1. Erhard product range Non return valves Sizes: Pressure:
DN DN 1400
PN 10 – PN 40
Types:
tilting disc check valve DN PN
swing check valve DN PN
NON SLAM nozzle“ type check valve DN PN
reflux valve DN PN
„ECR“ check valve DN PN
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ball check valve DN
PN 10
diaphragm check valve DN
PN 10

2. Erhard product range Non return valves Criteria for selection:
flow media (water, sewage)
size
pressure rating
headloss
space requirement
closing time (damping)
indication of position (visual, electric)
price
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3. Non return valves SWING type check valve SWING type check valve
DN 40 – PN
Design with external shaft – lever and weight
Design with internal shaft
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4. Non return valves SWING type check valve SWING type check valve
Features:
preferably for sewage (nearly full passage)
lever and weight (adjustability)
valve disc in stainless steel up to DN 300
with O-Ring seal
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5. Tilting disc check valve
Non return valves
Tilting disc check valve
DN 150 – PN
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design with hydraulic damping
with lever and weight

6. Tilting disc check valve
Non return valves
Tilting disc check valve
Features:
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7. Tilting disc check valve
Non return valves
Tilting disc check valve
Seat ring of stainless steel
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O-Ring for resilient seating

8. Tilting disc check valve
Non return valves
Tilting disc check valve
Design:
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9. Principle of hydraulic damping cylinder
Non return valves
Principle of hydraulic damping cylinder
Valve in fully open position
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10. Principle of hydraulic damping cylinder
Non return valves
Principle of hydraulic damping cylinder
Valve 45° closed
Valve closes without damping
Oil has free movement
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11. Principle of hydraulic damping cylinder
Non return valves
Principle of hydraulic damping cylinder
Valve closed
Oil must pass the flow control valve
damped closing
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12. Tilting disc check valve
Non return valves
Tilting disc check valve
Examples for use of hydraulic damping:
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13. Tilting disc check valve
Non return valves
Tilting disc check valve
Headloss characteristic
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14. Tilting disc check valve
Non return valves
Tilting disc check valve
Full opening device (opening cylinder)
Pneumatic cylinder
Valves is in fully open position also at low flow velocities
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Low headloss
Energy saving

15. Tilting disc check valve
Non return valves
Tilting disc check valve
Recommendation for installation:
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16. Tilting disc check valve
Non return valves
Tilting disc check valve
Arrangement of lever and weight:
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17. NON SLAM Nozzle check valve
Non return valves
NON SLAM Nozzle check valve
DN PN
Features:
silent closing
low headloss
short face- to face dimension
resilient seated
inside enamelled
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18. ERHARD NON SLAM Nozzle Check Valve Types
DN PN
Rubber-coated valve disc
Common features:
Internal body: zinc-free bronze
Outside: EKB epoxy
Inside: vitreous enamel
Guide bushes: special plastic material
Guide rod, spring: stainless steel
DN PN
Rubber-coated valve ring

19. Non Return Valves: Hydraulic Characteristics
Flow velocity
Flow retardation v0
In short, steep pipelines, the water column stops quickly, i.e. flow retardation a is high !
a = dv/dt
In long, flat pipelines, the water column does not stop quickly, i.e. flow retardation a is low !
Forward flow TR
0 m/s
time t TS T0
Reflux
vRmax

20. Reflux Preventers: Dynamic Characteristics
1,4
1,2 1
Tilting disc check valve with weight-loaded lever
DIN swing check valve
0,8
Check valve with slanted seat
Diaphragm check valve
0,6
Reflux velocity v in m / s
0,4
Nozzle check valve
Tilting disc check valve with slanted seat and spring
0,2
ERHARD NON SLAM Nozzle Check Valve 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
Long, flat pipelines
Short, steep pipelines
Flow retardation dv / dt in m / s²

21. Non return valves Waterhammer:
Max waterhammer according to formula of „Joukowsky“
= max. waterhammer (m WC)
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= surgewave velocity in water ( = 1200m/s)
= change in flow velocity (m/s)
= acceleration of earth (m/s²)

22. Calculation of the max. waterhammer at different reflux velocities
Non return valves
Calculation of the max. waterhammer at different reflux velocities
Reflux velocity – 1 m/s
Reflux velocity – 0,2 m/s
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23. Non return valves Reflux check valve DN 40 – 300 PN 10 - 16
body with epoxy – enamel or rubber lining
body with epoxy – enamel or rubber lining
water and sewage
with rubberlined disc
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24. Non return valves ball check valve DN 50 – 350 PN 10 DN 50 – 350 PN 10
for sewage
ball of steel rubber coated
epoxy coating
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25. Non return valves diaphragm check valve DN 40 – 400 PN 10 for water
soft closing
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26. Non return valves „ECR“ check valve DN 40 – 400 PN 10 - 25 wafer type
with NBR sealing
for use in water
quick acting
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