FTDF-V Duplex filter PN 10 – PN 64 DN 100-600 ANSI 4 – 24 JIS 100-600 GOST 100-600

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 phase. The filter combines so-called housing sizes (GR) with various nominal flange connection widths (DN). FTDF-V has a lid-combination 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. A danger analysis hast o be performed before start up acc. PED or applicable codes and standards.

Brief description and function

The duplex filter, comprises two identical single filters, connected via a valve-switching 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. The use of FTDF-V filters for gases requires a review by the manufacturer. Check the filter for intended operation prior to usage. Conformity assessment as per PED 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).


  • The pressure equalization line must be opened prior to commissioning.
  • Check whether all screws and locks have been tightened properly.
  • Check the position of the switching lever (here is an incised on the shaft, which defines the direction of flow and/or shows “in operation” on the filter pot. The handle must be fitted accordingly).
  • Both filter chambers shall be filled simultaneously by opening the switch device slowly to avoid fast pressure equalization of the empty chamber.
  • Venting: The sventing device fitted in the housing of each individual filter must be held open until fluid discharges. The filter is ready-to-operate after venting the single filter pot.
  • Check whether the pressure equalization line is closed after commissioning.


Caution: 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.
  2. IMPORTANT: The pressure equalization line must be opened before the switch-over. If this instruction is not followed, damage can occur during switching.
  3. Proceed with cleaning (removal of filter element) only after opening the venting device slowly and only after releasing the pressure from the chamber which shall be cleaned / pressure equalization with atmosphere pressure the cover can be removed. While removing or releasing pressure constantly check if the switch has closed the chamber and that there is no leakage. In case of leakage the process has to be stopped and the filter isolated via IN/OUT valves.
  4. 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 lid of the filter half to be cleaned.
  2. Note lid gasket integrity during assembly, replace if necessary.

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

Important information for switchover

For media having a corrosive effect on the material of the filter, switching must be actuated regularly (2-3 times) per week. Filters are alternatively available in bronze, or in stainless steel 1.4571 or 1.4408 (SS316).


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

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

Alternative materials

RG 10 G-CuSn(10)5

1.4571 stainless steel

Steel for example PGH 284, St 37.5 and others acc. ASTM


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