HYGIENIC CLASSES

FOR PROCESS VALVES

A guideline for users

GEA.com
2 Einleitung

HYGIENIC CLASSES
FOR PROCESS VALVES

Customers for process valves are always faced with the

challenge of evaluating suitable solutions for complex
production requirements. GEA’s aim with this brochure
is to provide current and future decision-makers with a
guide for selecting the right valve technology.

Constantly increasing product variety, longer production requirements for producers and products. For engineers,
cycles, different market conditions – all this makes plant this results in an increased need for consulting ­services to
­designs more complex for producers. At the same time, there offer manufacturers a suitable solution offer.
is an increase in consumer expectations and higher legal
3 Introduction

Application examples

Dairy
Milk, cream, desserts and
baby food

Beverages
beer, juices, soft drinks,
ready-to-drink coffee and tea

Pharma & healthcare

Medical food, liquid medicine
and WFI

Food
Liquid food, dietary supplements,
New Food, oils and fats

Home & personal care

Home care and personal care
products

The German Engineering Federation (VDMA) has published particularly critical factors. In the case of process valves, valve technology and over 35 years of aseptic experience.
various technical papers on hygienic classes, especially in possible contamination risks and their detection ­possibilities Our portfolio also includes hygienic pumps and tank cleaning
the field of filling technology, which have established helpful are decisive. Underlying the classification in both areas is equipment.
guide​lines for the industry. The concept of hygienic classes based on the properties that the producer ­expects from the
provides a suitable link for hygienic requirements between product to be marketed. Please contact us – we will be happy to discuss with you the
the machine and the product to be processed. GEA Flow right valve solution for your application.
Components is now transferring this concept to process This brochure is intended to provide a practical ­introduction
valves. to the subject of hygienic classes and to classify ­common
valve concepts, particularly with regard to ­microbial
As usual from the VDMA, valves are divided into hygienic ­contamination risks. The contents and arguments are
classes I – V; from Hygienic (I – III) through UltraClean / ESL ­intended to stimulate dialog. The aim is to equip your plant
(IV) to Aseptic (V). For filling machines, the sterilization with tailor-made valves for your products and your market.
rate in the sterile chamber and the packaging material are GEA Flow Components can draw on more than 80 years of
4 Product classification

Microbiology determines
the classification

The hygienic classes can be described by microbiological,

physicochemical and resulting sensory properties. An
important parameter for the classification of products to
be produced is the minimum shelf life.

The labeled minimum shelf life depends primarily on the The germ reduction required for microbial stability and forces or filtration. The process valves and components
microbiological stability of the product, and also on the ­minimum shelf life, measured in the logarithmic reduction of are an important part as well, as they can help avoid or
­planned distribution logistics. The matrix below ­serves the germ count, is primarily achieved by direct or ­indirect minimize the risk of microbial contamination. This is already
as a guide for classification into the classes Hygienic, heat treatment. The required microbial reduction must be valid before the microbial load reduction, as the initial cell
­UltraClean / ESL and Aseptic, whereby one characteristic achieved by taking into account the heat resistance of count is an important parameter for the reduction kinetics
can already be decisive and the transitions are fluid. relevant microorganisms, measured by D and Z values. of microorganisms and, thus, for process and product safety
These values are specific to microorganisms and can also and quality.
Important decision-making criteria are therefore the be influenced by the food matrix present, especially by
type of food and its suitability as a breeding ground for fat and protein. Microorganisms can also occur in different Classification in the hygienic classes
micro­organisms. Here, a distinction is made ­between forms, vegetative and non-vegetative, and can influence the
­pathogenic, i.e. food poisoners, and non-pathogenic microbial reduction within the food through the process. The Hygienic (I – III) /
­organisms. The latter have no direct influence on human goal is to have as little negative impact as possible on the Parameter UltraClean / ESL (IV) Aseptic (V)
health, but may very well have undesirable effects on physicochemical, nutritional and sensory properties of the pH-value < 4.5 > 4.5
the food itself. The ­consumer ultimately judges the product. aW-value < 0.85 > 0.85
­manufacturer and brand by the taste, odor and appear- Minimum shelf-life < 3 weeks > 3 weeks
ance of the products. In view of the important product This is, as mentioned, usually achieved by classical heat Distribution chilled ambient
image, product ­safety and the required process reliability treatment, sometimes combined with other unit operations, temperature

are of paramount importance. such as mechanical separation, electro-magnetic-induced Preservatives yes / no no

5 Hygienic

THE HYGIENIC CLASS

HYGIENIC

The essential requirement for process valves in

direct contact with food is their hygienic design.

In order to meet the basic requirement, the Machinery or edges. The background to this requirement is the
­Directive stipulates that the design must be such that any ­indispensable need to be able to produce food safely and
risk to health is excluded. In particular, it must be possible in consistent quality with an appropriate shelf life.
to clean the materials used before each use, and surfaces
in contact with the product must not provide any space
for microorganisms to settle, e.g. raised areas, recesses
6 Hygienic class Hygienic

Ensuring a permanently consistent and controlled process the necessary intensity of the cleaning process and thus where there are no stringent requirements regarding germ
system is the key to achieving this high goal. This is the use of the four parameters of Sinner‘s circle, namely reduction or shelf life for sensitive products – ­primarily
achieved in hygienic plants by means of a cleaning process time, temperature, chemistry and mechanics, to clean the in large parts of brewery, dairy, beverage, and food
tailored to the product and the system, which reliably valve completely. The efficient way to clean a valve is also ­production plants. Outside the food and beverage ­industry,
­returns the plant to a desired initial condition before each underlined by its compliance with relevant guidelines, hygienic valves are often found in pharmaceutical, health-
production run. Hygienic-class valves are designed to be such as EHEDG, 3-A, etc. These standards all promote the care, biotechnology, fine chemicals and cosmetics plants.
as reliably and completely cleaned in this process as the hygienic design of components, and in the case of EHEDG,
connected piping system. the clean­ability of a valve is tested against a reference
pipe under controlled and standardized conditions.
The distinguishing feature of valves in the Hygienic class
is not the cleanability per se, but often the efficiency of Hygienic-class valves are used in numerous applications
cleaning. The hygienic design of the valves determines in food and beverage production (and related industries)
7 Hygienic class Hygienic

Hygienic
valves

Hygienic valves are characterized by the use of high-

quality materials and the possibility of seamless
cleanability of all components and surfaces that come
into contact with the product.

A hygienic valve ensures complete cleanability in the course of pipeline

system cleaning (CIP – Cleaning In Place), so there is no need to remove the
valve for cleaning reasons.
8 Hygienic class Hygienic

Seat valves
Seat valves are used to shut off a pipeline. The valve is characterized in
particular by the low product-contacting sealing surface compared to the
Butterfly valves butterfly valve and its torsion-free loading with defined compression. In
Butterfly valves are the most widespread and simplest form of hygienic addition, seat valves allow two pipelines lying one above the other to be
valves on the market. This type of valve is particularly popular due to the safely shut off from each other, which leads to a considerable increase in
cost-effective possibility of shutting off the product flow within a pipeline. productivity in the process.

Microbiological Possible Possibility Microbiological Possible Possibility

contamination risk sources of failure of detection contamination risk sources of failure of detection
Product residues at Insufficient cleaning caused by none Elevator effect Microorganisms seated on the valve none
shaft connection bad sealing designs stem are brought into the product area
Valve shaft Malfunctioning sealing at the shaft Visual detection while activating the valve
sealing connection caused by high stress Contamination Badly designed sealing concepts can none
Surface damages High mechanical stress caused by Conditional behind seals lead to contamination behind a product
occuring torsion forces visual detection wetted seals
9 UltraClean

THE HYGIENIC CLASS

ULTRACLEAN / ESL

The UltraClean / ESL hygienic class has long been known in

the field of filling technology for food processing companies
and is defined primarily by the requirements placed on the
product to be processed.

The requirements primarily concern the declared shelf logistical parameters play a decisive role. Another ­advantage
life, which is largely determined by product-specific pH and of this process technology is the reduced or even eliminated
aw values. In addition, sensory and certainly increasingly use of preservatives while maintaining product shelf life.
10 Hygienic class UltraClean / ESL

The valve technology used for UltraClean / ESL ­processes to be manufactured serves as the basis for the ­decision. An important factor in UltraClean / ESL applications is
prevents or reduces the introduction of germs by If this is below the known limit of pH 4.5, the use of also the question of whether the product to be processed
­protecting the valve stem with steam or by ­hermetically UltraClean / ESL valve technology is recommended. (dairy-based foods excluded) can withstand repeated
sealing it against the atmosphere using a membrane. heat input in terms of quality, should unwanted contami-
­UltraClean / ESL valves are used for milk-based, lactic In addition, water-based mixed drinks such as spritzers nation occur – in other words, whether process errors are
acid or also ESL milk products. Due to an acidic product and mixed beer drinks are possible applications for forgivable or lead to complete product loss.
environment or the constantly guaranteed cold chain, an ­UltraClean / ESL valve technology. The growing sector of
improved product quality with also extended shelf life can sports and wellness drinks as well as sauces and delica-
be produced. tessen foods also lend themselves to this hygienic class.
Of course, UltraClean / ESL valves can also be used as a
Another important area of application is fruit juices and valve-side upgrade for classic hygienic processes such as
other fruit-based beverages. The pH value of the product in the brewing industry.
11 Hygienic class UltraClean / ESL

UltraClean / ESL
valves

UltraClean / ESL valves are characterized by increased

safety against contamination from the environment
and thus ensure the microbial stability of the product
throughout the entire process.

The increased safety of the UltraClean / ESL valve concepts lies in the
protection of the moving valve stem or other interfaces to the atmo-
sphere – either by a zone closed by means of steam or, similar to aseptic
valves, by hermetically sealing the valve stem by means of a diaphragm.
Analogous to the other valve types, the same hygienic design principles
apply to UltraClean / ESL valves as to all valves used in food applications.
12 Hygienic class UltraClean / ESL

Diaphragm and stem diaphragm

Both diaphragm and stem diaphragm valves are well known in the
industry. Normal diaphragm valves are usually used in pharmaceutical
processes; stem diaphragm valves, on the other hand, are frequently
used in ­food-related applications. The diaphragm is sealing the product
area ­hermetically against the atmosphere. Accordingly, this valve type
complies with the requirements of aseptic processes. Due to the limited
detection possibilities of the diaphragm material and the dynamically
stressed ­fixation points between stainless steel and synthetic material,
GEA ­primarily ­classifies the diaphragm technology as UltraClean.

Valves with sterile lock

The sterile lock can be mounted on existing hygienic valves in order to
upgrade these installations to UltraClean processes. In this concept, the
valve stem is protected by a steam barrier. Generally, this only allows a
steaming of the interface to the atmosphere. Normally, there is not an
Microbiological Possible Possibility
enclosed system to allow sterilization temperatures, this is why the solution
contamination risk sources of failure of detection
cannot be seen as equally safe as a hermetical sealing of the valve stem.
Membrane • Occuring blisters because of none
deformation unfavorable sterilization cycles
Surface damage • Micro scratches none
• Insufficient heat transfer caused by
Microbiological Possible Possibility low heat conductivity of the material
contamination risk sources of failure of detection Dynamically stressed • Undefined conditions at seal fixation Conditional
No sterilization of • No active steam circulation end, none fixation points points (e.g. temperature influences) visual detection
valve stem thus no sterilization • Detachable connection in product area
Valve stem sealing • No permanent steam barrier recommended none Hollow space in the • Composites none
(life time of the seal, product burn-ons) membrane (e.g. multi-layer membrane)
• Unintentional inoculation of the product Cracked membrane • Fatigue fracture Visual detection
with contaminated condensate • Precedent membrane deformations /
Loss of steam barrier • Power loss Temperature surface damages
• Problems with steam production monitoring • Hydraulic or thermal pressure hammer
13 Aseptic

HYGIENIC CLASS
ASEPTIC

In the Aseptic hygienic class, everything revolves

around the commercial sterility and the endeavor
to prevent any introduction of germs after product
sterilization under all circumstances.

Aseptic applications focus on three areas of equipment: manufactured specifically for specific consumer groups. In
sterilizing products, conveying / holding products in a ­sterile addition to classic UHT milk products, medical nutrition and
state, and filling products in a sterile state. Aseptic baby food also fall into this hygienic class.
­processes stand for long-life and / or highly refined products,
14 Hygienic class Aseptic

“Commercial sterility means the absence of microorganisms Injection

Direct
capable of growing in the food at normal non-refrigerated Infusion
conditions at which the food is likely to be held during Heating

manufacture, distribution and storage.” Plate heat exchanger

Indirect
Codex Alimentarius Commission ­(WHO/FAO) CAC/RCP 40-1993 Thermal Microwave
Tubular heat exchanger
sterilization treatment

Ohmic
heating

Sterilization

Pulsating
electro fields

Non-thermal Ultra-high
sterilization pressure

Sterile
filtration

Product sterilization Maintaining sterility Sterile filling

Sterilization of a product can be achieved by a wide variety In order to keep a product sterile, the installation needs to be Aseptic product filling is a complex field and takes ­various
of processes. The diagram shows an overview, but combi- highly automated and always kept in a defined overpressure. criteria into account. Nevertheless, any aseptic filling
nations of processes are also being investigated time and Furthermore, the installation has to be perfectly cleaned and ­machine must fulfill several factors: In the area of the filling
again, which, in the sense of the “hurdle concept”, aim at sterilized in-place. If the product gets stored in a tank before valves, the machine must operate in clean-room conditions
an overall reduced treatment of the product with complete filling, the tank needs to be maintained under pressure by with ­filtered air, and a laminar flow against the container
sterilization. As a general rule, the more valuable the product means of sterile gas. Aseptic process components greatly filling direction has to be ensured. On-place cleaning and
and the more heat-labile the food matrix, the more complex contribute to the aseptic operation of an installation. sterilization ­complete the basic criteria. To ensure aseptic
the technologies used, from sterilization to valves to filling filling across the production chain, the container and cap of
machines. a commercially sterile product must be pre-sterilized and
kept sterile until the final hermetic seal.
15 Hygienic class Aseptic

Aseptic
valves

Aseptic valves are characterized in particular by their

uncompromising hermetic sealing of the valve stem and
the minimization of contamination risks.

Unlike the lower hygienic classes, hermetic sealing of the product chamber
against the environment (atmosphere) is mandatory for aseptic valves.
In addition, the expected contamination risks are lowest. In combination
with the detection possibilities that are particularly given with metal
bellows, this results in the highest rating. Aseptic valves are subject to
special requirements in the plant due to the regular sterilization cycles
and thus frequently changing temperatures.
16 Hygienic class Aseptic

PTFE bellow
Valves equipped with PTFE bellows are well known in the aseptic market.
The main difference between PTFE and stainless steel bellows is their
possibility of failure detection. Other than with stainless steel bellows, and
similar to the diaphragm / membrane technology, a deformation and / or
partial damage of the hermetic seal is more likely to occur than a full crack.
In contrast to the diaphragm / membrane, this valve concept does not
include dynamically forced sealing connections, and due to the fabrication
method the risk of blistering is considerably reduced.

Microbiological Possible Possibility Stainless steel bellow

contamination risk sources of failure of detection
Aseptic valves with stainless steel bellows are considered the highest class
Bellow deformation • Flow combined with high temperature none
• Cold flow in the seat area
of aseptic valves. This is due to the material and the permanent joint at
• Valve activation during sterilization both sides of the bellow, as well as the bellow monitoring in the process.
• Hydraulic, thermal or mechanical
pressure hammer
Surface damage • Micro-scratches none
• Insufficient heat transfer caused by Microbiological Possible Possibility
low heat conductivity of the material contamination risk sources of failure of detection
Cracked bellow • Fatigue fracture Visual detection Cracked bellow • Fatigue fracture • Visual detection
• Precedent bellow deformations / • Hydraulic, thermal or • Optional via temperature
surface damages mechanical pressure with steam barrier
• Hydraulic, thermal or mechanical hammer • Optional via level with liquid,
pressure hammer sterile medium
17 Valve selection

THE RIGHT VALVE

FOR EVERY PROCESS

Hygienic classes

Aseptic Aseptic valves with stainless steel bellow

Aseptic valves with PTFE bellow

The choice of the right valve technology is based on

sound knowledge of the product and process. Both the UltraClean / ESL Stem diaphragm
intrinsic product factors and the extrinsic factors during Hygienic seat valves with sterile lock

storage and transport, as well as the respective consumer

target group, are decisive.
Hygienic Hygienic seat valves
Hygienic butterfly valves
It is clear that a final decision on the optimum valve tech- symbol shown indicates the minimum valve ­standard to be
nology must be made anew for each installation, ­taking considered in the respective process steps. A ­valve-side
into account the respective process. upgrade of the installation can be achieved by equipping
process steps with valves that meet a higher hygienic
The table on the next page shows an exemplary list of standard than the minimum recommended.
­typical products for the hygiene classes and should serve VDMA Hygienic classes:
as an initial orientation in a decision-making process. The I – III: Hygienic, IV: UltraClean / ESL, V: Aseptic
18 Valve selection

Product pH value Distribution Shelf-life Storage Preparation Preservation Filling

Aseptic (V) UHT milk, > 4.5 ambient > 3 months
UHT cream temperature
Ice tea (still) > 4.5 ambient > 12 months
temperature
Soft drinks (still) > 4.5 ambient several months
temperature
UltraClean / ESL (IV) Fruit juice ≤ 4.5 ambient several months
temperature
Ice tea (still) ≤ 4.5 ambient > 6 months
temperature
Fruit yoghurt ≤ 4.5 ambient > 5 weeks
heat-treated temperature
Hygienic (I – III) Fruit yoghurt ≤ 4.5 chilled 2 – 4 weeks

Beer ≤ 4.5 ambient > 6 months

temperature
Wine ≤ 4.5 ambient > 1 year
temperature

Decision-making
The final classification of valves into hygienic classes is guarantee reliable production. Just as in all other areas our comprehensive product portfolio and many years of
always subject to further evaluation on the basis of the of an installation, it is also necessary to assess which experience, we at GEA Flow Components aim to support
requirement profiles and feature weightings known only valve concept is best suited to the existing conditions current and future decision-makers in these considerations
to the user. In addition to the factors already mentioned, for the process valves. From this point of view, there are and to provide the right valve technology for every process.
particular consideration must be given to the influence on sometimes fluid transitions between the hygienic classes
follow-up costs, including the maintenance and inspection described, which must be evaluated by the plant operator
work to be carried out in order to be able to continuously and the person responsible for the product alone. With
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