Stressing Mono Jacks and Onion Jacks

Hydraulic post-tensioning stressing jack are manufactured in the UK and range from 17 to 30 tonnes and have a range from 5mm upto 16mm diameter strand wire capacities and are primarily used for pre-stressing and/or post-tensioning PC strand tendons with concrete slabs, decks and floors.
They are fully tested and calibrated in-house, making them safe and reliable within the toughest environments.
We offer over 8 different models of post-tensioning stressing jack from 17 to 30 tonnes in capacity with a variable strokes from 150mm to 300mm.
Our hire fleet stock is continuously introduced to meet all load and stroke requirements.

Selection Chart

Jack Type Stroke (mm)Capacity
(kNs)SJ25-150 Hydraulic –Double-Acting 150 250
SJ25-200 Hydraulic –Double-Acting 200 250
SJ25-300 Hydraulic –Double-Acting 300 250
SJ30-200 Hydraulic –Double-Acting 200 300
SJ30-300 Hydraulic –Double-Acting 300 300

Onion Jackand Assocaited Grouting Equipment

An onion jack is used in prestressing cables to create an anchor point. It creates an onion shape at the end of these cables by spreading and separating the wires.The machine is heavy duty in nature, yet is light and mobile, being able to be used by hand or machine operated pumps. The key advantages of the onion jack are that you remove the need for anchor plates, barrels and wedges.

Stressing Associated Equipment

Ref Description Capacity (SWL) –kNs
OJ-10 10te Onion Jack 100
SSJ-25 Heavy Duty Swag / Seating Jack 250
SP-110 Strain Pusher (110V) n/a
GP-110 Electric Grout Pump (110V) -150 litres 50 bars
SG-01 Staple Guns n/a
SCW-12 12.7mm Stressing Collar Wedge -
SCW-15 15.2mm Stressing Collar Wedge -
SW-12 12.7mm Seating Wedge -
SW-15 15.2mm Seating Wedge -
SJ-FLN Flat Nose Head 250 to 300 kNs
SJ-NOSE Solid Nose Head 250 to 300 kNs
SJ-HYN Hydraulic Nose Head 250 to 300 kNs

Key Features:

  • 8 different models
  • Safe working load of 175 kNs, 250 kNs and 300 kNs
  • Range of strokes from 150mm, 200mm and 300mm
  • Double-Acting Cylinder
  • Flat / Curved, Spring-Return, De-stressing and Hydraulic Noses available
  • Can suit 5mm and 16mm diameter wire strands
  • Pressure Relief Valve to eliminate over-loading
  • Expensive range of accessories and consumables
  • Stocks available for immediate dispatch


  • Suits from 5mm but primarily 12.7mm and 15.7mm strands and wires
  • Pre-stressing and Post-Tensioning systems
  • Compact and realible designs
  • Designed and tested to British Standards.

For all Hydraulic Accessories, please see here and here
We stock the largest extensive sales / hire fleet range with over 1,500 hydraulic jacks and accessories which are fully load-proof tested and traceable to UKAS.
We also offer full post-tensioning and pre-stressing equipment available for hire and sales ranging from electric grout pumps, stressing pumps, strand pushers, onion jacks, swag-jacks, strand dispensers / holders and consumable wedges, anchorages etc.

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Hydra-Capsule Limited
Hydra House - Bishops Frome

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