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100% Performance Check

All filter elements from production are checked for leaks and loss of pressure prior to shipment.

3K-, 3KA-, 3KAX- Filter Elements

Different versions of sintered filter elements.

Acoustic Hood, complete

Fan housing, the main purpose of which is to dampen the noise of outflows.

Air Recirculation

Clean air recirculation is the recirculation to the working space of the air which has been removed by vacuum extraction and cleaned in separators (clean air). (Source:


The ratio of volumetric flow to filter surface area » I-value.

Antistatic Version

Surface design for discharging electrostatic charges.


Directives concerned with the fireproof and explosion-proof design of machinery and plants.

Backup Filter

A backup filter is downstream of another filter and serves a safety function.
This is necessary in case the upstream filter no longer carries out its filtration function correctly because of damage.

What is known in the industry as a filter rupture, with resultant escape of dust to the clean gas side, is a problem associated with conventional filter media such as fabric filters (textile) or cartridge filters (paper).

The Herding sinter-plate filter, being an inherently rigid filter medium with classic surface filtration, is not affected by this.

A second filter stage in the form of a backup filter is not necessary for Herding sinter-plate filters.

Baffle Plate

The baffle plate/deflector plate in the Herding filter unit serves as a pre-separator for large particles which are brought into the filter unit with the air current. In addition, the baffle plate/deflector plate is also used for setting the air flow in the filter unit so that there is a homogeneous distribution of dust.

Bin Vent

See: Top Mounting Filter or Silo Filter

Blow Pipe

Part of the cleaning system that directs the cleaning pressure pulse into the filter element.

Calcium Carbonate

CaCO3: Dust-type inert solid for solid inertisation and precoating.

Clean Gas Dust Concentration

This is the concentration of dust relative to volumetric flow on the clean gas side of the filter unit and is normally expressed in mg/m³.

Synonymus with clean gas values and residual dust content.

Clean gas side

Space in the Herding filter unit is bordered by the slotted plate on which the Herding sinter-plate filters are installed and the housing cover or the acoustic hood. The cleaning unit is in the clean gas compartment.


Dislodging of the cake of filtered dust from the surface of the filter element.

Cleaning Cycles

All the filter elements of the Herding filter unit are cleaned once during a cleaning cycle.

Cleaning Pressure

Pressure of the cleaning gas in the pressure tank for the filter cleaning system.

Cleaning Unit

System for cleaning the filter elements, generally comprised of: pressure tank, diaphragm valves and blow pipes.


Surface coating of components or filter elements.


Component in the filter unit for guiding the base strips of the Herding sinter-plate filters.

Compressed Gas

Gas compressed to a specific pressure level.

Compressed gas reservoir

Pressure vessels are closed containers in which the pressure on the inside is higher than the ambient pressure. Unlike gas cylinders and transport containers as defined under traffic law, in which fluids are transported, the use of pressure vessels has to be restricted to a particular place of installation. The pressure vessel in Herding filter units is the compressed gas reservoir for the Jet-Pulse filter cleaning.

Control Device

Electrical or mechanical control of the function of the Herding filter unit. 

Cover Strip

Component used for sealing an empty installation point for a filter element in the slotted plate of the filter.

Cycle Cleaning

Cleaning runs on the basis of a pre-set cycle. One cycle means that each quick-opening valve is actuated once. The number of cycles and pause times can be set separately for each job and adjusted to the individual process requirements.

Damper in Acoustic Hood

Integrated manual plate flap on the acoustic hood for adjusting the volumetric flows within certain limits.

Differential Pressure Based Control

The filter elements are cleaned on the basis of the differential pressure.

Differential Pressure Loss

Pressure loss across the entire surface area of the installed filter.

Differential Pressure Switch

Electromechanical switching component which switches the in accordanced with the applied differential pressure.

Docking Device

Airtight device for connecting the dust collecting bin to the filter system hopper with a dustproof seal.

Double Coated

A double surface coating has the effect of smoothing out the range of pore diameters on the surface and therefore widens the range of uses for the filter elements.

Down Flow

Distribution and prevential flow direction of the raw gas in the raw gas chamber of the filter, which in this case is primarily from the top down and can therefore help the process of dust sedimentation during cleaning.

Dry Dust Separator

Sinter-plate, cartridge, hose, pocket and cassette filters with manual or fully automatic pressure pulse cleaning, plus the respective discharge system required for each. (Source


Filter element seal with a foam-filled seal body.

Dust Bin Docking Device

Mounting and locking device for the dust bin. See also docking device.

Dust Break Through

Occurs when dust on the raw gas side uncontrolled breaks through to the clean gas side either by a failure of the filter material or the filter gasket.

Dust Collecting Bin

This is available as an option for getting the cleaned dust from the filter elements out of the filter plant. The dust collecting bin is located below a hopper and is an intermittent discharge system. The dust collecting bin can only be emptied when the filter plant is switched off. If a shut-off mechanism is incorporated between the hopper and the dust collecting bin, the dust collecting bin can also be changed during operation as well.

A plastic sack can also be inserted in the dust collecting bin in addition. In combination with the applicable docking station, low-contamination versions are also possible (SafeChange plastic sack changeover system).

Dust EX zone barrier

Conventional filter media such as hose filters and cartridge filters are subject to flexing during suction mode and cleaning. In the case of rigid-body filters with a membrane on the surface there is a risk of the membrane being infiltrated.

These impairments of the filter media result in filter ruptures and dust transfer to the clean gas side. When such faults occur, the clean gas concentration drops briefly below the lower explosion limit LEL → Zone 22.

In the case of the Herding® sinter-plate filter as rigid-body filter with PTFE coating in the surface, filter ruptures with dust transfer to the clean gas side are unknown → Dust EX zone barrier (according to VDI 2263 Page 6.1).

Exhaust Air

Operating mode in which the filter's clean gas is transferred to the environment outside the operating areas.

Explosion suppression

A device for limiting the spread of an impending explosion on the inside of a vessel by injecting a suitable firefighting material.

Exposed to Product

This is the term for system components made of stainless steel which come into direct contact with the dust in the raw gas.

External Pressure Requirement

The pressure loss of the gas flow outside the filter (on the suction side upstream from the filter unit and on the outlet side downstream from the fan) which at least must be overcome by the fan.

Extinguishing Device

Part of the extinguishing system for extinguishing fires.
It is comprised of an extinguishing agent tank, pipe line and extinguishing nozzles.

The extinguishing agent in the extinguishing agent tank is specifically suited to the dust to be extinguished (extinguishing powder or extinguishing gas).
The pipe line is aerodynamic in design and construction.

The geometry of the extinguishing nozzles is specifically designed for the requirements of the extinguishing agent and special feeding of the extinguishing agent and the nozzles are fitted in an ideal position on the filter unit.

Extinguishing System

System for protecting the filter unit; for fire detection, fire alarm and fire extinguishing.
Detectors with VdS approval are used for fire detection purposes and these communicate with a VdS-approved control system.
Fire extinguishing with powder or gas specifically suited for the type of dust to be extinguished.

Face Velocity

Face velocity is a value derived from the specific filter surface load (I-value).

Filter Agent Material

Dust-type material which is inert in respect of filtration and which is metered into the raw gas flow on either a continuous or intermittent basis in order to protect the filter medium.

Filter Area

Characteristic of Herding® filter units: Installed filter area = effective filter area.

Filter Body

Filter element body. Provides the filter-active surface.

Filter Cake

Layer of filtered dust on the filter element.



Filter Capacity

Similar to loading per unit of filter area. This describes the ratio of volumetric gas flow to filter area » I-value.

Filter Control Device

Control unit of the filter unit, which is mainly for actuating the cleaning process.

Filter Element

Synonyms filter bag or filter pocket.

Filter Element Fixing

Mounting and fixture device for the filter elements.

Filter Element Support

Support structure for filter elements installed horizontally to reduce the load torque at the element clamping point.

Filter Head

Top part of the filter element with the mounts for fastening and for the seal.

Filter Housing

Welded and/or screw-assembly construction, cube-shaped or cylinder-shaped for mounting the filter elements, filter cleaning system, dust discharge system and, depending on the version, the fan.

Filter Insert

Filter unit comprised of a slotted plate, filter elements, cleaning system and clean gas housing.

Filter Surface

Filter-active surface of a filter element. Characteristic of Herding filter units: Installed filter area = effective filter are.

Filtering Medium

In this context synonymous with the filter element.

Fire Trap

Equipment for suppressing the spread of flames.


» washing installation


Flexing means the forming of materials by mechanical processes such as kneading, pressing or drawing. (Source In the case of filter elements made of fabric, this often leads to high wear. Sinter-plate filters from Herding are not exposed to flexing, because they are rigid bodies.


In this case through air injection of solid particles floating in the air, via a suitable air distribution system.

Follow-up Control

For operating the filter unit without the dust-generating machine.
Follow-up control is used for processes involving short interruption times on the dust-generating machine or where an air flow run-on is required on the machine in the ductwork and/or in the filter unit.

Free Available Suction Pressure

Pressure requirement which is available on the intake port of the Herding filter unit. This must be sufficient for the raw gas pipeline and the dust-generating machine.

Free of Fibers

This refers to the type of coating used for the surface of the filter.

Gas-tight Version

Gas-tight version of a filter unit for pressure and vacuum applications within certain limits.

HEPA Filter

HEPA filter (High Efficiency Particulate Airfilter), ULPA filter (Ultra Low Penetration Air) and SULPA filter (Super ULPA) are terms for filters of a particular particle filter class. Filters in this class are used for the filtration of viruses, respirable types of dust, mite eggs and excretions, pollen, smoke particles, asbestos, bacteria, diverse toxic dusts and aerosols from the air. (Source

Herding ALPHA

Filter series for maximum operating temperatures of 450 °C.

Herding ALPHA Cluster

Filter element of the Herding ALPHA filter series for maximum operating temperatures of 450 °C.

Herding COMP

Compact filter series with a rectangular housing and Herding DELTA/DELTA² filter elements mounted horizontally.

Herding DELTA

Design of the PE sintered filter element with a filter area of 3.75 m²/element for type 1500/9 and 1.82 m²/element for type 750/9.

Herding DELTA²

Design of the PE sintered filter element with a filter area of 4.75 m²/element for type 1500/9 and 2.2 m²/element for type 750/9.

Herding FLAMEX

The flame arrester Herding FLAMEX 220 IIC is a passive component that prevents flame spreading into the filter unit, when measuring the differential pressure with a ll flammable gases in gas explosion group IIA, IIB and IIC.

Herding FLEX

Modular filter series with a rectangular housing and Herding DELTA/DELTA² filter elements mounted vertically or HSL filter elements.

Herding FLEXTOP50

A series of Herding filter units comprised of pipe sections connected to each other with clamping rings. The Herding sinter-plate filter and the cleaning unit are mounted on the slotted plate. This slotted plate with mounted components is also clamped between two pipe sections with a clamping ring.

Herding MAXX

The Herding MAXX Series is designed especially for the handling of large air flows.
The modular design is based on a smart cell concept, which provides a high variability for design and configuration of the filter unit. At the same time this results in an enormous flexibility for the transport as well as for the installation on site.
Depending on the case it is possible to deliver basic components or major assemblies. The installation effort compared to traditional filter systems will be considerably reduced.


Equipment developed in-house for the automatic running of the process "precoating". Either a precoat material is used here which is different to the dust separated in the filter unit or dry dust is used which is similar to the dust separated.


A Herding filter unit that is suitable for potentially explosive dusts without constructional protection against explosion. Explosion volume limitation measures allow organic dust of dust explosion class St2 (up to K(St) = 300 barm/s) to be handled, as well as an explosion pressure of 10 bar and minimum ignition energy of greater than and less than 3 mJ.


Equipment developed in-house for the manual running of the precoating process. A precoat material can be used here which is either different to or the same as the dust separated in the filter unit.


A series of Herding filter units comprised of welded steel structures. Available in stainless steel and normal steel versions » Process filter.


Equipment developed in-house for the automatic running of the precoating process. The separated, transformable dust is used here as a precoating material.

Herding RESIST

Filter series with cylindrical design for the installation of Herding filter element. Typical roundfilters are e.g. resistant to pressure surges. 


With a Herding SELFCOATER, part of the cleaned dust is discharged back to the raw gas pipeline again. This circulating dust then serves as a filter additive.

Herding Sinter-Plate Filter

Herding Sinter-plate filter = Depressurized, sintered polyethylene filter element with different filter-active surface coatings.


The Herding SPARKSTOP is a cleanable spark pre-separator. It separates ignition sources entering from external at and in the ceramic ball pack cassette. The upstream expansion compartment provides the removal of bigger particles. An integrated pressure reservoir serves the cleaning of the ceramic ball pack cassette.

Hollow Profile Gasket

Filter element seal, made of extruded rubber material in the shape of a hollow body.

Hot Gas Filter (Herding ALPHA)

Special filter unit series for maximum operating temperatures of 450 °C.

Housing Cover

The top cover plate on the filter housing.


Herding sinter-plate filter element and series type of Herding. Abbreviation for Herding Sinter-Lamella- (or -Plate)-Filter element. 

HSL Filter Element

Type HSL filter element exclusively for vertical installation on both the raw gas and clean gas side.

HSL Type Series

Unit series type for installation of HSL filter elements.

HSL-C Type Series

Series type for installation of HSL filter elements for maximum operating temperatures of 100 °C.

HSL-C-Filter Element

PE sintered element of HSL design for maximum temperatures of 100 °C.


Specific filter area load, physical unit [m³/m²min] » face velocity.

Idling Time

See interval time


Conversion of a reactive dust into an inert dust (solid or gas inertization of combustible, potentially explosive dusts, or inertization for binding adhesive substances. See: precoating.

Inherently Stable

Component with certain material characteristics that help it to retain its geometric shape under the influence of external forces.

Initial Precoating

Application of precoat material on the installed filter elements prior to start-up.


When the dust is discharged, the separated dust is extracted and discharged by the compressed air flowing into the injector at high velocity and the vacuum effect that is generated (Venturi effect) at the dust discharge system (hopper).

Inlet Box

Separate or attached housing part of the filter apparatus for the raw gas inlet.

Interval Time

Pause between the opening intervals of the valves on the cleaning unit for the Herding sinter-plate filters.

Jet-Pulse Cleaning System

For cleaning the Herding sinter-plate filters with compressed gas.

Lamella Shape

Geometry of the Herding sinter-plate filters. Apart from an optimum inflow the lamella shape also provides for a large surface area and a sturdy structure.

Life Time

The length of time that a technical object can be used before it has to be replaced or completely fails.

Given the classic surface filtration process on a non-pliable rigid body, this is normally many years for Herding sinter-plate filters, if they are used as intended.
For example, 15 years in the cement industry in 3-shift operations, or more than 10 years in the chemicals industry.

Loading Station

Separate equipment for receiving the dust from the filter unit hopper e.g. combined with a pneumatic discharge. 

Local Exhaust

Vacuum extraction of an object such as a machine (dust-generating machine) in order to clear the machine of dust as it collects and to prevent the operating personnel getting covered in dust as well. This requires the use of a local filter (see local filter).

Local Filter

Filter unit with connected raw and clean gas pipelines and fan on the raw gas side for vacuum extraction of an object such as a machine (dust-generating machine). The purpose of the local filter is to remove the dust collecting in the machine so that the machine does not suffer any damage from the dust, and to prevent the hazardous dust coming into contact with the operating personnel - see local exhaust.

For the opposite to this, see process filter.

Locating Bar

Component made of powder-coated metal in the filter unit for guiding the base strips of the Herding sinter-plate filters » comb.

Low Contamination Dust Discharge

Dust discharge with least possible contamination/soiling of the environment surrounding the filter unit, and therefore for the protection of objects and persons, when the dust is removed from the filter unit.


Herding filter plants and filter elements require very little maintenance, because of their rugged design.


A version of surface coating for the Herding sinter-plate filter. M-coating is a mineral coating with high pH resistance. 

Modular Series

A series of Herding filter units comprised of modular units (see modular unit).

Modular Unit

A version of Herding filter units.
For applications involving larger volumes of air, the required filter surface area is achieved with a modular sequence of several filter housings.


Filter control system developed in-house for Herding filter units.
Processor unit for controlling and monitoring the cleaning of Herding sinter-plate filters, the vacuum generators such as fans or by-pass blowers, the discharge systems and other field devices on the filter unit.

NDU Uncoated Filter Element for Oil Mist

A version of the Herding sinter-plate filter. The uncoated filter elements are comprised of a microporous filter element without coating and act as deep-bed filters. The separation of oil mist or more generally of liquid droplets (mist) from the process gas is possible.

Non-chargeable Version

A version of the Herding sinter-plate filter.
The pore structure of these filter elements prevents the filter element from becoming charged by the inflow of dust particles with the process gas or during cleaning and therefore the keeps the dust particles separate from the filter elements.

Non-halogen Coating

Surface coatings which contain no halogenated substances (above all free of fluoride compounds).

Outlet Grille

Grille on the clean gas outlet of the dust collector to prevent access.

PE Matrix

The base body of the Herding sinter-plate filter is made of sintered polyethylene (PE) material. It is this material, in combination with the saw-tooth geometry of the filter surface, that makes the filter element so stable and non-pliant. In combination with the surface coating, the Herding sinter-plate filter acts as a classic surface filter and is very long lasting if used as intended.

Pneumatic Discharge

Emptying of the hopper by means of pressure or vacuum.

Pneumatic Valve Control

Pneumatic quick-opening valves can be actuated by pilot valves or by a pneumatic controller. A pneumatic controller controls a maximum of 20 filter pulse valves and replaces the solenoid control unit. The pulse valves are connected to the pressure chamber of the controller by small bore airlines (max. 2m long). The wiper arm assembly of the controller is operated by a pneumatic ratchet drive. It pauses between valve connections for a preset time which is adjustable by the user. The switching time is also user adjustable by means of a throttle valve accessed after removal of the bottom casing. During the switching time the wiper arm passes beneath a valve connection port and vents the pilot. The valve open and remains open until the wiper arm moves on to the next position. The pilot air is vented through the port underneath the manual override knob, which is marked to show the exact position of the wiper arm. (Source


The addition of an inert solid (see inertization, see calcium carbonate) will bind a dust which has adhesive characteristics. The result is an inert, non-adhesive mixture of substances that can be safely separated and cleaned in the Herding sinter-plate filter. Stable extraction from the dust generating-machine is possible.

Pressure Shock Proofed

The equipment is able to withstand a specific pressure surge.

Pressure Shock Resistant Design

Pressure shock resistant design of the apparatus in accordance with the required pulse of compressed air.

Pressure-resistant Design

Pressure-resistant design of the apparatus in accordance with the required pressure level.

Process Filter

Filter unit with connected raw and clean gas pipelines and fan on the raw gas side for vacuum extraction of a machine which is directly upstream. The process filter is for separating the solids from the air current and is used for the production of bulk material products suitable for further processing.
For the converse of this, see local filter.

Product Recovery

The dust separated in the Herding filter unit and discharged at the hopper can be fed on to a further working and treatment process. The converse of product recovery is the disposal of the dust as waste.

PTFE Coating

A version of surface coating for the Herding sinter-plate filter. The PTFE coating is a microporous coating which is bonded fast to the surface of the base body. This coating on the inherently stable and saw-tooth shaped base body made of polyethylene (see PE substrate) is what is responsible for the functional principles of the Herding sinter-plate filter as a classic surface filter (see surface filtration).

Pulse Time

Opening time of a valve on the cleaning unit for the Herding sinter-plate filters.

Quick-opening Solenoid Valve

Valve on the cleaning unit for the Herding sinter-plate filters.
This is actuated by electromagnetic actuators, and the special geometry of the valve enables it to open quickly and therefore send a shock-like pulse for cleaning the dust off the surface of the Herding sinter-plate filter.

Raw gas

Raw gas = the extracted air volume (volumetric flow) which is laden with air pollutants (emissions).

Raw Gas Loading

This is the concentration of dust relative to volumetric flow on the raw gas side of the filter unit and is normally expressed in g/m³.

Raw Gas Side

Dust side (=the system components that come into contact with dust in normal operation).

Synonym: The side in contact with the product; all components in this area are therefore referred to as components in contact with the product.

See components in contact with the gas.

Recirculating Air Operation

In circulating air mode there is no air fed in from outside (saving of saving), the air being recirculated instead (Extraction point -> Filter plant -> Extraction point (or building)).


Operation used for recoating used Herding sinter-plate filters involving measurements of the specific properties.

Reusable by Regeneration

Re-use of the treated and recoated base body of used Herding sinter-plate filters.

Rigid Matrix

Herding sinter-plate filters are designed as rigid bodies which are inherently stiff. Hence the Herding filter elements do not develop any signs of wear caused by flexing.

Rotary Air Lock

Rotary air locks are devices used for dosing, feeding or discharging fine-grained and dust-type products or granulates from the bottom section of a hopper. Rotary air locks are installed below filters and cyclones to enable bulk solid material to be discharged from air conveying systems with minimum possible loss of pressure.  (Source

Round filter

Filter unit with a cylindrical design. Typical round filters include, e.g. pressure shock resistant filter plants » Herding RESIST.

Run-on Cleaning

For cleaning the Herding sinter-plate filters without process gas and dust flowing through the filter unit.


Safe (low contamination) change of dust collecting bins or other system components. As a rule this is normally carried out with a sack board with two grooves and two O-rings. Also referred to as BIBO (bag in and bag out).

Sealing Wall

Partition wall between the clean gas compartment of the filter and the compressed air tank for the filter cleaning system.

Separation Rate

The percentage relationship between the difference between the raw and clean gas dust concentration relative to the raw gas concentration.

Service Life

The service lives of Herding filter plants often exceeds 10 years. We provide a 24 month warranty for the filter plant/elements as standard, subject to a maximum of 15,000 hours of operation. You are also welcome to extend the warranty period for the filter elements to a maximum of 5 years or 25,000 hours of operation by concluding a service contract with us. The service is carried out once a year and gives you enhanced operational reliability.


High-molecular polydimethylsiloxanes (PDMS, or known simply as "silicones"), and sloughage from synthetic materials (e.g. polyethylene, polytetrafluorethylene) and high-molecular polyglycols can cause severe surface deterioration even with the least contamination of our products when these are used in paint shops. Cross-linked silicones (e.g. silicon rubber) are by themselves harmless. But most silicon rubber products contain enriched high-molecular silicon oils as softeners. Such substances are highly incompatible with varnishes and they cause surface deterioration (sinkholes) in the varnish coating. (Source Silicon-free means not using any materials and products in production that contain silicon. An additional cleaning process is often required to ensure that this is the case.

Silo Filter

A filter which is mounted on top of a large storage tank and which allows the displaced air without dust to escape from the tank after filtering during filling.

Synonymous to bunker top filter.

Sinter Plates

Porous, seamless sintered PE plates.

Sinter-Plate Filter

We guarantee that our sinter-plate technology delivers clean gas values of < 0,1 mg/m³, even for types of dust with D50 < 1µm. The base body is made of sintered PE. An additional PTFE coating is embedded in the pores of the PE base body and forms a microporous, non-stick surface. This combination of materials is resistant to chemicals to the greatest possible extent. Herding® sinter-plate filters are exceptionally stable, non-pliable and water-proof and require only minimal maintenance. They can last for longer than 10 years.

Herding® sinter-plate filters offer top rates of separation and excellent environmental compatibility. The filters can be recycled without any problems, and there is no hazardous waste to be disposed of from the materials used for the elements.

Slotted Plate

The separation level between raw gas (dust side) and clean gas (clean side), on which the filter elements are secured.

Solenoid Valve

A quick-opening valve which is mounted on a pressurized tank. The opening of the valve generates a cleaning pulse which dislodges the dust from the filter elements against the flow direction.


Multipurpose, low-cost valve controller. In combination with the MP12 suitable for use as master and slave. The MP12 filter control center can only be used as a master whereas the SP16 valve controller can be used as both a master or slave. This provides maximum flexibility at the hardware level.

Spacers (on the filter element)

Assembly component for restricting the filter element seal pressure during installation.

Sparks Pre-Separator

Device for extinguishing sparks brought in from outside.

Surface Coating

The Herding sinter-plate filter has a coating on/in its surface (not a membrane). This microporous coating permits classic surface infiltration of the dust particles on the stable and non-pliable base bodies of theHerding sinter-plate filters when the process gas flows through.

Surface Filtration

In surface filtration the dust particles are held back on the surface of the filter medium. The dust particles form a filter cake which is responsible for the actual filtration function. The thicker the filter cake layer becomes, the greater the dust separation. This leads to an increase in differential pressure and reduction in volumetric flow. The cleaning of the filter elements counteracts the increase in pressure and reduction in volumetric flow. In classic surface filtration on the Herding sinter-plate filter, continuous cleaning ensures that suction ratios are maintained at a constant level.

Surface Resistance

Surface resistance is the electrical resistance measured on the surface of an object.
It is measured between two parallel electrodes of minimal width and both with lengths of 100 mm, positioned 10 mm apart and in contact with the surface to be measured. The surface resistance is expressed in Ω.

Toe Board

Stabilization rail on the foot of a filter element

Top Mounting Filter

Generally filter units used for the direct venting of silo systems. See also silo filter bunker filter and bin vent.

Total Separator

Total separators are used for separating large volumes of dust held in the feed air. Since the feeding process requires high levels of pressure, the plants are designed as round filters. The raw gas inflow is often tangential because of the high product loads involved.


Stabilization on the filter elements' head.

Vacuum Feeder

The vacuum feeder is a discharge device which is installed at the lower end of a hopper. The negative pressure in the filter unit keeps the vacuum feeder closed. When the separated product (dust) or a cleaning pulse exerts a high enough load, the vacuum feeder will open and the product (dust) will be discharged. As soon as the negative pressure and the load return to a state of equilibrium, the vacuum feeder will close again.

Valve Compartment

In the Herding FLEX series the valve compartment is integrated in the area of the clean gas compartment. This can be made with a sealing wall so that the cleaning valves can be accessed from the outside during operation. In addition, the sealing wall can also seal the valve compartment in such a way that the valves do not come into contact with the volumetric flow of clean gas. In terms of ATEX, the valve compartment of Herding FLEX filter units falls under the same zone as the surrounding area.

Valve Control Board

Herding GmbH Filtertechnik uses an MP12 or SP16 for the control unit for the valves as standard. This enables a wide range of cleaning programs to be used.

Valve Heater

It is advisable to install a valve heater for filter plants installed outdoors. This prevents condensation water from freezing in the cleaning unit when temperatures fall below zero, thereby preventing malfunctions on the quick-opening valves.




A washable filter element can be washed considering the Herding washing instructions.

Washing Installation

Herding filter plants can be supplied with a first-rinse system or with a WIP system. With the first-rinse the elements are rinsed with a rinsing fluid prior to removal, thereby enabling the hazardous dust, if present, to be bonded so that no dust is raised when the filter elements are removed. With a WIP system the element is rinsed in such a way that only a minimal amount of dust is left over.


WIP = washing-in-place » washing installation.

Zone Barrier

Herding sinter-plate filters can be used as an ATEX zone barrier for dust explosions. The clean gas side can be declared as zone-free if there is an ATEX Zone 20/21 or 22 in the raw gas section and Herding sinter-plate filters are used.



Herding Filtration L.L.C.
5479 Perry Dr. Suite D
Waterford, MI 48329
Tel: +1 248 673 4514
Fax: +1 248 673 4926