{"product_id":"aircomparts-asme-safety-relief-valve-1-2-npt","title":"AirComParts ASME Safety Relief Valve, 1\/2 in. NPT, 50 to 175 PSI","description":"\u003cp\u003e108 to 321 CFM, depending on which set pressure you pick. That range is the reason to go to a 1\/2 in. valve instead of a 1\/4 in. one: a quarter inch valve tops out around 275 CFM even at 325 PSI, and most of them flow far less. If your compressor outruns the valve, the valve is decorative.\u003c\/p\u003e\n\u003ch3\u003eAvailable set pressures\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e50 PSI, 108 CFM (S1300)\u003c\/li\u003e\n\u003cli\u003e75 PSI, 150 CFM (S1301)\u003c\/li\u003e\n\u003cli\u003e100 PSI, 190 CFM (s1306)\u003c\/li\u003e\n\u003cli\u003e125 PSI, 235 CFM (S1302)\u003c\/li\u003e\n\u003cli\u003e175 PSI, 321 CFM (S1304)\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eThe 150 PSI version of this valve is \u003ca href=\"\/products\/5in-150-psi-278cfm-tank-pressure-safety-relief-valve-s1303\"\u003elisted separately as S1303\u003c\/a\u003e, and the 200 PSI version as \u003ca href=\"\/products\/5in-200psi-safety-valve-s1305\"\u003eS1305\u003c\/a\u003e.\u003c\/p\u003e\n\u003ch3\u003eSizing it against the compressor, not the pipe\u003c\/h3\u003e\n\u003cp\u003eThe port size is 1\/2 in. male NPT, but that is a fitting dimension, not a capacity rating. What matters is whether the CFM figure above exceeds what your compressor can deliver at that pressure. Take the pump's rated output, not the motor horsepower, and not the number on the tank. A 10 HP two stage reciprocating pump at 175 PSI is doing roughly 34 CFM, so the 321 CFM valve has enormous headroom. A 50 HP rotary screw at 125 PSI is closer to 220 CFM, and now the 235 CFM valve is the right call rather than an obvious one.\u003c\/p\u003e\n\u003cp\u003eWhere a single valve will not cover the output, fit two. ASME allows multiple relief devices on one vessel and their capacities add.\u003c\/p\u003e\n\u003ch3\u003eSet pressure against the tank\u003c\/h3\u003e\n\u003cp\u003eRead the maximum allowable working pressure off the ASME data plate on the receiver. The valve's set pressure must be at or below that figure. Shops routinely fit a 175 PSI valve to a tank stamped 150 because the compressor is set to cut out at 165, which gets the logic exactly backwards. Replace the tank or lower the cut out, don't oversize the valve.\u003c\/p\u003e\n\u003cp\u003eThese are brass bodied, ASME coded, with a stainless pull ring for the manual lift test. Factory set and sealed. If one weeps at pressure, replace it rather than trying to reseat it, because a safety valve that has been apart is no longer coded.\u003c\/p\u003e","brand":"AirComParts","offers":[{"title":"50 PSI \/ 108 CFM","offer_id":67953432166675,"sku":"S1300","price":24.99,"currency_code":"USD","in_stock":true},{"title":"75 PSI \/ 150 CFM","offer_id":67953432199443,"sku":"S1301","price":26.99,"currency_code":"USD","in_stock":true},{"title":"100 PSI \/ 190 CFM","offer_id":67953432232211,"sku":"s1306","price":26.99,"currency_code":"USD","in_stock":true},{"title":"125 PSI \/ 235 CFM","offer_id":67953432264979,"sku":"S1302","price":26.99,"currency_code":"USD","in_stock":true},{"title":"175 PSI \/ 321 CFM","offer_id":67953432297747,"sku":"S1304","price":26.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0825\/3141\/8387\/files\/S1065THRUS1509.jpg?v=1793875531","url":"https:\/\/aircompressorstore.com\/products\/aircomparts-asme-safety-relief-valve-1-2-npt","provider":"Warthog Air Compressor Store","version":"1.0","type":"link"}