{"product_id":"castair-1-2-npt-50-250psi-asme-safety-relief-valve-sf50","title":"Castair 1\/2\" NPT 50-250PSI ASME Safety Relief Valve SF50","description":"\u003ch2\u003eCastair SF50 — 1\/2\" NPT ASME Safety Relief Valve, 50–250 PSI\u003c\/h2\u003e\n\n\u003cp\u003eThe Castair SF50 is an ASME-rated pressure safety relief valve with a 1\/2-inch NPT connection and a pressure range of 50 to 250 PSI. A safety relief valve is not optional — it is a required component on every pressurized air receiver tank. This is the last line of defense if the pressure switch fails to cut the compressor off: the relief valve opens automatically when tank pressure exceeds the set point, expelling air until pressure drops back to safe operating levels, then reseats.\u003c\/p\u003e\n\n\u003cp\u003eThe ASME stamp means this valve has been manufactured and tested to the American Society of Mechanical Engineers pressure vessel code requirements for safety relief devices. On commercial and industrial compressor installations, an ASME-stamped valve is typically required for code compliance and insurance purposes. Do not substitute a non-ASME valve on a pressure vessel — and do not ignore a weeping or leaking relief valve. Either replace it or investigate why it is activating.\u003c\/p\u003e\n\n\u003ch3\u003eWhy Safety Relief Valves Fail\u003c\/h3\u003e\n\u003cp\u003eRelief valves are designed to open and reseat repeatedly at their set pressure. But every time a valve lifts — whether from overpressure or from manual testing — the seat takes wear. Valves that have been manually pulled many times, valves that have accumulated corrosion or mineral deposits on the seat, or valves that are operating near their set pressure on every cycle will eventually begin to weep — leaking air at normal operating pressure rather than seating cleanly. A weeping valve needs to be replaced. Attempting to reseat it by manually pulling the test lever repeatedly makes it worse.\u003c\/p\u003e\n\n\u003ch3\u003eKey Features\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eASME Code Compliant:\u003c\/strong\u003e Manufactured and tested to ASME Section VIII Division 1 pressure-relieving safety device requirements — required for code-compliant commercial and industrial installations\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003e1\/2-Inch NPT Connection:\u003c\/strong\u003e Standard pipe thread — fits the majority of compressor tank safety valve ports in the 1\/2-inch size class, including most Cast Air industrial-series tanks\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003e50–250 PSI Operating Range:\u003c\/strong\u003e Covers the full operating range of reciprocating piston air compressors — order at the correct set pressure for your specific tank MAWP\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eAutomatic Pressure Relief:\u003c\/strong\u003e Opens at set pressure, relieves air until pressure drops, reseats automatically — no manual operation required for pressure relief function\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eTest Lever:\u003c\/strong\u003e Manual test lever allows periodic verification that the valve will open — test annually per ASME guidelines (note: do not test excessively as this causes seat wear)\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eCast Air Compatible:\u003c\/strong\u003e Sized for Castair compressor tanks using 1\/2-inch NPT safety valve ports\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eTechnical Specifications\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePart Number:\u003c\/strong\u003e SF50\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eConnection Size:\u003c\/strong\u003e 1\/2 inch NPT\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePressure Range:\u003c\/strong\u003e 50–250 PSI\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eRating:\u003c\/strong\u003e ASME Section VIII code compliant\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eManufacturer:\u003c\/strong\u003e Cast Air (Castair)\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePrice:\u003c\/strong\u003e $32.19\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003e\u003cem\u003eImportant: Safety relief valves must be set to a pressure at or below the tank's MAWP (Maximum Allowable Working Pressure). The set pressure is stamped on the valve body. Match the valve set pressure to your tank's rating. Call us if you need help determining the correct set pressure for your specific compressor tank.\u003c\/em\u003e\u003c\/p\u003e\n\n\u003ch3\u003eSF50 vs. ST25 — Choosing the Right Safety Valve\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eSF50 (this product)\u003c\/strong\u003e — 1\/2\" NPT, 50–250 PSI, ASME rated. Standard safety valve for Cast Air industrial-series compressor tanks ($32.19)\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eST25\u003c\/strong\u003e — 1\/4\" NPT, soft-seat design, ASME rated. Smaller port valve for small tanks, secondary vessels, and auxiliary pressure lines ($12.71)\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eWhen to Replace Your Safety Relief Valve\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003eValve is weeping or leaking at pressures below the set point — the seat is damaged and the valve is not seating cleanly\u003c\/li\u003e\n  \u003cli\u003eValve has been manually pulled more than a few times — manual actuation damages the seat, eventually causing it to weep\u003c\/li\u003e\n  \u003cli\u003eValve shows external corrosion or mineral buildup that may be affecting operation\u003c\/li\u003e\n  \u003cli\u003eValve is more than 5 years old and has never been replaced — particularly important in humid environments where internal components are exposed to moisture\u003c\/li\u003e\n  \u003cli\u003eCompressor has been reassigned to a higher or lower pressure application and the existing valve set pressure no longer matches\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eWhy Buy From Air Compressor Factory Direct?\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e\u003cstrong\u003eAuthorized Cast Air dealer since 2016\u003c\/strong\u003e\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFree shipping\u003c\/strong\u003e on qualifying orders\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFree technical support\u003c\/strong\u003e at 866-217-0063 — we can help you confirm the correct set pressure and confirm the SF50 fits your tank before you order\u003c\/li\u003e\n  \u003cli\u003e\u003cstrong\u003eFull manufacturer warranty\u003c\/strong\u003e\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003e\u003cstrong\u003eCall 866-217-0063 for quick answers and help!\u003c\/strong\u003e\u003c\/p\u003e","brand":"Cast Air","offers":[{"title":"Default Title","offer_id":53342602166485,"sku":"SF50","price":59.64,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0622\/8466\/0949\/files\/reliefvalve.jpg?v=1772652932","url":"https:\/\/aircompressorfactorydirect.com\/products\/castair-1-2-npt-50-250psi-asme-safety-relief-valve-sf50","provider":"Air Compressor Factory Direct","version":"1.0","type":"link"}