Caleffi 311530 3/4 Inch Safety Relief Valve 3 Bar

The 311530 is the 3/4 inch female-by-female brass safety relief valve of the Caleffi 311 series, factory set at 3 bar. It sits on a heat generator or hot-water storage vessel and opens to atmosphere if pressure climbs, so that boilers, calorifiers and expansion-vessel circuits are never exposed to dangerous pressure.

A spring-and-diaphragm relief valve for closed hot-water circuits

The 311, 312, 313, 314, 513 and 514 series are described in the datasheet as standard membrane safety relief valves for pressure control on heat generators in heating systems, on hot-water storage units in hydraulic and domestic water systems, and in hydraulic systems generally. Once the setting pressure is reached the valve opens and discharges into the atmosphere. This 311530 is the 3/4 inch version with a 3 bar setting, so it opens at about 3.6 bar (20 % above the setting) and must close again above 2.4 bar (20 % below).

Key features from the datasheet

• Certified standard valve; CE marked under the Pressure Equipment Directive 2014/68/EU, category IV
• Brass body, EPDM diaphragm and obturator seal, steel spring, ABS control knob
• Opening overpressure 20 % of setting and closing differential 20 % of setting
• Settings from 1.5 to 9 bar across the 311 series; 3/4 inch type offered at 2, 2.5, 3, 3.5, 4, 5, 5.5, 6, 7, 8 and 9 bar
• Suitable medium: water and air; nominal pressure PN 10; working temperature 5 to 110 °C
• Related 527 EST series adds fail-safe operation and 10 % overpressure, but is a separate range

Technical specification

Values for the discharge flow rate and generator potential are taken from the 3 bar line of the 3/4 inch row in the datasheet table.

Selection and ordering guide

Pick the setting from the maximum working pressure of the generator or vessel, and the size from the heat output it must relieve. The datasheet table lists the discharge flow rate and the maximum generator potential for each setting; for 3/4 inch valves they rise from 61.8 kW at 2 bar to 211.2 kW at 9 bar.

Series 312 and 514 have male-female connections, 313 and 314 add a pressure gauge or gauge connection, and 513 covers 1 and 1 1/4 inch inlets.

Installation requirements

• Size and install the valve through qualified technical personnel in line with current regulations; any use other than the intended use is prohibited.
• Fit vertically or horizontally, never upside down, and follow the flow arrow on the body.
• Heating systems: mount on top of the generator or on the flow pipe no more than 1 metre from it, with no interruption in the connecting pipe.
• Hot-water storage: install close to the vessel with no shut-off device between valve and storage.
• The discharge must be visible and carried in suitable collection pipework; a tundish is advised for low-capacity valves.
• The datasheet notes that, under Italian legislation, standard valves may be applied to heat generators rated below 35 kW; check your own national rules.

Applications in Gulf heating and hot-water plants

Hot-water calorifiers, solar thermal storage, electric water heaters and small boiler sets are common across Oman and the GCC, and each closed vessel needs a certified relief valve. The 311530 fits small to medium storage and heating loops. Solar thermal systems in hot climates may reach temperatures close to the 110 degree C limit, so check the setting and temperature range against the actual installation. The valve is for water and air, not steam or process fluids.

Selection and installation notes

A safety relief valve protects the vessel, so it must be selected from the set pressure, the discharge capacity and the connection size and must never be used for any other purpose. Fit it in the position shown by the maker, pipe the discharge to a safe visible place without a valve in the line, never tamper with the seal on the setting and test it by lifting the lever at the intervals required by the system rules.

Information needed for a quotation

Send the full model code, the quantity, the delivery location in Oman or the GCC, the intended use and any accessories needed, so that the complete package can be quoted together.

Documents and supply information

The manufacturer data sheet is attached to this page and should be read together with the project specification and the site risk assessment before a purchase is confirmed. Ratings, standards and dimensions are quoted as printed on that sheet. Lead time, stock position and certificates available with the shipment are confirmed in the quotation, and we supply to Oman and the wider GCC region for industrial, utility and building services projects.

Accessories and related items

Frequently asked questions

At what pressure does the Caleffi 311530 open?

It is set at 3 bar and, per the datasheet 20 percent opening overpressure, reaches full discharge at about 3.6 bar; it closes again at 2.4 bar.

What connections and medium does it have?

3/4 inch female by female threaded connections for water or air, PN 10, 5 to 110 degrees C.

Is it CE marked?

Yes. The datasheet states the 311 series meets Directive 2014/68/EU, is classified as category IV and carries the CE mark.

Where must it be installed?

On top of the generator or on the flow pipe within 1 metre, or close to the hot-water storage, with no shut-off device between valve and vessel, and not upside down.

Who supplies the Caleffi 311530 in Oman?

Seven Star LLC is an independent supplier in Muscat and quotes against the exact code. Confirm the setting, size and system requirements before ordering.

Documents and quotation

The official Caleffi safety relief valve datasheet 01253/20 EN (2020) is linked on this page. Send the code, quantity and system pressure to request a quotation. See more in Safety Relief Valves.