Low temperature snubbers
DALT
Introduction
Low Temperature Snubbers (DALT) are used in special ambient temperature, designed for special low temperature applications.
Special fabrication on demande.
Raw materials
Special high mechanical resistance material at low temperature (- 40°C) for body, rod and internal parts.
Special low temperature surface protection by 3 coats painting system.
Special low temperature oil.
Dynamic characteristics at ambient temperature, 15°C to 35°C
Hereofter standard values, (others available on demand)
FN is the Nominal load of the snubber
Locking speed:
2 mm/s to 10 mm/s or as requested
Drag force at slow speeds, before locking
f < 500N if FN ≤ 30 kN
f < 2.0 % FN if 30 kN < FN ≤ 200 kN
f < 1.5 % FN if FN > 200 kN
Drift speed after locking,
at FN : 0.1 mm/s to 2.0 mm/s or as requested
Peak-to-peak motion under sinus alternating load FN from 3 to 10 Hz (depending on model)
< 4 mm if FN ≤ 100 kN
< 5 mm if FN ≤ 600 kN
< 6 mm up to FN = 600 kN
Environment conditions
For nuclear or conventionnal applications
Temperature:
Normal operating conditions : -40°C to +80°C
Minimum storage temperature : – 40°C
Humidity: 100 %
External pressure:
Service pressure : 1 bar
Accidental pressure : 5 bar
Stiffness
Snubber stiffness is defined according to the following diagram where:
Peak-to-Peak is the total stroke under alternative load
And Snubber Stiffness is: K=(2 x FN)/Peak-to-peak
| Model | Nominal Load FN | Stiffness * |
| (kN) | (kN/mm) | |
| DA1 | 14 | 13 |
| 11 | ||
| DA2 | 30 | 23 |
| 16 | ||
| DA3 | 47 | 33 |
| 25 | ||
| DA4 | 100 | 69 |
| 47 | ||
| DA5 | 200 | 124 |
| 76 |
* Tolerance on stiffness value : ± 25%
Permissible load in kN
The permissible load in terms of dynamic stress in the table below has been calculated in accordance with RCCM code vol. H level S1.
Load definition :
Normal/Disturbed – Level A/B: Here are estimated all loads due to normal functioning, including normal transitional regime during operation of the plant. And also some disturbed loads due to normal functioning of the plant.
Emergency : Level C: Here are estimated all loads outside to normal operation due to particulars situations, possibly safety shutdown earthquake.
Faulted : Level D: Here are estimated all loads due to accidental situations. The snubbers should undergo verification after such an event.
| Model | Total stroke | FN load level A/B/80°C |
Emergency load level C/80°C |
Faulted load level D/150°C |
| (mm) | (kN) | (kN) | (kN) | |
| DA1 LT | 100 | 14 | 18 | 24 |
| DA2 LT | 100 | 30 | 39 | 49 |
| DA3 LT | 100 | 47 | 62 | 77 |
| DA4 LT | 100 | 100 | 133 | 140 |
| DA5 LT | 100 | 200 | 266 | 280 |
| DA6 LT | 100 | 320 | 425 | 545 |
| DA7 LT | 100 | 600 | 798 | 1020 |
Life under dynamic stress
The snubbers may be subject to the total dynamic loads below, without any adverse effect on operating, at temperature less than 80°C.
| Load (in % FN) | Number of cycles |
| 10% | 5 x 106 |
| 50% | 106 |
| 100% (level A/B) | 105 |
| 133% (level C) | 103 |
| (level D) | 102 |
Dimensions
| Type | Nominal Load Level B |
Faulted Load Level D |
Stroke
|
A min |
A half stroke |
A max |
M half stroke |
Ø B
|
C
|
Ø D
|
E
|
F1
|
P
|
R1
|
Weight without bracket |
| (kN) | (kN) | (mm) | (mm) | (mm) | (mm) | (mm) | (mm) | (mm) | (mm) | (mm) | (mm) | (mm) | (mm) | (kg) | |
| DA1LT-100 | 14 | 24 | 100 | 489 | 539 | 589 | 486 | 102 | 50 | 17 | 20 | 19 | 25 | 28 | 12 |
| DA2LT-100 | 30 | 50 | 100 | 512 | 562 | 612 | 509 | 115 | 50 | 20 | 25 | 23 | 25 | 28 | 21 |
| DA3LT-100 | 47 | 77 | 100 | 502 | 552 | 602 | 489 | 154 | 60 | 25 | 28 | 28 | 30 | 32 | 33 |
| DA4LT-100 | 100 | 140 | 100 | 547 | 597 | 647 | 524 | 170 | 70 | 30 | 32 | 30 | 38 | 39 | 49 |
| DA5LT-100 | 200 | 280 | 100 | 672 | 722 | 772 | 614 | 220 | 105 | 45 | 43 | 40 | 52 | 58 | 82 |
| DA6LT-100 | 320 | 545 | 100 | 850 | 900 | 950 | 732 | 254 | 165 | 45 | 43 | 40 | 75 | 65 | 120 |
| DA7LT-100 | 600 | 1020 | 100 | 1070 | 1120 | 1170 | 897 | 324 | 220 | 60 | 63 | 60 | 92 | 100 | 330 |
Other load, stroke or characteristics on demand.
