: EPDM rubber, suitable for water, dilute acids, alkalis, etc., from -30°C to +110°C.

Oil-Resistant: Nitrile rubber, suitable for media containing mineral oil (e.g., emulsion, hydraulic oil).
The gasket structure is typically "C-type" or "lip-type", achieving self-tightening sealing under internal pressure. A physical and mechanical properties report for the rubber material (hardness, tensile strength, elongation at break, compression set, etc.) shall be provided.

Bolts and Nuts: The strength grade of matching bolts and nuts shall meet the working pressure requirements of the coupling (e.g., 700kPa, 1200kPa, 2500kPa grades). The surface shall be treated with Dacromet, hot-dip galvanizing, or other high-grade anti-corrosion treatments to prevent rust seizure in the damp underground environment.

Connection System Performance Requirements

Working Pressure: The rated working pressure of the complete connection system (including steel pipe, groove, coupling, gasket) must be specified and verified through static and cyclic pressure tests.

Deflection and Angular Movement: Grooved couplings allow a certain degree of axial and angular movement (typically ±1° to ±3°, depending on the model) to accommodate floor heave, deformation, or installation errors in roadways. This is one of their core advantages compared to flanged connections. The allowable maximum deflection angle shall be provided.

Installation Performance: The coupling shall be designed for quick installation, typically requiring only a torque wrench or socket wrench without special tools. Installation instructions (including bolt torque values) must be clear and accurate.

Participation Conditions and Qualification Documents:

Exclusion Grounds: Bidders must submit a Single European Procurement Document or corresponding declaration

certifying the absence of the following exclusion grounds: participation in a criminal organization, corruption, fraud, terrorism, money laundering, child labor, tax evasion, non-payment of social security contributions, agreements with other bidders distorting competition.

Capital Link Declaration: A declaration must be submitted stating whether the bidder belongs to the same capital group as other bidders (as defined by the Act of 16 February 2007 on Competition and Consumer Protection).

Bidding Rules:

Only Polish language bid documents are accepted.

Submission must be made electronically via https://platformazakupowa-pkw.carthena.pl/

An advanced or qualified electronic signature or seal compliant with (EU) No 910/2014 is required.

Electronic catalogues are not permitted.

Alternative offers are not permitted.

Consortium Bidding: A consortium bid must designate an authorized representative responsible for handling the bid and/or signing the contract.

Bid Opening Information: The bid opening date is 24 March 2026, 12:30 (UTC+01:00).

Payment Terms: Payment within 60 days upon receipt of a correctly issued invoice.