Viscous Fluid Damper-VFD

High Damp Seismic Isolation Lead Rubber Bearing
Shock Transmission Unit (STU)

Viscous Fluid Damper-VFD

Viscous Fluid Damper-VFD

The viscous fluid damper(VFD) is a damper device that uses a cylinder-type structure filled with a damping medium to drive the flow of the internal medium through the reciprocating motion of the piston to generate a damping effect, thereby converting kinetic energy into thermal energy.

When a viscous damper is used on a bridge, one end of the damper is mounted on the bridge and the other end is mounted on a pier or abutment, and displacement (speed) occurs at both ends of the damper under earthquake or wind loads.

Design principle

The viscous fluid damper(VFD) is mainly composed of piston, cylinder block, end cover, seal part, damping medium and connector. The piston divides the cylinder into two chambers, during the reciprocating motion of the piston in the cylinder, the damping medium flows rapidly in the two chambers. The medium and the medium, the medium and the piston generate intense friction, the medium creates a large energy-saving damping as it passes through the piston holes, the resultant force of these effects becomes the damping force. The damping force generated in the flow, the ground vibration energy, is converted into heat by the reciprocating motion of the piston in the viscous liquid, so that the moving speed of the piston is gradually reduced to achieve the purpose of damping energy consumption.



Viscous fluid damper(VFD) are mainly used for bridges and high-rise buildings in earthquake, cross-sea bridges, footbridges and typhoon-prone areas.

Applicable standard

  • European Standard: EN15129;
  • Chinese standard: JG-T209-2012; JT T926-2014.


Viscous Fluid Damper

1-end cover; 2-damping medium ; 3-cylinder block; 4-piston; 5-piston rod; 6-connector.

No leakage viscous damper

1-end cover; 2-cylinder block; 3-piston; 4-damping medium ; 5-oil feeding tank; 6-connector.


  1. steel elements

The Material And Standard Of Steel Elements

Steel parts Material Standard
End cover Q345B EN15129;


JT T926-2014

Cylinder block 45#
Piston Q345B
Piston rod 40Cr
Connector 45#


  1. damping medium

The damping medium of viscous fluid damper and no leakage viscous fluid damper is silicone oil, this fluid have the follow advantages:

  • The small viscosity-temperature coefficient;
  • Resist lower and hot temperature(-50℃~+250℃);
  • Radiation resistance;
  • Electrical insulation;
  • Resistance to ozone, corona, dampproof.

Quality control at BAOLI

BAOLI damper products should strictly meet the requirements of the design drawings, and the mechanical properties should conform to the EN15129 standard.

Product hysteretic loop

Energy dissipation testing

Energy dissipation testing machine at BAOLI lab

Installation and inspection

Measure temperature

Set position

Install joints and piping for adjustment

Adjust until desire


Viscous fluid dampers(VFD) are typically designed to have a service life of more than thirty years and are maintenance-free. However, according to different occasions, emergencies, etc., the following maintenance management should be carried out:

  • Initial inspection after 1 year of installation;
  • Regular inspection every 5 to 10 years;
  • Construction disasters such as strong earthquakes, strong winds etc.



  • Quality assurance: Quality control from raw material to finished product.
  • On time delivery “No waiting around”.
  • Cost saving options “Getting you the best price”.
  • Small quantity acceptable “Every piece is valuable to us”.
  • Professional packing plan to save cost for customers, customers won’t suffer any problem.


Quotations are supplied on the basis of the types and numbers of the dampers required. We can also design if you proveded the follow information:

  • The use area, bridge or building;
  • Installation type;
  • Damper force and design displacement(the maximum displacement);
  • Dampering coefficient and dampering exponent.


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