21 400/117 ED

1/2

MRQA

UNLOADING VALVE

(FOR CIRCUITS WITH ACCUMULATOR)

SERIES 42

PERFORMANCE RATINGS (measured with mineral oil of viscosity 36 cSt at 50°C)

HYDRAULIC SYMBOLS & DIAGRAM

OPERATING PRINCIPLE

MOUNTING SURFACE

21 400/117 ED

SUBPLATE MOUNTING

ISO 4401-03

p max

350 bar

Q max 40 l/min

ATPB

SO 4401-03-02-0-05

(CETOP 4.2-4-03-350)

— MRQA is a pressure relief and safety valve with automatic

unloading. Upon reaching the set value, the valve freely unloads

the pump and puts it under pressure again when the pressure

values descend in the circuit to correspond to 63% or 75% of the set

value.

In order to assure this operation, it is necessary to use an

accumulator (see hydraulic diagram) that guarantees pressure

maintenance in the circuit. A check valve, incorporated in the panel

or available as a plate under the valve MRQA/C, prevents the

accumulator unloading through the open valve.

This system maintains the pressure in the hydraulic circuit, avoiding

heating of the oil and reducing energy consumption.

It is recommended to place the accumulator as close as possible to

the MRQA, without reducing the connection size.

— The cycle time depends on the pump flow rate, the accumulator

capacity and pre-charge, and the flow requirement of the system.

Maximum operating pressure bar 350

Maximum flow rate l/min 40

Ambient temperature range °C -20 / +60

Fluid temperature range °C -20 / +80

Fluid viscosity range cSt 10 ÷ 400

Fluid contamination degree

According to ISO 4406:1999

class 21/19/16

Recommended viscosity cSt 25

Mass: MRQA

MRQA*/C

3,3

4,2

MRQA MRQA-*/C

21 400/117 ED

2/2

MRQA

SERIES 42

REPRODUCTION IS FORBIDDEN. THE COMPANY RESERVES THE RIGHT TO APPLY ANY MODIFICATIONS.

1 - IDENTIFICATION CODE

Seals: omit for mineral oils

V = viton for special fluids

Series No. (the overall and

mounting dimensions remain

unchanged from 40 to 49)

Unloading valve

Automatic unloading for

circuits with accumulator

2 - CHARACTERISTIC CURVES (values obtained with viscosity of 36 cSt at 50°C)

4 - OVERALL AND MOUNTING DIMENSIONS

Size ISO 4401-03

C = Check valve (omit if not required)

Pressure adjustment range:

3 = 25 ÷ 70 bar

5 = 50 ÷ 210 bar

6 = 100 ÷ 280 bar

Differential pressure (values ± 2.5%)

1 = pump switch on at 75% of adjustment value

2 = pump switch on at 63% of adjustment value

M = Adjustment with SICBLOC knob

(omit for adjustment with hexagonal head screw)

dimensions in mm

M R Q A - / / / / 42 /

3 - HYDRAULIC FLUIDS

Use mineral oil-based hydraulic fluids HL or HM type, according to ISO 6743-4. For these fluids, use NBR seals. For fluids HFDR type

(phosphate esters) use FPM seals (code V). For the use of other kinds of fluid such as HFA, HFB, HFC, please consult our technical

department. Using fluids at temperatures higher than 80 °C causes a faster degradation of the fluid and of the seals characteristics.

The fluid must be preserved in its physical and chemical characteristics.

4030

Q[l/min]

p[bar]

ADJUSTMENT RESETTING PRESSURES PRESSURE DROPS p-Q

PRESSURE CYCLE

Mounting surface with sealing rings:

4 OR type 2037 (9.25x1.78) - 90 Shore

Hexagonal head adjustment screw.

Spanner 13.

Clockwise rotation to increase pressure

SICBLOC adjustment knob.

To operate, push and rotate at the

same time.

Pressure gauge port 1/4” BSP

Check valve for version /C

FASTENING SCREWS:

MRQA

4 SHC screws ISO 4762 M5x95

MRQA/C

4 SHC screws ISO 4762 M5x135

Tightening torque: 5 Nm