WA Type
Welded
Diaphragm
Accumulators
saip.it
Welded
Diaphragm
Accumulators
WA Type
One of the primary functions of hydraulic accumulators
is to store a certain quantity of pressurized liquid from a
hydraulic system and then release all or part of it back into
the system when required. As pressurized vessels, they must
be sized to withstand the maximum operational (over)
pressure, while considering the acceptance standards
applicable in the installation country. In the majority of
hydraulic systems, accumulators with a separation element
between the liquid side and the gas side are employed.
Maintenance-free diaphragm accumulators, such as the
WA type, consist of two high-strength steel caps that are
electron-beam welded together. The U-shaped diaphragm
separates the gas side from the liquid side. A dedicated
bottom plate seals the opening on the liquid side when the
accumulator is precharged to prevent diaphragm extrusion.
The gas valve is available in the classic M28x1.5 version with
a locking hexagon socket screw and a metal-rubber sealing
washer (for precharging, the DP100 precharging and control
equipment must be used). The liquid connection is available
in standard threaded connections as specified in the table, in
both female and double-threaded versions for quick, secure,
and costeffective anchoring through the external threading
and locking nut (optional, see Accessories section), as well as
an appropriate female connection. Compared to other types
of accumulators, these diaphragm accumulators offer high
energy efficiency due to their higher energy density (energy
content per unit mass). This characteristic is attributed to the
nearly spherical shape of the accumulator body. WA Type
Diaphragm Accumulators can be installed in any position.
Maintenance-free WA type diaphragm accumulators cannot
be repaired.
Non-repairable diaphragm accumulator with
carbon steel caps, electron-beam welded, and
painted, designed for use in mobile machinery
and stationary systems.
• Energy storage in intermittent operation
systems for pump power reduction.
• Energy reserve for emergency situations,
such as pump unit failure or power outage.
• Compensation for losses due to leakage.
• Pressure compensation (balancing).
• Vibration damping in cases of periodic
oscillations.
• Volume compensation in the presence of
pressure and temperature variations.
• Hydraulic suspension spring for vehicles.
• Shock absorption in the event of mechanical
impact.
Principle
Of Operation
Product
Description
Applications
2
Features
A Upper Cap
B Ring
C Diaphragm
D Bottom Plate
E MAG Welding
F Fluid connection
G Lower Cap
H Electron beam welding
General
Features
Nominal Volume
from 0,05 to 3,5 liters
Maximum pressure
MAX 350 barg
Compliant with
PED 2014/68/EU EN
14359:2017
EN13445-3:2021
Technical
specifications
Non-repairable
electron beam welded
construction
High-strength alloy
steel body
Standard painting
Two-component
anti-corrosion primer with
water-based epoxy resins,
alternatively
treatment of
Zinc-nickel plating
Gas side connection: M28x1.5
Fluid side connection
(see table)
separator element
material : NBR, ECO
(see table for technical details)
RAL 9005
B
A
C
E
F
D
G
H
3
WA Type welded diaphragm accumulators
EXAMPLE CODE*
WA
•
2
•
0,75
•
1
•
O
•
G4
•
A
•
210
3. NOMINAL VOLUME
0,05
0,16
0,35
0,5
0,75
1
1,4
2
3
3,5
5. BODY MATERIAL
O
COATED CARBON
STEEL
OZN
CARBON STEEL WITH
ZINC-NICKEL
TREATMENT**
2. GAS CONNECTION
(NITROGEN)
2
CONNECTION
M28X1,5
6. FLUID CONNECTION
G4
F. 1/2” BSP-P
A2
M. 1/4” BSP-P
G4
F. 1/2” BSP-P
M8
F. M18X1.5
G4
F. 1/2” BSP-P
M8
F. M18X1.5
G4
F. 1/2” BSP-P
M8
F. M18X1.5
G4
F. 1/2” BSP-P
E1
M. M33X1.5
+ F. 1/2” BSP-P
M8
F. M18X1.5
G4
F. 1/2” BSP-P
E1
M. M33X1.5
+ F. 1/2” BSP-P
G4
F. 1/2” BSP-P
E1
M. M33X1.5
+ F. 1/2” BSP-P
G4
F. 1/2” BSP-P
E1
M. M33X1.5
+ F. 1/2” BSP-P
M8
F. M18X1.5
G4
F. 1/2” BSP-P
E1
M. M33X1.5
+ F. 1/2” BSP-P
G4
F. 1/2” BSP-P
Y9
F. 3/4” BSP-P
G4
F. 1/2” BSP-P
E1
M. M33X1.5
+ F. 1/2” BSP-P
Y9
F. 3/4” BSP-P
Y9
F. 3/4” BSP-P
8. DESIGN PRESSURE
250
250
100 250
210
100 210 280
350
210 280
140 250
350
140 250
350
250
250
Description
Electron Beam Welded Diaphragm Accumulator WA Type - M28x1.5 - Vol. 0.75 L - NBR - Carb. Acc. - Fem. 1/2” GAS - Mod. 210 bar
1 2 3 4 5 6 7 8
* For different codes or specifications, please contact SAIP • ** 800 h salt spray resistance according to ISO 9227
1. ACCUMULATOR
TYPE
WA
4. SEPARATOR ELEMENT
MATERIAL
1
NITRILE (NBR)
8
EPICHLOROHYDRIN
(ECO)
7. CERTIFICATION
A
PED 2014/68/EU
EN 14359:2017
EN13445-3:2021
4
Type
Nominal
volume
Effective
volume
Design
pressure*
MAX ΔP **
dynamic
P
2
- P
1
MAX
Compression
ratio
P
0
: P
2
MAX***
Flow rate
MAX****
Precharge
PED
Category
(for group
2 fluids)
Weight
[L] [L] [barg] [barg] [L/min] [barg] [Kg]
WA 0,05
0,05 0,05 250 120 8:1 10 130 Art.4 Par.3 0,5
WA 0,16
0,16 0,16 250 120 8:1 10 130 Art.4 Par.3 0,9
WA 0,35
0,35 0,35
100 100 8:1 40 70 Art.4 Par.3 1,0
250 140 8:1 40 130 Art.4 Par.3 1,7
WA 0,5
0,5 0,5 210 140 8:1 40 130 Art.4 Par.3 2,2
WA 0,75
0,75 0,75
100 120 6:1 90 70 Art.4 Par.3 2,0
210 150 6:1 90 130 Art.4 Par.3 2,8
280 150 6:1 90 130 Art.4 Par.3 3,1
350 150 4:1 90 180 Art.4 Par.3 5,2
WA 1
1 1
210 140 6:1 90 130 Cat: II 3,5
280 140 6:1 90 130 Cat: II 3,7
WA 1,4
1,4 1,4
140 80 6:1 90 100 Cat: II 4,0
250 140 6:1 90 130 Cat: II 5,5
350 140 4:1 90 180 Cat: II 8,5
WA 2
2 2
140 60 4:1 130 100 Cat: II 4,8
250 140 4:1 130 130 Cat: II 6,5
350 140 4:1 130 130 Cat: II 9,7
WA 3
3 3 250 140 4:1 130 130 Cat: II 10,0
WA 3,5
3,50 3,50 250 140 4:1 130 130 Cat: II 11,5
Technical Data
* Design Pressure calculated in accordance with EN14359:2017 (for pressure values in accordance with other standards, please contact SAIP).
** Maximum Allowable Differential Pressure (difference between maximum operating pressure P2 and minimum operating pressure P1) for an infinite
cycle life (greater than 2,000,000 cycles).
*** Flow rate measured using mineral oil with a viscosity of 36 cSt at 50°C and ΔP = 5 bar.
**** For value higher than this, please contact SAIP.
5
Technical drawing / Fluid connection G - M- Y
Technical drawing / Fluid connection G
Technical drawing / Fluid connection E - A
Technical drawing / Fluid connection E
WA Type welded diaphragm accumulators
Models up to 280 bar
Models up to 350 bar
C
ED
CH
A
20
M28 X 1,5
ø B
CH
E
G
H
F
D
C
ED
CH
A
20
M28 X 1,5
ø B
CH
E
G
H
F
D
C
CH
A2
18
M28 X 1,5
ø B
CH
E
G
F
D
C
A
E
D
C
CH
A2
18
M28 X 1,5
ø B
CH
E
G
F
D
C
A
E
D
6
Models up to 280 bar
Type
Design
pressure
Gas
connection
(Nitrogen)
A
[mm]
B
[mm]
Fluid connection G/M/Y fluid connection E / A
C
E
[mm]
D
[mm]
CH
[mm]
G H
E
[mm]
F
[mm]
D
[mm]
CH
[mm]
[barg]
WA 0,05
250 M28x1,5 65 55 F. 1/2” BSP-P 15 20 30
- - - - - -
250 M28x1,5 65 55
- - - - -
M 1/4” BSP-P 9 17 25 19
WA 0,16 250 M28x1,5 81,7 69
F. 1/2” BSP-P 15 20 30
-
F. M18x1,5 15 20 30
WA 0,35
100 M28x1,5 99 91,5
F. 1/2” BSP-P 15 15 30
-
F. M18x1,5 15 20 30
250 M28x1,5 112 97
F. 1/2” BSP-P 15 20 30
F. M18x1,5 15 20 30
WA 0,5
210 M28x1,5 126 105
F. 1/2” BSP-P 15 20 30
-
F. M18x1,5 15 20 30
WA 0,75
100 M28x1,5 134 109
F. 1/2” BSP-P 15 20 30
F. 1/2” BSP-P M.M33x1.5 15 24 38 41
F. M18x1,5 15 20 30
210
M28x1,5 132 117
F. 1/2” BSP-P
15 20 30 F. 1/2” BSP-P M.M33x1.5 15 24 38 41
280 F. M18x1,5
WA 1
210
M28x1,5 168 117
F. 1/2” BSP-P
15 20 30 F. 1/2” BSP-P M.M33x1.5 15 24 38 41
280 F. M18x1,5
WA 1,4
140 M28x1,5 153,2 143
F. 1/2” BSP-P
15 20 30 F. 1/2” BSP-P M.M33x1.5 15 24 38 41
F. M18x1,5
250 M28x1,5 154 153
F. 1/2” BSP-P
15 20 30 F. 1/2” BSP-P M.M33x1.5 15 24 38 41
F. M18x1,5
WA 2
140 M28x1,5 196 143
F. 3/4” BSP-P 18 22 41
-
F1/2” BSP-P 15 20 30
250 M28x1,5 193 153
F. 3/4” BSP-P 18 22 41
F1/2” BSP-P 15 20 30
WA 3 250 M28x1,5 242 174 F. 3/4” BSP-P 18 22 41
-
WA 3,5
250 M28x1,5 276 174 F. 3/4” BSP-P 18 22 41
-
Dimensions
Model
Pressione
di Design
Gas
connection
(Nitrogen)
A
[mm]
A2
[mm]
ØB
[mm]
Fluid connection G Fluid connection E
C
E
[mm]
D
[mm]
CH
[mm]
C F
E
[mm]
G
[mm]
D
[mm]
CH
[mm]
[barg]
WA0,75
350 M28x1,5 171 189 134 F. 1/2” BSP-P 16 20 41 F. 1/2” BSP-P M.M33x1.5 16 18 37 41
WA 1,4
350 M28x1,5 201 219 162 F. 1/2” BSP-P 16 20 41 F. 1/2” BSP-P M.M33x1.5 16 18 37 41
WA 2
350 M28x1,5 246 264 162 F. 1/2” BSP-P 16 20 41 F. 1/2” BSP-P M.M33x1.5 16 18 37 41
Dimensions
Models up to 350 bar
7
Status conditions
WA Type welded diaphragm accumulators
1
2 3
P
0
/ V
0
P
1
/ V
1
P
2
/ V
2
ΔV
8
Sizing
Certifications
Usage information
Safety Equipment
The sizing of an accumulator requires the consideration of
various factors:
• Minimum (P1) and maximum (P2) working pressures.
• Minimum (T1) and maximum (T2) working
temperatures.
• Precharge pressure (P0).
• Required volumes.
For the correct sizing, you can find the formulas
in the document under the section
GENERAL INFORMATION -> SIZING
All hydraulic accumulators are pressure vessels and
are subject to national regulations and the directives
applicable in the country of installation. WA type
accumulators are constructed in accordance with the
European Directive PED 2014/68/EU.
In the Technical Data table, the category of use is
specified for non-hazardous fluids (Group 2).
For use with hazardous fluids (Group 1), please contact
SAIP. For other countries, applications, or regulations,
please get in touch with SAIP for further information and
guidance.
Warning:
Hydropneumatic accumulators must be protected against
operation beyond permissible limits in accordance with
Directive 2014/68/EU on pressure equipment.
Please refer to the following SAIP documents:
• WA USER AND MAINTENANCE MANUAL
• USER MANUAL FOR THE STORAGE AND PRESERVATION
OF HYDRAULIC ACCUMULATORS/PULSATION
DAMPENERS
1. DO NOT OPERATE WITHOUT SUFFICIENT DRY NITROGEN GAS PRECHARGE.
2.
RELEASE ALL PRESSURE PRIOR TO SERVICING OR DISASSEMBLY.
3.
CONSULT THE INSTRUCTION MANUAL BEFORE USE.
4.
DO NOT OPERATE BEYOND STAMPED MAXIMUM WORKING PRESSURE.
5.
DO NOT WELD OR MODIFY THIS UNIT IN ANY WAY.
CAUTION!
HIGH PRESSURE ACCUMULATOR
NEVER USE OXYGEN OR SHOP AIR.
use & maintenance manual
9
Membrane Compatibility / Temperature / Fluid *
1
Nitrile
Butadiene
Rubber
(NBR)
-15 / +80°C
Suitable for:
Mineral greases and oils.
Aliphatic hydrocarbons (propane, butane, gasoline, mineral oils, diesel fuel,
heating oil, kerosene).
HFA - HFB - HFC fluids.
Many diluted acids.
Saline solutions.
Water.
Water-glycol solutions.
8
Epichlorohydrin
Rubber
(ECO)
-30 / +120°C
Low gas permeability, good resistance to ozone, aging,
and atmospheric agents.
Suitable for:
Mineral greases and oils.
Aliphatic hydrocarbons
(propane, butane, gasoline).
Silicone oils and greases.
Water at room temperature.
fluid connection
G4
F. 1/2” BSP-P (without grooving)
M8
F. M18x1,5 (without grooving)
Y9
F. 3/4” BSP-P (with grooving ø 34)
E1
M. M33x1,5 + F. 1/2” BSP-P (without grooving)
A2
M.1/4” BSP-P
* For use with other fluids and/or temperatures, please contact SAIP.
Surface treatments
O
carbon steel painted RAL 9005 two-component anticorrosive primer
with water-based epoxy resins
OZN
zinc-nickel plated carbon steel, 800 h resistance in salt spray
before the appearance of red corrosion according to ISO 9227
WA Type welded diaphragm accumulators
10
Technical Drawing / Fastening collar light series
Technical Drawing / NUT
Fastening Nut
Used for securely and easily fastening accumulators
throgh
the external threading on the fluid side fitting
M33x1.5 or M45x1.5 and/or through the gas side
connection M28x1.5 threading.
The nuts are made
of carbon steel with a white zinc plating treatment,
providing excellent corrosion resistance.
Fastening Collars
The SAIP fastening collars type CFOZ_LF_ can be used
to securely fasten the various types of WA accumulators
and guarantee an independent, non-rigid mounting on
the systems. The NBR rubber insert reduces the
the transmission of vibrations, compensates
manufacturing tolerances and relieves external stresses
on the connection. This type of collar has a two-piece
construction for easier installation, greater modularity
and stability according to requirements and available
space.
Accessories
Description
Material
Salt spray
resistance according
to ISO 9227 [h]
STD COLLAR
galvanised carbon
steel
72
INOX COLLAR
AISI 316 stainless
steel
400
Type Description
MATERIAL Dmin Dmax A B C E Weight WA usage
AISI 316L
CARBON
STEEL
[mm] [mm ±1] [mm ±0,5] [Kg] WA Model (barg)
CFXZ72LF120 CFOZ72LF120
67 72 124 81 45 13
0,3 WA 0,16
CFXZ96LF120 CFOZ96LF120
91 96
124 81 45 13
0,3
WA 0,35 (100)
CFXZ96LF160 CFOZ96LF160
144 93 45 17
0,5
CFX102LF160 CFOZ102LF160
97 105 144 93 45 17
0,5 WA0,35 (250) - WA 0,5 (210)
CFX111LF160 CFOZ111LF160
106 114 144 93 45 17
0,5 WA 0,75 (100)
CFX120LF160 CFOZ120LF160
115 123 144 93 45 17
0,5
WA 0,75 (210, 280) - WA1 (210-280)
CFX137LF160 CFOZ137LF160
133 141 144 93 45 17
0,5 WA 0,75 (350)
CFX146LF160 CFOZ146LF160
141 154
144 93 45 17
0,5
WA 1,4 (140 -250) -2 (140-250)
CFX146LF210 CFOZ146LF210
214 145 50 24
0,5
CFX159LF160 CFOZ159LF160
155 167
144 93 45 17
0,5
1,4 (350) - 2 (350)
CFX159LF210 CFOZ159LF210
214 145 50 24
0,5
CFX172LF160 CFOZ172LF160
168 181
144 93 45 17
0,5
WA 3-3,5 (250)
CFX172LF210 CFOZ172LF210
214 145 50 24
0,5
Type
D SW [mm] H [mm]
DADORM2-OZ28
M28 x 1,5 41 7
DADORE1-OZ33
M33 x 1,5 50 7
CH
D
H
C
B
A
Dmin ÷ Dmax
6.5
10
3
HEX 13
E
ø9
CH
D
H
C
B
A
Dmin ÷ Dmax
6.5
10
3
HEX 13
E
ø9
11
saip.itWA - rev. February 2026
SAIP S.r.l.
Hydropneumatic
Accumulator Company
Via Lambro 23/25/27
20073 Opera (MI) Italy
P.Iva 10218550159
DONWLOAD
DATA SHEET
