Piston accumulator stations in the hydropower industry

Turbines Provision of power for emergency shut-down of control equipment for all turbine types (e.g. control device for the Francis turbine)

Shut-off valvesProvision of power for emergency shut-down of ball valves or ball check valves

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CONTENTS Page

1. GENERAL 2

2. ACCUMULATOR STATIONS 3

3. PISTON ACCUMULATORS 4

4. SAFETY AND SHUT-OFF BLOCK 10

5. NITROGEN BOTTLE 11

6. CHARGING AND TESTING BLOCK F+P 11

7. GAS-SIDE SAFETY ELEMENTS 12

8. FRAMES 13

9. FURTHER ACCESSORIES 14

1. GENERALFluid power in hydro-electric energy Nowadays, hydro-electric power stations make a significant contribution to the supply of sustainable energy.For HYDAC, one of the leading companies in fluid power, hydraulics, process technology and electronics, this is yet another area where it proves its expertise, helping to make optimum use of the power of water.Hydraulic systems, like no other drive technology, provide a high degree of operating safety and power density, compact design, fatigue strength, minimum maintenance and – in conjunction with electronics – excellent control and monitorability. Ideally suited, therefore, to hydropower.This document has been designed for hydraulic accumulator applications in hydropower and provides HYDAC accumulator technology and engineering from a single source.We ensure that shut-off valves and turbines are supplied with power sufficiently and at the right times.Our specialists are happy to help.

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2. ACCUMULATOR STATIONS

HYDAC supplies completely piped, operationally ready accumulator stations, pipe fittings and safety devices either as an individual accumulator unit or back-up version with nitrogen bottles for enlarging the usable volume.The modular structure of the systems makes it possible for individual customer specifications to be incorporated into the project planning. HYDAC can calculate the required accumulator volume using the accumulator simulation program, taking the customer’s own operating data into account.Please read the relevant operating manuals for the individual HYDAC components:

z Piston accumulator (3.301.BA) z GSV/GMP (3.504.BA) z Charging and testing unit (3.501.BA) zSafety and shut-off block (3.551.BA)

2.2 MODEL CODE

SS210 K – 1 x 500 / 12 x 75 (U)

Series SS = accumulator station (e.g. SS210 = accumulator station with a pmax. of 210 bar)

Type code letter K = piston accumulator B = bladder accumulator N = nitrogen bottles

Number of accumulators

Nominal volume [l] of the accumulators

Number of nitrogen bottles

Nominal volume [l] of nitrogen bottles

Certification code (U) = European Pressure Equipment Directive (PED)

Piston accumulator station

2.1 TECHNICAL SPECIFICATIONOperating pressure 210 barOperating fluid zMineral oil HLP to DIN 51524, Part 2

zHLP 22 – HLP 68 (observe viscosity in operating temperature range)

Oil operating temperature -10 °C ... +60 °C Ambient temperature -10 °C ... +80 °CCoating of parts/components Primer + topcoat to HYDAC standardCoating of steel construction Sand blasting + primer + topcoatPiping (on gas side) Type: Walform

Material: galvanised (optionally stainless steel) Size: DN 26

Acceptance European Pressure Equipment Directive (PED) (others on request)

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3. PISTON ACCUMULATORS3.1 DESIGNHYDAC piston accumulators consist of:

z a cylinder with very finely machined internal surface; z covers on the gas side and the oil side (sealed with O-rings); z the floating steel or aluminium piston which can easily be accelerated due to its low weight; z a sealing system adapted to the particular application.

The piston floats on two guide rings which prevent metal-to-metal contact between the piston and the accumulator wall.

3.2 PISTONPiston design type Type 3Application z Low-friction design

zSimple-to-fit seals zSlow movements without stick-slip effect

Max. piston velocity 0.8 m/sFiltration NAS 1638 – class 6

ISO 4406 – class 17/15/12

3.3 DIMENSIONSL ±3 [mm]Volume[l]

Ø D1 [mm]180 250 355 490

50 2260 100 4250 2490 150 3470 2050 200 4490 2550 1760250 5510 3060 2030300 3560 2290350 4070 2560400 4570 2820450 3085500 3350

3.4 CONNECTIONSØ D1 [mm] 180 250 355 490Fluid side 1 1/2" 2" 2" 2"Gas side M28x1.5 M28x1.5 M28x1.5 M28x1.5

Gas valve

end cap safety device

Cover

piston

sealing system

cylinder

external seal

end cap safety device

Fluid port

Design of piston accumulator

Piston type 3

Dimensions

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3.5 PISTON POSITION MEASUREMENT SYSTEM3.5.1 Cable tension measurement systemUsing the cable tension measurement system, the position of the piston can be determined by means of a cable which is fixed to the piston base. The cable is attached to a roller which is tensioned by a spring. During the piston movement, this roller alters the electrical resistance via an attached rotary potentiometer. The resistance is converted to an electrical signal by a measurement transducer. A display unit can be added to the system. This allows the position of the piston to be displayed, up to four positions to be tapped for wiring system parts and the electrical signal to be transmitted to a PLC, for example.

Components: zMeasurement transducer: - 4 – 20 mA

zDigital display unit (optional): - HDA 5500, 2 switch points, AC - HDA 5500, 2 switch points, DC - HDA 5500, 4 switch points, AC - HDA 5500, 4 switch points, DC

Limits of application: zMax. piston acceleration: 7 ... 30 g zMax. piston velocity: 0.5 m/s zAccumulator installation: vertical, gas side up z Limits for piston accumulators: see following table

Cable tension measurement system possible

Volume [l]Piston diameter [mm]180 250 355 490

50 –100 –

150

200

250 –

300

350

400

450

500

Cable tension measurement system

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3.5.2 Magnetic flapper indicationThe magnetic flapper indication visualises the position of a piston on the basis of red/white flaps which are visible externally.An anti-magnetic tube uses a cable fastened to the piston on the gas side with a magnet located at its end to move the magnetically folding red/white flaps. The change in colour in the display makes it possible to read the piston position.Additional components can be added optionally (e.g. components to control system parts).

Components:The components described below are available as options and can be combined to suit the particular application and customer specifications. Please contact us and we will support you in selecting the system that is right for you.

z Transducer: The transducer is attached to the outside of the upright tube, opposite the indicator rail. Various models are available, depending on the particular piston stroke. These are described in the following table:

Technical data HLT 2150 Reed chain type 31967-W-010-10Function The HLT is used up to a piston

stroke of 3765 mm.A ferro-magnetic conductor is tensioned and supplied with a current pulse (magnetostrictive measuring element – wave guide) inside a tubular cable protection. From the current pulse, a radial magnetic field arises around the conductor. The magnet fastened to the piston generates a longitudinal magnetic field in relation to the wire.If the two magnetic fields meet at the measurement point, a torsion pulse is triggered that spreads out from the measurement point with constant ultrasonic speed, moving along the wire in both directions. The ultrasonic sound signal is recorded via a sensing element inside of the sensor head and converted into an electrical output signal. The measured delay between sending out the current pulse until the torsion pulse arrives is converted into a 4 - 20 mA signal by the measurement electronics.

The reed chain is used for piston strokes of 3766 mm and above.The magnet actuates the reed switches in the transducer as it passes, which causes the resistance value to change. The resulting change in voltage is converted to a standardised 4 - 20 mA signal by an internal converter.

Housing Stainless steel (1.4301 / 1.4571)

Stainless steel (1.4401 / 1.4404)

Supply voltage 12 ... 30 V DC 14 ... 40 V DC

Electrical connection

Male connector M12x1 (analogue: 4-pin, digital: 5-pin)

Cable 2x0.75 mm²

Current consumption without output

≤ 100 mA -

Signal output 4 ... 20 mA 4 ... 20 mAResolution Analogue: 12 bit, ≥ 0.1 mm 10 mmOperating temperature

-40 °C ... +85 °C -20 °C ... +50 °C

Sampling rate (internal)

2 ms -

Cable - PVC, grey, length 5mProtection class IP 67 IP 68

Magnetic flapper indication

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zSwitches: Three different magnetic switch versions are available: latching, N/C contact and N/O contact. Each one has a reed switch that switches when the magnet is present. The following overview describes the technical data, including the mode of operation:

Technical data Latching BN310-RZ

N/C contact BN310-01Z

N/O contact BN310-10Z

Mode of operation When the magnet passes, the contact is closed, remains closed and is only opened when the magnet returns.

The contact is open when the magnet is present.

The contact is closed when the magnet is present.

Material of housing Plastic, glass-fibre-reinforced thermoplasticMaterial of cable HD03VV-FWeight 0.65 kg 0.75 kg 0.65 kg

Electrical connection

Cable 2x0.75 mm², 1 m long

Service life, mechanical

Min. 109 switching cycles

Service life, electrical

106 – 109 switching cycles

Shock resistance 30 g / 11 ms Oscillation resistance

10 ... 55 Hz, amplitude 1 mm

Bounce time 0.3 ... 0.6 msActuation speed Max. 18 m/sRestart accuracy +/- 0.25 mm (T = constant)Ambient temperature

-25 °C ... +75 °C

Protection class IP 67 to IEC/EN 60529Switching speed Max. 18 m/s - -Switching time, “closing”

0.3 ... 1.5 m/s - 0.3 ... 1.5 m/s

Switching time, “opening”

Max. 0.5 m/s Max. 0.5 m/s -

Switching frequency < 300 HzFlash-over voltage > 600 V AC (50 Hz)Switching voltage Max. 250 V AC/DCSwitching current Max. 3 ASwitching capacity Max. 120 W

Limits of application: zMax. piston velocity: 0.5 m/s zAccumulator installation: vertical, gas side up

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3.5.3 Piston position switchesPiston position switches detect the position of a piston inside the piston accumulator through the wall of the cylindrical jacket. The piston position switch can be retrofitted with a clamp, with no further modification to the piston accumulator required. This makes fitting possible without disrupting operation. A clamp mount in the form of a clamp-on solution is provided for this purpose. The measurement principle is based on the ultrasonic pulse echo method. An electrical pulse is used to generate ultrasonic sound that is reflected on the rear wall of the cylinder and then evaluated. A rear wall echo that has been received is then signalised.The piston position switch detects the transition from oil to piston, at which point the signal is switched off. This is the case if the piston is in the sound path or has passed it. Furthermore, two piston position switches can be connected to each other. This makes it possible for the piston to move between two specified positions.

Components:

BF1 – standard design BF3 – design for highly viscous media

Device type Piston position switch: ultrasonic position switch for pistons in piston accumulators and cylinders with no fittings

Number of sensors per piston accumulator*

1 → for single operating mode 2 → for synchronous operating mode

Sensor design Compact sensor unit consisting of sensor element and evaluation electronics

Measurement principle

zNon-contact ultrasonic pulse echo method zNo sensor contact with fluid zNormally no structural changes required to the cylinder, as measurements are taken through the wall from outside

Measurement repetition rate

Max. 155 Hz

Mounting to cylinder, coupling

Mounting in desired position with mounting clamp and mounting plate with M30 thread Coupling to cylinder with couplant

Accuracy Static ± 1 mm, measured from centre of sensorPiston accumulator dimensions

zExternal diameter: 98 ... 950 mm z Internal diameter: 70 ... 800 mm

Fluids zMineral oil (HL, HLP) zHFA (HFB) zHFC zHFD zWater

Viscosity of the medium

up to 100 cSt up to 500 cSt

Supply voltage z 18 to 30 V DC, max. 80 mA, ripple 10 % zUndervoltage detection zReverse polarity protection zOvervoltage detection

Switching output zNPN or PNP zMax. switching current: 60 mA (external fuse provided) with maximum switching current of 30 V DC zMax. switching capacity: 1.8 W

zNPN or PNP zMax. switching current: 200 mA (external fuse provided) zMax. switching voltage: positive operation voltage

Serial interface 1-wire interface for configuration and synchronisation (with programming adapter and PC)

Connections zSensor connector M12 zCable 4-pin without shield - brown: positive operation voltage 18 to 30 V DC - blue: negative operation voltage (GND) - black: switching output - white: synchronisation, serial programming

for configurationSensor cable length 2 (or 5) metres with right-angle plugSwitching point display

LED integrated into right-angle plug (green, yellow)

Piston position display

* Multiple sensors possible on request

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BF1 – standard design BF3 – design for highly viscous media

Temperature range zAccumulator temperature: -20 °C ... +80 °C (observe viscosity) zAmbient temperature: -20 °C ... +60 °C zStorage temperature: -40 °C ... +85 °C

Protection class IP 67, oil resistantHousing zAluminium, anodised

zH x Ø: 50 x 50 mm z Thread M30 x 1.5 zEarthed to GND

Weight Approx. 170 g Approx. 250 gIndividual parts None, only complete moduleMaintenance If sensor is repositioned, new couplant requiredRegulatory information

zProtection class: IEC529 (DIN 40050) zEMC active: EN 50081; EN 55011 zEMC passive: EN 50082; IEC 61000-4-2, -3, -4, -5, -6

Scope of delivery Sensor(s), mounting clamp(s), couplant, connection cable, operating manual (scope in accordance with quotation)

Restrictions:None

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4. SAFETY AND SHUT-OFF BLOCK4.1 GENERALThe HYDAC safety and shut-off block SAF is a hydraulic accessory that is used to shut off and discharge hydraulic accumulators.The HYDAC safety valve (DB12) is used in the SAF series. It is a direct-acting pressure relief valve in poppet valve construction with excellent opening and closing characteristics. This version of the DB12 complies with the requirements of the European Pressure Equipment Directive (PED).

4.2 DESIGN AND CONNECTIONSThe safety and shut-off block SAF is structured as follows:

Pressure relief valve DB12

M1 port (optionally with pressure gauge) ISO 228 - G 1/4 for SAF10 ISO 228 - G 1/2 for SAF20, SAF32

Shut-off valve

Release spindle

M2 port (e.g. for p0-guard) ISO 228 - G 1/4 - for all sizes

These devices are combined in the compact HYDAC safety and shut-off block. The following devices are also available: Solenoid-operated unloading valve

(optional for version SAF…E…) Needle valveAdditional port designations:P Pump portT Tank port

4.3 SAF DESIGNInternal diameter piston accumulator [mm]

180 200 355 490

Recommended SAF block DN 10 DN 20 DN 32

Design ManualThreaded connection ISO 228 (BSP)Supplementary equipment

L = lockable main shut-off valve (locking device)LPI = model L with additional position monitoring (inductive

proximity switch)Set pressure range (at PR) 210 bar

e.g.: SAF with additional equipment L or LPI

Circuit diagram SAF

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Design of nitrogen bottle

Minimess connection

Nitrogen bottle

5. NITROGEN BOTTLETo increase the gas volume in the hydraulic accumulator, nitrogen bottles are used in back-up form. The advantage of doing this is that smaller accumulators can be used for the same gas volume and the costs of the entire volume package can be reduced.

5.1 DIMENSIONSVolume Connections to ISO 228 (Type AA) Height ±

25 mmWeight

[l] Drain side Connection side [mm] [kg]50 D G 3/4 D G 3/4 1650 8775 D G 3/4 G G 1 1/2 2310 123

Charging and testing block

Circuit diagram accumulator station with F+P

Circuit diagram F+P

6. CHARGING AND TESTING BLOCKThe HYDAC charging and testing block F+P is used to charge and test back-up-type hydraulic accumulator stations. It has connections for the charging and testing unit FPU-1 and the pressure gauge. HYDAC supplies the following safety devices to secure against excess pressure and/or excess temperature increases:

z Temperature fuse (see section 7.1) z Bursting disc (see section 7.2) z Gas safety valve (see section 7.3)

These can be screwed into the F+P.In addition, it allows the back-up nitrogen bottles to be shut off from the hydraulic accumulator.

6.1 RECOMMENDED F+PDescription Max. operating

pressure [bar]

Weight [kg]

Suitable for piston accumulator internal diameter [mm]

F+P-16 400 4.3 180 ... 250 F+P-32 350 14 355 ... 490

6.2 OPTIONSOptionally HYDAC can provide the possibility of attaching the connection for the charging and testing device to the frame at operator height. This comprises:

zShut-off valve zPressure gauge zGas charging valve zMinimess connection z 1 vacant connection (e.g. for pressure switch)

Nitrogen bottles

Hydraulic accumulator

Safety and shut-off block

Charging and testing block

connection for gas safety valve

Connection for charging and testing unit FPU-1*

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7. GAS-SIDE SAFETY ELEMENTSAs established in the national regulations of numerous countries, it is recommended or mandatory that hydraulic accumulators be protected from excessive pressures.

Design of bursting disc

7.2 BURSTING DISC7.2.1 FunctionIf the pressure exceeds the permitted level, the bursting disc is destroyed. This permanently opens the port and reduces the gas pressure by discharging the nitrogen completely.Bursting discs are designed for different burst pressures and are supplied with a certificate of conformity.Bursting discs are made either entirely from stainless steel or from an alloy based on stainless steel and nickel.

Discharge opening

Screw-in thread1/4" NPT or ISO 228 - G 1/4

Design of GMP 6

7.1 TEMPERATURE FUSE7.1.1 FunctionHYDAC offers a temperature fuse of the type GMP 6 that is approved according to the European Pressure Equipment Direction (PED). It consists of a stainless steel housing that contains a fusing element that melts when the trigger temperature is reached and thus depressurises the accumulator.Temperature fuses are “devices with a safety function” and are used to release the gas pressure by discharging the nitrogen completely when an increase in temperature reaches unacceptable levels (e.g. in the case of fire).

7.1.2 Technical dataPermitted operating pressure 50 ... 420 barTemperature range -40 °C ... +120 °CMelting temperature Between +160 °C and +170 °CRecommended temperature fuse GMP6-10-CE1637Acceptance Europ. Pressure Equipment Directive

(PED) with CE marking, delivery with declaration of conformity and operating manual

Housing

Discharge opening

Threaded connection ISO 228 - G 1/4

7.3 GAS SAFETY VALVE7.3.1 FunctionThe gas safety valve provides protection by reducing the pressure in a controlled way if pressure exceeds the permitted level unexpectedly. It consists of a housing which contains a compression spring for setting the cracking pressure. The spring is pre-set on the pressure side and lead-sealed by the authorised representative. It is also supplied with a certificate of conformity and operating approval.7.3.2 Technical dataDimensioning zEuropean Pressure Equipment Directive (PED)

zEN ISO4126-1 zEN 13445-6 zOthers on request

Module category z IV in accordance with European Pressure Equipment Directive (PED) zModule B + D (EC type approval) zModule G (EC individual approval) on request

Nominal size 6 mmConnection ISO 228 – G 1/2 A Material zStainless steel

zClosing element with flexible seat sealMedium Nitrogen (N2)Operating pressure range 30 ... 370 barTemperature range -20 °C ... +80 °CWeight 1.1 kgLength 206 mmDiameter 35 mm

Design of gas safety valve

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8. FRAMES8.1 FOR PISTON ACCUMULATORSPiston accumulators with Ø D1

Accumulator volume

Height Width Length Weight of frame

[mm] [l] [mm] [mm] [mm] [kg]

180 50 2700

540 510242

100 4720 252

250

100 2700

620 560

212150 3710 259200 4720 305250 5225 324

355

150 2700

700 630

234200 3205 264250 3710 284300 4215 313350 4720 332400 5225 350

490

200 2200

830 760

245250 2475 255300 2660 262350 2975 287400 3240 297450 3505 307500 3770 317Frame SK (example)

Width Length

Hei

ght

Width

Width

Length

Length

Hei

ght

Hei

ght

Frame SN (50 l)

Frame SN (75 l)

8.2 FOR NITROGEN BOTTLESVolume N2 bottle

Max. number of N2 bottles

Height Width Length WeightN2 bottle

Frame Total

[l] [l] [mm] [mm] [mm] [kg] [kg] [kg]

50

4

1992 900

650

95

149 529 6 910 169 739 8 1170 175 93510 1430 189 113912 1690 200 1340

75

4

2800 900

650

133

206 738 6 910 236 1034 8 1170 252 131610 1430 268 159812 1690 284 1880

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Design of FPU-1

Dimensions

9. FURTHER ACCESSORIES9.1 CHARGING AND TESTING UNIT FPU-1The HYDAC charging and testing unit FPU-1 is used to charge accumulators with nitrogen or to check or to change the existing pre-charge pressure in accumulators.For this purpose the charging and testing unit is screwed onto the gas valve of the hydraulic accumulator and connected to a nitrogen bottle via a flexible charging hose with a pressure reducer.Handling, inspection intervals and other operating-related information are given in the operating manual.9.1.1 DesignThe HYDAC charging and testing unit for piston accumulators consists of:

zValve body zSpindle zCheck valve zRelease valve zPressure gauge

The standard scope of delivery also includes: zCharging hose (2.4 or 4 m) zAdapter A3

The adapter A3 is included in the scope of delivery as standard, but it is not needed in connection with the piston accumulator.

Release valve

Spindle

Check valve

Pressure gauge

Diagram of charging and testing procedure for bladder accumulator with FPU-1

Fluid port

Nitrogen bottle

Hydraulic accumulator

Adapter AG1 Charging hose

Adapter G Pressure reducer Charging and testing unit FPU-1

9.1.2 Dimensions with adapter for HYDAC hydraulic accumulator

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9.1.3 Charging hosesCharging hoses are designed for the particular maximum permitted operating pressure marked on them and 10,000 charging processes. HYDAC charging hoses comply with the EC Machinery Directive and with DIN EN 982 and DIN EN 853 to 857.

Type Connection Length [m]

Setting range

F to DIN 477, Part 1

2.5

up to 200 bar

410152028

FM to DIN 477, Part 5 up to April 2002

2.5up to 300 bar

4

FW to DIN 477, Part 5 up to April 2002 2.5 up to 300 bar

Nitrogen bottle

Condensate drain set

Draining hose

Condensate drain set

Charging hose F

Charging hose FM

Charging hose FW

9.2 CONDENSATE DRAIN SETThe condensate drain set consists of a needle valve and a suitable condensate draining hose. It is used to drain any condensate from the nitrogen bottle, in a controlled way.

Description Length [m]Condensate drain G 3/4 – Minimess M16x1.5 -Condensate drain set 0.4

11.6

Needle valve

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HYDAC TECHNOLOGYGMBH

Industriegebiet66280 Sulzbach/SaarGermanyPhone+49 6897 509-01Fax:+49 6897 509-454Internet: www.hydac.comE-mail: speichertechnik@hydac.com

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