Pressure control for stainless steel seamless pipes must be implemented throughout the entire production, design, and use process. The key is to ensure safe operation within the rated pressure and avoid rupture or leakage caused by overpressure through material selection, process optimization, quality inspection, and standardized use.
1. Production: Controlling Pressure Capacity at the Source
The production process determines the fundamental pressure-bearing performance of seamless pipes. Key control steps are as follows:
Raw Material Control
Select standard stainless steel billets (such as 304 and 316L) to ensure that mechanical properties such as tensile strength and yield strength meet standards. Different grades of stainless steel have different heat and pressure resistance characteristics and must be matched according to the application. For example, 316L offers superior corrosion resistance and high-temperature pressure resistance than 304.
Rolling and Heat Treatment Processes
Cold drawing and hot rolling processes are used to control the uniformity of pipe wall thickness and outer diameter accuracy. Excessive wall thickness deviation can lead to localized pressure concentrations.
Subsequent heat treatment (such as solution treatment) can eliminate processing stresses, improve the material’s toughness and fatigue resistance, and prevent cracking under long-term pressure. Hydraulic Pressure Testing
Each batch of seamless pipes undergoes a hydraulic pressure test before shipment. According to standards (such as GB/T 14976), a test pressure of 1.5 times the rated working pressure is applied and maintained for a specified period (usually more than 30 seconds). Leakage and deformation are observed, and products that fail to meet the pressure requirements are screened out.
2. Design Phase: Determine Pressure Parameters Based on Operating Conditions
During the design phase, the pressure limits of seamless pipes must be clearly defined based on actual usage scenarios. The key steps include:
Determine the Rated Working Pressure (PN)
The rated pressure is calculated using a formula based on the pressure and temperature of the conveying medium (such as water, steam, or corrosive fluids), as well as the nominal diameter and wall thickness of the pipe. For example, with the same wall thickness, small-diameter pipes generally have higher pressure-bearing capacity than large-diameter pipes.
Reserve a Safety Factor
During design, consider the impact of medium and temperature fluctuations on pressure. A safety factor of 1.2-1.5 times should be reserved to prevent the actual pressure from approaching or exceeding the pipe’s maximum pressure rating. Supporting Pressure Control Components
Pipeline systems require installation of pressure gauges, safety valves, and pressure-reducing valves to monitor pressure in real time and automatically relieve pressure. For example, when pressure exceeds a set value, the safety valve opens to release pressure, protecting the seamless pipe from damage.
3. Operational Aspects: Avoiding Overpressure
Operating procedures during daily use are key to maintaining stable pressure:
Regular Inspection and Maintenance
Regularly inspect pipelines for corrosion, wall thickness reduction, and joint leaks. This is especially true for pipelines transporting corrosive media or high-temperature fluids. Corrosion can weaken the pipe material and reduce its pressure-bearing capacity.
Regularly calibrate pressure gauges and safety valves to ensure the accuracy of pressure monitoring and protective components.
Controlling Media Operating Conditions
Avoid frequent fluctuations in media pressure and temperature. For example, slowly increase the pressure when starting a pump to prevent transient pressure shocks from damaging the pipe. Overheating is strictly prohibited. High temperatures can degrade the mechanical properties of stainless steel, reducing its pressure-bearing capacity.
Emergency Management of Overpressure Situations
If an abnormally high pressure is detected, immediately stop the relevant equipment, open the pressure relief valve to reduce the pressure, and investigate the cause of the overpressure (such as a clogged valve or pump failure). Resume operation only after the problem is resolved.
Cherry
Website: www.jinyoumetal.com
Email: Cherry@jinyoumetal.com
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