Suction-return filters.


Hydraulic oil returning from the circuit (R) passes through the filter element (1), is pressurized by a 0.5 bar check valve (2) and is supplied to the feed pump (S). Excess oil flows filtered over the integral check valve into the reservoir (T). As the feed pump is always fed with pressurized oil, the risk of cavitation is minimized and full performance is available even during the critical cold start phase.

An integral bypass valve (3) in the filter element (1) prevents too high back pressure (eg with cold start or contaminated filter element).

A bypass valve protection filter ensures that under no circumstances can unfiltered oil enter the feed pump.

A bypass valve protection filter ensures that under no circumstances can unfiltered oil enter the feed pump.

While with the use of separate filters, both circuits operate independently of each other, the combination of the two circuits through a suction return filter causes interaction between the circuits. By following the design criteria outlined below, you can take full advantage of the benefits provided by the suction-return filter concept.

E 178
E 088

Return flow required in the system

To maintain a precharge pressure of approx. 0.5 bar at the feed pump inlet, the return flow must exceed the suction flow under any operating conditions.

Allowable feed pump flow

  • At rated speed and operating temperature, the fill pump volume flow should not exceed 80% of the filter rated volume flow rate (for example, with a return suction filter with a rated volume flow / return flow of 200 l / min, the volumetric flow of the filling pump should not be more than 160 l / min).
  • In extreme cold starts (ν = 1000 mm² / s) and slightly increased idle speed.

(n = 1000 min-1), the volume flow of the filling pump must be ≤ 80% of the return flow.

Pressure loss in suction lines

Under the cold start conditions mentioned above, the pressure loss in the suction lines must not exceed 0.4 bar. This ensures that the fill pump is supplied with sufficient oil even with a partially contaminated filter element.

Back pressures in the system return lines

When draining oil from the hydrostatic drive is directed through the filter, allowable leakage oil pressures must be observed to protect the shaft seals. Here, in addition to the filter back pressure, the pressure loss caused by leaks from the oil pipes and the oil cooler must also be considered.

Depending on the application, the use of a cooler bypass valve is recommended.

Filter quality and oil cleanliness degrees

As standard, for all return suction filters, two ARGO-HYTOS filter grades are available: 10EX2 and 16EX2. Both with the patented EXAPOR®MAX2 design. The following oil cleanliness can be achieved according to ISO 4406:

  • 10EX2: 18/15/11… 14/11/7
  • 16EX2 20/17/12… 17/14/10

Los fabricantes de accionamientos hidrostáticos recomiendan principalmente para el funcionamiento normal una limpieza de aceite del 20/18/15 y a partir del 19/17/14 para mayores requisitos > Even with the fineness of the 16EX2 filter, these requirements are 100% met.

Online mounting

Until now, return suction filters have only been offered as a tank top mount version. As particularly with compact machines, the tank is often difficult to achieve, ARGO-HYTOS, as the only manufacturer to date, has developed return suction filters for in-line mounting. These in-line mounting versions can be integrated in an easily accessible location on the return line and the suction line.

E 068 / E 088

E 178 / E 258

Nominal flow

up to 100 l/min, two length variants

up to 250 l/min, two length variants

Filter fineness

10EX2 and 16EX2

10EX2 and 16EX2

Operating pressure, max.

10 bar

10 bar

Bypass valve cracking pressure

2.5 bar

2.5 bar

Bypass valve protection strainer

mesh size 125 μm

mesh size 200 μm

Return connections

G ¾ (1x)

G1 (4x)

Suction connections

G ¾ (1x)

G1 (3x)

Tank connection

G ¾


Clogging indicator ports

M12x1.5 (plugged) (2x)

M12x1.5 (plugged) (2x)