What is the difference between a swing check valve and a wafer check valve?
A swing check valve uses a single hinged disc inside a full valve body — it opens fully with forward flow and closes by gravity and reverse flow, providing minimal pressure drop through the valve. Swing checks are best for larger diameters (DN50–DN1200), low-velocity clean service, and applications where the valve body weight is acceptable. A wafer (dual plate) check valve is a compact device that fits between pipe flanges with two spring-loaded plates that close rapidly when flow stops or reverses. Wafer checks are significantly lighter (up to 80% less weight), much shorter in face-to-face dimension, and close faster to reduce water hammer. Choose swing check for minimal pressure drop and large diameters; choose wafer check for space-constrained installations and fast-closing backflow prevention.
Where are check valves used?
Check valves are universally used wherever backflow prevention is required to protect equipment and ensure system safety. Typical installations include: pump discharge lines (protecting pumps from reverse rotation damage upon shutdown), compressor discharge piping (preventing high-pressure backflow), boiler feedwater systems, steam condensate return lines, water and wastewater pump stations, fire protection risers and sprinkler systems, pipeline cross-connection prevention, tank fill systems, heat exchanger bypass circuits, chemical injection points, and any location where reverse flow could cause contamination, equipment damage, or process upset. TANGGONG supplies check valves for all of these applications across 35+ countries.
Can a check valve be installed vertically?
Yes, certain check valve types function reliably in vertical (upward flow) pipelines. Piston check valves with spring assistance are ideal for vertical installation — the spring ensures positive closure regardless of orientation. Wafer and dual plate check valves with spring-loaded plates work in any orientation, including vertical upward flow. Swing check valves can be installed vertically with upward flow — the disc opens by flow pressure and closes by gravity when flow stops (but require positive flow to stay open). Ball check valves with gravity-assisted closure work in vertical upward flow. TANGGONG recommends specifying installation orientation when ordering so we can configure spring settings and verify the model's suitability.
What causes check valve water hammer and how to prevent it?
Check valve water hammer occurs when a sudden reversal of flow slams the valve disc closed, creating a high-pressure shock wave that travels through the piping system. This typically happens when: (1) the valve closes too slowly and flow reversal is already underway when the disc seats, (2) the valve is oversized and the disc never fully opens (flutters), or (3) the piping system has long runs where fluid momentum creates high reverse velocity. Prevention methods: use spring-loaded wafer or dual plate check valves that close before reverse flow develops; install piston check valves with short stroke and spring-assisted or damped closure; add external hydraulic dampeners or dashpots on large swing check valves; properly size the valve so normal flow keeps the disc fully open without flutter. TANGGONG's dual plate and piston check valves are specifically designed for non-slam closure and minimal water hammer in high-velocity applications.
What certifications do TANGGONG check valves have?
TANGGONG check valves carry comprehensive certifications: API 594 (wafer and dual plate check valves), API 6D (pipeline valves including swing check types), BS 1868 (steel swing check valves), CE (Pressure Equipment Directive), TUV, SGS, and ISO 9001:2015 quality management. All valves undergo API 598 shell and seat leak testing before shipment. For project-specific needs, we provide EN 10204 3.1 material certificates, NDE reports (radiography, ultrasonic, PT, MT), positive material identification (PMI), and third-party inspection by Lloyd's Register, DNV, Bureau Veritas, ABS, or TUV. Fire-safe certification per API 6FA and fugitive emission testing per ISO 15848 are available on request for specific check valve models.
