Page 1
Accumulators
SK 210 / 350 / 600
Piston Accumulators
Maintenance and Parts
Index
1. Description
2. Deliver y Inspection
3. Installation and Mounting
4. Connection
5. Commissioning and Precautions
6. Inspection and Maintenance
7. Storage and Preservation
8. Disassembly, Inspection and Assembly
9. Special Tools and Spare Parts
1. Description
These Operating and Maintenance Instructions apply to HYDAC
piston accumulators of the series SK210, SK350 and SK 600 having
the following specifications:
permiss. operating pressure: 210 / 350 bar
permiss. operating temperature: –10 / 80°C with NBR seal
max. pre–charge pressure p0: p
permiss. pressure ratio p0: p2 ≤ 1 : ∞
Design, Approval: PED/AD–Regulations, ASME
For volumes, dimensions and weights (when empty),
see drawing or brochure.
≤ p1 – 5 bar
0,tmax
2. Delivery Inspection
Prior to delivery, HYDAC accumulators undergo a careful inspection.
Upon receipt of the accumulator, check that:
• no damage has been sustained during transport. In particular,
check the gas valve and the hydraulic connection for damage,
• the details shown on the model code correspond to the order
details,
• the test certificates (if required) are present and correspond
to the factory number of the accumulator,
• the protective cap of the gas valve is tightly closed,
• the hydraulic connection has been closed off with a
protective plug.
After discharging and/or completely
draining the accumulator (e.g. to
depressurize the hydraulic system before
work is carried out), the accumulator can
build-up an amount of pressure again when
CAUTION!
PN#02068195 / 04.13 / ACU1102-1326
the lines are later shut off on the fluid side.
This problem must be taken into account
generally and in particular before carrying
out work on hydraulic systems which
include connected hydraulic accumulators.
All the fluid-side lines connected
to the accumulator must therefore
be depressurized and after that the
lines remain open. Only then may the
appropriate work (e.g. disassembly of the
accumulator) be carried out.
PRESSURIZED VESSEL USE DRY
NITROGEN GAS ONLY
Please refer to HYDAC Operating
and Installation Instructions
CAUTION!
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Maintenance
3. Installation and Mounting
3.1. Mounting Position
The piston accumulators can be mounted in any position. However,
the vertical mounting position with the gas valve at the top is
generally preferred.
Sufficient clearance must be left to mount and disconnect the
piston accumulator. In particular, an area of at least 150 x 150 x 150
mm must be left above the gas valve for fitting and operating the
charging and gauging unit.
3.2. Mounting
In accordance with the recommendations of the HYDAC brochure
“Mounting Components”, HYDAC piston accumulators must be
mounted vibration free using clamps and base brackets.
Note: Mounting elements must never be welded to the
piston accumulator.
4. Connection
The connection of the accumulator to the system must be
stress free and torque free.
It must be possible to isolate the accumulator from the pressurized
hydraulic system.
5. Commissioning and Safety Precautions
5.2. Venting
Prior to commissioning, the accumulator must be vented on the oil
side. Then apply the maximum operating pressure to the complete
hydraulic system and check for leakages.
5.3. Safety Precautions
IMPORTANT!
Only use nitrogen to charge the accumulator, never
oxygen or compressed air (risk of explosion).
If the pressure of the nitrogen bottle is higher than
the permissible operating pressure of the accumulator,
a pressure regulating valve must be fitted.
6. Inspection and Maintenance
On the whole, nitrogen losses on piston accumulators are very low.
However, it is advisable to check the precharge pressure p0 at least
once during the first week following commissioning so that larger
nitrogen losses can be detected immediately. During the course of
the first two months check the precharge pressure every two weeks,
and thereafter every four weeks. If af ter this period no pressure
change is detected, an annual check of the nitrogen pressure is
sufficient.
6.1. Checking the Nitrogen Pressure without
a Charging and Gauging Unit
In this case, as shown in the following drawing, a pressure gauge is
connected to a line which is directly connected to the accumulator.
5.1 Commissioning
Prior to connecting the accumulator to the pressurized system, the
precharge pressure should be rechecked. If the accumulator was
precharged at HYDAC the pressure level can be found on the label.
The level of the precharge pressure generally depends on the
following criteria:
• type of system,
• expected changes in operating temperature,
• intended function of the accumulator.
The following precharge pressures are recommended:
for energy storage:
p
≤ P1 - 5 bar
0,tmax
p
≥ 2 bar
0,tmin
for volume compensation:
p0 = static pressure of the system
Further information on the gas precharge pressures can be found in
the HYDAC accumulator brochure “Piston Accumulators”. Charging
and gauging of the precharge pressure is described in Point 6
“Inspection and Maintenance”.
E
A
Isolate the fully charged piston accumulator from the hydraulic
system by closing the shut off valve A. Slowly discharge the
accumulator on the fluid side via drain valve E. The pressure gauge
must be constantly monitored during this process. A slow, steady
pressure drop is displayed. The pressure only drops abruptly when
the accumulator has been completely discharged. The pressure
displayed before the drop corresponds to the precharge pressure
of the piston accumulator. If this pressure lies below the permissible
value, the charging procedure must be carried out, as described in
the following section.
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Maintenance
enough to overcome recommended torque)
6.2. Charging Procedure with the Charging
and Gauging Unit
Using the charging and gauging units, hydraulic accumulators can
be charged with nitrogen or tested to the precharge pressure P0.
First, isolate the piston accumulator from the hydraulic system by
closing the shut off valve A and discharge it on the fluid side. Then
remove the valve seal cap of the piston accumulator.
When using accumulators with gas valves version 1 the gas valve
insert must first be unscrewed slightly (approx. 1/2 turn) using a 6mm
allen wrench.
The T-handle of the FPU-1 must not be used for this. Now the
charging and gauging unit can be connected.
When using accumulators with gas valve version 4, the valve seal
cap must first be unscrewed. Only then can the charging and
gauging unit and the nitrogen bottle be connected in accordance
with the operating instructions (with adapter A3). Ensure that the
pressure release valve of the charging and gauging unit is closed.
Turn the spindle in a counter-clockwise direction to unscrew the
internal hex screw of the gas valve. Then slowly open the valve of the
nitrogen bottle so that the nitrogen is released into the accumulator.
Wait until approximately 1 bar precharge pressure has been reached
and the piston is at the fluid side before opening the shut off valve of
the nitrogen bottle further to enable faster charging.
Gas Valve Version 1Gas Valve Version 4
Valve protection cap
valve
protection
cap
(where applicable)
Valve
seal cap
(where applicable)
O-ring (where applicable)
Allen Wrench 6 mm
(to be used to crack open M8 SHCS.
T handle on FPK Charging is not robust
Socket Head
Cap Screw (M8)
6.3. Pressure Testing
For piston accumulators with a permissible operating pressure p
greater than 1 bar and a pressure capacity p*V > 1000, for noncorrosive fluids, a pressure test must be carried out by an approval
authority every 10 years, otherwise every 5 years.
An internal inspection must be carried out ever y five years and an
external inspection every two years.
7. Storage and Preservation
If the period of storage until commissioning is no longer than three
months, it is sufficient for the precharged accumulator to be stored
in a cool, dry place, protected from direct sunlight, providing that
the inside of the accumulator has first been coated with the intended
hydraulic fluid. The accumulator can be stored in any position. To
prevent contamination from entering the accumulator, ensure that
the hydraulic connection is plugged.
If the accumulator is to be stored for longer than three months,
check the required precharge pressure of the accumulator before
commissioning.
If the accumulator has not been precharged, it must be plugged
on the gas side and conserved with the intended operating fluid or
another suitable conservation fluid.
O-ring
Interrupt the charging procedure from time to time and check
the precharge pressure reached. When the required precharge
pressure has been reached, close the shut-off valve of the nitrogen
bottle. Wait for approx. five minutes until temperature equalization
is reached (a longer period must be allowed for larger systems quantities),
then recheck the precharge pressure and adjust if necessary. If the
pressure is too high, it can be lowered via the pressure release valve
of the charging and gauging unit.
Turn the spindle clockwise to securely tighten the internal hex screw.
Then discharge the charging and gauging unit via the pressure
release valve and remove it by loosening the cap nuts. On piston
accumulators with gas valve version 1, the internal hex screw must
be tightened to a torque rating of 20 Nm and with version 4 the valve
seal cap must be tightened to a torque rating of 30 Nm. Finally check
for leaks on the accumulator gas valve using a leak detector spray.
Screw on valve protection cap.
Further details can be found in the operating instructions for part
number 02068202.
Seal ring
PN#02068195 / 04.13 / ACU1102-1326
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Maintenance
Assembled view
PISTON TYPE 2
8. Disassembly, Inspection and Assembly
8.1 Removal From System
• Carefully clean the area around the end caps on the gas
and fluid side.
• On backup type piston accumulators the nitrogen feed line must
be isolated by means of the shut off valve.
• Completely release the pressure on the fluid side of the
accumulator. This causes the piston to move down to the end
cap on the fluid side with the aid of the gas precharge pressure.
• Connect the charging and gauging unit according to the
operating instructions and section 6.2. and release the pressure
slowly by opening the pressure release valve.
• Remove all non pressurized lines on the gas and fluid side and
remove the complete piston accumulator from the system.
8.1.1 Disassembly
Further disassembly should be carried out in a suitable, clean area.
• Clamp piston accumulator to a work bench and remove the gas
valve and all adapters and accessories.
• Unscrew end caps on the gas and fluid side. This can be
achieved by using 2 bolts or threaded rods positioned opposite
each other. On large end caps an extension rod can be used.
• If the end cap is in two parts, then the connection screws
between the threaded ring and end cap must be loosened first.
Unscrew the threaded ring by approximately 3 turns and screw
in the connection screws again. This pulls the end cap out.
Carry out this process several times until the end cap is
completely free.
• Push the piston out of the accumulator in the direction of the
fluid side (use suitable plastic or wooden rod and a r ubber mallet).
Both threaded bores in the piston can be used for this purpose.
8.1.2 Testing and Cleaning
a) Cylindrical tube
Carefully clean the inside of the cylindrical tube (piston body) with
a non aggressive, non abrasive cleaning agent and then dry with
a lint free cloth. Check the inside of the tube for rough spots and
grooves. If these are found, it is possible for HYDAC to remachine
the cylindrical tube within certain tolerances.
If any external or internal damage is found, the pressure vessel must
be submitted to the manufacturer and, if applicable, the appropriate
inspection authority for assessment.
b) End caps
Carefully clean the end caps and replace both O– rings.
c) Piston
Remove all seals and guide rings and clean the piston thoroughly.
8.1.3 Assembly
a) Fitting the piston seals
Piston design type 2:
• Guide the mounting sleeve (see point 9 – Special tools and spare
parts) over the piston from the fluid side as far as the groove
provided for the center seal (see part of center seal).
• Draw the elastomer ring over the sleeve into the groove provided.
Then heat the center seal ring to 150°C to facilitate fitting and
push it over the mounting sleeve into the designated position
(shoulder towards the oil side). This process must be completed in
10 to 15 seconds.
• Push the quadring into the recess of the seal ring (see figure).
• Withdraw the mounting sleeve as far as the groove for the seal
ring and fit elastomer O-ring. Then heat the seal ring to 150°C to
facilitate fitting and press into the designated position over the
mounting sleeve (shoulder towards the oil side). This process must
be completed in 10 to 15 seconds.
• Fit guide rings both on the gas as well as the oil side with the
ends displaced by 180°.
Gas side
Guide ring
Ptfe seal
Quad ring
Elastomer ring
Ptfe seal ring
O-ring
Guide ring
Fluid side
Guide ring
Elastomer ring
Seal ring
Piston design type 3:
• Fit elastomer O-ring into the designated groove and then draw
the seal ring over it.
• Fit guide rings both on the gas as well as the oil side with the
ends displaced by 180°.
b) Fitting the piston
• Lubricate the upper area of the cylinder wall and the guide ends
of the piston with a suitable lubricating agent (filtered operating
fluid). Do not use grease or water - water is not a lubricant!
• Place mounting sleeve (see section 9 - Special tools and spare parts )
onto the cylindrical tube.
• With the hollow side towards the gas connection, insert the
piston fully into the tube. A plastic or wooden rod or a rubber
mallet can be used for this purpose.
• Grease both O-rings and the threads on the end caps.
• Screw both end caps, or end caps with threaded ring, into the
cylindrical tube, if necessary with the aid of the two bolts and a
rod, until they are level with the ends of the accumulator.
• If specified, the accumulator must be filled on the gas side with
the designated quantity of oil.
• Fit the gas valve and all adapters and other accessories.
• Connect HYDAC charging and gauging unit and charge the
accumulator according to the instructions (see section 6.2) with
the required precharge pressure.
• On piston accumulators with the gas valve version 1, the internal.
hex. screw must be tightened to a torque rating of 20 Nm and
with version 4, the valve seal cap must be tightened to a torque
rating of 30 Nm.
• Screw on valve protection cap.
c) Fitting the accumulator into the system
Reconnect the piston accumulator to the system and check for leaks
according to section 6 - Inspection and Maintenance.
Assembled viewExploded view
Exploded view
PISTON TYPE 3
Gas side
Fluid side
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Maintenance
8.2. Piston Accumulator
with Protruding Piston Rod
8.2.1 Disconnection, Disassembly, Testing
and Cleaning
Disconnect the piston accumulator as described in section 8.1.
8.2.2 Assembly
a) Fitting the piston seals
Fit the piston seals as described in point 8.1.4 a)
b) Assemble the piston accumulator
• Fit piston rod into the piston base.
• Lubricate the upper part of the cylinder wall and the guide ends
of the piston with a suitable lubricant (filtered operating fluid). Do
not use grease or water - water is not a lubricant!
• Place mounting sleeve (see section 9 - Special tools and spare parts )
onto the cylindrical tube.
• With the hollow side towards the gas connection, insert the
piston fully into the tube. A plastic or wooden rod or a rubber
mallet can be used for this purpose.
• Grease both O-rings and the threads on the end caps.
• Screw in both end caps, or end caps with threaded ring, into the
cylindrical tube, if necessary with the aid of the two bolts and a
rod, until they are level with the ends of the accumulator.
• If specified, the accumulator must be filled on the gas side with
the designated quantity of oil.
• Fit the gas valve and all adapters and other accessories.
• Push the guide block, fitted with an O–ring, over the piston rod
and screw it firmly to the end cap.
• Fit the rubber packing seal kit in the groove provided.
• Place the sealing flange with the skimmer in position and
screw on.
• Connect HYDAC Charging and Testing Unit FPU–1 and charge
the accumulator according to the instructions (see section 6.2)
with the required pre–charge pressure.
• On piston accumulators with the gas valve version 1, the internal.
hex. screw must be tightened with a torque rating of 20 Nm
and with version 4, the valve seal cap must be tightened with a
torque rating of 30 Nm.
• Screw on valve protection cap.
c) Fitting the accumulator into the system
Reconnect the piston accumulator to the system and check for leaks
according to section 6 - Inspection and Maintenance.
8.3. Piston Accumulator with Electrical
Limit Switch
For item numbers, see section 9.2.3.
8.3.1 Disconnection, Disassembly, Testing
and Cleaning
Disconnect the piston accumulator as described in section 8.1.
8.3.2 Assembly
a) Fitting the piston seals
Fit the piston seals as described in section 8.1.4 a )
b) Assemble the piston accumulator
• Lubricate the upper part of the cylinder wall and the guide ends
of the piston with a suitable lubricant (filtered operating fluid). Do
not use grease or water - water is not a lubricant!
• Place mounting sleeve (see section 9 - Special tools and spare parts )
onto the cylindrical tube.
• With the hollow end towards the gas connection, insert the
piston fully into the tube. A plastic or wooden rod or a rubber
mallet can be used for this purpose.
• Grease both O–rings and the threads on the end caps.
• Fit the limit switch with the O–ring in place.
• Screw in both end caps, or end caps with threaded ring, into the
cylindrical tube, if necessary with the aid of the two bolts and a
rod, until they are level with the ends of the accumulator.
• If specified, the accumulator must be filled on the gas side with
the designated quantity of oil.
• Fit the gas valve and all adapters and other accessories.
• Connect HYDAC Charging and Testing Unit FPU–1 and charge
the accumulator according to the instructions (see section 6.2) with
the required precharge pressure.
• On piston accumulators with the gas valve version 1, the internal.
hex. screw must be tightened with a torque rating of 20 Nm
and with version 4, the valve seal cap must be tightened with a
torque rating of 30 Nm.
• Screw on valve protection cap.
c) Fitting the accumulator into the system
Reconnect the piston accumulator to the system and check for leaks
according to section 6 - Inspection and Maintenance.
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Maintenance
Exterior
ol
Assembly T
Cross Section
Gas V
Seal
9. Seal Kits & Replacement Pistons
For seal kits other than Buna N, and for sizes not listed please consult factory.
Example: SK 350 - 20 / 2112 S - 210 FCF - VE - 18 E - 1 (see page 33 for deta ils)
Piston Type Diameter
Piston Seal Kits
Diameter Type 2 (NBR) Type 3 (PUR)
06 (60mm) — 3016 210
08 (80mm) 2123 89 0 3013230
10 (10 0m m) 363268 2123414
12 (125mm) — 2128104
15 (15 0m m) 3016 235 3145418
18 (18 0m m) 363270 2123415
25 (250mm) 363266 3016 213
31 (310mm) 301600 —
35 (355mm) 363272 —
49 (490mm) 3104100 —
Replacement Pistons - w/ Seals
Diameter Type 2 (NBR) Type 3 (PUR)
06 (60mm) — 3009372
08 (80mm) 352225 2119 931
10 (10 0m m) 35 6847 21155 47
12 (125mm) 3016232 3016150
15 (15 0m m) 3016228 3016231
18 (18 0m m) 2118 451 3046277
25 (250mm) 353980 3 016171
31 (310mm) 356382 —
35 (355mm) 356382 —
49 (490) 3462428 —
Tools
Diameter Seal Assembly Piston Insertion
08 (80 mm) 359537 35 9614
10 (10 0m m) 352198 290056
12 (125mm) 3016278 2128 223
15 (15 0m m) 2124157 2124161
18 (18 0m m) 350148 290049
25 (250mm) 290035 290046
31 (310mm) 2127304 212730 5
35 (355mm) 3 54147 3389677
49 (490mm) 31142 2 0 3440695
Seals Included with Piston Seal Kit
alve Seal O-ring
End Cap O-ring
Guide Ring
Center Seal
Seal Ring
Guide Ring
Type 2Type 3
Guide Ring
Center Seal
Piston Accumulators: Tools
When repairing a piston accumulator, it is critical to use
the appropriate tools to avoid seal damage. There are two tools
required:
Seal Assembly Tool:
allows for gradual and even stretching of the seals when installing
them onto the piston
Piston Insertion Tool:
a tapered shroud that protects the seals from the threaded portion of
the shell, and provides even seal compression and piston alignment
when inserting the piston into the shell.
For items not listed please consult factory.
WARNING: Only qualified persons should perform maintenance on any type of accumulator.
For addition information please contact HYDAC.
End Cap O-ring
Seals
ool
Piston
HYDAC TECHNOLOGY CORPORATION
Accumulator Division
2260 City Line Road • Bethlehem, PA 18017
Tel 610.266.0100
Fax 610.231.0445
Piston
Insertion To
Shell
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