1. Structural form
Core features: It has four fluid ports (usually marked as A, B, C, D) and a ball with a specific channel inside.
Ball channel: It is the key to the four-way function. Common forms are:
L-type channel: There are two L-shaped channels at 90 degrees to each other on the ball. This is the most common form of four-way ball valve.
T-type channel/X-type channel: It is relatively rare. The ball channel is T-shaped or cross-shaped (X-shaped), which can provide different flow path combinations.
Valve body structure:
One-piece/two-piece/three-piece: Similar to ordinary ball valves, but the structure is more complex to accommodate four ports. The three-piece type (one main valve body + two side covers) is the most common and easy to maintain and process.
Port connection: Flange, thread (NPT, BSP), butt welding, clamp (sanitary grade), etc.

Operation method: Manual (handle, gear box), pneumatic, electric, or hydraulic actuator drives the valve stem to rotate 90 degrees (usually) or 180 degrees (depending on the channel design), driving the ball to rotate.

2. Working Principle
Core Function: By rotating the ball 90° or 180°, the connection relationship between its internal channel and the four valve body ports is changed to achieve the switching, confluence or diversion of the fluid flow direction.
2.1 L-channel four-way ball valve
Structural principle
Ball design Ball internal processing Two L-shaped channels at 90° to each other, the two channels are orthogonal at the center of the ball but do not communicate with each other (similar to two independent L-tubes crossing).
The channel opening is located on the surface of the ball, corresponding to the four ports of the valve body (A/B/C/D).
Flow path switching mechanism (90° rotation operation)
After L channel 1 rotates: connects A port ↔ D port
After L channel 2 rotates: connects B port ↔ C port
→ The flow path is completely cross-switched (such as: hot medium A→D, cold medium B→C).
L channel 1: connect port A↔port B
L channel 2: connect port C↔port D
→ form two pairs of independent flow paths (e.g. hot medium A→B, cold medium C→D).
Position 1 (0°):
Position 2 (90°):
Key features
No mixing position: In any position, the A/B flow path and the C/D flow path will never communicate with each other to avoid cross contamination of the media.
Dual flow path synchronous switching: a single 90° operation changes the direction of the two flow paths at the same time.
Shutoff capability: At the 0° or 90° position, all ports are covered by the channel and there is no completely closed state.
Typical application scenarios
Heat exchanger flow direction switching: quickly reverse the cold/hot medium path (e.g. A→B is heating, and after switching, A→D is cooling).
Reactor inlet and outlet interchange: realize the feed/discharge direction exchange (e.g. A in B out → A out D in).
Dual system isolation switching: such as the backup system is enabled (the main route A-B switches to the backup route A-D).
2.2 T-channel/X-channel four-way ball valve
Structural principle
1. Ball design
T-channel: The inside of the ball is a single T-shaped channel (one in and two out or two in and one out structure).
X-channel: The inside of the ball is a cross-through channel (four ports are fully connected).
2. Flow path switching mechanism (usually requires 180° rotation)
At any position, the four ports are partially connected (such as: A→B+D, C→B+D).
The rotation angle adjusts the flow distribution ratio (such as: A→B/D equal flow at 90°).
Position 1 (0°): T vertical arm connects A↔B, one end of the horizontal arm connects to C, and the other end is closed.
→ A→B (mainstream) + A→C (divider)
Position 2 (90°): T vertical arm connects A↔D, one end of the horizontal arm connects to B, and the other end is closed.
→ A→D (mainstream) + A→B (divergence)
Position 3 (180°): T vertical arm connects C↔D, one end of the horizontal arm connects to A, and the other end is closed.
→ C→D (mainstream) + C→A (divergence)
Typical flow path of T-type channel (operated in 180° steps): Note: The specific flow path depends on the design of the T-shaped opening direction.
X-type channel flow path (symmetrical diversion):
3. Key features
Multi-port interconnection: T/X-type channel is essentially a three-way or four-way mixture, and a single flow path cannot be completely isolated.
Diversion/merging function: suitable for media distribution or mixing conditions (such as: A port inlet, B/D port diversion).
No completely closed position: all positions have at least three ports interconnected.
Typical application scenarios
Media distribution system: distribute a single input to a dual outlet (such as: T-type channel realizes A→B+C).
Mixing process: combine two media for output (e.g. X-type channel realizes A+C→B).
Symmetrical flow regulation: X-type channel is used in situations where flow needs to be evenly distributed (e.g. parallel branch of heat exchanger).
2.3 Technical design points
1. L-type channel:
The orthogonal accuracy of the two L-channels must be ensured (error ≤ 0.05°) to avoid flow crosstalk.
The sealing surface of the ball and the valve seat must fully cover the four ports to prevent internal leakage.
2. T-type/X-type channel: The flow channel needs to transition smoothly to reduce turbulence and pressure drop during diversion.
The angle positioning accuracy is required to be high (±1°) to ensure the flow distribution ratio.
Note: T-type/X-type four-way valves are rarely used in practice because their functions can be achieved through simpler three-way valves or multi-valve combinations. L-type has become the mainstream design of four-way valves due to its dual flow path independent switching capability.

3. Core Technology
1. Sealing Technology:
Valve Seat Sealing: Two-way (or one-way) reliable sealing must be achieved between the ball and the valve seat at all four port positions. Involving soft seals (PTFE, PEEK, rubber) or metal seals (hard alloy cladding).
Valve Stem Sealing: Dynamic rotary sealing to prevent leakage of the medium. Usually a stuffing box (multiple sets of packing rings) or a bellows seal (zero leakage requirement) is used.
2. Low Torque Design: Reduce operating torque, especially for large-diameter or high-pressure differential conditions. Involving:
Optimizing ball roundness and surface finish (mirror finish).
Low friction coefficient valve seat material (such as PTFE composite material).
Reducing the contact width/area of the sealing surface (under the premise of ensuring sealing).
Valve seat elasticity design (such as spring-loaded valve seat).
3. Flow channel optimization: Design full-bore or reduced-bore flow channels, optimize the shape of the fluid channel (such as Venturi type), reduce flow resistance and pressure drop, and reduce the risk of cavitation/flash evaporation.
4. Accurate channel processing and positioning: The geometric accuracy and finish of the complex channels (L, T, X) on the ball and the precise angle positioning of the ball in the valve body are the basis for achieving correct flow switching and leak-free sealing.
5. Material compatibility and treatment: Select the appropriate material combination and surface hardening treatment (such as hard chrome plating, supersonic spraying WC/Co) for different working conditions (corrosion, wear, high temperature, low temperature).

4. Key points of design
1. Flow path definition and verification: Clearly define the flow path connection relationship under all operating positions and verify it through models or prototypes.
2. Ball channel geometry design: Channel angles, intersection points, and dimensions must be accurately calculated to avoid flow path interference, dead zones, or excessive stress concentration.
3. Sealing system design:
Valve seat structure (floating, fixed, spring-loaded).
Calculation and optimization of sealing pressure ratio (ensuring the minimum pressure ratio required for sealing, while avoiding excessive pressure ratio leading to high torque or seat damage).
Thermal expansion compensation design (high temperature conditions).
Fire safety design (metal seals can still maintain a certain seal after soft seals fail).
4. Torque calculation and balance: Accurately predict the opening and closing torque to provide a basis for actuator selection. Optimize the design to balance the sealing force of each port and reduce the total torque.
5. Structural strength and stiffness: The valve body, ball, and valve stem must withstand medium pressure (especially pressure test pressure), operating force, and possible external loads. Commonly used in finite element analysis (FEA).
6. Anti-blowout stem design: Ensure that the stem will not be blown out of the valve body under pressure.
7. Operating angle and limit: Accurately set and reliably limit the rotation angle of the ball (usually 90° or 180°) to ensure that the flow path is accurately switched in place.
8. Installation and maintenance friendliness: Consider the bolt layout space, grease nipple position, and ease of disassembly and assembly, etc.

5. Key points of production control
1. Raw material control: Strictly inspect the material certification (MTC) and physical and chemical properties of raw materials such as valve body, ball, valve stem, valve seat, packing, etc., and conduct re-inspection (PMI, mechanical properties) when necessary.
2. Key dimensions and tolerances:
Ball: ball diameter roundness, ball channel size/angle/position, surface roughness (Ra value).
Valve seat hole: hole diameter, roundness, position, surface roughness.
Valve body: flow channel size, port flange surface/thread accuracy, center distance, coaxiality.
Valve stem: diameter, keyway/flat square size, surface hardness/roughness.
Assembly clearance: ball and valve seat clearance, valve stem and packing/bearing clearance.
3. Surface treatment and hardening: Strictly control the hardened layer thickness, hardness, bonding force and surface finish (such as grinding and polishing) of the ball and valve seat sealing surface.
4. Cleanliness control: All parts must be strictly cleaned before assembly to remove iron filings, oil stains, and impurities to prevent obstruction or damage to the sealing surface. Clean assembly environment (especially for food, medicine, and high-purity conditions).
5. Assembly accuracy control:
Ensure the precise alignment of the ball, valve seat, and valve body port.
The matching accuracy of the valve stem and the ball groove.
Even compression of the packing gland.
Accurate installation and commissioning of the operating angle limit device.
6. Sealing test:
Valve seat sealing test: Perform a bidirectional (or unidirectional as required) air pressure or hydraulic sealing test on each valve seat. Common method: Close one port, pressurize the adjacent port, and check the leakage of the other two ports (in accordance with API 598, ISO 5208 and other standards).
Valve stem sealing test: Test the sealing performance of the stuffing box or bellows.
Shell strength test: Verify the pressure bearing capacity of the valve body.
7. Functional test: Operate the valve throughout the process to check whether the flow path switching is smooth and in place, and whether there is any jamming or abnormal noise.
8. Torque test: Measure and record the opening and closing torque to ensure that it is within the design range.
9. Documentation and traceability: Complete quality records (material reports, inspection records, test reports, heat treatment records, non-destructive testing reports, etc.) and product identification (serial number) to ensure traceability.
6. Material
Valve body/valve cover:
Commonly used: carbon steel (WCB, WCC, LCB), stainless steel (CF8/304, CF8M/316, CF3/304L, CF3M/316L), alloy steel (WC6, WC9, C5, C12).
Special: Duplex stainless steel (F51/2205, F53/2507), Hastelloy (C276, B2), Monel (Monel 400/K500), titanium and titanium alloys, nickel-based alloys (Inconel 625, 825).
Low temperature: Austenitic stainless steel (316L), low temperature carbon steel (LCB, LCC).
Sphere:
Commonly used: stainless steel (304, 316, 316L), surface hardening treatment (hard chrome plating, spray welding/surfacing Stellite 6/21, supersonic spraying WC-Co).
Special: integral hardening alloy (such as 17-4PH precipitation hardening stainless steel), Monel, Hastelloy, titanium alloy.
Valve seat/sealing ring:
Soft seal: PTFE (pure polytetrafluoroethylene), RPTFE (reinforced polytetrafluoroethylene), PCTFE (polychlorotrifluoroethylene), PEEK (polyetheretherketone), Nylon (nylon), various rubbers (EPDM, NBR, Viton/FKM).
Metal seal: Stainless steel, Stellite alloy, tungsten carbide hard alloy.
Valve stem:
Common: Stainless steel (304, 316, 17-4PH, 416, 440C).
Special: Monel, Hastelloy.
Surface hardening treatment (nitriding, chrome plating).
Packing:
Common: Flexible graphite (ring), PTFE (V-ring, braided packing), graphite + PTFE composite packing.
Special: Spring-loaded PTFE packing system, bellows seal (metal).
Bolts/nuts: Carbon steel (ASTM A193 B7 / A194 2H), stainless steel (A193 B8/B8M, A194 8/8M), alloy steel.
7. Applicable working conditions, temperature, pressure Applicable working conditions:
Heat exchange system (switching heating/cooling medium flow direction).
Reactor/container inlet and outlet switching. Multi-source or multi-way distribution system (such as oil depot loading and unloading).
Process flow switching (such as A/B line switching, cleaning/production switching).
Instrument air/factory air system switching. Compressor/pump loading/unloading or circulation.
Purge and drainage system.
CIP/SIP (online cleaning/sterilization) process in food, beverage and pharmaceutical industries.
Main uses: Occasions where it is necessary to switch flow paths, change medium flow direction, merge or split.
Typical applications:
Applicable temperature: a wide range, depending on the material and sealing form.
Soft seals: Generally -50°C to +200°C (PTFE upper limit about 230°C, PEEK can reach 300°C+, rubber depends on the type such as FKM about -20°C to 200°C).
Metal seals: Up to 800°C (special alloy design), low temperature can reach -196°C (liquid nitrogen) or lower.
Common range: -196°C (deep cold) to +550°C (high temperature).
Applicable pressure: Range from vacuum to ultra-high pressure.
Standard grade: ANSI Class 150, 300, 600 (PN16, PN40, PN100).
Medium and high pressure: Class 900, 1500, 2500 (PN160, PN250, PN420).
Ultra-high pressure: Can reach Class 4500 (PN760) or higher (special design).
Note: Maximum allowable working pressure (MAWP) decreases with increasing temperature (refer to valve material pressure-temperature rating standards, such as ASME B16.34).
8. Stem Packing
Function: Form a seal where the valve stem passes through the valve cover to prevent the medium from leaking along the valve stem to the external environment. Common types:
Flexible graphite packing: High temperature resistance (up to 650°C+), good chemical resistance, self-lubricating, and low thermal expansion coefficient. It is the current mainstream choice.
PTFE packing (V-ring, braided packing): Excellent corrosion resistance, low friction coefficient (low torque), but limited temperature resistance (usually <230°C), and there is a cold flow problem.
Composite packing (such as graphite impregnated PTFE): Combines some advantages.
Spring-loaded PTFE packing system: Provides continuous sealing force compensation and better sealing effect.
Key control points: Material grade, density, number of rings, preload (applied through gland bolts, tightened evenly according to manufacturer's requirements to avoid high torque due to compression or leakage due to insufficient pressure), anti-extrusion ring at the bottom of the stuffing box.
9. Seat
Function: Installed in the valve body port, tightly fit with the surface of the ball to achieve valve closure and sealing.
Key types and features:
Material: Stainless steel (304, 316, 17-4PH), Stellite 6, 21, tungsten carbide.
Advantages: High temperature, high pressure, wear, abrasion, erosion, fire safety (can still maintain sealing after soft seal failure).
Disadvantages: Initial sealing requires extremely high processing accuracy (mirror grinding required); torque is usually large; sensitive to particles (easy to scratch); requires higher sealing pressure ratio.
Materials: PTFE, RPTFE, PCTFE, PEEK, Nylon, rubber (EPDM, NBR, FKM).
Advantages: Excellent initial sealing (up to bubble level), low torque, certain elasticity to compensate for minor defects or thermal deformation.
Disadvantages: Not as resistant to heat, pressure, wear and abrasion as metal seals; may be eroded by high-speed fluids; easy to swell or degrade under certain media; poor fire safety (auxiliary metal seals need to be designed).
Soft seal valve seat (elastic seal):
Metal seal valve seat (rigid seal):
Spring-loaded valve seat: Regardless of soft or hard seal, a spring (disc spring, coil spring) is installed behind the valve seat. Advantages: Provide initial preload to ensure low-pressure sealing; compensate for preload loss caused by temperature and wear; reduce operating torque fluctuations. Design key: valve seat structure (geometry), sealing surface width, material matching (with ball, medium), spring force design, and fire protection design considerations.

Summary of application scenarios
L-type four-way valve: switching adsorption towers in air separation equipment (cyclic switching of A/B towers).
T-type four-way valve: multi-way feed control of reactor (acid + alkali + solvent confluence).
High temperature type: metal hard seal + graphite packing is used for steam system (350℃/40 bar).
Low temperature type: LNG loading and unloading (-162℃) uses cryogenically treated 316L+PEEK valve seat.