Hydraulic grips – single actuator

Symmetrical and asymmetrical gripping

Hydraulic grips are primarily used when test loads of 50 kN and over, with associated high gripping forces, are required (Fmax from 10 kN to 2500 kN possible). .

The clamping pressure can be adjusted and reproduced with a high degree of accuracy.
Defined force application ensures optimum gripping of sensitive materials.
ZwickRoell's "Force Constant Hold" force stabilization system reliably protects the specimen from unwanted tensile or compression forces due to material flow or grip deformation during the closing and clamping process.
The ratio between gripping and tensile forces can be adjusted individually, ensuring that the specimen is held securely (at maximum tensile force approximately double gripping force is required).

Advantages & features

Advantages

Hydraulic grips have an eccentric piston shape with a long piston stroke, achieving a deep clamping surface position and a large opening width.
The alignment of the jaws, specimen grips, and piston facilitates gripping of short specimens as well.
Defined force application ensures optimum gripping of sensitive materials.
Contact pressure can be reproduced exactly
Specimen grips can be installed in testing systems at three different angle settings (0°, 45°, and 90°).
T-slots in the lower part of the basic body serve as a mounting for the T-slot system, enabling the accommodation of smaller load cells, specimen grips, test tools, and fixtures (except hydraulic grips, type 8392, Fmax 10 kN).
Prismatic jaws (jaws with V-slots) can be rotated and have two-fold use: For round and flat specimens or for round specimens with various diameters (jaws with crosswise arranged V-slots)
The upper and lower grips can be opened and closed either individually or together via remote control or PC.
The ratio between gripping and tensile forces can be adjusted individually, ensuring that the specimen is held securely (at maximum tensile force approximately double gripping force is required).
Hydraulic grips are designed to offer optimal specimen feeding.
An adjustable, scaled stop ensures precise vertical specimen gripping for manual special feeding.
For easier specimen centering, a centering stop can be used.
For safety reasons, specimen tongs can be used to insert the specimen.

Operating principle

The oil pressure is set at the hydraulic power pack according to the required closing pressure for the specimen grips. The control unit controls the closing and opening procedure separately for the top and bottom specimen grips.

Furthermore, the closing procedure is divided into a closing phase and gripping phase when a a universal hydraulic power pack is used. In the closing phase, the specimen is initially held on the upper end for safety reasons. During gripping, the full gripping force is applied. The force value is based on the expected tensile force.

Double-sided actuators

All hydraulic grips are equipped with double-sided actuators. This means the specimen grip opens hydraulically and not by means of spring return mechanism. The closing and opening pressure can be adjusted.

In contrast to single-acting actuators that open by means of a spring return mechanism, double-sided actuators ensure that the specimen grips always open safely . This also applies if the specimen is crooked or jammed. Additionally, the full opening stroke is not necessary because the opening procedure can be interrupted at any point using the Stop button. The opening stroke can be adjusted according to thickness. Especially with thin specimens, the test time is reduced and the risk of pinching parts of the body is minimized.

Single-sided and double-sided closing specimen grips

Single-actuator hydraulic grips can be used for the symmetrical and asymmetrical gripping of specimens (for example, for shear tests). The thickness of the specimen is set by means of screw unit.

The single-actuator hydraulic grips are also available with a tandem cylinder to enable uniform force application to the specimen (especially suitable for tests on fabrics, textiles and geotextiles).

Double-actuator hydraulic grips always close symmetrically with respect to the tensile axis. This means the specimen is gripped in a precise axial position, thereby eliminating the need for thickness adjustment.

T-slotted system

The T-slotted system makes it possible to accommodate small load cells, specimen grips, test tools, and fixtures quickly, without having to dismantle the specimen grips.

T-slots are integrated in the gripping area of the specimen grip. These serve as mounts for the T-slotted mounting. The T-slotted mounting is clamped there. Other fixtures can now be mounted, saving time needed to mount other tools and fixtures.

Properties according to force range

Item No.	320719¹²
Type	8392
Operating principle/identification	For fleece and other compressible specimen
Test load F_max	10	kN
Operating pressure	10 ... 150	bar
Gripping force at max. pressure	20	kN
Dimensions
Height	152	mm
Width	359	mm
Depth	76	mm
Opening width, max. with jaws, thickness 5 mm	78	mm
Gripping travel	50	mm
Gripping of the specimen	The specimen must be gripped with at least 1/2 of the jaw height
Connection, stud	Ø 20	mm
Ambient temperature	+10 ... +35	°C
Weight per specimen grip, approx.	12.1	kg
Scope of delivery	2	pieces

Recommended and approved for strain rate control to the standards DIN EN ISO 6892-1:2009 and ASTM E8-09
Includes connecting hoses

Item No.	317178¹
Type	8802
Operating principle/identification	Single-sided closing
Adjustability of the opposing jaw	Stepless
Test load F_max	100	kN
Operating pressure	12 ... 300	bar
Gripping force at max. pressure	255	kN
Dimensions
Height	303	mm
Width	423	mm
Width with screw unit, open completely	461	mm
Depth	170	mm
Gripping travel	35	mm
Gripping of the specimen	The specimen must be gripped with at least 2/3 of the jaw height
Connection, stud	Ø 60	mm
Ambient temperature	+10 ... +35	°C
Weight per specimen grip, approx.	70	kg
Scope of delivery	2	pieces

Recommended and approved for strain rate control to the standards DIN EN ISO 6892-1:2009 and ASTM E8-09

Item No.	317180¹
Type	8803
Adjustability of the opposing jaw	Stepless
Operating principle/identification	Single-sided closing
Test load F_max	250	kN
Operating pressure	12 ... 480	bar
Gripping force at max. pressure	410	kN
Opening width, max. with jaws	59	mm
Dimensions
Height	303	mm
Width	423	mm
Width with screw unit, open completely	423 (461)	mm
Depth	170	mm
Gripping travel	70	mm
Gripping of the specimen	The specimen must be gripped with at least 2/3 of the jaw height
Connection, stud	Ø 60	mm
Ambient temperature	+10 ... +35	°C
Weight per specimen grip, approx.	70	kg
Scope of delivery	2	pieces

Recommended and approved for strain rate control to the standards DIN EN ISO 6892-1:2009 and ASTM E8-09

Item No.	317677	317669	316734
Type	8393	8493	8593
Test load F_max	50	100	250	kN
Operating pressure	50 ... 450	50 ... 350	50 ... 480	bar
Gripping forceat max pressure.	300	600	1200	kN
Dimensions
Height	255	340	352	mm
Width	390	500	550	mm
Depth	260	315	345	mm
Opening width, max. with jaws	35	35	35	mm
Gripping of the specimen	The specimen must be gripped with at least 2/3 of the jaw height
Connection, stud	Ø 36	Ø 60	Ø 60	mm
Ambient temperature	+15 ... +35	+15 ... +35	+15 ... +35	°C
Weight per specimen grip, approx.	65	160	235	kg
Scope of delivery	2	2	2	piece(s)

Picture gallery of hydraulic grips for geotextiles

Hydraulic grips 250 kN for Geotextiles

The specimen is fed into the grips via the rail and is then clamped.

Using the work panel, the textile specimen is easily gripped in the rail without significant deformation.

Do you have any questions regarding our products?

Please feel free to contact our product experts.
We look forward to discussing your needs.

Contact us

Related products and accessories

Download

Product brochure: Specimen Grips and Test Tools PDF 4 MB
- DE
- EN
Product information: Hydraulic grips, Fmax 50 kN PDF 425 KB
- DE
- EN
Product information: Hydraulic grips, Fmax 100 kN / 250 kN PDF 638 KB
- DE
- EN
Product information: Hydraulic grips with large opening, Fmax 10 kN PDF 604 KB
- DE
- EN
Product information: Hydraulic specimen grips for geotextiles, Fmax 50 kN / 100 kN / 250 kN PDF 525 KB
- DE
- EN

Single Actuator

Advantages

Operating principle

Double-sided actuators

Single-sided and double-sided closing specimen grips

T-slotted system