1. A molecule with potential and risks in conveyor technology

Challenges typically arise from the high vapour pressure, which is present even at moderate ambient temperatures, the low boiling point, and the tendency to cavitate when local pressure drops. Due to these physical properties, high requirements for tightness, material resistance and controllability of the pump technology used must be met. Therefore, pumping units must be both process-stable and explosion-proof (ATEX-compliant) to ensure safe operation, even under dynamic load changes or in Ex zones.

2. Challenges when pumping ammonia

a) Medium-specific properties

Careful technical design is required for the pumping of ammonia, taking into account both the hydraulics and the materials. Key properties include:

1. Toxicity and chemical reactivity: even the smallest leak can endanger people and the environment. Reacting with moisture leads to the formation of ammonium hydroxide, which is a highly corrosive compound that damages materials and seals.
2. Thermal instability: with a boiling point of -33 °C and a vapour pressure of around 8.6 bar at 20 °C, ammonia can evaporate abruptly with even a slight drop in pressure. This leads to volumetric expansion and increased stress on the system.
3. Cavitation tendency: liquid ammonia is sensitive to pressure fluctuations in the inlet area of the pump. If the local pressure drops below the vapour pressure, vapour bubbles form. These can cause damage to valves and plungers when they implode.

Properties of ammonia in detail

1. Molecular formula: NH3
2. Boiling point (1 bar): -33.3 °C
3. Vapour pressure (20 °C): approx. 8.6 bar
4. Critical temperature: 132.4 °C
5. Explosion limits (LFL/UFL): 15 to 28 vol.
6. Auto-ignition temperature: approx. 651 °C
7. Water solubility (20 °C): 529 g/l (highly exothermic)
8. Corrosivity: strongly corrosive to Cu, Zn, Al
9. ATEX relevance: Zone 2, IIA, T1 to T2

These physical effects necessitate precise design of the suction conditions. This includes maintaining low flow velocities, ensuring short pipe runs and sufficient net positive suction head (NPSHa) is available, and using pumps with a particularly low net positive suction head required (NPSHr). Only then can the safe, long-term, low-wear operation of high-pressure systems be ensured.

b) Choice of materials

The chemical reactivity of ammonia, particularly when it is present in water, places high demands on all components of a conveyor system that come into contact with the medium. In humid environments, ammonium hydroxide (NH4OH) is formed, creating a strongly alkaline solution that attacks various materials, including copper, brass, zinc, and unprotected aluminium alloys. Due to these corrosive mechanisms, many conventional materials are ruled out from the outset.

Additionally, austenitic steels are susceptible to intergranular stress corrosion cracking (SCC), particularly at fluctuating temperatures and in the presence of chloride-containing substances. Therefore, long-term and safe operation can only be achieved with highly resistant materials.

High-strength materials, such as super duplex or nickel-based alloys, are preferred as they provide excellent protection against cracking and embrittlement, even when subjected to fluctuating pressure and temperature conditions. A one-piece forged construction without flange connections reduces potential leak points even further.

Overview of suitable materials

1. 1.4404 / AISI 316L: conditionally resistant, susceptible to stress corrosion cracking. Only suitable for use in exceptional cases.
2. 1.4462 (duplex): very good resistance to NH4OH and chlorides. Standard in chemical applications.
3. 1.4410 (super duplex): high strength, excellent pitting and SCC resistance. Recommended for high loads.
4. Inconel 625 / 2.4856: virtually inert to ammonia, temperature stable. First choice for extreme conditions.

c) Sealing technology

When transporting ammonia, selecting and designing the right sealing technology is key to ensuring operational safety. Due to the medium's high volatility, vapour pressure and toxicity, the highest standards of tightness must be met for environmental and health protection reasons, as well as to maintain process integrity.

Conventional sealing solutions, such as stuffing boxes or simple ring seals, quickly reach their limits in this context. Instead, what is required are high-density, leak-free systems that can be relied upon to operate over the long term, even under changing operating conditions.

One well-established solution is the use of cartridge sealing systems. These are compact, pre-assembled sealing units that are integrated into the pump head in a modular fashion. These systems offer the following technical advantages:

1. Use of chemically resistant sealing materials such as PTFE, FFKM or specially formulated elastomers, which exhibit high long-term resistance to ammonia and ammoniacal solutions.
2. No external lubrication is required, which reduces the risk of additional sources of leakage and potential ignition sources in potentially explosive atmospheres.
3. Self-adjusting sealing elements that mechanically readjust to maintain a constant sealing effect, even when there are changes in pressure or temperature.
4. Dry-running capability for short-term operation without medium, for example during start-stop pumping processes or commissioning.
5. Ease of maintenance: the cartridge seal can be replaced quickly without having to remove the entire pump head or dismantle the high-pressure pump.

In addition, high-quality cartridge sealing systems are designed to ensure a stable seal even under fluctuating pressure conditions and during pulsating operation. This is particularly relevant for plunger pumps, where the flow is inherently pulsating due to their design. In safety-critical applications, such as in potentially explosive atmospheres, an ATEX-compliant design (for example equipment category 2G or 3G) is also required, and the choice of materials has to match the duty.

d) Explosion protection and ATEX

Explosion protection is a key aspect of safety-related plant design when conveying ammonia. Ammonia forms an ignitable gas mixture with air at a volume fraction of approximately 15 to 28 percent. Its ignition temperature is around 651 °C, justifying its classification in explosion group IIA and temperature class T1. Therefore, ammonia must be classified as a potentially explosive medium, particularly in systems with open ventilation routes or potential sources of leakage.

In accordance with European Directive 2014/34/EU (ATEX), equipment and protective systems intended for use in potentially explosive atmospheres must be classified and designed accordingly. For pump technology, this results in a multi-stage safety concept:

1. Zone classification according to EN 60079-10-1: classification is based on the probability of release, ventilation, and system design. Ammonia applications often involve Zone 2, and in areas with potential leakage sources, Zone 1 as well.
2. Equipment categories: category 3G for equipment in Zone 2, category 2G for equipment in Zone 1.
3. Temperature classes: ammonia is assigned to temperature class T1. Accordingly, the maximum permissible surface temperatures of the components used must not exceed 450 °C.
4. Ignition protection types: electrical components must be designed with appropriate protection types depending on the zone, for example Ex-e (increased safety), Ex-d (flameproof enclosure), or Ex-i (intrinsic safety).
5. Mechanical explosion protection: non-electrical components such as pumps are also subject to the requirements of EN ISO 80079-36 and 80079-37. In particular, an ignition source analysis must be performed to avoid potential risks such as hot surfaces, friction, or mechanically generated sparks.

In practice, this means that motors, sensors, control valves, frequency converters and cabling must all be supplied and documented as explosion-proof. Additional requirements must also be observed, such as those relating to earthing and equipotential bonding, the avoidance of electrostatic charging, and the use of conductive materials for housing parts and connections.

The mechanical components of a high-pressure pump, such as seals, plungers and piping, must also undergo ATEX assessment if they are to be operated in hazardous areas. In these cases, an analysis of ignition sources in accordance with EN ISO 80079-36 is required. Therefore, a comprehensive explosion protection concept that integrates all relevant components and is documented in accordance with standards is an integral part of an ammonia-carrying conveyor system.

e) Regulation and process control

Precise control of pressure and volume flow is crucial when conveying ammonia, both to avoid pressure surges and to safely control process dynamics. This is important in batch processes, during load changes and in start-stop operation. Due to ammonia's physical properties, particularly its tendency to evaporate when pressure drops, a smooth conveying process without abrupt changes in pressure or volume is required.

One proven solution is to use frequency converters to control the pump's speed. This enables the volume flow and outlet pressure to be regulated according to load and demand, eliminating the need for additional bypass systems or throttling devices.

Technical advantages of frequency converter control

1. Pressure surge-free delivery: starting the system up in a controlled manner by gently ramping up the speed is a significant advantage for media with high vapour pressure, such as ammonia.
2. Load-adapted operation: the delivery rate can be adjusted in real time to match variable process requirements, for example between 10 percent and 100 percent of the rated speed depending on the pump type.
3. Reduced energy consumption: operating the pump in the optimum efficiency range enables a significant reduction in power consumption in partial load operation.
4. Protection of mechanical components: reduced acceleration and braking forces decrease the load on mechanical drive elements, thereby extending the service life of bearings, seals, and valves.
5. Interface integration: modern converters offer communication interfaces such as Profinet, Modbus and CANopen, which enable integration into higher-level process control systems with remote monitoring, condition diagnostics and predictive maintenance.

In potentially explosive areas, particular care must be taken to ensure that the frequency converter is either installed outside the Ex zone or operated within a certified protective enclosure. Suitable motor protection concepts must be implemented to ensure safe operation in all operating states, such as temperature sensors, speed monitoring and standstill detection. Frequency converter control enables high levels of process reliability, flexibility, and energy-efficient, low-wear operation, making it essential for conveying demanding media such as ammonia. To achieve almost completely pulsation-free pumping, resonators are used on the suction and pressure side as required.

3. Conclusion and outlook

The pumping of ammonia places special demands on pump technology, material selection, seal design and plant safety. Due to its high vapour pressure, toxic effects, thermodynamic instability and explosion hazard, ammonia is one of the most challenging substances in chemical and energy technology processes. The following aspects are therefore crucial for the safe and reliable operation of ammonia conveying systems:

1. Selection of corrosion-resistant materials such as super duplex or nickel-based alloys.
2. Use of leak-free sealing systems made from chemically resistant materials.
3. Explosion-protection compliant plant technology in accordance with the ATEX directive, including mechanical ignition source assessment.
4. Process-stable control concepts with variable-speed drives to avoid dynamic load peaks.

Safe, efficient and low-maintenance operation in an industrial environment can only be achieved by combining these measures. This is particularly important for continuous high-pressure applications or safety-critical areas, such as marine engineering, offshore supply and power-to-X systems.

Ammonia as a key medium in the energy transition

As green ammonia is increasingly established as a CO2-free energy source, its applications outside the traditional chemical industry are becoming significantly more important. The following developments are particularly noteworthy:

1. Maritime propulsion systems: ammonia as an emission-free marine fuel within the framework of IMO regulations.
2. Power-to-ammonia plants: storage and reconversion of renewable energy in the form of chemically bound energy.
3. Fuel cell development: use of ammonia as a hydrogen carrier and direct medium in novel SOFC systems.
4. Decentralised energy storage solutions in regions with high renewable energy production.

In demanding applications, plunger pumps play a central role: they enable the high-pressure transfer of ammonia and the precise, volumetrically controlled injection into downstream processes, such as combustion systems. Due to their design-based, pulsating delivery principle, flow rates can be precisely metered and flexibly adjusted via speed-controlled drives. Combined with media-resistant materials and a modular system design, plunger pumps are particularly well-suited for dynamic, safety-critical, and high-performance processes.

Tailor-made plunger pump technology for ammonia applications

Thanks to its flexible, modular system and in-depth knowledge of materials, KAMAT can provide robust solutions for the continuous conveyance and injection of ammonia:

1. Pump heads made of duplex, super duplex, Inconel or other special materials
2. Cartridge sealing systems for absolute tightness under changing pressure and temperature profiles
3. ATEX-certified designs for potentially explosive atmospheres
4. Frequency-controlled drives for smooth start-up and precise pressure control
5. Pulsation damping through resonators
6. Engineering and manufacturing in Germany: modular, traceable and customisable

Whether for green ammonia production, maritime injection technology or power-to-X chains, KAMAT positive displacement pumps enable sustainable, reliable processes under pressure, offering flexibility, precision and future-proofing.

Practical example: transporting ammonia safely in industrial refrigeration technology

There were repeated problems with the conveyance of liquid ammonia in an industrial refrigeration system for food and storage management. Uncontrolled flash formation, leakage risks, and thermally stressed sealing systems resulted in higher maintenance costs and uncertainty regarding continuous operation.

The challenge

1. Pumping a highly toxic, subcooled medium with a high vapour pressure
2. Minimising all emissions and leaks
3. Ensuring safe operation in the event of thermal fluctuations during continuous 24/7 operation
4. Ensuring compliance with ATEX requirements, the Pressure Equipment Directive and customer-specific standards

The solution

KAMAT developed a plunger pump system specifically designed for the conveyance of ammonia:

1. Integrated suction channel for optimised flow and reduced cavitation-related pressure fluctuations
2. Special sealing system for toxic media with optional leakage monitoring and a barrier chamber
3. Oil-air cooling to stabilise bearing temperature and protect seal-sensitive components
4. Safety monitoring with pressure and temperature sensors, relief valves and ammonia gas detection
5. Service-friendly design with clearly defined maintenance points and modular replacement systems

Key technical data

1. Flow rate: 340 l/min
2. Suction pressure: 76 bar
3. Differential pressure: 101 bar
4. Medium: subcooled liquid ammonia in accordance with DIN 8949

Result

Since commissioning, the system has operated stably without any unscheduled downtime. It meets all safety requirements, and the predictable maintenance strategy, which includes early leak detection and regulated temperature management, has led to a measurable reduction in service calls. The project shows how a media-compatible pump design, well-considered suction geometry, intelligent sealing technology and a monitoring system ensure operational safety, availability and process stability with a demanding medium such as ammonia, without compromising environmental protection or personal safety.

Standards, guidelines and technical regulations

1. ATEX Directive 2014/34/EU on equipment and protective systems intended for use in potentially explosive atmospheres
2. DIN EN ISO 80079-36:2016-12, non-electrical equipment for use in potentially explosive atmospheres, fundamentals and requirements
3. DIN EN 1127-1:2019-07, explosive atmospheres, fundamentals and methodology
4. API Standard 674, positive displacement pumps, reciprocating, 4th edition, American Petroleum Institute, Washington D.C., 2020
5. DIN EN ISO 13709:2009-07 (API 610), process pumps for petroleum, petrochemical and gas industries
6. IEC 60079-10-1, explosive atmospheres, classification of areas
7. VDMA Standard Sheet 24284, pumps, terms, parameters and definitions
8. TRGS 507, technical rules for hazardous substances, activities involving ammonia, BAuA, 2022

KAMAT GmbH & Co. KG, Witten, Germany, www.kamat.de. The article was published in Process Technology & Components 2026. KAMAT exhibits at the Hydrogen and Carbon Capture Technology World Expo in Hamburg, hall B4, stand 4C20.