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More capacity | Scottish craft brewery BrewDog PLC has ordered the next lauter tun brewhouse from Ziemann Holvrieka GmbH, Ludwigsburg, Germany. With the new brewhouse the brewery will be able to produce up to 12 brews per day, each with 500 hl of cold wort.

Always up-to-date | “Monday moaning meetings” – the start of the week for breweries is frequently met with a groan. It is when the folders and reams of data come out. As one of the breweries pioneering a digital innovation developed in a GEA design sprint, Störtebeker Braumanufaktur can in the future dispense with this paper chaos. GEA InsightPartner Brewery provides real-time data, helping quality control and making the Stralsund-based brewery faster, more productive – and smarter. The tool not only gives Störtebeker an intuitive overview of performance data, but also something even more precious: time.


Components of centrifugal pumps | Centrifugal pumps, in particular rotary pumps and side-channel blowers, play a central role in production of beverages. This second part of the series of articles about pumps describes the design of the drive and pump shaft and explains the requirements relating to these types of pumps used in beverage production.


Introduction and designs | Pumps are central elements in breweries and beverage operations, they are workhorses that keep processes running. A multi-part contribution covers the different common designs and criteria for use of pumps. This first part deals with general questions, pump designs and centrifugal pumps.

Pumps are used for conveying fluids. Fluids can be clear liquids (water, condensate, wort, beer, all types of beverages), solids-containing liquids (suspensions as e.g. mash, filter aids such as kieselguhr, perlites), higher-viscosity media (for example yeast) or gases (e.g. air).

Energy has to be expanded for conveying the above-mentioned media in order to

  • reach the required geodetic discharge pressure;
  • compensate for the resistance of elements through which the media flow; and
  • overcome friction losses of pipelines and fittings used for conveyance (“pressure losses”).
Fig. 1 Geodetic discharge pressure of a pump (reference line middle of suction connection)
Fig. 1 Geodetic discharge pressure of a pump (reference line middle of suction connection)

Geodetic discharge pressure

The geodetic discharge pressure indicates the difference in height between the liquid level on the suction side of the pump and the outlet of the discharge port (fig. 1). When the pump draws in liquid from a pressure vessel or when the medium flows into the pump, the discharge pressure is reduced by the vessel pressure or the height of the liquid column. The potential energy of the liquid is thus increased by the pump work supplied (equation 1):

Resistance of elements through which media flow

Elements in the brewing industry include e.g. heat exchangers (e.g. plate heat exchangers [PHE] for wort cooling, PHE for the flash pasteuriser [FP]) or filter plants for beer filtration (usually membrane filters or precoat filters) or cross-flow filter plants for residual beer recovery from excess yeast.

So that a liquid can flow through these elements, they require a pressure differential Δp. For the sake of better illustration or simplified representation, a pressure differential can also be given in “metres discharge pressure”.

A water column (WC) 10 m high exerts a pressure of about 1 bar on the base area (the exact number is 0.981 bar, the error thus amounts to just about 2 %). Consequently, a pressure differential of 1 bar approximates a discharge pressure of 10 m WC. This is mirrored in equation 2:

Example: discharge pressure 20 m, density 1000 kg/m3, gravitational acceleration 9.81 m/s2; giving rise to Δp = 20 m x 1000 kg/m3 x 9.81 m/s2 = 196 200 N/m2 ≈ 200 000 Pa = 2 bar.

Using the “overall discharge pressure” of a pump, the required theoretical pump output Preq can be calculated relatively easily (equation 3):

The required drive power of the motor is, naturally, larger because the hydraulic efficiency of the pump and the mechanical efficiency (due to friction losses) have also to be taken into account (equation 4):

Example: Preq = 10 kg/s × 9.81 m/s2 × 20 m = 1962 Nm/s = 1962 W; ηhydr = 60 % = 0.6; ηmech = 95 % = 0.95

The difference to Preq is converted into thermal energy. The electric efficiency of the motor gives rise to a further loss. This should be as large as possible, motors of efficiency class IE3 or IE4 should be installed. The pressure loss caused by the elements is primarily a function of volume flow, flow velocity and viscosity (viscosity depends on temperature), i.e. ultimately of the Reynolds number.

Overall discharge pressure

The overall discharge pressure (overall pressure loss) that the pump has to “overcome” is the sum of geodetic discharge pressure, resulting pressure differential of elements and pressure losses due to pipework friction.

Note: all energy for conveyance of liquids supplied to overcome pressure differentials is ultimately converted to thermal energy. The same is true for energy losses caused by hydraulic, mechanical and electrical efficiency. This thermal energy is generally a heat loss and thus cannot be used further in the process.

Pump designs

Pumps use mechanical energy supplied for conveyance of fluids. The energy is transferred either to positive displacement machines or continuous flow machines. Consequently, losses arise; these are generally released as thermal energy. As already mentioned, these losses cannot be used. Hydraulic efficiency is relatively small, generally 50… ≤ 70 per cent in the case of centrifugal pumps in the beverage industry. When larger pumps are installed (not in the beverage industry), efficiency is generally better compared to small ones.

Many different pump designs are available. Design is usually a function of intended use. Important designs are for example:

  • piston pumps;
  • centrifugal pumps;
  • rotary piston pumps;
  • helical rotor pumps;
  • peristaltic pumps;
  • impeller pumps;
  • membrane pumps;
  • dosing pumps;
  • vacuum pumps;
  • jet pumps.

In addition, special designs exist for special purposes, such as e.g. “condensate lifters”.

For more detailed information about pumps and pump sizing/calculation, please refer to the technical literature, e.g. [1], [2], [3], [4].

Historical designs and the history of pumps are described very well in a publication by GEA Hilge/Bodenheim [5]. A visit to the Pump Museum in Bodenheim is also highly recommended [6].

Pumps, pump sizing and construction elements are described in numerous German and international standards. Reference is made e.g. to [7].

Centrifugal pumps

Centrifugal pumps encompass in particular rotary pumps and side channel blowers. The latter are self-priming and thus can also convey gases.

The pump housing with connections for suction and discharge, pump shaft, shaft bearings, pump impeller and the shaft seal are important assemblies, see also fig. 2.

Fig. 2 Centrifugal pump (rotary pump) for chemical applications, schematic sectional view (according to KSB); 1) suction connection, 2) pump housing, 3) pressure connection, 4) impeller, 5) pedestal of housing, 6) shaft seal, 7) bearing block, 8) pump shaft, 9) fixed bearing, 10) floating bearing, 11) cover of pump housing

Rotary pumps for general usage

Generally, rotary pumps are not self-priming, the medium being conveyed has thus flow to the pump. As soon as the suction line is filled with liquid, the pump is able to self-prime. The maximum suction pressure (about ≤ 8 m) or the steam pressure is a function of temperature. The suction line is then closed by means of a foot valve so that it remains filled. Rotary pumps can be subdivided according to impeller shape, housing construction, body material, number of stages and drive.

Rotary pumps for general usage are standardised by many suppliers. They are known by the designation “DIN pumps” (“standardised pumps”) (e.g. standardised pumps for water and chemicals) and their machine data (in particular nominal diameter of the suction and discharge port, volume flow, discharge pressure, connection dimensions) are adjustable according to a modular system.

The so-called standardised pumps for chemicals are made of corrosion-resistant materials and are suitable e.g. for conveyance of water and in CIP plants.

Other special designs are manufactured e.g. for conveying wastewater or sludge.

Fig. 3a General impeller shapes for rotary pumps; a) radial impeller, b) radial impeller with blades pulled forward, c) semi-axial impeller, d) axial impeller
Fig. 3b Impeller shapes for rotary pumps; a) double-suction impeller (double-flow impeller), b) free-flow impeller, c) single-blade impeller, d) single-channel ivmpeller, e) double-channel impeller, f) three-channel impeller

Impeller design

A distinction is made between radial impellers, axial impellers and half-axial impellers, see figs. 3a and 3b. Impellers can be “open” or “closed”. They can also be single-flow or dual-flow. The one-channel impeller, the two-channel impeller and the non-clog impeller are special designs. Fig. 4 shows available impellers.
Selection is made in accordance with solids content and gas content, clear liquids can be conveyed by every impeller shape.

Fig. 4 Impeller examples (according to Hilge); a) open impeller, b) closed two-channel impeller, c) closed impeller, d) free-flow impeller, e) open impeller (according GEA-Tuchenhagen)

Body construction

Fig. 5 shows a pump in the shape of a standardised pump, mounted on a base plate made of rolled steel. The pump housing is screwed to the bearing support. The base plate can be made of cast iron or rolled steel. The so-called block design is an alternative (see also figs. 7 and 8 and part 2 of this series of artic-
les).

Fig. 5 Rotary pump in the shape of a standardised pump, schematically (according to Hilge); 1) base plate, 2) shaft seal, 3) impeller, 4) suction connection, 5) pump body (rolled steel), 6) discharge, 7) pedestal (“bearing block”), 8) spraying disc, 9) pump shaft, 10) coupling, 11) drive motor

Suction and pressure connections are designed as flange connections. In principle, screwed connections (according to DIN 11581), aseptic screwed connections (according to DIN 11864-1), Tri-Clamp® screwed connections (according to ISO 2852 or DIN 11864-3) and aseptic flanges (according to DIN 11864-2) are also possible. The discharge can be connected to the body either tangentially (fig. 7) or radially (fig. 6). Bodies are generally designed such that they can remain undisturbed when the impeller and the rear wall of the housing are dismantled. The rear wall of the housing can be pulled out of the housing together with the impeller.

Fig. 6 Spiral housing shapes for rotary pumps; a) single spiral, b) combined annulus spiral housing, c) annulus housing, d) double spiral

Suction and discharge connections to the pump housing with the rear wall can be implemented as a clamp connection with a clamping ring or a flange connection, depending on the potential operating pressure (fig. 8). An O-ring is used for sealing following the principles of hygienic design.

Fig. 7 Body with tangential discharge flange

The shaft sealing is an important component. A part of this series of articles will deal primarily with this element.

Fig. 8 Variants of body mountings (Euro-HYGIA® according to Hilge); a) body mounting using a tension ring (clamp ring), b) body mounting using a flange ring; 1) tension ring, 2) housing flange, 3) pump housing (rolled steel), 4) rear wall of pump housing, 5) O-ring

Depending on usage, bodies are manufactured in various variants (fig. 6). Heated bodies are also an option.

Body material

For general use, the body material can be cast iron or grey cast iron or nodular cast iron. In the beverage industry, CrNi or CrNiMo steels are mainly used, both as cast material as well as rolled sheet (“sheet material”). These materials are also referred to as stainless steel, stainless®.

Other pump materials also exist, e.g. titanium, chilled casting, ceramics, plastics (epoxide resin) or lining the pump with hard rubber.

Rolled steels are usually welded, bodies are manufactured by deep drawing.

Important steel types are e.g. AISI 316Ti (1.4571); AISI 316L (1.4404); (1.4435) according to DIN EN 10027 and DIN EN 10088-1. The most important selection criteria for defining the material relate to the properties of the medium conveyed (pH value, temperature and chlorine ion concentration).

Material surfaces

Average roughness values of Ra = ≤ 1.6 or ≤ 0.8 µm are ideal. Lower values require electropolishing and are relatively cost intensive. For sterile processes, Ra ≤ 0.4 µm according to the 3A standards 3A3.06, 3A3.07, 3A3.37 are required.

As the price of materials and processing costs depend on the average roughness value, the maxim should apply: “as low as possible” (stating roughness Rt or average roughness Rz does not make a lot of sense). Note should also be taken of the fact that e.g. pipes are supplied only with the following average roughness values:

  • seamless pipes with Ra ≤ 2.5 µm and und Ra ≤ 1.6 µm (DIN 17456);
  • welded pipes with Ra ≤ 1.6 µm und Ra ≤ 0.8 µm (DIN 17455).
  • It does not make any sense to install lower average roughness values (at higher costs) at some points of the installation (chain principle: the weakest link determines the properties). It must also be assured that the same average roughness values have been achieved at all points of the installation after mounting.

It is important to adjust process parameters for CIP cleaning to suit the material.

Sealing materials

Sealing materials used are EPDM (ethylene propylene diene mixed polymers), silicon rubber food grade (VMQ, partly stained red, FDA conformity); PTFE (Teflon®) and other fluoric polymers (FKM e.g. Viton® or FFKM e.g. Kalrez®) approved by the FDA.

EPDM, FKM and FFKM are usually stained black (filling material soot).

The sealing material NBR (nitrile butadiene rubber) stained blue in some instances cannot be used for plants cleaned with hot caustic.

Seals are preferentially designed as O-rings (i.e. round rings). The seal has to be inserted such that the seal ring is pressed or tensioned only in a defined manner and cannot be squeezed (principle of sterile seal in aseptic screwed connections according to DIN 11864-1).

The next parts of this series of pump articles will be published in the following issues of BRAUWELT International.

References

  1. Dubbel: “Taschenbuch für den Maschinenbau”, 2nd ed., Springer-Verlag, 2001.
  2. Wagner, W.: “Kreiselpumpen und Krei-selpumpenanlagen”, 2nd ed., Vogel-Buchverlag, Würzburg, 2004.
  3. Bohl, W.; Elmendorf, W.: “Strömungsmaschinen 1, Aufbau und Wirkungsweise”, 9th ed., Vogel-Buchverlag, Würzburg, 2004.
  4. 4Bohl, W.: “Strömungsmaschinen 2, Berechnung und Konstruktion”, 7th ed., Vogel-Buchverlag, Würzburg, 2005.
  5. Berdelle-Hilge, P.: “Die Geschichte der Pumpen, Kapitel I bis IX”, 2nd ed., Special print No. 21 by Philipp Hilge GmbH, Bodenheim/Rhein, 1995.
  6. Förderverein Deutsches Pumpen-Museum e.V., Hilgestraße, D-55294 Bodenheim/Rhein (www.hilge.de/de/pumpenmuseum).
  7. Deutsches Informationszentrum für technische Regeln im DIN, Deutsches Institut für Normungen e.V. (ed.): “DIN-Katalog für technische Regeln” (annual new edition); Beuth-Verlag, Berlin.

Developers want feedback | On October 1, 2020, Dr. Mark Schneeberger assumed leadership of Application Development Beverage & Beer at GEA in Kitzingen, Germany. He succeeded Dr. Rudolf Michel, who went into well-deserved retirement at the end of March 2021. BRAUWELT interviewed Dr. Schneeberger about his new position, one year on.


Green hydrogen | A continuously growing number of companies are choosing to reduce their CO2 footprint or even achieve CO2 neutrality. For production companies, including those from the brewing sector, this often raises the question of how to provide process heat in a climate-neutral way. The use of green hydrogen in boiler systems represents a significant opportunity. As well as generating a high boiler efficiency rate of up to 98 %, its combustion is entirely CO2 neutral. The following technical report focuses on solutions using hydrogen boilers and on technical measures for safe, clean hydrogen combustion.


Centrifugal pumps | VLB Berlin has developed new methods for determining whether a pump is conveying fluids in a gentle manner and has thus created a new service that allows centrifugal pumps to be evaluated with regard to their pumping properties. The new method is based upon the formation of β-glucan gel from barley in response to shearing forces. Unlike established methods derived from the field of microfluidics, the pump does not need to be modified. It can be tested in the same condition as it would be supplied to the customer.


Hüll aroma hops | The climate change brings particular challenges for hop growers and brewers. Aurum, the new Hüll aroma variety with a Tettnanger background, presents itself not just as a climate-tolerant noble hops but also with a fine-hoppy aroma in combination with a pleasant subtle bitterness and lives fully up to its name in numerous brewing tests.


Test brews | Yield of hop bitter substances is key to efficient use of hops. However, solubility of α-acids in an aqueous environment strongly depends on pH value and temperature. In this respect, wort does not offer optimal conditions for adequate isomerisation of α-acids. When ionising water, a by-product having an alkaline environment is formed. This is used for isomerisation of hop α-acids and for raising yield of bitter substances.


Comprehensive guide | With the “Beer Brewing Guide – the EBC Quality Handbook for Small Breweries”, published in June 2021, the Brewers of Europe and the European Brewery Convention commissioned a new must-have book that provides small breweries and aspirational professional brewers with practical tips to improve the way they brew on all critical quality points, from receiving the ingredients to ensure their beer is poured the perfect way.


Historic brews | At Colonial Williamsburg, a 1.22-km2 (301-acre) “historic district and living-history museum” [1] in the heart of the small City of Williamsburg in the state of Virginia, history indeed comes alive … literally. As you stroll along painstakingly reconstructed residences, workshops, inns, and taverns dating from the late 18th century, interpreters and actors in period costumes recreate daily life from the time of the American Revolution (1775–1783), when such luminaries as the United States’ first president, George Washington, its third president, Thomas Jefferson, and its fourth president, James Monroe, walked the district’s streets.