News Details

1、 Core requirements of API 7K standard and technical characteristics of cement hoses

The API 7K standard is developed by the American Petroleum Institute (API) and is a technical specification for flexible hoses used in drilling equipment to transport drilling fluids, cement slurries, and other media. This standard imposes strict requirements on hoses used for transporting water-based mud under high pressure: the inner rubber layer must withstand corrosion from water-based mud with a pH value of 4-12, and the volume expansion rate should not exceed 8% after continuous operation at 120 ℃ for 200 hours; The reinforcement layer needs to withstand a working pressure of at least 5000 psi (approximately 34.5 MPa), and the burst pressure needs to reach more than three times the working pressure. For example, the API 7K 3-inch hose used in a certain oil field has a working pressure of 5000psi and a burst pressure of ≥ 15000psi.

 

The structural design of cement hoses directly affects their performance. A typical structure includes an inner adhesive layer, a reinforcement layer, and an outer adhesive layer. The inner rubber layer is made of chloroprene rubber or hydrogenated nitrile rubber, which has the characteristics of wear resistance, oil resistance, acid and alkali resistance. The Shore hardness is controlled at 65 ± 5 degrees, ensuring that the inner wall wear rate is ≤ 0.05mm/1000 hours when transporting water-based mud with a sand content of 10%. The reinforcement layer is usually composed of multiple layers of steel wire winding or weaving. For example, a hose produced by a certain manufacturer uses four layers of high-strength steel wire cross winding, with a steel wire tensile strength of ≥ 2200MPa. The layers are fixed by special adhesives to prevent slippage between the layers under high pressure. The outer rubber layer is made of chlorosulfonated polyethylene rubber, which has weather resistance and ozone resistance. It can maintain flexibility at low temperatures of -30 ℃ and has a UV aging resistance time of ≥ 500 hours.

 

The API 7K standard also stipulates that hoses must pass multiple performance tests. The static pressure test requires holding at 1.5 times the working pressure for 5 minutes without leakage; The pulse test is cycled 250000 times at 1.25 times the working pressure to simulate pressure fluctuations in actual operating conditions; The bending test requires 1000 cycles at a bending radius of 10 times the outer diameter to ensure the reliability of the hose in complex pipeline layouts. According to data from a third-party testing agency, hoses certified with API 7K have an average service life 3-5 times longer than non-standard products.

 

2、 Global major manufacturers' technological strength and market layout

（1） Gates Corporation, USA

As a global fluid power solution, Gates has over 50 years of experience in the API 7K hose field. The MegaTuff inner layer used in its MegaSys series cement hoses has a 40% increase in wear resistance compared to traditional materials. When transporting water-based mud containing quartz sand, the service life can reach 3000 hours. The reinforcement layer adopts four layers of high-density steel wire winding, combined with Gates' PowerBond bonding technology, which increases the interlayer bonding strength by 25%. This series of hoses has passed API 7K certification and obtained type approval from DNV and LR, and is widely used in ultra deep well drilling projects in the Middle East, North America, and other regions.

 

（2） ContiTech GmbH, Germany

ContiTech relies on the technological accumulation of Continental Group, and its DrillFlex series cement hoses are known for their lightweight design. By optimizing the weaving angle and number of layers of steel wire, the weight is reduced by 15% compared to similar products while maintaining a working pressure of 5000psi. The inner rubber layer adopts a rubber formula filled with nano-sized silicon carbide, which improves the uniformity of hardness to ± 3 degrees and effectively reduces the flow resistance of mud. This series of hoses has passed dual certification of API 7K and ISO 14693, and performs well in extreme environments such as North Sea oil fields and the Gulf of Mexico. Customers include international oil service giants such as Schlumberger and Halliburton.

 

（3） Manuli Company, Italy

Manuli's Flexor series cement hoses are known for their flexibility, with a small bending radius of only 8 times the outer diameter, making them suitable for drilling platforms with limited space. The reinforcement layer adopts a "spiral+cross" mixed winding process, which reduces the stiffness of the hose while maintaining the high-pressure bearing capacity. Adding graphene material to the outer layer increases wear resistance by 50%, making it suitable for high wear environments such as deserts and oceans. This series of hoses has passed API 7K and ATEX explosion-proof certifications and is widely used in projects of Eni Group in Italy and Petrobras in Brazil.

 

3、 Production Quality Control and Industry Development Trends

（1） Whole process quality control system

Leading manufacturers generally establish a full traceability system from raw materials to finished products. For example, Gates company uses SAP system to manage batch information of raw materials such as steel wire and rubber, and the chemical composition and tensile strength data of each roll of steel wire are entered into the database. During the production process, the density of steel wire winding is detected by X-ray inspection to ensure the uniformity of the reinforcement layer; Real time monitoring of the thickness of the inner adhesive layer using a laser thickness gauge, with a deviation controlled within ± 0.1mm. Before leaving the factory, the finished product needs to pass 12 tests including water pressure blasting test and low-temperature bending test, with a pass rate of 99.9%.

 

（2） Upgrading of intelligent production technology

With the advancement of Industry 4.0, hose production is moving towards automation and digitization. Hengyu Rubber has introduced German KUKA robots to achieve precise control of processes such as wire winding and rubber extrusion, resulting in a 40% increase in production efficiency. ContiTech uses an AI visual inspection system to capture surface defects on hoses through high-definition cameras, with an accuracy rate of 98%. In addition, 3D printing technology has been applied to the prototype development of hose joints, shortening the research and development cycle by 50%.

 

（3） Environmental Protection and Innovation in High Performance Materials

In response to environmental regulations, the application of bio based rubber materials has become a trend. The polylactic acid based inner rubber layer developed by Manuli company has improved biodegradability by 30% while maintaining oil resistance, making it suitable for environmentally sensitive offshore drilling. In terms of reinforcement layer, carbon fiber composite materials have begun to replace some steel wires. Data from a certain laboratory shows that carbon fiber reinforced hoses have reduced their weight by 40% and improved their fatigue resistance by 2 times, but the cost still needs to be further reduced.

 

（4） Ultra high pressure and extreme working conditions demand

With the increase of deep and ultra deep well drilling, the working pressure of the hose is developing towards 10000psi (about 69MPa) or above. Gates Corporation has launched the 10K series hose with API 7K certification, featuring a six layer wire winding structure and a burst pressure of up to 45000psi. At the same time, the research and development of special hoses that can withstand extreme cold temperatures of -50 ℃ and high temperatures of 200 ℃ has accelerated. For example, the polar hose developed by a Russian manufacturer has worked continuously for 500 hours without any faults in the Arctic Circle test.

 

（5） Service oriented transformation and full lifecycle management

Leading enterprises are transforming from mere product suppliers to solution service providers. ContiTech launches the "Hose Health Management System", which embeds RFID chips in hoses to monitor parameters such as pressure, temperature, and bending times in real time and predict remaining lifespan. Gates provides a "trade in" service, where recycled old hoses are remanufactured to achieve 80% performance of new products and reduce costs by 30%, in line with the concept of circular economy.

 

In the future, with the adjustment of global energy structure and the upgrading of drilling technology, the API 7K cement hose industry will present a development trend of high pressure, lightweight, intelligence, and environmental protection. Manufacturers need to continue to increase research and development investment, optimize production processes to adapt to extreme working conditions such as shale gas and deep-sea oil and gas, and occupy the technological high ground in global competition.