Views: 0 Author: J-VALVES Publish Time: 2024-06-26 Origin: Site
In industrial pipeline systems, the connection methods of GATE VALVES directly affect the sealing performance, maintenance costs and service life. This article provides a reference for engineering selection by comparing the three mainstream connection methods: flange connection, threaded connection and welded connection.
I. COMPARISON TABLE OF CONNECTION METHODS
Comparison Dimension Flange Connection Threaded Connection Welded Connection
Comparison Dimension | Flange Connection | Threaded Connection | Welded Connection |
Applicable Diameter | DN15 - DN600 | DN15 - DN50 | Applicable for full bore |
Pressure Rating | 150LB - 2500LB | Below 800LB | Up to 4500LB |
Temperature Range | -29°C - 350°C | -20°C - 120°C | -269°C - 1200°C (Special materials can reach 3430°C) |
Sealing Performance | Relies on gaskets and bolt preload, requiring regular maintenance | Relies on thread tape/sealant, prone to leakage due to vibration | Permanent seal, no leakage risk |
Installation Difficulty | Requires alignment of flange holes, complex operation | Quick tightening, simple operation | Requires professional welding skills, irreversible |
Maintenance Cost | Detachable for replacement, relatively high maintenance cost | Thread is easily damaged during disassembly, difficult to maintain | Non-detachable, maintenance requires cutting of pipelines |
Economy | High cost of flange + bolts | Lowest cost | Low initial cost, high maintenance cost in the later stage |
Typical Applications | Main pipelines for oil and natural gas | Household water heating, instrument pipelines | High-temperature and high-pressure pipelines in nuclear power plants and ethylene projects |
II. DETAILED ANALYSIS
1.Flange Connection
·Advantages:
l Standardized interfaces with strong adaptability, supporting multiple flange types such as RF and RTJ.
l Detachable design, facilitating valve replacement or system expansion.
·Disadvantages:
l Bolts are prone to loosening and leakage at high temperatures (>350°C).
l It occupies a large space and is not suitable for compact installation scenarios.
·Applicable Scenarios:
Medium and high-pressure systems such as petrochemical and LNG stor
2. Threaded Connection
·Advantages:
l Quick installation without the need for professional tools, suitable for pipelines below DN50.
l Low cost and widely used in low-pressure water heating systems.
·Disadvantages:
l Threads are easily loosened due to vibration and require regular inspection of the sealing performance.
l Not suitable for high-temperature, high-pressure or corrosive media.
·Applicable Scenarios: Low-pressure environments such as household water supply and pressure gauge interfaces.
3. Welded Connection
·Advantages:
l No leakage risk, suitable for extreme temperatures/pressures.
l Compact structure without the weight of additional connectors.
·Disadvantages:
l Requires professional welders, and disassembly requires cutting of pipelines.
l Weld seams may fail due to medium corrosion or vibration fatigue.
Applicable Scenarios:
Long-term high-load systems such as nuclear power plants and ethylene cracking units.
III. SELECTION SUGGESTIONS
1. Give priority to flange connection: For medium and high-pressure pipelines that require frequent maintenance or system expansion (such as refineries).
2. Give priority to threaded connection: For low-pressure, small-diameter and vibration-free scenarios (such as household water supply).
3. Give priority to welded connection: For harsh working conditions with ultra-high temperature/high pressure and requirements for permanent sealing (such as nuclear reactor cooling systems).
IV. PRECAUTIONS
1. Flange Connection: When choosing RF or RTJ flange types, it is necessary to match the pipeline pressure rating.
2. Threaded Connection: Be sure to use NPT standard threads and wrap sealing tape.·
3. Welded Connection: Weld seam inspection should be carried out in accordance with the ASME B31.3 specification.
