Dorman Long Technology
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DLT viscous dampers and lock up devices
DLT passive viscous dampers and lock up devices are for use in tall buildings, bridges, power stations, petrochemical installations and other applications where a structure needs to be designed to economically resist high seismic or dynamic loads such as wind, snow, tsunami and braking forces. Viscous dampers are integrated into the structure to allow it to flex under the action of the dynamic
loads and to absorb energy as that flexure takes place, thus damping the movement to a structurally acceptable level. Lock up devices are used to 'lock' movement joints within a structure (usually a bridge) when the structure is subject to high dynamic loading and to allow the movement joint to behave normally under the action of temperature and concrete shrinkage movements.
Typical examples of the integration of viscous dampers into a structural frame are as follows :
Our viscous dampers use silicone oil as the damping medium which gives very stable and durable performance and is rated for use in temperatures from -50 to +250 deg C. Every damper is fully performance tested and certified prior to leaving the works, comprising a low speed resistance to motion test and a dynamic test to check compliance with the customer's specification.

All our viscous dampers are made to order as the requirements for each project can vary considerably. Our dampers can be designed to resist a Nominal Load of between 60 - 3000 kN and can have any stroke up to +/- 500 mm. Please provide the following data when requesting a quotation :
  • Nominal length between end connections (mm) and end connection type (pinned or bolted end plate)
  • Max +/- stroke required (+/- mm)
  • Nominal load (kN) Not less than the maximum damping force F calculated from the following three parameters.
  • Damping coefficient C (kN/ (mm/sec))
  • Maximum velocity of piston V (mm/sec)
  • Velocity exponent A, betweem 0.1 to 1.0, where 1.0 = linear damping

When modeling the effect of dampers in your structure the damping force
F = C x V A

For lock up devices the following parameters need to be specified :

  • Nominal length between end connections (mm) and end connection type (pinned or bolted end plate)
  • Max +/- stroke required (+/- mm)
  • Maximum load that must be resisted (kN).
  • Lock up velocity (mm/sec)
  • bleed velocity (mm/sec)