In 2024, the imported diaphragm coupling supplied for air compressors from Man Turbine Machinery Co., Ltd. at Zhongmei Ordos Energy & Chemical Co., Ltd. was damaged due to an accident. With an import procurement cycle of 10 weeks, the company plans to localize production in order to resume operations as quickly as possible. This coupling has a total length of 2,261 millimeters, delivers a power output of 11,500 kilowatts, and operates at a speed of 5,369 rpm.
　　In the process of domestic production, our company tackled the challenging task of machining the long, thin-walled intermediate section of the coupling by developing a well-structured plan and actively coordinating with all partner organizations. Through seamless collaboration and highly efficient operations, we ensured perfect alignment across every stage—from design to manufacturing—delivering the coupling successfully in just 15 calendar days. Today, the coupling is running smoothly and reliably.

● In 1999, the ShenGong Branch Factory supplied a compressor G11 (complete with coupling) to the Jinxi Chemical Plant. After being put into operation, the unit consistently experienced severe vibration, making it impossible to smoothly complete production tasks and forcing the plant into frequent maintenance downtime. ShenGong sent technicians multiple times to troubleshoot and even re-balanced the rotor dynamically—but the issue persisted. By 2003, facing mounting frustration, Jinxi Chemical and ShenGong’s Branch Factory convened another joint technical consultation. The root cause was finally identified: the diaphragm coupling had an excessive clearance of up to 0.8 mm between its drive bolts and bolt holes—far exceeding the design specifications. Following the replacement with a Schenck coupling, the equipment has since been running smoothly and reliably.
● In 2002, the coupling used with the fan at Baogang Sintering Plant experienced complete bolt failure less than half an hour after startup.
● In September 2003, the coupling used with the fan at the Shandong Rizhao Sintering Plant fractured all its bolts and shattered the diaphragm within just 6 seconds of startup. At the same time, couplings installed by Sanhuan for the plant’s two other smaller fans also faced issues, including difficulties in installation and excessive runout readings. After switching to Schunk couplings, the system now operates smoothly.
● In April 2004, Shen Gang had two units equipped with triple-ring couplings that broke immediately upon startup.
● A cement plant in Fujian uses six sets of triple-ring couplings in its mill; four sets broke down within half a month of operation.
● In 2011, a manufacturer produced two couplings (intended for trial use by Shaanxi Drum), which broke immediately after being put into operation. Upon inspection, it was discovered that while the drawings specified the material as alloy steel, the actual material used was carbon steel.
● The H403 unit produced by Shenyang Blower Group for Liuzhou Chemical Plant was equipped with a matching diaphragm coupling. However, due to excessive vibration, the unit remained stuck in the factory for nearly two weeks of test runs—preventing it from being shipped out. Under intense pressure from the customer, who urgently needed the equipment, the entire plant rallied together. Led by the Technical Director, a dedicated task force was formed, drawing on experts from across various departments. After thorough consultations and exhausting all other options, the plant ultimately concluded that the issue stemmed from a design flaw—since the manufacturer insisted their couplings were flawless. As a result, the plant decided to re-cast the machine housing, incurring direct costs exceeding one million yuan. Meanwhile, the Design Department found itself under immense pressure from top management. Out of sheer determination to resolve the problem, Shenyang Blower Group reached out to Schenck, requesting them to produce an identical coupling for verification purposes. To everyone’s relief, when the Schenck coupling was installed, the unit passed its first test successfully—reducing vibration amplitude from 36μ to 16μ, fully meeting the original design specifications. Following this breakthrough, Shenyang Blower Group’s Plant Manager immediately issued an order: henceforth, the plant would no longer rely on the original manufacturer’s couplings.
● A blower at Henan Jiyuan Steel Plant, equipped with a diaphragm coupling from a certain supplier, broke immediately after startup.
● In 1996, Shanghai Jinshan Petrochemical selected two couplings from a certain supplier; however, one of them experienced excessive vibration during startup and could not operate.
● In early 2003, the first blower at Hangyang experienced coupling failure—breaking immediately after startup—when using a coupling supplied by a certain manufacturer.
● In October 2006, the Shenyang Aircraft Research Institute entrusted Schenck with the development of two extra-long couplings (5000 kW, 11.7 m in length), while simultaneously delivering two 4-meter-long and two 6-meter-long couplings to another coupling company within the AVIC Systems Group for production. Remarkably, Schenck’s extra-long couplings were successfully put into operation on their first attempt. However, within just two weeks of operation, all four couplings produced by this manufacturer broke down one after another. In response, four senior executives from the user organizations under this manufacturer visited Schenck to extend their congratulations and express heartfelt gratitude. The technical challenges associated with these ultra-long couplings primarily involve controlling static and dynamic deflections in the middle section, managing critical speeds, and precisely regulating rotor dynamics.
● In February 2006, the G63 gasification unit (14,000 rpm), manufactured by Shenyang Blower Works for Sinopec Yueyang Shell Company and utilizing a diaphragm coupling from a certain manufacturer, experienced excessive vibration during commissioning tests. Despite the manufacturer’s attempt to rebuild the unit, the vibration issue persisted. Only after switching to a Schenck coupling did the unit successfully pass the initial test run. Notably, the Schenck coupling weighed just 17.3 kg—4 kg lighter than the one provided by the original manufacturer. All performance metrics met internationally advanced standards, earning high praise from foreign representatives, Ms. Wei from Sinopec, and Vice General Manager Kong of Shenyang Blower Works.
● In 2010, three couplings supplied to a chemical plant in Chongqing—end users of Shenyang Blower Group—experienced complete fracture of their coupling membrane bolts during the initial on-site startup. After remanufacturing, the same issue occurred again. It was only after increasing the bolt dimensions for the third attempt that reliable operation was finally achieved.
● In 2011, a certain coalbed methane generator set experienced the membrane coupling from a particular manufacturer breaking after just 3 minutes of operation. After replacing it with a new unit, that also failed shortly afterward. Switching to a Schunk coupling has ensured smooth operation ever since.
  
Imported Coupling Maintenance and Overhaul:
● Since 1995, Schenck has been importing and localizing coupling components for major corporations.
● In 1995, Shanghai Jinshan Petrochemical Ethylene Plant successfully converted its 7 imported gear couplings into diaphragm couplings during a single test run.
● In 1997, a diaphragm coupling for an Elliott centrifugal hydrogen compressor (manufactured by Kopflex, USA), imported from the United States by Harbin Petrochemical, fractured. Schenck urgently fabricated a replacement diaphragm coupling within four days, and it has been operating safely ever since.
● In 1998, the flexibox coupling imported for the flue gas turbine at Daqing Refining & Chemical (formerly the Additive Plant) experienced a diaphragm failure after just 3.5 months. Schenck then retrofitted the original coupling, enabling safe and continuous operation for three years—with no issues reported during subsequent inspections—and it is still running reliably to this day.
● In 2000, the American coupling diaphragm accompanying the expander (1,100 kW / 40,000 rpm) imported by CNOOC Jinzhou Plant No. 102 ruptured. The plant subsequently switched to a Schenck coupling, reducing the outer diameter from φ120 mm to φ95 mm. As a result, vibration levels dropped from 25 μm to 13 μm, earning high praise from foreign experts. Additionally, another imported coupling at the plant was also entrusted to Schenck for inspection, correction, and improvement.
● From 2000 to 2010, Schunk Company refurbished more than 30 sets of imported diaphragm and membrane disc couplings (from Ameridrive USA, EKK Japan, and BHS Germany) for Shanghai Baosteel, Ansteel, Daye Steel Plant, Changzhi Steel Plant, and Beitai Coal Chemical Industry— all of which are now operating successfully.
● In 2004, Schunk was designated by GE USA as China's partner for the coupling project, jointly participating in several imported coupling retrofit projects subcontracted by GE.
● In 2004, six imported high-speed couplings—both front and rear units at Ningxia Petrochemical—were retrofitted with Sankyo diaphragm couplings (manufactured by Kopflex USA), ensuring safe and reliable operation of each unit.
● In 2007, the nitrogen compressor imported by Beigang Group's Northern Coal Chemical Industry experienced a broken original gear coupling, and even the protective cover was damaged.
● The 2008 raw gas compressor, after being retrofitted with a Schunk diaphragm coupling, has been running smoothly ever since.
● In 2009, the membrane discs and intermediate sections of two imported compressors from the propylene unit at Liaoyang Petrochemical’s Olefins Plant, originally supplied by UK-based Turboflex, were successfully replaced with Schenck components during a single commissioning attempt. This achievement earned high praise from the British engineers (who served as on-site project managers) as well as from Liaoyang Petrochemical’s chief engineer.
● In November 2010, a safety coupling (a Japan-Sweden collaboration) imported as part of the granulator equipment at Tianjin Ethylene (a Sino-Saudi joint venture) fractured, resulting in daily losses exceeding 1 million yuan. Schenck Engineering Company, however, managed to design and rapidly manufacture a replacement safety coupling within just one week, ensuring the system has been running safely ever since.
● In October 2010, a membrane disc coupling (manufactured by Japan's EKK) from the four-in-one nitric acid import unit at Jilin Cornell Petrochemical experienced a fracture. Schenck promptly fabricated a replacement intermediate membrane disc and middle section, ensuring they perfectly matched the original half-coupling—leading to a successful first test run.
● In August 2010, the oxygen compressor imported membrane disc coupling (EKK) at Anshan Houying Steel Plant experienced a grinding disc failure. After consulting Shen Goo and turning to SNEC, the equipment was retrofitted into a SNEC-standard diaphragm coupling, which has been running smoothly ever since.
● In 2010, Shengu complied with the compressor user's request and imported a high-torque diaphragm coupling from Germany’s Flanders. However, during the trial run of compressor H985, vibration levels exceeded the standard. After switching to a Schunk diaphragm coupling, the compressor successfully passed its first test run.
● In 2011, a KOPFLEX coupling imported by Dalian Petrochemical experienced a sudden failure of all the connecting bolts in its intermediate section, leading to deformation of the connecting flange. However, due to urgent production needs and limited time, Schenck repaired the intermediate segment and replaced the bolts, ensuring that operations could resume without delay. Additionally, Schenck manufactured and provided a brand-new, standard Schenck diaphragm coupling as a backup, which was installed immediately after the equipment was shut down. The system passed its first test run successfully.
● In 2011, the imported coupling (Kopflex) for Liaohua's cracked gas compressor was retrofitted with a Sankel flexural disc coupling, and the trial run was successful on the first attempt.
● In 2011, the ShenGong H985 unit was equipped with an imported high-torque diaphragm coupling (from Germany’s Flanders) at the customer’s request. However, during compressor commissioning, vibration levels exceeded the allowable limits. After switching to a Schenck diaphragm coupling, the unit successfully passed its first test run, enabling smooth operation for the customer.
● In 2011, the methanol compressor at Tianjin Alkali Plant experienced a failure of its Japanese EKK diaphragm coupling disc, leading to the successful first trial run after switching to a Schunk diaphragm coupling.
● In 2011, Tianjin Alkali Plant successfully completed the first trial run after replacing three Japanese EKK membrane disc couplings in its syngas compressors with Schunk diaphragm couplings.
● In 2012, the Kopflex spherical axial-limiting diaphragm coupling used by Yingde Gas in the U.S. broke down. Three companies submitted bids, and Schenck won the contract with the highest offer.
● In 2012, Schunk was named by U.S.-based GE as China's partner for the coupling project, jointly participating in several imported coupling retrofit projects subcontracted by GE.
● In 2012, six imported high-speed couplings—both before and after the Ningxia Petrochemical project—were retrofitted with Sank-Schaefer diaphragm couplings (manufactured by Kopflex USA), ensuring safe operation of each unit.
● In 2013, the nitrogen compressor imported by Beigang Group's Northern Coal Chemical Industry experienced a broken original gear coupling, and even the protective cover was damaged.
● The 2008 raw gas compressor, after being retrofitted with a Schunk diaphragm coupling, has been running smoothly ever since.
● In 2013, the membrane discs and intermediate sections of two imported compressors from the propylene unit at Liaoyang Petrochemical’s Olefins Plant, originally supplied by UK-based Turboflex, were successfully replaced with Schenck components during a single commissioning attempt. This achievement earned high praise from the British engineers (who served as on-site project managers) as well as from Liaoyang Petrochemical’s chief engineer.
● In November 2013, a safety coupling (a Japan-Sweden collaboration) imported as part of the granulator equipment at Tianjin Ethylene (a Sino-Saudi joint venture) broke down, resulting in daily losses exceeding 1 million yuan. However, Schenck Engineering managed to design and rapidly manufacture a replacement safety coupling within just one week, ensuring the equipment has been running safely ever since.
● In 2013, the Siemens compressor at the West Gate of Tianjin Alkali Plant experienced failure of its Japanese EKK coupling, prompting a switch to a Schunk diaphragm coupling, which has since been operating smoothly.
● In 2014, Tianjin Alkali Plant replaced all three of its high-speed compressor units with Schenck high-performance couplings, resulting in reduced vibration levels during operation.
● In early July 2014, the turbine compressor unit at Gansu Huating Group’s Pingliang Methanol Plant—equipped with a German BHS coupling (shaft power: 12,300 kW, speed: 10,749 rpm)—suffered damage. The company’s general manager, Mr. Zhang, personally traveled to Shenyang’s Schenck Company seeking assistance. In just six days, Schenck designed and manufactured a replacement coupling, which was then airlifted to Pingliang. The unit was successfully started up on the first attempt, and vibration levels were even lower than those of the original imported coupling. The company’s general manager personally called to express his heartfelt gratitude.
● In late August 2014, a high-speed gear coupling on a turbine compressor at the Nanyang Oilfield failed. After being retrofitted with a Sankel membrane coupling, the equipment has been running smoothly, with performance significantly surpassing that of the original coupling.
● In November 2014, the American Ameridrive diaphragm coupling—originally supplied for XinJinhua Machinery’s centrifugal compressor—failed shortly after being put into operation in Shandong. The system was subsequently switched to a Schunk coupling, which has been running smoothly ever since.
● In October 2014, a membrane disc coupling (made by Japan's EKK) from the four-in-one nitric acid import unit at Jilin Cornell Petrochemical broke. Schenck promptly manufactured a replacement intermediate membrane disc and intermediate section, which perfectly matched the original half-coupling, enabling a successful trial run on the first attempt.
● In March 2015, the high-speed coupling of a centrifugal compressor at Cangzhou Zhengyuan Chemical experienced severe damage. Schenck Company produced a replacement coupling in just 5 days, and after installation, it operated smoothly.
● In March 2015, the two butanol blowers (from Germany's KKK) at Tianjin Alkali Plant were successfully retrofitted with Schunk couplings, and they have been operating smoothly ever since.
● In April 2015, a compressor unit at Shanxi Coking Group experienced severe vibration exceeding the allowable limits in its high-speed section, rendering it unable to operate normally. After Shen Goo’s specialists disassembled the unit and conducted multiple rounds of inspection and testing, the vibration levels remained stubbornly high. However, upon replacing the German-imported BHS diaphragm coupling on the unit with a fully balanced coupling manufactured by Shenyang Schenck, the machine successfully passed its first test run—with vibration levels dropping significantly below the international API standard (25.4 microns). Following the successful commissioning of the unit, the vibration readings further improved, falling well below 20 microns. The General Manager of the Coking Group promptly called to express gratitude, praising the exceptional performance of our company’s high-performance couplings. He also announced that their organization would gradually replace all existing couplings in their large-scale equipment with Schenck’s advanced, high-quality alternatives.
● In July 2015, another compressor unit at Shanxi Coking Group experienced excessive vibration levels. After expert diagnosis, it was determined that the issue was caused by a coupling originally imported from Germany. Following the replacement with a Schunk diaphragm coupling, the unit successfully started up on the first attempt, with vibration levels dropping below 16 microns.
● In August 2015, the oxygen compressor imported membrane disc coupling (EKK) at Anshan Houying Steel Plant experienced a grinding disc failure. After consulting Shen Goo and identifying Schaeffler as the solution, the plant retrofitted the equipment with a Schaeffler-standard diaphragm coupling, which has been running smoothly ever since.
● In 2015, a KOPFLEX coupling imported by Dalian Petrochemical experienced a sudden failure of all the connecting bolts in its intermediate section, leading to deformation of the connecting flange. However, due to urgent production demands and limited time available, Schenck promptly repaired the intermediate segment and replaced the bolts, ensuring that operations could resume without delay. Additionally, Schenck manufactured and delivered a brand-new, Schenck-standard diaphragm coupling as a backup, which was installed immediately after the equipment was shut down. The system passed its first test run successfully.
● In October 2015 and May 2016, Shanxi Coking Group separately placed orders with Schenck for two high-performance couplings intended for the maintenance of their high-speed compressor units. Schenck diaphragm couplings have now become the coking group’s preferred alternative to imported couplings.
● Over a hundred such instances have been recorded, and each one is running smoothly!
● In 2016, the imported coupling (Kopflex) for Liaohua's cracked gas compressor was successfully converted to a Sankai diaphragm coupling during the first test run.
● In 2017, Tianjin Alkali Plant imported an EKK diaphragm coupling from Japan for its methanol compressor; however, the diaphragm disk broke. Schenck then provided a matching set of diaphragm-type intermediate sections, and the equipment successfully passed its first test run.
● In 2018, Tianjin Alkali Plant replaced three imported Japanese EKK diaphragm couplings on its syngas compressors with Schunk diaphragm couplings. (Not yet put into operation.)
● In 2018, an imported coupling at Huadian Qinbei Power Plant was successfully retrofitted with a SANKEN diaphragm coupling, enabling safe and continuous operation for three years—with no issues reported during routine inspections—and the unit is still running today. Building on this success, the remaining three units’ imported couplings were gradually upgraded in 2019 and 2020, bringing Huadian Qinbei’s technological renovation project to a seamless conclusion.
● In 2019, a set of imported membrane disc couplings from Shaanxi Aowei was repaired—specifically, a middle-section component—by Schenck. After reassembling the repaired part with the original product and conducting dynamic balancing, the unit successfully passed its initial test run, ensuring it met production requirements.
● In 2019, Yingde Gas imported Kopflex diaphragm couplings featuring a spherical axial-limiting design. Three domestic manufacturers competed in the bidding process, with Schenck emerging as the winner at the highest price.
● Over a hundred such instances have been recorded, and each one is running smoothly.
● In 2019, the company designed and manufactured a high-power diaphragm coupling rated at 37,000 kW for Yanshan Steel, replacing the imported German Flender coupling.
● In 2021, Fujian United Petrochemical replaced its imported couplings with GIICL13 drum-type gear couplings—2 units in total.
● In 2021, Yichang Xingxing Lantian Chemical implemented a project to upgrade and modernize its coal gasification energy-saving technology, involving three key components: the motor side – gearbox, gearbox – 2MCL606, and 2MCL606 – 3MCL607.
● In 2023, Sino-Saudi Petrochemical successfully localized the import of one reducer for a mixer.
● In 2023, Liaoning Steam Turbine Huludao Co., Ltd. localized the production of imported diaphragm couplings (from Ameridrives, USA).
● In 2024, Fujian United Petrochemical successfully localized the import of diaphragm couplings from Germany's John Crane and Ameridrive diaphragm couplings from the U.S.
● Over a hundred such instances have been recorded, and each one is running smoothly.
● Schunk can conduct on-site measurements, develop a tailored solution, and ensure that the new coupling excels the original in terms of quality distribution, torsional stiffness, critical speed, and other rotor dynamics characteristics.