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HydacUSA Corp. Hycon Div.

Piston Accumulators

Piston Accumulators

Fluids are practically incompressible and cannot therefore store pressure energy.
The compressibility of a gas (nitrogen) is utilized in hydro-pneumatic accumulators for storing fluids. HYDAC piston accumulators are designed on this principle, using nitrogen as the compressible medium.
 
A piston accumulator consists of a fluid section and a gas section with the piston acting as a gas proof screen. The gas section is precharged with dry nitrogen gas.
The fluid section is connected to the hydraulic circuit so that the piston accumulator draws in fluid when the pressure increases thus compressing the gas. When the pressure drops, the compressed gas expands and forces the stored fluid into the circuit.
 
HYDAC piston accumulators consist of:
  • a cylinder with a finely finished internal surface.
  • an end cap on the gas side and the oil side, sealed with o-rings.
  • lightweight metal piston.
  • a variety of sealing systems are available depending on the application
  • Three types of pistons for a variety of applications
    • Type 1 - standard design for general accumulator operation without special requirements. Note: Piston friction must be taken into account for sizing purposes.
    • Type 2 - low-friction design for higher piston speeds, slow movements without stick-slip effect and high number of actuations (millions). Note: Filtration ≤ 10µ absolute (ISO 16/13).
    • Type 3 - general duty, cycle requirements 100,000's.
SEALING SYSTEMS
Precise information about the proposed operating conditions is required in order to select the most appropriate sealing system. Important criteria for this selection are:
  • design pressure.
  • effective pressure differential.
  • number of actuations or cycles.
  • temperature fluctuation.
  • operating fluid.
  • cleanliness of fluid.
  • maintenance requirements.
SEAL MATERIALS
The following elastomers are available, depending on the operating conditions:
NBR / acrylic nitrile butadiene rubber (trade name Perbunan)
FKM / fluoro-rubber (trade name Viton)
AU / polyurethane (trade name Vulkollan)
Suitable materials are also available for low temperature applications.
SYSTEM MOUNTING
HYDAC piston accumulators operate in any position. Vertical installation is preferable with the gas side up.
 
ADVANTAGES OF HYDAC PISTON ACCUMULATORS:
  • complete range from 1 quart to 100 gallons nominal volume.
  • high ratios possible between precharge pressure and maximum working pressure.
  • high flow rates - up to 4700 gpm from one accumulator.
  • power savings.
  • gas-proof and leak-free.
  • no sudden discharge of gas when seal is worn.
  • space efficient.
  • piston location monitoring available.
Further advantages of using the low-friction sealing system (Type 2 piston):
  • minimum friction.
  • suitable for low pressure differentials.
  • no start-up friction, no stick-slip.
  • low noise, no vibration.
  • high piston speeds up to 12 fps continuous.
  • improved accumulator efficiency.
  • high life expectancy.
  • low maintenance requirements.
EFFECT OF SEAL FRICTION
The permissible piston velocity depends on the sealing friction. Higher piston velocities are possible where there is less sealing friction.
 
HYDAC piston accumulators with low friction seals allow continuous operating velocities of 12 fps with short excursions to 15 fps.
Small pressure differentials between gas and oil side improve the effectiveness of HYDAC piston accumulators. The effect of the working pressure on the sealing friction is particularly striking in piston Type 1.
 
 

SK Series Piston Accumulators

These piston accumulators come in two basic models. Model SK 330 has a 3000 PSI rating. Model SK 600 has a 5000 PSI rating. There are 22 SK 330 sizes in three cylinder sizes and 16 SK 600 sizes in two cylinder sizes with capacities ranging from 2-1/2 to 80 nominal volume gallons. Final pressure vessel codes vary depending on the country of installation. In the US and Canada pressure vessels are governed by the ASME pressure vessel code. HYDAC manufactures according to these standards. For installations in countries outside of the US, please consult Flo-Products Sales for appropriate certifications. There are five piston diameters ranging from 80 to 355 mm. Additional equipment available is three lengths of electrical end position control, extending position rod, and an ultrasonic system. Gas and fluid threaded connections come in five sizes depending on piston diameter. Gas and fluid flanged connections come in 17 variations depending on piston diameter. Flanged connections are not available for the smallest size piston (80mm) and only one variation is available for the 100mm piston.
 
Elastomer Compatibility Table
In order to maximize system performance it is important to match your system fluid and its temperature range with the appropriate elastomer compound. The table below illustrates the most common ones. For special requirements, please consult Flo-Products sales.
Compound Operating Temperature Range Some Typical Fluids
NBR (BUNA N) +  5° F to + 180° F mineral oil
+ 32° F to + 180° F water and water-glycols
AU (POLYURETHANE) + 14° F to + 176° F mineral oil
FPM (VITON) +  5° F to + 300° F chlorinated hydrocarbon
Notes:
  1. The operating temperature range does vary with fluid types, please consult Flo-Products for more specific fluid data.
  2. The above typical fluids are some examples of the most common fluids, please consult Flo-Products for more specific data. For non hydraulic process fluids, HYDAC MUST be consulted.
  3. For temperatures below - 40° F and above + 200° F, please consult Flo-Products for maximum allowable working pressures of the pressure vessels.
  4. For other applications not listed, please consult Flo-Products.

 
SK 350 - 20 C C - 2 1 2 / 1 1 2 S - 210 C D 18 A Piston Accumulator; 3000 psi; size 20; SAE fluid connection; SAE gas connection; seal system 2 piston made of aluminum with NBR seals; carbon steel end cap and shell with NBR seals; US installation; maximum working pressure of 3000 psi; 1-5/16 - 12 UNF fluid connection; 1-7/8 - 12 UNF gas connection; 180mm piston diameter; electrical end position control - 1.4 in stroke.
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A
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C
K
U		 Additional Equipment
Elect. end position ctrl - 1.4 in stroke
Elect. end position ctrl - 7.9 in stroke
Elect. end position ctrl-19.7 in stroke
Extending piston rod
Ultrasonic system
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08
10
18
25
35		 Piston Diameter
80mm (3.15 in.)
100mm (3.94 in.)
180mm (7.09 in.)
250mm (9.84 in.)
355mm (13.98 in.)
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A
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S
T		 Fluid Side Connection Size
Gas Side Connection Size
SAE (ANSI B1.1)
7/8 - 14 UNF (SAE)
1-1/16 - 12 UNF (SAE)
1-5/16 - 12 UNF (SAE)
1-7/8 - 12 UNF (SAE)
2-1/2 - 12 UNF (SAE)
NPT (ANSI B2.1)
3/4" (NPT)
1" (NPT)
1-1/4" (NPT)
1-1/2" (NPT)
2" (NPT)
Flange
DN 32 (Flange)
DN 40 (NG 52) (Flange)
DN 50 (NG 62) (Flange)
DN 65 (NG 82) (Flange)
DN 80 (NG 102) (Flange)
1" Code 61 (Flange)
1-1/2" Code 61 (Flange)
2" Code 61 (Flange)
1-1/4" Code 61 (Flange)
2-1/2" Code 61 (Flange)
3" Code 61 (Flange)
1-1/4" Code 62 (Flange)
1-1/2" Code 62 (Flange)
2" Code 62 (Flange)
1" Code 62 (Flange)
2-1/2" Code 62 (Flange)
3" Code 62 (Flange)
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210
330		 Maximum Working Pressure in PSI
3000 PSI
5000 PSI
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S
S1
E		 Country of Installation
USA/Canada
Canada
Mexico
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2
5
6
7
8		 Shell Seal Material
NBR (Buna N)
NBR (low temperature Buna)
FPM (Viton)
Others
AU (Polyurethane)
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1
3
6		 +
1
3
6		 Shell End Cap and Cylinder Material
carbon steel
stainless steel (316)
low temperature carbon steel (< -20°F)
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2
5
6
7
8		 Piston Seal Compound
NBR (Buna N)
NBR (low temperature Buna)
FPM (Viton)
Others
AU (Polyurethane)
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1
2
3
5		 Piston Material
aluminum
carbon steel
stainless steel (316)
carbon steel II
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1
2
3		 Piston Seal System Type
Type 1
Type 2
Type 3
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1
4
A
B
C
F		 Gas Side Connection
M28x1,5 (FPK - connection)
8V1 - ISO 4570 (FPS - connection)
BSP (ISO 228)
Metric (DIN 13, ISO 965/1)
SAE (ANSI B1.1)
Flange connection
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A
B
C
D
F		 Fluid Side Connection
BSP (ISO 228)
Metric (DIN 13, ISO 965/1)
SAE (ANSI B1.1)
NPT (ANSI B2.1)
Flange connection
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4
6
10
16
20
30
40
50
60
75
100
115
135
150
170
190
250
300		 Size
Size 4 - 1 gallon
Size 6 - 1.5 gallons
Size 10 - 2.5 gallons
Size 16 - 4 gallons
Size 20 - 5 gallons
Size 30 - 7.5 gallons
Size 40 - 10 gallons
Size 50 - 12.5 gallons
Size 60 - 15 gallons
Size 75 - 20 gallons
Size 100 - 25 gallons
Size 115 - 30 gallons
Size 135 - 35 gallons
Size 150 - 40 gallons
Size 170 - 45 gallons
Size 190 - 50 gallons
Size 250 - 65 gallons
Size 300 - 80 gallons
+
SK 350
SK 600		 Series
3000 PSI
5000 PSI

 
Threaded Connection Availability
Size Code A B C D G
Piston Diameter SAE Threads
7/8 - 14 UNF 1-1/16 - 12 UNF 1-5/16 - 12 UNF 1-7/8 - 12 UNF 2-1/2 - 12 UNF
ø 3.15
ø 3.94
ø 7.09
ø 9.84
ø 13.98		 X
X
 
 
 		  
X
 
 
 		  
 
X
X
 		  
 
X
X
X		  
 
 
X
X
Piston Diameter NPT Threads
3/4" 1" 1-1/4" 1-1/2" - 11-1/2" 2" - 11-1/2"
ø 3.15
ø 3.94
ø 7.09
ø 9.84
ø 13.98		 X
X
 
 
 		  
X
 
 
 		  
 
X
X
 		  
 
X
X
X		  
 
 
X
X

 
Flanged Connection Availability
Flange Size/Type Piston Diameter
Size Code Size and Pressure Rating ø 3.94 ø 7.09 ø 9.84 ø 13.98
A
B
C
D
G
Y
H
I
K
P
Q
E
L
M
N
S
T		 DN 32
DN 40 (NG 52)
DN 50 (NG 62)
DN 65 (NG 82)
DN 80 (NG 102)
1"        Code 61   3000 psi
1-1/2"  Code 61   3000 psi
2"        Code 61   3000 psi
1-1/4"  Code 61   3000 psi
2-1/2"  Code 61   2500 psi
3"        Code 61   2000 psi
1-1/4"  Code 62   6000 psi
1-1/2"  Code 62   6000 psi
2"        Code 62   6000 psi
1"        Code 62   6000 psi
2-1/2"  Code 62   6000 psi
3"        Code 62   6000 psi		 X
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 		  
X
X
X
 
X
X
 
X
 
 
X
X
 
X
 
 		  
X
X
X
X
X
X
X
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X
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X

 
Piston Accumulator Specifications
Types 1 & 2 SK 350 (max. wrk. pressure 3000 psi) SK 600 (max. wrk. pressure 5000 psi)
Size Eff. Gas Vol. Gals. Weight lbs. Height minus conn. in. Piston Dia. In. Shell Dia. In. Weight lbs. Height minus conn. in. Piston Dia. In. Shell Dia. In.
10
16
20
30
40
50		 2.5
4
5
7.5
10
12.5		 233
283
316
400
482
566		 28
37.2
43.4
58.9
74.4
89.9		 7.09 8.62 302
402
447
606
736
884		 28
37.2
43.4
58.9
74.4
89.9		 7.09 9.61
40
50
60
75
100
115
135
150
170
190		 10
12.5
15
20
25
30
35
40
45
50		 788
882
974
1114
1347
1488
1676
1816
2004
2194		 49
57.1
65
77.1
97.1
109.2
125.3
137.4
152.4
168.4		 9.84 12.21 1110
1254
1396
1611
1969
2184
2472
2689
2977
3265		 49
57.1
65
77.1
97.1
109.2
125.3
137.4
152.4
168.4		 9.84 13.31
100
115
150
190
250
300		 25
30
40
50
65
80		 1859
1986
2287
2630
3144
3572		 61.9
67.9
81.8
97.7
121.6
141.5		 13.98 17.09  
Type 3 SK 350 (max. wrk. pressure 5000 psi)  
4
6
10
20
40
60		 1
1.5
2.5
5
10
15		 137
157
199
304
513
723		 16.9
21.5
30.3
52.6
97.2
141.7		 5.9 7.1  

 
If you are located in Missouri, Kansas, Nebraska, or Illinois, you may contact us at the following telephone and fax numbers with your requests or questions:
St. Louis telephone 314.428.4000 fax 314.428.4097
Kansas City telephone 913.829.5900 fax 913.829.0815
 
For ALL OTHER AREAS Please use the Info Request form for specific product information, pricing or other information. Please include company name, contact name, address, phone number and fax number to ensure a timely response.
 
Send e-mail to webmaster@flo-products.com with questions or comments about this web site.
Copyright © 2003 Flo-Products Company
Last modified:
Brochure: 02068597/ 11.98