Modular SMF®-AR System

Owing to greatly differing application profiles with exhaust-gas temperatures that are frequently too low, mobile machinery and stationary applications are usually fitted with active systems, such as the SMF®-AR (Sintered Metal Filter with thermoelectric selfregeneration) system developed by HJS. With this system, the particulate filter can be regenerated at almost any engine operating point, irrespective of exhaust-gas temperature.

The heat necessary to burn off the particulate matter is generated by the SMF®-AR system itself. Thanks to the compact and modular design of the SMF®-AR
system, it can be put to use in many different applications. Pipes and brackets can be modified as required to match the different machines and vehicles. As a rule, SMF®-AR systems replace the original silencer.

Application examples for SMF®-AR systems:

Construction machinery and construction equipment, such as forklift trucks, mini hydraulic excavators, wheel loaders, industrial trucks and power generating sets.

Functional description

The SMF®-AR system filters the exhaust gases until an optimum quantity of soot for regeneration has been collected in the filter. The system makes use of the positive active properties of a fuel additive that on the one hand lowers the soot’s ignition temperature and on the other hand increases its burn-off speed.

The soot trapped in the filter can, therefore, be burned off automatically in a regeneration process when the exhaust-gas has a temperature of around 400°C. If, however, the necessary temperature is not reached – which is frequently the case in the low-load range – the system’s active, thermoelectric regeneration function cuts in.

Technical description: air mass flow meter (AMFM) and exhaust flow sensor (EFS)

The AMFM forwards the intake air mass flow measured to the ECU. The HJS EFS (exhaust flow sensor) uses the pressure difference in a Venturi nozzle to measure the exhaust-gas volumetric flow or mass flow that flows through this nozzle.

The pressure sensor communicates with the ECU via the CAN bus. With the aid of a temperature sensor, the exhaust-gas volumetric flow is converted to a mass flow. The mass flow is used to control the electric heater.

Active, thermoelectric regeneration

The control unit triggers (active) regeneration by means of the heating elements that encircle the filter. The soot that has built up in the filter is ignited by the energy radiated by the heating elements. After the initial ignition of the soot layer, the regeneration process runs automatically until completed, that is, all the soot has been burned off. This occurs at regular intervals. However, the control unit not only triggers ignition of the soot, but also doses the optimum amount of additive, monitors the filter load and, with the help of sensors, calculates the best timing for regeneration. In addition, a self-learning driving-cycle recognition functionality generally ensures that a regeneration cycle that has already started is not interrupted when the engine is switched off.

Thanks to the high soot holding capacity of the SMF®-AR system, there isn’t just one single ideal moment for regeneration, rather regeneration takes place within a wide time slot. Terminating regeneration by switching off the engine therefore poses absolutely no problem to reliable, safe operation of the SMF®-AR system.

A further advantage of the SMF® is its high ash holding capacity,which allows for long servicing and cleaning intervals.

SMF®-AR advantages at a glance

✔ Suitable for OE and retrofitting applications
✔ Reduction of soot particles and fine particulate matter by more than 99%
✔ Particularly suitable for low-temperature applications
✔ Fully automatic, active regeneration
✔ Robust thanks to the use of sintered metal (SMF®) – Suitable for use in construction machinery
✔ Reliable operation
✔ Low maintenance
✔ Longer service life
✔ NO2-neutral regeneration
✔ Use of fuels with a high share of sulphur as well as other “special” fuels (e.g. kerosene) on request

Technical data and requirements

  • Max. safe temperature operation for SMF®*: 650°C exhaust-gas temperature
  • Filter material: high-temperature-resistant chrome-nickel steel
  • Filter housing material: 1.4301
  • Ash holding capacity: max. 50 g/l filter volume
  • Filtration efficiency rate: (number concentration in range from 20 – 300 nm) > 99%
  • Filtration efficiency rate: (in relation to soot mass) > 97%
  • Length of regeneration period: 3 – 7 minutes
  • Max. power consumption of heater: SMF®-AR 1.2 m2 – 3.8 m2: 1 kW with 12-V on-board supply system
  • Max. power consumption of heater: SMF®-AR 5.4 m2 – 8.1 m2: 2.2 kW with 24-V on-board supply system
  • Min. size alternator: 80 Ah
  • Particulate load before regeneration: 20 – 30 g/m2
  • Surface temperature during regeneration without insulation: max. 800°C (peak)
  • Surface temperature during regeneration with insulation: max. 300°C
  • Additive consumption: 1 l/2000 l diesel (depending on volume of particulates emitted by engine)
  • Additive contents: organometallic iron compound
  • Additive pollutant categories: Xn; R48/22, R65, R66

Application and operating conditions

The following application and operating conditions must be complied with in order to ensure the modular SMF®-AR systems from HJS function optimally:

  • Engine fulfils Stage II, Stage IIIA or B in Europe, Tiers II, III and IV in the USA
  • Diesel fuel in compliance with DIN EN 590
  • Exhaust-gas temperatures from 150°C for regeneration
  • Crucial factors when selecting the additive tank (sizes available: 2 l, 3 l and 5 l) are the installation space available and the maintenance interval desired
  • Tank size in line with the average consumption figure and annual mileage covered or number of operating hours
  • Strain-free, vibration-isolated installation and secure, gas-tight connection to the existing exhaust system
  • Systems never mounted on the engine-gearbox unit
  • Only components approved and released by the system supplier are fitted

Perfect connection of the system pipework ensures the exhaust backpressure is low. HJS offers insulating components for all its systems to reduce their surface temperature. The systems are operated in conjunction with the HJS Service Unit (included in the delivery scope).

In order to ensure the systems operate as intended, HJS and its authorised partners offer a temperature-measurement service and one-on-one application consulting. Make sure that personnel are protected against (accidental) contact with hot components!

Dimensioning the filter

HJS offers SMF®-AR systems with filter surface areas ranging from 1.2 m2 to 8.1 m2.

To help you choose the right size of filter, the diagram below shows the exhaust back pressure generated by each size of filter (not taking the inlet and outlet modules into account).

Filter surface areas* from 1.2 m2 to 8.1 m2

Example calculation

In the case of a construction machine with a power output of e.g. 250 kW and a maximum permissible exhaust back pressure of 150 mbar (as specified by the engine manufacturer), a filter with a surface area of 3.8 m² can be installed. In this simplified example, it should be noted that the back pressure flow of the inlet
and outlet modules is disregarded. Radial modules tend to result in a slightly higher back pressure. Further technical data are required if the filter is to be dimensioned more precisely

Considering the installation space available for SMF®-AR systems

After determining the size of the filter, it’s time to see how much space is available for installing them. As a rule, the filter system replaces the original silencer. Alternatively, the particulate filter system can be installed upstream of the silencer.

When selecting the installation position, make sure that there is sufficient clearance between the filter and other components and that the filter can be removed easily for servicing and maintenance work.

The filter unit can be installed horizontally or vertically. The matching inlet and outlet modules must be selected in line with the amount of installation space available in the machine (AXIALAXIAL, AXIAL-RADIAL, RADIAL-AXIAL, RADIAL-RADIAL). To secure the filter, system mounts must be used.

Dimension tables

The dimension tables contain all dimensions of relevance to installation. All dimensions are stated in millimetres (mm). This section describes and illustrates the different versions of filter systems with a surface area of 1.2 m2 to 8.1 m2.

The dimension tables contain the data of the:

  • Inlet module
  • SMF®-AR
  • Outlet module

Scope of delivery

The item numbers listed describe fully assembled filter units with inlet and outlet module, regeneration unit, system clamp, gasket set, wire mesh set, dosing pump (12V/24V), voltage transformer and HJS Service Unit. In addition, all relevant technical documentations, such as the installation guidelines and
maintenance manual, are included in the scope of delivery. The system mounts, additive, air mass flow meter/EFS, transformer, insulation set and tank must be ordered separately.

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