In the equipment procurement and engineering construction of industrial flue duct system, the technical specification of flue expansion joint is the core technical document for bidding, contract signing and quality acceptance. A complete and standardized technical specification can not only ensure that the expansion joint meets the requirements of working conditions, but also effectively divide the responsibilities of both supply and demand parties to avoid later disputes. This paper will systematically explain the main points of the technical specification of flue expansion joint from the aspects of compilation basis, core chapters, technical parameters, material requirements and acceptance criteria, so as to provide professional reference for engineering design and purchasing personnel.
I. What is the technical specification of flue expansion joint?
The technical specification of flue expansion joint is a technical document prepared by the buyer (buyer) during the purchase process of flue expansion joint equipment. It is used to specify the technical requirements of the functional design, structure, performance, manufacture, installation and testing of the expansion joint。 After confirmation by both suppliers and demanders, this document will be used as an attachment to the ordering contract, and has the same legal effect as the main text of the contract。
The preparation of technical specifications follows the following basic principles:
- Minimum requirements: The specification sets out the minimum technical requirements, which the seller must meet
- Standard Application Principle: In case of contradiction, stricter standards shall be implemented
- Deviation must be confirmed in writing: If the deviation is not submitted in writing, it will be deemed that the requirements of the specification have been fully accepted
Scope of Application of Technical Specifications and Project Overview
The following contents shall be specified at the beginning of the technical specification:
1. Project background
- Project name, construction scale (unit capacity)
- Applicable range of expansion joints (such as desulfurization system flue, boiler flue duct, etc.)
Equipment operating environment
- Site location, meteorological conditions (temperature, wind, rain and snow load, etc.)
- Equipment placement location (indoor/outdoor open air)
3. Overall requirements
- The Seller shall provide mature, reliable and technologically advanced products
- The seller is fully responsible for the equipment (including subcontracting and purchasing products)
- Equipment coding with KKS identification system
3. Key Points of Compiling Technical Parameter Table
The technical parameter sheet is the core attachment of the technical specification for flue expansion joints. The following key data should be filled out one by one：
| Parameter category | Contents of specific parameters |
|---|---|
| Equipment information | Equipment name, number, quantity |
| Interface Size | Sectional dimensions (length × width or diameter), mode of connection (welded/flanged) |
| Operating condition | Design pressure/temperature, use pressure/temperature, media composition (dust content, corrosive components) |
| Compensation requirements | Requirements for axial compensation, transverse compensation and angular displacement |
| Special requirements | Anti-corrosion requirements, heat preservation requirements, anti-wear measures |
Note: The parameters of the original flue and the net flue of the desulfurization system differ greatly. The original flue temperature is usually 150℃, which can reach 350℃ in a short time, and the dust content is high; The net flue temperature is low (about 50~80℃), but the moisture content is high and the corrosion is strong。
IV. Specification for the preparation of equipment performance requirements
The technical specifications need to make clear restrictions on the performance of expansion joints:
4.1 Basic Performance Requirements
- Displacement compensation: The expansion joint shall be able to absorb all the axial and radial displacements of the flue, and it is prohibited to transmit displacement and force to the connecting equipment
- Sealing requirements: The connection with the flue shall have 100% tightness, and the air leakage rate usually requires ≤2%
- Pressure margin: can withstand the maximum design positive/negative pressure of the system plus 1000Pa margin
- Design life: The overall design life shall not be less than 30 years, and the replacement cycle of wear parts shall be specified
- Overall supply principle: The expansion joint should be manufactured in the whole workshop, and the whole supply should be made in principle. If it needs to be disassembled for shipping reasons, it shall be disassembled only to meet the minimum scope of transportation, and temporary fixing brackets must be attached to ensure installation accuracy
4.2 Structural Design Requirements
- Rectangular expansion joint connectors shall be formed by cold-forming carbon structural steel
- Unnoted tolerances shall be carried out according to the requirements of Class B and F of JB/T 5000.3
- The matching washer of the large tie rod shall be of spherical type to ensure uniform force
- Expansion joint frames are manufactured and drilled in the shop floor
V. Material and anti-corrosion requirements
5.1 Non-metallic expansion joint (conventional flue)
5.2 Non-metallic expansion joint (desulfurization and anti-corrosion flue)
- Structural parts: Q235-A lined with glass flakes or FRP corrosion protection
- Skin: fluororubber cloth + polytetrafluoroethylene + glass filament cloth and other composite layer
- Condensate discharge: setting D N150 drain connector (FRP material)
5.3 Metal Expansion Joints
VI. Requirements for painting, insulation and packaging
6.1 Painting
- Rust removal grade: Jet/ejection rust removal is not less than Sa2, manual rust removal is not less than St2
- Coating requirements: Both bottoms and two sides, each coat of primer ≥30 μ m, each coat of topcoat ≥30 μ m
- Stainless steel, galvanized steel need not be painted
6.2 Insulation Requirements
- Equipment with external temperature> 50℃ shall be insulated
- The seller shall provide the thermal insulation design and support, and the main thermal insulation layer shall be responsible for the buyer
- Expansion joints containing insulation layer shall be able to be disassembled for maintenance
6.3 Packaging and Transportation
- All processing waste, rust and grease must be removed before assembly of the expansion joint
- All open ends shall be protected against the entry of debris
- Equipped with temporary supports to prevent deformation during transportation, and attached with eye-catching warning signs, removed immediately after installation
- The sealing surface of the expansion joint shall be coated with rust inhibitor and protective measures shall be taken
Quality Assurance and Acceptance Standards
7.1 Applicable Standard Specifications
The technical specification shall explicitly quote the following main standards:
7.2 Quality Assurance Requirements
- The seller shall provide product inspection certificate and material inspection report
- If the expansion joint is damaged due to manufacturing problems within 8000 hours from the first start, the seller shall repair or replace it free of charge
- The main materials, expansion and sealing shall be functionally inspected and tested according to the drawings
7.3 Performance Guarantee Value
The Seller shall commit to the following performance indicators：
- Leakage amount
- Expansion and contraction amount
- Service life
- Stress tolerance
Scope of Supply and Data Delivery
8.1 Scope of Supply
The Vendor's Supply shall include but not limited to：
- Expansion joint body
- Flanges and connectors
- All fasteners and seals
- Spare parts during warranty period
- Special installation and maintenance tools
8.2 Technical Data Delivery
The seller shall provide within the specified time after the contract is signed：
- General shape and installation drawing (including weight and interface size)
- List of Wear Parts and Supply List
- Installation, operation and maintenance instructions
- Product Quality Certificate
IX. SUMMARY
Compiling a complete and rigorous technical specification for flue expansion joints is the key to ensure reasonable selection, standardized procurement and well-documented acceptance of expansion joints. The core points are summarized as follows:
- Clear general principles: clear scope of application, definition of responsibility and principle of standard application, which is the "legal basis" of the specification。
- Complete parameters: Fill in the equipment technical data sheet parameter by parameter, covering key information such as cross-section size, compensation amount, temperature and pressure, media composition, etc。
- Performance constraints: clarify core indicators such as sealing (air leakage rate ≤2%), displacement compensation ability, pressure margin, and design life (≥30 years)。
- Material specification: distinguish conventional flue from desulfurization and anti-corrosion flue according to working conditions, and specify the specific material requirements of metal parts, deflectors, skin, heat insulation layer and anti-corrosion layer。
- Evidence of acceptance: Quality certification documents and performance assurance values are required by referring to GB/T 12777, EJMA and other current standards。
- Clear responsibility: clear warranty period (such as free replacement within 8000 hours) and after-sales service requirements 。
It is suggested that when preparing the technical specification book, users can refer to the mature models of desulfurization engineering in electric power industry or energy and chemical industry, and adjust the parameters according to the specific project working condition data. Before the specification is issued, it must be countersigned and confirmed by thermal control, electrical and other professionalsTo ensure that the content is complete and there are no technical omissions. Only in this way can the expansion joint products with reliable performance and durability be selected to ensure the long-term safe and stable operation of the flue system.