api 594 vs api 598
API STD 594 Check Valves: Flanged, Lug, and Weld-on Types. API Standard 594 covers the design, materials, face-to-face dimensions, pressure-temperature ratings, and inspection, testing, and examination requirements for both types of check valves.
API 598 Valve Inspection and Testing. This standard covers the inspection, supplementary inspection, and pressure testing requirements for resilient-seat and metal-to-metal seated gate valves, globe valves, plug valves, ball valves, check valves, and butterfly valves. This relates to the buyer's inspection and any supplementary inspections the buyer may require at the valve manufacturer's facility.
1. Standard Nature and Scope
API 594:
Applicable to: Specifically designed for check valves (such as swing and lift valves), suitable for industrial pipelines in oil and gas industries to prevent backflow of media.
Core Content: Specifies the design, materials, manufacturing, and testing requirements for check valves, emphasizing sealing performance and structural integrity.
API 598:
Applicable to: Industrial valves (such as gate valves, globe valves, ball valves, check valves, etc.).
Core Content: Verifies the integrity and sealing performance of valves through shell testing and sealing testing.
2. Differences in Core Content
API 594:
Design Specification: Specifies the structural, dimensional, and material requirements for check valves.
Manufacturing Requirements: Includes the manufacturing process and quality control of key components such as the valve body, valve cover, and valve stem.
Inspection and Testing: Specifies the inspection and testing requirements for valves to ensure their performance and safety.
API 598:
Test Types:
Shell Test: Inspects the strength and leakage of pressure-bearing components such as the valve body and bonnet.
Top Seal Test: Verifies the sealing performance between the valve stem and bonnet (only applicable to valves with a "top seal" structure).
Seat Seal Test: Checks the sealing performance between the valve seat and the opening/closing element when the valve is closed.
Test Methods:
Shell Test: With the valve in a semi-open state, inject water or air into the valve cavity, pressurize to 1.5 times the maximum working pressure, and hold the pressure for ≥60 seconds (DN≤100mm) or ≥120 seconds (DN>100mm).
Top Seal Test: With the valve fully open, pressurize to 1.1 times the maximum working pressure, and hold the pressure for the same time as the shell test.
Seat Seal Test: High-pressure seal test (pressurize to 1.1 times the maximum working pressure and check for leakage on the other side) and low-pressure seal test (use air or inert gas, immerse in water and observe for bubbles).
Acceptance Criteria:
Shell Test: No visible leakage, deformation, or sweating in the valve body.
Top Seal Test: No leakage at the valve stem packing.
Seat Seal Test: No visible droplets in liquid tests; leakage ≤ permissible value in gas tests (e.g., ≤20 bubbles/minute for a DN50 valve).
3. Application Scenarios
API 594: Applicable to check valve selection in industries such as oil and gas, such as pump outlets and compressor outlets where backflow prevention is required.
API 598: Applicable to valve inspection and testing in industries such as oil and gas, ensuring valve integrity and sealing.
API 598 and API 594 Valve in stock
