Air Receiver / Pressure Vessel (Including Pre-Action Tank)

An air receiver (Air Receiver) is a sealed steel vessel that stores compressed air under pressure and balances the compressor's operation against the demand of the systems it feeds. It is a pressure vessel in every respect, and so in Israel it is among the equipment requiring periodic inspection by an authorized party — neglecting it may end in a dangerous mechanical failure and a breach of the law.

An air receiver is just one item among the dozens of systems that every building must maintain on a fixed cycle. The right way to manage them all together is a preventive maintenance program — see the complete PPM guide.

How the System Works

An air compressor compresses air and drives it into the receiver. The receiver stores the compressed air and serves as a "pressure reservoir": it supplies steady air to the consumer, dampens pressure fluctuations, and allows the compressor to work in on-off cycles rather than running continuously. A pressure gauge, a relief valve, and a lower water-drain cock are an inseparable part of it — the relief valve releases air if the pressure rises above the permitted value, and the drain cock removes the condensate (water) that accumulates at the bottom.

A common and especially sensitive use is the pressure tank of a pre-action system. In a pre-action sprinkler system, the piping is dry and filled with compressed air instead of water; a drop in the air pressure in the piping is one of the conditions indicating a fault / an opened sprinkler. The receiver/pressure tank is the source that maintains the constant air pressure in the dry piping — and so its integrity is critical to the reliability of the entire fire-suppression system, not just to operational convenience.

Why the System Is Needed + Risks of Neglect

A vessel that stores air under pressure also stores energy. Internal corrosion from condensate, wall thinning, a stuck relief valve, or a false pressure gauge — all of these may lead to a rupture of the vessel, a violent event that endangers life and property. In a receiver feeding a pre-action system the risk is doubled: a silent fault in the pressure source may disrupt the readiness of the fire-suppression system at the very moment of truth.

Beyond safety, an air receiver is a pressure vessel subject to a statutory inspection obligation. A vessel without a valid inspection report is a breach that may draw personal liability onto the building manager/occupier, difficulties with the insurer in the event of damage, and enforcement by the authorities. Neglect here is not a "saving" — it is direct legal and insurance exposure.

The Maintenance Regime — What, How Often, and How

According to Domera's PPM matrix, based on the Israeli inspection requirements, an air receiver / pressure vessel has two separate inspection tracks:

• Inspection by a licensed air-receiver inspector ("air receiver — including a pre-action pressure tank") — a periodic inspection by a licensed air-receiver inspector, whose result is an inspection report. This is a statutory requirement applying to every site. The inspection frequency is set per the standard and the current guidance of the inspector/authority according to the vessel type and service conditions — it should be verified with the licensed inspector and not relied on by estimate.
• Hydrostatic test ("air receiver / steam") — a water pressure test on a 120/72 cycle (that is, up to ten years for the hydrostatic test and a shorter cycle accordingly), by the same licensed air-receiver inspector. The result of the hydrostatic test is documented within the receiver's inspection report. This too is a statutory requirement.

Between the periodic inspections, the routine maintenance team must drain water from the receiver regularly, verify that the pressure gauge shows a reasonable value, and check that there are no air leaks, external corrosion, or a blocked relief valve. Documenting these actions is part of the operational discipline of a pressure vessel.

Who Is Authorized to Maintain and Certify

The periodic certification of an air receiver / pressure vessel is within the authority of a licensed air-receiver inspector only — both for the periodic inspection and for the hydrostatic test. A compressor technician or a general maintenance worker should not suffice for the statutory inspection: only a licensed inspector may issue the report that qualifies the vessel for continued use. A sibling vessel — a steam receiver / steam boiler — is inspected by an inspector licensed for its field (steam receivers/boilers), and not by the same inspector, owing to the different nature of the risk.

Routine maintenance (draining, visual inspection, servicing the compressor) may be carried out by the maintenance team or by the compressor manufacturer's service company — but the legal qualification of the vessel remains with the licensed inspector.

Standards and Regulation

An air receiver is a pressure vessel included among the equipment requiring periodic inspection by a licensed inspector, under Israel's occupational safety legislation (the Occupational Safety Ordinance and its regulations concerning pressure vessels). The inspection — both the periodic and the hydrostatic — is a statutory requirement applying to every site where such a vessel is installed. Standard numbers, exact frequencies, and inspection conditions are set per the standard and the current guidance of the authority/licensed inspector and according to the vessel type — and should be verified with the inspector each cycle, not relied on from general figures.

Required Documentation and Forms

The binding document to keep in the building file is the receiver's inspection report, issued by the licensed inspector. The hydrostatic test is not a separate document — it is documented within that same inspection report of the receiver. Alongside the report, it is recommended to keep the vessel's manufacturer specification, the name-plate with the maximum working pressure, and documentation of drains and routine maintenance actions. This vessel has no dedicated fire form — the evidence of its fitness is the valid report.

For the full documentation picture of all building systems, see the PPM guide and the Knowledge Hub.

Common Faults and Warning Signs

• Water accumulation at the bottom of the vessel — condensate that is not drained accelerates internal corrosion and thins the wall. A sign of poor draining.
• A "stuck" relief valve — if it does not release in a manual test, the vessel loses its protection against overpressure. A critical fault.
• A stuck or false pressure gauge — hides the true high/low pressure; also misleads the pre-action system.
• The compressor runs continuously / cycles on-off too frequently — usually an air leak or a fault in the receiver.
• External corrosion, rust weeping, or wall deformation — requires stopping use and an inspection by a licensed inspector before resuming.
• A drop in air pressure in the pre-action piping — may indicate a fault in the pressure source; the receiver should be checked alongside the sprinkler system.

The Value of Professional Maintenance Management / How Domera Helps

An air receiver is a "quiet" vessel — it works in the background until it fails. The way to prevent failure is discipline: inspection on time, by the right party, with a valid certifying document. Domera manages the receiver as an item in a PPM program: one open maintenance instance per plan, closing only against an approved inspection report, and an automatic reminder before the report's validity expires — so the vessel is never left a single day without a certificate. The compliance reports centralize the receiver's status alongside all the building's other systems in one place.

Frequently Asked Questions

What is an air receiver and why is it considered a pressure vessel?

An air receiver is a sealed steel vessel that stores compressed air under pressure and balances the compressor's operation. Because it stores energy under pressure, it is classified as a pressure vessel and requires periodic inspection by a licensed inspector.

Why does a pre-action system's air tank require a licensed inspector?

The pressure tank maintains the constant air pressure in the pre-action system's dry piping; a pressure drop is one of the conditions for detecting a fault. Because it is a pressure vessel, its statutory inspection is within the authority of a licensed air-receiver inspector only.

What is a hydrostatic test and how often is it done?

A hydrostatic test is a water pressure test verifying the integrity of the vessel wall. For an air / steam receiver it is managed on a 120/72 cycle, by a licensed air-receiver inspector, and documented within the receiver's inspection report.

Who is authorized to inspect and certify an air receiver?

A licensed air-receiver inspector — both for the periodic inspection and the hydrostatic one. A maintenance worker or a compressor technician can carry out routine maintenance, but they are not permitted to issue the report that qualifies the vessel.

Which document should be kept in the building file?

The valid inspection report of the receiver. The hydrostatic test is documented within that same report and is not a separate document; it is recommended to attach the manufacturer specification and name-plate as well.

What is the difference between an air receiver and a steam boiler/receiver?

Both are pressure vessels, but a steam receiver/boiler operates at high temperature and a different risk, and so it is inspected by an inspector licensed for the steam field, whereas the air receiver is inspected by a licensed air-receiver inspector.

What are the warning signs that require stopping use?

Marked external corrosion, wall deformation, a relief valve that does not release, or a stuck pressure gauge — all of these require taking the vessel out of service and an inspection by a licensed inspector before resuming operation.

Further Reading

• Pre-action system — the dry-pipe sprinkler system whose air pressure is fed by the receiver; the central context of the pressure tank.
• Sprinkler and fire-suppression system maintenance in Israel — how sprinklers and fire pumps are maintained and inspected, alongside the pre-action system.
• The complete PPM guide — the process and full matrix that manage all building systems, including pressure vessels.
• Domera's Knowledge Hub — all the building-systems articles in one place.