Engineering methodology for selecting shut-off valves in the design of pipeline systems
The correct selection of pipe fittings is not only a matter of functionality, but also the foundation of the economic efficiency of the project. Errors at the design stage lead to excessive redundancy, when the weight of the reinforcement grows to 25% of the weight of the entire system, and the installation density exceeds 10 units for every 100 meters of pipe.
In order to avoid unnecessary costs and ensure safety, it is necessary to follow the system selection algorithm, supported by the output control on the test equipment.
Reinforcement selection algorithm
Stage 1. Technological audit of operating conditions
At the initial stage, the target purpose and parameters of the working environment are determined.
- Important limitation: According to engineering standards, shut-off valves are not recommended for viscous, solidifying media, as well as media with a high content of abrasives, pulps and slurries.
- Priority application: shut-off valves are an ideal solution for refrigeration and cryogenic equipment, as well as for systems with high operating pressure (Pp≥6.4 MPa).
Stage 2. Definition of quality criteria
The requirements for tightness and reliability are established. Valves are chosen in situations where it is critically important:
- High tightness of the locking body (due to the planar contact).
- Tightness relative to the external environment (especially in bellows design).
- Maintainability under operating conditions.
Stage 3. Selection of structural materials
The body material is selected based on chemical aggressiveness and ambient temperature (from cryogenic temperatures up to +600 ° C). Cast iron, carbon, alloy and heat-resistant steels, titanium or polymers are used.
Stage 4. Geometric and mounting parameters
The nominal diameter (DN) is determined. The optimal range of shut-off valves is DN ≤ 20 mm (recommended) and up to DN 200 mm (allowed). With large diameters, the use of valves becomes economically and technically impractical due to a sharp increase in spindle forces.
Stage 5. Management and automation
The choice between a manual flywheel and a drive (electric, pneumatic, hydro). For valves, it is important to take into account that they have high hydraulic resistance, which requires increased drive power at high pressure drops.
Stage 6. Verification and bench tests
This is a critical stage that is often omitted in theory, but which is mandatory in practice. Any theoretical choice must be confirmed by testing on the shut-off valve stands.
The role of test benches in the design and acceptance process
Even a perfectly matched valve can become a "weak link" in the system due to hidden defects.