Thermal Network Engineering

The urban heating network is the centralized heating system of a city. “ Blood vessel ”， Bellows compensator It ensures the safe and stable operation of the pipeline network. Core Flexible Components , the industry is currently in Renovation of Aging Pipe Networks + Smart Upgrade + Low‑carbon transformation The critical period of development.

The urban heating network is a thermal transmission system that connects heat sources—such as thermal power plants, boiler houses, and heat pumps—to heat users. The transmission medium is high‑temperature hot water or steam, and it is an essential component of urban infrastructure, directly impacting public livelihood and energy security.

I. Core Technologies and System Architecture of Thermal Pipeline Networks:

1. Pipeline Laying Methods

Direct Burial Installation : Mainstream, requires little land, offers excellent thermal insulation, and allows for rapid construction—requires supporting facilities. Directly Buried Bellows Compensator 。
Overhead installation Suitable for industrial parks and suburban areas, easy to maintain but costly.
Comprehensive Utility Tunnel : Intensive development trend, with utility pipelines for water supply and drainage, as well as power lines, laid in the same corridor.

2. Key Equipment and Accessories

Pipeline Seamless steel pipes and spiral welded pipes, externally coated with a polyurethane insulation layer.
Valve Gate valves, globe valves, and check valves are used for control and isolation.
Compensator : Addressing thermal expansion and contraction, Bellows compensator A definitive mainstay.
Other : Fixed / Guide supports, steam traps, flow meters, and insulation structures.

2. Bellows Compensator (Core Component):

1. Core Role (Pipeline Network) “ Flexible joint ” )

Absorption displacement Compensating for expansion, contraction, settlement, and vibration in pipelines. Axial, lateral, and angular displacement 。
Reduce stress : Eliminate thermal stress and prevent pipe rupture and weld cracking (approximately… **70%** Leakage incidents are related to expansion joints.
Protective bracket Reduce the thrust on the fixed supports and extend the system’s lifespan.

2. Operating Principle

Utilize Multi-layer thin-walled metal bellows Elastic deformation to absorb displacement and release stress.

3. Main Types (Commonly Used in Thermal Networks)

Table

Type	Compensation Direction	Features	Applicable Scenarios
Axial Type	Axial	Compact structure, small footprint, and easy installation.	Directly buried / Overhead straight pipe sections are the most commonly used.
Horizontal type	Horizontal	Large compensation amount requires matching tie rods.	Pipe bends and areas with limited space
Angular type	Angular	Universal rotation, multiple units working in tandem.	Complex piping systems, multi‑directional displacement
Directly Buried Type	Axial / Lateral	Corrosion‑resistant, soil‑pressure resistant, maintenance‑free	Directly buried hot water pipeline network, mainstream
Pressure-balanced	Axial	Eliminates internal pressure thrust, eliminating the need for large fixed piers.	High-pressure, large-diameter pipelines

4. Material and Performance

Mainstream materials ： 304/316L Stainless steel (Corrosion‑resistant, long service life), carbon steel (economical).
Work parameters Temperature **-20 °C ~450 °C Pressure 0.6–4.0 MPa** Fatigue life **≥1000 Next loop **。
Lifespan : Design Life of High-Quality Stainless Steel Direct-Buried Expansion Joints 30 Year 。

5. Selection and Installation Key Points

Based on Pressure, temperature, displacement, medium, installation method Selection.
Directly Buried Pipeline Network First External Pressure Directly Buried Type , prioritize overhead pipe networks General Axial Type 。
Installation required. Guide support , to prevent instability; pre‑stretching is strictly prohibited. / Overcompressed.

3. Industry Development Trends:

1. Technological Upgrade

Smartization IoT, digital twins, intelligent inspections, predictive maintenance.
Decarbonization : Fourth-generation low-temperature heating ( ≤65 °C ) – Multi-energy complementarity, nuclear energy / Geothermal heating demonstration.
Efficiency enhancement : Reduce heat loss to 15% The following ( 2030 Objective) Long-distance transportation technology.

2. Market Hotspots

Renovation of Aging Pipe Networks : Batch replacement of compensators, Stainless Steel Direct-Buried Type Become standard.
Comprehensive Utility Tunnel Construction : Driving demand for high‑quality compensators.
Southern Heating Expansion : Household division in the Yangtze River Basin / Centralized heating is on the rise.

3. Trends in the Bellows Expansion Joint Industry

Product Upgrade High corrosion resistance, long service life, integrated design, maintenance-free.
Standardization : Implement the “Code for Design of Urban Heating Networks” ( CJJ/T34-2022 ), forcibly replace aging expansion joints.
Intelligentization : With sensor Intelligent Compensator , real‑time monitoring of displacement, stress, and leakage.

IV. Summary:

The urban heating network is a critical piece of infrastructure for people’s livelihood and energy supply. Bellows compensator It ensures its safe and efficient operation. “ Heart components ” The industry is shifting from “ Protection-oriented ” Toward “ Low-carbon + Wisdom + Service-oriented ” Driven by both transformation, renovation of existing facilities, and new construction, the market is creating vast opportunities for core equipment manufacturers such as bellows expansion joints.