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Industrial shock absorbers from ACE

Shock absorbers protect safety valves in refinery

Overpressure in refinery pipes can lead to catastrophic consequences. In the event of overpressure, safety valves must therefore be opened in fractions of a second. Neither electric actuators nor pneumatic actuators are an option here. The Doedijns Group and ACE shock absorbers have developed a customized solution.

Detail of the actuator designed by DGI with integrated, adjustable ACE industrial shock absorber for a compressor package in a natural gas refinery (right). The pneumatic control in the actuator has the task of opening the 24-inch throttle valve shown below within half a second in the event of overpressure in order to equalize the pressure. (Image: ACE)

Where natural gas is compressed at high pressure and sent through pipelines at high temperatures, things can get hot in more ways than one. This is also the case in a refinery on the Red Sea in Yanbu, Saudi Arabia's second most important port city. Due to the flammability of the medium to be transported, explosion-proof compressors compress the gas and liquefy it. The compressors are there to regulate the pressure in the pipes: If the pressure is too low, they switch on, if the pressure is too high, they switch off or freewheel.

To ensure that the compressors maintain the desired working pressure as evenly as possible and are also optimally protected against overpressure, the Dutch company DGI develops pneumatic actuators, manufactures them in its own production halls and supplies them to refineries all over the world. If the pneumatic control system there should ever fail or be damaged, the actuators are developed and installed to generate additional volume for the safety of the system.

Hydraulic industrial shock absorbers are also used in combination with these modules. In this tailor-made design, the main task of the latter is to absorb the energy generated by the opening of the safety valves in the event of overpressure. The shock absorbers reliably brake the piston rods of the pneumatic cylinders that are responsible for opening.

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Opening hours 50 times faster

The special feature of the design described is the emergency opening speed it implements. Normally, an actuator for butterfly valves opens at a speed of one second per inch. In the case of the refinery project in the port of Yanbu, however, the dimensions of the pipelines and therefore also those of the valves required for the butterfly valves are very large at 24 inches. This means that the safety valve would only open after 24 seconds. Such a sluggish safety valve works far too slowly in an emergency. In this case, the speed must be around 50 times faster. This outlines the core problem that the engineers face in the design. Christian Junghans, the product manager responsible for industrial shock absorbers at ACE, explains: "Although the emergency that is to be assumed hardly ever occurs, a single incident would be enough to literally tear the entire construction apart."

DGI is one of the world's leading suppliers of hydraulic and pneumatic solutions for the oil and gas industry and the shipbuilding sector. With the Magnum industrial shock absorbers from ACE, they have a powerful solution at hand for these problems.

The ACE industrial shock absorbers of the Magnum family are available as self-adjusting or adjustable machine elements with thread sizes M33, M45 and M64 and strokes from 25 to 150 millimetres inside 24 hours from stock in Langenfeld. (Image: ACE/DGI)

As the pipeline pipes and their compressor packages are defined during the course of the project, the space available for the safety valves is determined. In the process, important design requirements were identified in the form of severe spatial limitations. This has an impact on the design and selection of the relevant damping elements. Due to the compactness of the actuators and the safety valves with pneumatic drive installed in them, the design team opted for industrial shock absorbers from ACE, type MA3325EUM, which only function in an emergency stop in this application.

Only task: Braking the piston rod

Their sole task is to slow down the piston rod of the pneumatic cylinder when the valves have to open within half a second in an emergency. During this process, the rod of the air cylinder hits the dampers at the front and rear of the cylinder with full force. These must then be able to restrain the horizontally moving piston rod. The solutions from ACE's Magnum family act as the last man standing during this process if the compressor does not switch off automatically in the event of overpressure.

If the construction's safety valve were not opened efficiently, a domino effect could occur: firstly, the pneumatic cylinder and compressor could be destroyed, gas could escape and possibly endanger all other system components. In addition, the possible explosion of the gas-air mixture would pose a great danger to people, other systems in the vicinity and the environment. Considering the immense negative impact of a single incident, it is understandable that DGI and the Saudi Arabian client, Saudi Aramco Lubricating Oil Refining Company (Luberef), played it safe.

Christian Junghans from ACE is highly satisfied with the solution found: "We are delighted to be able to contribute the industrial shock absorbers for the very important actuators in this project. The slogan of our Dutch partner DGI 'Engineering your ambitions' fits perfectly with this project. There were real challenges for the Saudi Arabian customer in terms of actuator speed. Thanks to our many years of experience in shock absorber technology and DGI's proven expertise in valve automation, we were able to develop this solution together and are proud to make an important contribution to the safety of the overall design with shock absorbers as compact as they are powerful, such as those of the Magnum type, which are equipped with sealing technology that has been tried and tested for many years, a hardened guide bearing and an integrated fixed stop. In addition, the front and rear adjustments, clamping flanges and the continuous external thread of the Magnum are also decisive for installation." as

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