SS Venturi Injector

Product Overview

The SS Venturi injector is the all-stainless variant of our standard Venturi line, intended for installations where the body material must withstand high temperature, high pressure, or aggressive chemistry that would attack the PP or PVC alternative. The body is precision-machined from solid SS316L bar stock or fabricated from SS316L plate (for DN100 and above) with a fully welded construction. The throat is machined to a tolerance of ±0.05 mm, which is what allows the device to deliver a repeatable discharge coefficient C_d = 0.60-0.70 across the production run — important when multiple injectors are deployed in parallel and must share the same flow characteristic.

Three service environments drive the SS Venturi specification. The first is high-temperature water and CIP in food, beverage, and dairy plants, where the cleaning cycle reaches 80-95°C with 1-3% NaOH and 1% HNO₃ rinses. PP softens above 60°C and is not usable here; SS316L handles the temperature, the CIP chemistry, and the steam sterilization cycles that follow. The second is hot-process chemical injection in chemical plants — for example, hot sulfuric acid injection at 120-180°C in a sulfonation process, or hot caustic injection at 150°C in a biodiesel transesterification reactor. The third is pharmaceutical and biotech, where the surface finish must support CIP/SIP validation and the wetted material must be documented for FDA / EMA submission.

The SS Venturi is also the right choice where the chemical includes organic solvents (which would attack PP and PVC) or hot oils (which would soften PP and require a metal construction for fire safety). For the most aggressive chemistries — concentrated sulfuric acid above 90%, hot concentrated NaOH above 50%, wet chlorine gas — the body is upgraded to higher-nickel alloys: Alloy 20 (Carpenter 20), Hastelloy C-276, or Inconel 625. These are available on request with extended lead times.

Design Features & Working Principle

The SS Venturi operates on the same Bernoulli principle as the standard PP/PVC Venturi, but with three engineering refinements specific to the high-performance duty cycle. First, the throat is machined with a converging half-angle of 21° and a diverging half-angle of 7°. The 21° convergence ensures that the flow remains attached to the wall at all operating points (no vena contracta effect), which gives a predictable C_d. The 7° divergence is below the natural boundary-layer separation angle, so the diffuser recovers 70-80% of the throat pressure drop without flow separation — important for minimizing the motive pressure loss.

Second, the suction port geometry is a lateral tap with a 6 mm bore on the throat centerline, located 1-2 mm downstream of the throat minimum. This position has been experimentally verified to give the lowest pressure coefficient (C_p = -0.92 to -0.95) and hence the highest suction lift, while remaining far enough from the diffuser start that the suction flow is not disturbed by the diffuser's pressure recovery.

Third, the end connections are flanged (DN50+) or tri-clamp (DN15-DN40), and the flange faces are machined flat to within 0.05 mm to ensure a metal-to-metal seal with the gasket. For tri-clamp service, the ferrules are machined to ISO 2852 or DIN 32676, with surface finish Ra ≤ 0.8 μm (electropolished optional to Ra ≤ 0.4 μm). The tri-clamp design allows the injector to be removed in under a minute for periodic throat inspection — important in sanitary service where the inspection interval is typically 3-6 months.

For high-temperature service above 150°C, the body is fitted with a thermal-expansion bellows on the suction line. The bellows absorbs the differential thermal expansion between the SS316L body and the (typically) carbon-steel motive pipe, which would otherwise stress the suction connection during heat-up and cool-down cycles. Without the bellows, repeated thermal cycling can crack the suction-port weld after 200-500 cycles.