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I. Cyclic Law of Volume Change

All pump heads transport media through a sealed chamber's "expansion-contraction" cycle. In reciprocating pump heads (such as plunger and piston pumps), the linear reciprocating motion of the plunger or piston causes the sealed chamber's volume to change in a pulsed manner: during the intake phase, the volume increases from minimum to maximum, creating a negative pressure to draw in the media; during the discharge phase, the volume decreases from maximum to minimum, compressing and discharging the media. This volume change curve is a sinusoidal wave, and the flow rate pulsation rate can reach 20%-30%, requiring the use of an accumulator or multiple cylinders in parallel (such as a ternary plunger pump) to offset fluctuations.

Rotary pump heads (gear and vane pumps) create a continuously changing sealed chamber through gear meshing or vane rotation. In a gear pump, for example, the sealed chamber formed by the gear valley and the pump casing alternates between the intake zone (volume increase) and the discharge zone (volume decrease) as the gears rotate, reducing the flow rate pulsation rate to 5%-10%. However, the rotation process can create "oil trapping"—the enclosed oil in the meshing area is squeezed, generating high pressure. This pressure must be released through a designed relief groove to prevent component damage.

II. Pressure and Flow Control Logic

The pump head's output pressure depends on sealing performance and structural strength. Plunger pump heads, with their precise 0.001-0.01mm clearance, create a hydrodynamic seal capable of withstanding high pressures of 100-200 MPa. Gear pump heads, on the other hand, have larger gear meshing clearances (0.02-0.05mm), requiring compensating structures such as floating sleeves to boost pressure to 30 MPa. Seal failure (such as plunger wear or blade breakage) can directly lead to a sudden drop in pressure, a key indicator of pump head failure. Flow control methods vary depending on the structure: Reciprocating pump heads precisely control single-shot displacement by varying plunger stroke (like eccentric adjustment in metering pumps), achieving a flow control accuracy of ±1%. Rotary pump heads adjust flow by varying speed, but due to the trapped oil effect, volumetric efficiency drops from 90% to below 60% at speeds below 500 rpm. Furthermore, double-acting vane pumps achieve stepless flow control by adjusting the stator eccentricity, adapting to varying operating conditions.

III. Design Logic for Media Adaptability

The pump head's structural details determine its media adaptability. When pumping clean, high-pressure media (such as hydraulic oil), plunger pump heads utilize paired, ground metal seals. When pumping media containing particles (such as slurry), piston pump heads utilize elastic seals (rubber, polyurethane) for wear compensation. When pumping high-viscosity media (such as lubricating oil), the wide tooth valley design of gear pump heads reduces flow resistance. Enhanced designs for special operating conditions represent an extension of the core mechanism: Food-grade pump heads utilize stainless steel and seamless flow paths to prevent media residue; high-temperature pump heads utilize thermal compensation structures (such as bellows seals) to offset thermal deformation; and corrosion-resistant pump heads utilize fluoroplastic linings to withstand corrosion from acidic and alkaline media. These designs are all based on maintaining the integrity of the seal chamber, ensuring stable operation of the volume change mechanism.

In summary, the core operating mechanism of a pump head can be summarized as follows: based on the cyclical volume change of the seal chamber, structural design enables precise control of pressure and flow, while seals and kinematic joints are optimized based on the media's characteristics, ultimately achieving efficient and stable fluid delivery. Understanding this mechanism is key to pump head selection, troubleshooting, and performance optimization.