Seals for fertiliser production

Compatible fertilisers are needed to compensate for crop losses and tackle the problem of feeding the world.

Every day, the world's population increases by 200,000 people and the same number move to urban areas. The UN predicts that our planet will be home to around ten billion people by 2050. According to the FAO, agriculture will have to increase food production by 50% by 2050 compared to 2012 in order to feed this growing population. In addition, climate change is leading to an increased incidence of pest infestations that threaten crop yields. There is an urgent need for compatible fertilisers to compensate for crop losses and address the global food problem. A global manufacturer of seals is supporting a fertiliser producer in Qatar by providing specialised sealing technologies, contributing to safe and efficient production.

The fertiliser producer faced a fundamental problem: The seals in the carbamate feed pumps regularly failed after a very short operating time of just two weeks to three months. "The mechanical seals originally used were unsuitable for this application," explains Gabriela Lopez Martinez, Application Engineer in the Oil and Gas division at EagleBurgmann. The seals quickly exhibited high leakage rates and failed prematurely. "A critical factor was the use of high-purity water as a barrier fluid, which led to electrical corrosion on the seal surfaces due to its low electrical conductivity. Other significant problems were the flaking of the silicon carbide and the softening of the carbon used," she adds. Since the pumps were still under warranty and the original seal supplier was unable to fix the problem after several attempts, the pump manufacturer turned to EagleBurgmann to find a permanent solution to the repeated seal failures, Lopez explains.

Alternative to the faulty seals

The pump manufacturer turned to EagleBurgmann because of a long-standing business relationship. "It was a challenging application. We had to develop a solution that had both a low leakage rate and avoided chemical damage caused by oxidation, which could be caused by the oxygen content of the water and the temperature in the sealing gap," emphasises Lopez. "We decided in favour of EagleBurgmann's SHI mechanical seals." This type of seal is particularly suitable for extremely high pressures, sliding speeds and temperatures due to its design features, such as the loosely inserted seal face. The choice of materials for the seal faces was particularly challenging. "Initially, we opted for DiamondFace® technology for both the seal face and the stationary counter ring. This method is widely used and proven in the oil and gas industry," explains Lopez. However, the repeated seal failures and leaks could not be successfully remedied with this combination of hard sliding materials.

The right solution thanks to knowledge transfer from different industries

A strong plus point at EagleBurgmann is the interdisciplinary cooperation between the departments. The company's "Technical Sales Support" division brings together specialists from different industries and markets under one management. "We hold regular team meetings to ensure the exchange of knowledge between contacts from different industries," says Lopez. Challenging application possibilities are discussed in these meetings. "After the original hard/hard combination was unsuccessful, I presented the problem to my colleagues during our 'team table'," explains Lopez. A solution was then proposed by the power plant department.

"The use of high-purity water as a barrier fluid is common in the power plant industry, but not in the oil and gas industry," explains Maximilian Huber from the power plant department. "Due to the very low electrical conductivity of this water, the electrical charge generated by friction on the sliding surfaces cannot be dissipated by the insulating water. This leads to corrosion on the sliding surfaces."

The power plant department had learnt from various applications that the problem could be effectively solved with a combination of DiamondFace® and Buka 30 (carbon-silicon impregnated materials) as sliding materials. "This method has proven itself in mechanical seals that have to operate in high-speed applications with high-purity water. It increases the reliability and availability of the seals and reduces operating costs," explains Huber. This solution results in a lower leakage rate than combinations of hard materials. EagleBurgmann has been using this technology in power plant applications for over ten years.

EagleBurgmann SHI mechanical seals are specially designed for very high pressures, high sliding speeds and high temperatures thanks to a loosely inserted seal face and other design features.

A tried and tested solution

A key advantage of this solution was its proven effectiveness through rigorous testing at EagleBurgmann. "Extensive laboratory testing and field applications have proven that the DiamondFace® coating is electrically insulating and therefore resistant to electrical corrosion," Lopez clarifies. EagleBurgmann was able to identify the causes of the failures and developed a solution that could withstand the demanding conditions, including high sliding speeds (>31 m/s) and the processing of a carbamate-containing liquid that tends to form crystals. The SHI mechanical seal is safeguarded by two processes: Plan 54, which was already implemented in the original seal, and Plan 32, which provides for external flushing; both use deionised water. Plan 32 is used to prevent the accumulation and crystallisation of the medium in dead spaces, which can lead to blockages and therefore premature seal failure. "Plan 54 ensures that the process fluid does not enter the environment and thus prevents environmental damage," explains Huber.

This solution has a positive effect on operating costs (OPEX) due to the longer service life of the seals. The service life of the seals was extended to over five years without the need for replacement."No adjustments were necessary during the six-month test phase. The seals have now been in operation for five years without any failures. In addition, the lower leakage rate leads to a cleaner production process," confirms Lopez.

"This project is an excellent example of our 'Innovating together' approach," explains Huber. This involves joint development with customers or within the company. This approach enables several people to participate in the discussion and solution finding process. The consistency in leadership and regular meetings about complex applications contribute significantly to expanding our knowledge and expertise," emphasises Lopez. EagleBurgmann's global presence also played a key role in the success of the project. EagleBurgmann Japan relied on a strong partnership with the local pump manufacturer and handled all customer communication, while EagleBurgmann Germany developed the solution and carried out the necessary tests.