Hydraulic snubbers
Applications
The snubbers are dynamic linear supports designed to limit unwanted sudden movements of components such as:
• Pipes
• Tanks
• Control valves
• Steam generators
• Safety valves
• Pumps, motors, etc.
The snubbers enable slow movements due to thermal dilatation in both directions. When a dynamic event which could be harmful to the installation occurs, the snubbers lock and transfer the energy to the fixed structure. Once the disturbance has passed, the device returns to its initial state and enables slow movements once again. In that way, the snubbers provide temporary additional support to the installation in order to prevent if from entering into resonance and thereby minimizing the risk of breaking due to vibrations.
The snubbers prevent damage due to:
• Earthquakes
• Water hammer effects
• Violent thrusts due to safety valve discharge
• Wind
• Other similar disturbances
Design of QUIRI Snubbers
Raw materials
All raw materials are forged or rolled steel. This technology reduces the risk of porosity and failure, compare to molded and welded steel. QUIRI snubbers are designed to withstand the hot, humid and irradiated atmospheres prevalent in nuclear and thermal power plants.
Operation mode
Type A mode: Lock and drift
Valves V1 and V2 allow a limited fluid flow between chambers CH1 and CH2. The drift speed after locking is generally set from 0.1 mm/s to 2 mm/s or as requested. The drift movement is required to relax a pipe subject to thermal dilatation which has sustains a sudden thrust, leading to the locking of the valves.
Type B mode: Lock with no drift in compression
When complete blocking is desired, e.g. in the case of a valve reaction, valve V1 is without restriction. (Complete blocking in compression)
Type C mode: Lock with no drift in tension
When complete blocking is desired, e.g. in the case of a valve reaction, valve V2 is without restriction. (Complete blocking in tension)
Metal bellows compensation device
The system of rod volume compensation and fluid thermal dilation is located inside the snubber and is maintenance free. It is located in the piston B1, between the 2 chambers CH1 and CH2. This technology has been used in all QUIRI snubbers for more than 35 years. The compensation tank constituted by the hollow piston and the metal bellow (B), forms simultaneously reserve of oil and provides an internal permanent pressurization. This particular device allows a symmetrical and compact construction, without external element destabilizing the snubber. This design facilitates greatly the on-site installation of the snubbers.
The metal compensation bellows are subject to 100% tightness testing.
Other features
The seals are Viton® – based (used by Quiri on the snubber for more than 35 years)
Irradiation care test shows that the snubber remains functional after 600 kGy of radiation. Perfect fluid filling by vacuum, to remove air from oil and insuring better lifetime expectancy for fluid, lockup valves, nozzles and tightness materials. This filling technology allows lower peak to peak values and higher stiffness than obtained by traditional filling.
The lifespan of these snubbers is 60 years.
Self Cleaning Lockup Valve (SCLV)
Lockup valve defining the lockup velocity are tested one by one in our factory. Lockup valves are designed and sized to be independent from the fluid viscosity and temperature. QUIRI uses Self Cleaning Lockup Valve.
The self cleaning lockup valve (SCLV) ensures 2 functions: block and drift. The integration of both functions is made by machining a «V» shape slit on the working area of the valve so that:
• The SCLV is never totally closed to ensure the decompression
• After drift trough the «V» shape slit, the pressure will decrease and allows the opening of the valve. This process ensures the self-cleaning of the valve comparing to a classic nozzle which would be definitively stopped in case of impurity contains in the oil.
With this technology, we can realize very low drift speed without risk to plug the nozzle.
Painting
The painting applied on our (nuclear) snubbers is decontaminated type and ensures a corrosion protection for the snubber life expectancy. It allows a resistance of more than 200 hours on normalized salt spray test.
The life expectancy of these snubbers is 60 years (outcome from our manufacturing experience for more than 35 years).
Nickel coatings are available on demand.
Snubber selection criteria
Dynamic load:
At the nominal load FN, Check that the snubber is capable of handling dynamic forces during normal operation and/or operating basis earthquake conditions (level A/B). In the upset situation, check that the snubber is capable of handling the forces expected at level D, safe shutdown earthquakes.
Stroke:
The selected snubber must be able to make the fixing points cover the maximum travel between the assembly position and extreme operating position. Users should select the snubber with a minimum margin of 10 mm is available in the assembly position.
A travel indicator on the body’s snubber allows to verify the good operation position.
Available space:
Make sure that when the snubber is in place, the expected movements are possible with the minimum margins. Add an extension if the space available is larger than travel capability of the snubber.
The snubber may be assembled in either direction. Make sure that the spherical bearings can move freely, in the assembly position and in the operating position.
Reference list for snubbers
FRANCE (EDF/FRAMATOME):
• 48 units 900 MW and 1300 MW (6000 snubbers up to 200 KN) – 1980-1994
• 1 unit SUPER PHENIX up to 1300 kN (1000 snubbers) – 1980
• 65 snubbers for the nuclear steam supply system of French aircraft carrier Charles de Gaulle – 1994
• 90 large bore snubbers 1150 kN (for 900 MW, France) – 2004-2006
• 20 large bore snubbers 450T/850T and piping snubbers for the EPRTM Flamanville, France – 2007
• Spare snubbers 900 MW-1300MW for French nuclear power plants – 2007-2015
• Spare piping snubbers for the EPRTM Flamanville, France – 2017
• 52 Large bore snubbers for EDF (SG for French nuclear power plants) – 2016-2021
• Piping snubbers for extension service life for 900 MW – 1300 MW EDF, France – 2017-2024
EXPORT:
• 200 snubbers for PEC (Ansaldo-Nira in Italy) – 1984
• 2 units 900 MW in South Africa (500 snubbers) – 1985
• 2 units 900 MW in Korea (1000 snubbers) – 1986
• 4 units in China (Daya Bay and Ling Ao) (1700 snubbers) – 1988-1998
• 850T large bore snubbers for EPRTM Olkiluoto (Finland) (20 snubbers) – 2005
• Spares for 900 MW (Korea) (70 snubbers) – 2005
• Spares for 900 MW (South Africa) – 2007-2009
• 230 snubbers up to 2000kN for NPCIL (India) – 2004
• 40T snubbers for Qinshan plant (China) – 2007
• 450T snubbers for CZEC (China Chasnupp 2 project) – 2007
• More than 3000 snubbers for CNPEC, (CPR1000 projects in China) – 2008
• Large bore snubbers and piping snubbers for EPRTM Taishan (China) – 2009
• 570 snubbers for BHAVINI (India) – 2010
• Snubbers for Spend fuel cask transfer machine FA3 for SKODA (Czech Republic) – 2010
• Large bore snubbers for HAINAN project (CNEIC) (China) – 2010
• Large bore snubbers for CZEC project (C3-C4) (China) – 2011
• Large bore snubbers for Fangchenggang project (CNPEC) (China) – 2013
• Large bore snubbers for Fuqing project (CNPE) (China) – 2018
• Spare piping snubbers for EPRTM Taishan (China) – 2017
• Spare parts piping snubbers for 1300 MW Korea (Hanul NNP 1&2) 2016 – 2018
• 850T large bore snubbers for EPRTM Olkiluoto (Finland) (2 snubbers) – 2019
• Spare parts piping snubbers for CNPEC, (CPR1000 in China) – 2020-2023
• Spare parts piping snubbers for Koeberg, (south Africa) – 2021-2023
• 36 large bore 450T/850T snubbers for the EPRTM HPC in England – 2018-2024
• 48 piping snubbers snubbers for the EPRTM HPC in England – 2021-2024
• Large bore snubbers 450T for Koeberg NNP (South Africa) – 2024
• Conventional snubbers for coal, petrochemical and fossil fuel plants (China) – 2004 – 2024
• Conventional snubbers for thermal power station for BHEL (India) – 2009 – 2020
• Conventional snubbers for gas-fired and solar power plants (Korea) – 2009 – 2024
In total QUIRI supplied more than 25000 snubbers in the nuclear industry (from 6 kN to 8500 kN)