Project Background

As the hydrogen energy industry develops, electrolyzer equipment demands increasingly higher standards for assembly precision, sealing performance, and operational reliability.

In the manufacturing of alkaline and PEM electrolyzers, the stack is assembled by stacking multiple electrolytic cells, bipolar plates, and membrane components. During assembly, high-precision bolt pre-tensioning is required to provide uniform and stable clamping force. This clamping force ensures proper sealing between components, preventing leakage of hydrogen and oxygen, as well as seepage of electrolyte.

Hydraulic bolt tensioners use hydraulic power to elongate bolts elastically. While the bolts are elongated, the nuts are tightened. After pressure release, the bolts rebound, generating a stable pre-tensioning force. This force acts on the end plates, completing the locking of the stack. Thus, the stack assembly of electrolyzers meets requirements for high load capacity, high precision, and even stress distribution.

hydraulic_bolt_tensioning_solutions_of_hydrogen_electrolyzers

Customer Needs and Technical Challenges

1. High-load bolt pre-tension requirements

The electrolyzer stack structure requires a substantial overall compressive force to ensure proper contact between the bipolar plates and sealing components.

In this project, the client requested to address:

  • Bolt specification: M68×6
  • Nut spanner size: 100 mm
  • Nut thickness: 120 mm

Implementation:

  • Maximum tensile force: 1500 kN
  • Bolt stretching stroke: 225 mm

2. Multi-point synchronized tensioning requirement

Since the electrolyzer consists of multiple stacked components, it is necessary to ensure uniform force distribution among the bolts.

Traditional manual fastening methods are prone to:

  • Uneven bolt loading
  • End plate tilting
  • Insufficient local sealing pressure
  • Increased risk of leakage

Therefore, the customer requires the hydraulic tensioning system to enable synchronized operation of multiple tensioners and allow zonal control according to actual needs.

3. Automation control requirements

To improve the installation efficiency of hydraulic tensioners, enhance process control capabilities, and reduce safety risks associated with manual operations, this project requires the system to have:

  • Auto-locking function
  • Adjustable tension force control
  • Tension displacement setting
  • Real-time data monitoring
  • Abnormal pressure warning
  • Data storage and export function

Hydraulic Bolt Tensioning Solutions from EKXIA

To meet the assembly requirements of hydrogen electrolyzers, EKXIA has designed and supplied an integrated automated hydraulic pre-tensioning solution comprising:

  • Hydraulic bolt tensioners
  • Split-type hydraulic pump station
  • PLC intelligent control system
  • HMI (Human-Machine Interface) system
  • Displacement detection system

This system tensions 18 stud bolts simultaneously. It automates nut-tightening, making it adjustable, visible, controllable, and able to log data.

hydraulic_bolt_tensioning_solutions_of_hydrogen_electrolyzers_from_EKXIA

Solution Configuration

1. Hydraulic Bolt Tensioner System

The hydraulic bolt tensioner utilizes a high-pressure hydraulic drive system. Hydraulic pressure controls the precise elongation of the bolt. Once the bolt reaches the set elongation, the nut is tightened and the tensioner completes the locking process upon pressure release.

Key Technical Parameters:

Parameter Value
Maximum Working Pressure 70 MPa
Maximum Pulling Force 1800 kN
Effective Piston Area 25,728 mm²
Stroke 35 mm
Bolt Size M68×6
Puller Fatigue Life ≥10,000 cycles
Cylinder Service Life ≥30,000 cycles

The equipment features:

  • Ultra-high-strength alloy steel construction
  • Self-locking quick-connect couplings
  • Detachable coupling design
  • Overtravel limit mechanism
  • Hydraulic retraction mechanism

Designed to meet the demands of long-term, heavy-duty industrial applications.

hydraulic_bolt_tensioner_system

2. Automatic Locking System

The system is equipped with a hydraulic motor that drives the rotation of the nut. The rotation of the nut enables automatic locking while the bolt is elongated.

Key Features:

  • Eliminates the need for manual tightening assistance
  • High-torque automatic rotation
  • Increases installation efficiency
  • Ensures consistent preload

Hydraulic Motor-Driven Nut:

  • Driving torque: 120 Nm
  • Nut run-down torque: Approx. 150 Nm

3. Separate Hydraulic Pump Station System

The hydraulic pump station adopts a separate design for the control module and the oil supply module, which improves the flexibility of on-site installation.

Key specifications:

Parameter Value
Maximum Working Pressure 70 MPa
Power Supply 380 V / 50 Hz
Motor Power 5.5 kW
Flow Capacity 3 L/min
Oil Reservoir Capacity 60 L

The system utilizes:

  • Siemens S7-1200 PLC control
  • MCGS HMI (Human-Machine Interface)
  • 10-inch touchscreen LCD display

The HMI enables:

  • Parameter settings
  • Real-time monitoring
  • Data storage
  • Data export
separate_hydraulic_pump_station_system

4. Intelligent Synchronous Control System

The system supports multiple tensioning control modes:

  • 18-group synchronous tensioning
  • 9×2 zoned control
  • 6×3 zoned control
  • Independent control for individual groups

System configuration:

  • 18-channel valve control system
  • 18-channel tension monitoring
  • 6 displacement sensors

One displacement sensor is provided for every three tensioners. The sensors monitor displacement changes in each tensioner in real time. Based on this data, the system ensures high-precision synchronous tensioning.

System Functional Features

Precise Tensioning Control

The system supports setting target tensioning force or target displacement values. It can switch between pressure mode and position mode to meet the needs of different assembly processes.

Real-time Parameter Monitoring

The system displays key parameters in real-time, such as tensioning force, hydraulic pressure, tensioning displacement, and ambient temperature. It visually presents the changes throughout the tensioning process via curves.

Data Recording and Traceability

The system supports parameter saving, USB data export, and PC upload. Supported data formats include XLSX, CSV, and TXT.

 

Equipment Installation and Operation Procedures

Step 1: Install the tensioner base.

In accordance with the equipment’s structural requirements, the installers mounted the 18 tensioner bases at the designated locations.

install_the_tensioner_base

Step 2: Manually install the guide rods.

manually_install_the_guide_rods

Step 3: Install the hydraulic tensioner.

Workers hoisted 18 tensioning hydraulic cylinders and secured them to the mounting bases.

install_the_hydraulic_tensioner

Step 4: Remove the guide rod and install the core puller.

remove_the_guide_rod_and_install_the_core_puller

Step 5: Connect the hydraulic and electronic control systems.

Connect the hydraulic motor oil pipe and the hydraulic motor valve group in sequence. Connect the hydraulic system oil lines and electrical cables to the corresponding ports on the tensioning equipment according to the numbering.

connect_the_hydraulic_and_electronic_control_systems

Step 6: Install the displacement sensor.

Install six displacement sensors and arrange them evenly as required.

install_the_displacement_sensor

Project Value

With this hydraulic bolt tensioning solution, the customer gains:

  • Enhanced assembly efficiency

Synchronized operation of 18 hydraulic tensioners reduces repetitive manual tasks, significantly boosting electrolytic cell assembly efficiency.

  • Improved preload consistency

Dual control of pressure and displacement ensures uniform load distribution across all bolts, maximizing the sealing reliability of the electrolytic cells.

  • Reduced operational risk

Automated control minimizes manual intervention in high-load environments, improving overall on-site safety.

  • Digital management

Comprehensive recording of tensioning parameters enables full assembly process traceability and quality management.

EKXIA Hydraulic Solution Capabilities

EKXIA not only supplies hydraulic tools but also provides customized hydraulic system solutions tailored to specific customer application requirements.

Our solutions encompass:

  • Hydraulic bolt tensioning systems
  • Hydraulic torque tightening systems
  • Hydraulic jacking systems
  • Hydraulic cylinder systems
  • Automated hydraulic control systems

By combining hydraulic technology, system design, and engineering expertise, EKXIA delivers reliable and efficient hydraulic solutions for industries such as hydrogen energy, power generation, bridge construction, and heavy equipment.