Hygienic precision metering pump assembly for injecting flavours and additives into a beverage stream
Beverage ingredient dosing · hygienic diaphragm liquid ends, flow-proportional injection of flavour into the product main, safety diaphragms and CIP limits
In a beverage plant the metering pump that adds flavour extract, colour, sugar solution or a stabiliser does not dose into a tank on its own schedule; it injects into a moving product line and has to follow that line's flow while being cleaned in place with it. That makes the assembly more than a pump: a hygienic diaphragm liquid end with product-safe wetted materials, a drive that can be speed- or stroke-controlled, a flowmeter signal to pace it, and the suction vessel, filter and overpressure protection around it.
Hygienic-design diaphragm metering pumps and their assemblies used to dose liquid ingredients (flavours, colours, sugar solutions, enzymes, stabilisers, filter aids) into beverage and liquid-food streams: liquid-end finish and materials, cleanability certificates, flow-proportional control, safety diaphragms and connections. Diaphragm, plunger, peristaltic and gear metering pumps for chemical dosing in water treatment and process plants are covered on the Metering pump page. Ceramic-piston pumps that dispense a set volume per shot are covered on the Precision metering pump for filling and dispensing page; packaged duty/standby skids for water treatment on the Chemical dosing pump skid page; detergent and sanitiser dosing into CIP circuits on the CIP chemical dosing unit page; and gear metering pumps for resins on the Metering pump/valve set for resin page. Dosing by weight or Coriolis mass flow into a batch is covered on the Beverage ingredient dosing station page, sterile-side dosing after heat treatment on the Aseptic in-line proportioning dosing unit page, and pumpless dosing through banks of solenoid valves on the Solenoid valve manifold assembly for ingredient dosing page.
CNFX editorial research · Sources checked October 13, 2026 · 4 sources
Liquid ends finished below Ra 0.8 µm, free of dead space and certified for cleaning in place
LEWA states that the pump head of every ecodos hygienic variant is shaped so that there are virtually no gaps or dead spaces, keeps a low fluid volume in the working chamber to speed rinsing, emptying or drying, and is electropolished stainless steel with a surface roughness below 0.5 µm. In 1.4435 stainless steel the heads are rated for pressures up to 20 bar, media at 80 °C and short-term SIP at up to 130 °C; a polypropylene head is offered where temperature and pressure demands are lower. Since mid-2023 the LEE size has held an EHEDG EL Class I certificate, which certifies inline cleaning without disassembly; LEWA describes it as the only motor-driven oscillating diaphragm metering pump with that certificate. [1]
ProMinent's sigma Hygienic liquid end is specified with smooth surfaces of Ra < 0.8 µm, free of welded seams and of shaft passages such as mechanical seals, with rapid-action clips and a sealing design to DIN 11864. It is rated CIP-capable up to 130 °C at a maximum of 2 bar for a maximum of 15 minutes, carries the DGUV test certificate NV 23083 marked "Hygiene-tested", and offers EN 10204 3.1 material certificates and a 2.2 certificate for the surface roughness on request. [4]
LEWA's beer flavour-injection reference specifies a roughness below Ra 0.8 µm in SS 316L for all materials in contact with the product, not only the pump head, and its food and beverage article lists DIN 11851 milk-pipe connections or hygienic screw fittings on the pump. [3][2]
Ask for the wetted material grade, the measured Ra and its certificate, the cleanability certificate and the exact pump size it covers, the CIP and SIP temperature, pressure and time limits, and the connection standard.
02
Pacing the dose to the beer or juice flow with a magnetic flowmeter
In LEWA's reference for injecting flavouring agents into beer, the aroma is held in a reservoir with an agitator, a cleaning ball and two level switches; a filter on the suction side keeps solids out of the pump valves; an electromagnetic flowmeter and control loop adjust the pump continuously to keep the dose in proportion to the beer flow; and a contactor on the discharge side protects the pump against overpressure. The system runs under PLC control or manually, with a potentiometer setting the rate. [3]
The two LEWA articles give different adjustment ranges for the same series. The earlier food and beverage article says a servomotor and intelligent control increase the adjustment range to 1:50; the 2023 EHEDG article says up to 1:200. Both give metering accuracy of ±1%. Ask which range applies to the size and drive you are offered. [2][1]
ProMinent states the sigma Hygienic's precision as better than 1%, qualified as under correct and constant conditions, with correct installation and calibration, relative to maximum stroke volume. Stroke length is set from 0 to 100% in 1% steps, the metering volume can also be changed by stroke rate, and the pump connects to process control through PROFIBUS or CANopen. [4]
Editorial calculation: a line running 20,000 l/h that needs flavour at 0.2% by volume calls for 40 l/h from the pump. At 1:50 a head whose top rate is 360 l/h, the largest sigma/2 figure, could go down to about 7.2 l/h; at 1:200 to 1.8 l/h. The dose fraction and line rate are assumed for illustration. [4][2][1]
Give the supplier the product line's minimum and maximum flow, the dose ratio for each recipe, the flowmeter signal available, and the back pressure at the injection point.
03
Multi-layer safety diaphragm, rupture monitoring and a 16,000-hour diaphragm life
LEWA uses a leakage-monitored multi-layer safety diaphragm in the hygienic ecodos and gives its ideal service life as around 16,000 operating hours, which it equates to two years of continuous use, depending on how often CIP/SIP heats it. If the product-side layer is damaged, the production step in progress can still be completed. [1]
ProMinent's sigma Hygienic uses a PTFE multi-layer diaphragm, at least two layers on top of each other, with diaphragm rupture control as standard and condition monitoring. Both makers describe their pumps as hermetically sealed, with no shaft passing into the metering chamber. [4][1]
Editorial calculation: 16,000 hours divided by 8,760 hours in a year is 1.83 years of non-stop running, consistent with LEWA's "two years"; a line running two shifts on five days a week (about 4,160 hours a year) would reach it in a little under four years. The shift pattern is an assumption. [1]
04
LEWA ecodos hygienic and ProMinent sigma Hygienic side by side
Two makers publish enough on their hygienic diaphragm liquid ends to compare them line by line; the values are each maker's own statements, not a test.
What to send for a beverage ingredient metering pump
Paste it into your enquiry below or into an email to a maker, then replace every bracket.
Ingredient: [flavour, colour, sugar solution, enzyme, filter aid; viscosity; solids]
Dose: [ratio per recipe; line flow min and max]
Control: [flowmeter signal; PLC or manual; fieldbus]
Pressure: [back pressure at the injection point]
Hygiene: [wetted material; Ra and certificate; EHEDG or other cleanability evidence]
Cleaning: [CIP and SIP temperature, pressure, time]
Connections: [DIN 11851, DIN 11864 or other]
Diaphragm: [layers; rupture monitoring; service interval]
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Compiled and source-reviewed by the CNFX editorial team.
Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review
· Page last updated 13 October 2026
Buyer questions
How smooth should the wetted surfaces of a hygienic metering pump be?
ProMinent specifies Ra < 0.8 µm for its sigma Hygienic liquid end; LEWA electropolishes its ecodos hygienic heads to below 0.5 µm. [4][1]
How is the flavour dose kept in step with the beverage flow?
In LEWA's beer reference an electromagnetic flowmeter and control loop adjust the pump continuously to keep the dose proportional to the beer flow. [3]
Can the pump be cleaned in place?
ProMinent rates the sigma Hygienic for CIP at up to 130 °C, 2 bar and 15 minutes; LEWA gives short-term SIP at up to 130 °C for 1.4435 heads. [4][1]
How long does the diaphragm last?
LEWA gives around 16,000 operating hours for its multi-layer safety diaphragm, depending on CIP/SIP thermal cycling. [1]
Sources and what still needs a direct check
Sources checked 2026-10-13. Three pages from LEWA (an EHEDG certification article, a food and beverage article, and a beer flavour-injection reference) and ProMinent's product page for its hygienic-design sigma pump. All are maker statements about their own products.
