Erhard product range
Non return valves
Sizes:
Pressure:
DN 40 - DN 1400
PN 10 – PN 40
Types:
tilting disc check valve
DN 150 - 1400
PN 10 - 40
swing check valve
DN 40 - 800
PN 10 - 16
NON SLAM nozzle“ type check valve DN 80 - 600
PN 10 - 40
reflux valve
DN 40 - 300
PN 10 - 16
„ECR“ check valve
DN 40 - 600
PN 10 - 25
ball check valve
DN 50 - 350
PN 10
diaphragm check valve
DN 40 - 400
PN 10
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
Non return valves
SWING type check valve
DN 40 – 800 PN 10 -16
Design with external shaft
– lever and weight
Design with internal shaft
Non return valves
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
Non return valves
Tilting disc check valve
DN 150 – 1400
PN 10 - 40
with lever and weight
design with hydraulic
damping
Non return valves
Tilting disc check valve
Features:
Non return valves
Tilting disc check valve
Seat ring of
stainless steel
O-Ring for resilient
seating
Non return valves
Tilting disc check valve
Design:
Non return valves
Principle of hydraulic damping cylinder
Valve in fully open position
Non return valves
Principle of hydraulic damping cylinder
Valve 45° closed
Valve closes
without damping
Oil has free
movement
Non return valves
Principle of hydraulic damping cylinder
Valve closed
Oil must pass
the flow control
valve
damped closing
Non return valves
Tilting disc check valve
Examples for use of hydraulic damping:
Non return valves
Headloss characteristic
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
Low headloss
Energy saving
Non return valves
Tilting disc check valve
Recommendation for installation:
Non return valves
Tilting disc check valve
Arrangement of lever and weight:
Non return valves
NON SLAM Nozzle check valve
DN 80- 600
PN 10 - 40
Features:
 silent closing
 low headloss
 short face- to face dimension
 resilient seated
 inside enamelled
ERHARD NON SLAM Nozzle Check Valve Types
DN 80 - 300 PN 10 - 40
Rubber-coated valve disc
Common features:
Internal body: zinc-free bronze
Outside:
Inside:
EKB epoxy
vitreous enamel
Guide bushes: special plastic material
Guide rod, spring: stainless steel
DN 350 - 600 PN 10 - 16
Rubber-coated valve ring
Non Return Valves: Hydraulic Characteristics
Flow velocity
v0
Flow retardation
In short, steep pipelines, the water
column stops quickly, i.e. flow
retardation a is high !
a = dv/dt
Forward flow
In long, flat pipelines, the
water column does not stop
quickly, i.e. flow retardation
a is low !
TR
0 m/s
TS
Reflux
T0
vRmax
time t
Reflux Preventers: Dynamic Characteristics
1,4
1,2
Reflux velocity v in m / s
1
0,8
0,6
0,4
0,2
0
1
2
Long, flat
pipelines
3
4
5
6
7
8
9
10 11 12 13 14 15 16 17 18 19 20 21
Flow retardation dv / dt in m / s²
Short, steep
pipelines
Non return valves
Waterhammer:
Max waterhammer according to formula of „Joukowsky“
p 
a  v
g
p
= max. waterhammer (m WC)
a
= surgewave velocity in water ( = 1200m/s)
v
= change in flow velocity (m/s)
g
= acceleration of earth (m/s²)
Non return valves
Calculation of the max. waterhammer at different reflux
velocities
Reflux velocity – 1 m/s
Reflux velocity – 0,2 m/s
p 
1200 1
 122m(WS )
9,81
1200  0,2
p 
 24m(WS )
9,81
Non return valves
Reflux check valve
DN 40 – 300
PN 10 - 16
body with epoxy – enamel or
rubber lining
water and sewage
with rubberlined disc
Non return valves
ball check valve
DN 50 – 350 PN 10
for sewage
ball of steel rubber
coated
epoxy coating
Non return valves
diaphragm check valve
DN 40 – 400 PN 10
for water
soft closing
Non return valves
„ECR“ check valve
DN 40 – 400
PN 10 - 25
wafer type
with NBR sealing
for use in water
quick acting