Air Vessels for Fire Pump Systems

Applications

Air vessels serve fire pump systems with jockey pumps maintaining line pressure in charged wet riser and sprinkler networks. Every system where the jockey pump cycles more than a few times per hour benefits from properly sized air vessel installation.

Common applications include commercial building hydrant systems in Bhuj and Ahmedabad, warehouse sprinkler networks in Gandhidham, and industrial fire water systems in Dahej where large pipe volumes create significant pressure fluctuation between demand events.

• Jockey pump discharge lines on hydrant and combined hydrant-sprinkler systems
• Small booster pump applications maintaining pressure in remote system zones
• Retrofit on existing systems where jockey pump short cycling causes frequent motor and contactor failure
• Systems with large pipe volume where thermal expansion causes pressure variation in charged lines

Technical Specifications

Air vessels consist of a steel tank with internal bladder or diaphragm separating the air cushion from system water. Pre-charge air pressure is set below jockey pump cut-in pressure — typically 0.2 bar below cut-in — to ensure the vessel absorbs pressure drops before the jockey pump starts.

Common sizes range from 24 litres to 500 litres capacity depending on system volume and allowable pressure drop. Larger systems with extensive pipe networks (warehouse ring mains, multi-building campus systems) require larger vessels or multiple vessels on different zones.

Working pressure ratings match fire system design pressure — typically 10–16 bar for standard hydrant systems. Vessels must be ASME or IS-compliant with pressure relief valve and drain connection.

Sizing and Selection Guidance

Air vessel sizing depends on total system water volume (pipe content), jockey pump cut-in and cut-out pressure settings, and allowable pressure drop before jockey restart. Undersized vessels provide minimal benefit; oversized vessels add cost without proportional improvement.

We calculate required vessel volume during hydraulic design or during retrofit assessment when diagnosing jockey pump short cycling. Provide system pipe volume estimate, jockey pump settings, and current cycling frequency for sizing recommendations.

Pre-charge pressure must be checked and adjusted during commissioning and annually during AMC. Loss of air pre-charge — common after extended system maintenance — reduces vessel effectiveness and restores short cycling behaviour.

Supply and Integration

Rachna Fire & Safety supplies air vessels matched to your pump controller settings and system volume. Installation on the jockey pump discharge line — before the first check valve — with isolation valve for maintenance access is standard practice.

We verify compatibility with existing pump controllers during supply or retrofit, ensuring cut-in/cut-out settings align with vessel pre-charge pressure for optimal cycling reduction.