A field-driven approach to leaks

Field experience shows that nearly 30% of failures in chemical leak sealing interventions come from the incorrect selection of sealing compounds. In fertilizer manufacturing, where installations handle aggressive fluids like sulfuric acid, nitric acid, ammonia, and phosphate derivatives, selecting the wrong compound can lead to premature seal failure, reinjections (which are not a norm), safety risks, and costly downtime.

Unlike low-demand applications sealing, leak repair in chemically aggressive environments requires materials that are both chemically compatible and mechanically resilient. The diversity of chemical media, combined with variable operating temperatures, pressures, and leak geometries, makes compound selection a complex critical task.

This article presents a structured, field-based approach to selecting sealing compounds for online leak sealing in fertilizer plants. It is supported by performance data, chemical compatibility guidelines, and real-world application feedback from Petroseal.

Chemical environments in fertilizer plants

Fertilizer production processes involve a variety of corrosive fluids. Understanding their specific properties is crucial for effective leak management. For instance:

Sulfuric acid (98%)

Sulfuric acid is highly corrosive and dense, requiring compounds with excellent chemical resistance and mechanical integrity, especially at elevated temperatures. The presence of even trace amounts of water can generate heat and accelerate corrosion, which limits the choice of injection compounds to those proven in oxidising acid service.

Nitric acid (60 - 70%)

Nitric acid is not only corrosive but also a strong oxidiser. Compounds injected into systems carrying this media must exclude any reactive fillers or fibres, and their decomposition temperatures must exceed operational margins to prevent any thermal runaway.

Ammonia (NH3)

Ammonia presents entirely different risks: its volatility and low boiling point (-33°C) demand compounds that remain flexible and stable under both cryogenic and high-temperature transitions. The sealing system must also resist pressure fluctuations and prevent gas release, which could pose toxic or explosive hazards.

Phosphoric acid

Phosphoric acid and phosphate-based fluids tend to be viscous and may contain solids or crystals. This influences flow behaviour during injection and requires sealing compounds with carefully calibrated rheology to ensure distribution inside clamps or flanges without plugging injection ports.

Ultimately, no universal compound can address all fluid types or process conditions. The correct approach involves a detailed review of process parameters and leak geometry, paired with the selection of a chemically compatible and mechanically adapted compound, validated by a compound manufacturer with field experience.

Mechanisms of failure and associated risks

Selecting an incompatible sealing compound can lead to several issues.

One of the most common failure modes is material degradation due to chemical incompatibility. Certain compounds, particularly those based on organic fillers or synthetic elastomers, may undergo softening, swelling, or even complete dissolution when exposed to strong acids, solvents, or oxidising agents. This can rapidly compromise the integrity of the sealing, leading to renewed leakage or even uncontrolled release of hazardous media.

Another critical risk is the occurrence of exothermic reactions. Some sealants, especially those containing reactive fillers or metal oxides, can react with certain media (e.g., nitric acid or chlorinated solvents) and generate heat. This not only accelerates compound degradation but can also lead to local pressure spikes, rupture of the injection system, or violent ejection of the compound from the clamp interface (posing a serious hazard to personnel).

Failures can also result from injection mismatch, either due to poor viscosity selection or inappropriate granulometry. A compound that is too fluid may not remain in place in the presence of high leak velocities or large voids. On the other hand, a compound that is too dense or fibre-rich may block injection ports, especially in tight injection rings or small-diameter fittings. This is particularly problematic in emergency situations where time is limited.

Finally, thermal cycling fatigue is a common failure mode in fertilizer plants, where piping is subject to frequent temperature changes (either due to start-up/shutdown sequences or process variation). If the compound lacks thermal elasticity or exhibits shrinkage over time, microcracks can form at the interface between the compound and the metal surface, leading to progressive loss of sealing efficiency. Over time, this may necessitate frequent reinjections or complete replacement of the clamp or enclosure.

These risks underline the importance of selecting compounds not just based on nominal pressure or temperature ratings, but on a thorough understanding of media reactivity, fluid dynamics, and application geometry – all supported by Petroseal field-proven formulations and operational feedback.

Selecting the appropriate sealing compound

To minimise sealing failures and ensure long-term performance, the selection of a sealing compound must be based on five interrelated criteria.

First and foremost is the chemical nature of the fluid. Acidic, alkaline, oxidising, or solvent-based media can all interact differently with compound ingredients. Misjudging this aspect can lead to rapid degradation or dangerous reactions. Second, the operating temperature and pressure must be taken into account, not just in nominal terms but also considering potential process fluctuations. The third criterion is the geometry and severity of the leak. A fine crack with a low-pressure leak requires a very different sealing behaviour than a large jet leak through a corroded gasket. Fourth, the mechanical configuration of the clamp or enclosure must be considered, including tolerances, fit, and surface condition, all of which affect the required compound viscosity and structural integrity. Finally, the injection behaviour and expected volume play a decisive role: high-flow leaks may demand compounds with reinforced structure or higher granulometry to resist ejection, while delicate injection rings require smoother, low-viscosity compounds.

Neglecting any one of these parameters can compromise the success of the intervention. Conversely, an integrated assessment of all five ensures a safer, more efficient sealing process tailored to the specific challenges of fertilizer industry environments.

Read the article online at: https://www.worldfertilizer.com/special-reports/14072025/a-field-driven-approach-to-leaks/