FTDF-K Duplex filter PN 16 DN 15 – 125 ANSI 1/2 – 5 JIS 15-125 GOST 15-125

Application areas

The FTDF duplex filter can be used in pressure and suction modes and is versatile for coarse and fine filtration. It is characterized by continuous filter operation during the cleaning possibility. The filter is compatible with the KSF series. The filter combines the so-called housing sizes (GR) with the various nominal widths (DN) of the flange connection. FTDF-K has a bolts and nuts lock and can also be delivered with screws and nuts as well as with a quick acting lever lock (medium-dependent – risk analysis required). Subsequent on-site retrofitting is also possible.

Brief description and function

The duplex filter, cast as a component, comprises two identical single filters, connected via a cockswitching device to a filter side or can be operated in parallel. Medium to be filtered enters the filter basket from the top and flows through the insert inside out.Dirt thus remains in the filter element. As a special version, the filter is also available with star filters (changed inflow).

Safety instructions

Filters with lever locks are not suitable for the filtration of hazardous media (e.G. poisonous, inflammable or corrosive). In such cases, screws and nuts must be selected as lid closures. Generally, use of filter with switching valve must be checked for hazardous media (leakage rate permitted by the design). FTDF-K filters are not suitable for the filtration of gases.

Check the filter for intended operation prior to usage. Conformity assessment as per PED EN 97/23 EC. must be done for changes in operating conditions or the media (kindly contact us for the same or run a risk analysis with conformity assessment).


  • Check whether all screws and locks have been tightened properly.
  • Check the position of the switching lever (there is a covered on the switching valve, which defines the direction of flow and/or shows “in operation” on the filter pot. The handle must be fitted accordingly).
  • Venting: Venting device fitted in the housing of every single filter is open till the fluid discharges. The filter is ready-to-operate after venting the single filter.


3.1. Certificate, DGRL / TÜV, GL, LS, DNV, ABS, GOST/RTN


Note: Since it is a pressure vessel, it is important to ensure that the container is without pressure prior to beginning of maintenance.

  1. As soon as the filter half is dirty (increasing differential pressure on the indicator or decreasing operating
    pressure in the system), the clean filter half is put into operation by gradual switching of the plug valve.
  2. Proceed with cleaning (removal of filter element) only after opening the venting device slowly and
  3. after opening the drain plug and draining the remaining fluid from the container (filter side to be cleaned):

Caution: note maximum differential pressure of the filter (standard Dp = 1 bar).


The filter side to be cleaned must be depressurized (open vent carefully after switching over to the other filter side).

  1. Then lift by loosening the filter cap or the screws and nuts of the cover of the filter half to be cleaned.
  2. Note cover gasket integrity during assembly, replace if necessary.

Important: Duplex filter with switching valves have a permissible leakage rate, leakage rate of the FTDF filter at delivery condition at max. design pressure (Pdesign) is approx. 20% of the contents of the vessel in approx. 30 minutes.

INFORMATION: Hence, do not leave the opened filter unattended and if required, keep an already cleaned reserve filter element ready for replacement.

Important information for switchover

For media having corrosion effect on the material of the filter, switching must be actuated regularly (2-3 times) per week. Alternative to the standard switching valves in EN GJS-500-7, switching valves in bronze, stainless steel 1.4571 and/or 1.4408 (SS316) are also available.


DIN EN GJS-500-7 / (GGG-50)

alternatively annealed GJS-400-18 / (GGG 40.3)

Alternative vessel material

RG 5/10 G-CuSn5(10)ZnPb


Filters may be additionally fitted with heaters for smooth start and continuous reduction in the viscosity of the medium to be filtered.

Advantages of FTDF-K