{"id":651,"date":"2026-10-02T13:17:39","date_gmt":"2026-10-02T11:17:39","guid":{"rendered":"https:\/\/www.valfonta.com\/producto\/pressure-relief-valve-s3\/"},"modified":"2026-10-22T09:22:58","modified_gmt":"2026-10-22T07:22:58","slug":"pressure-relief-valve-s3","status":"publish","type":"product","link":"https:\/\/www.valfonta.com\/en\/product\/pressure-relief-valve-s3\/","title":{"rendered":"S3 pressure relief valve"},"content":{"rendered":"<div class=\"wp-block-group vf-raiz vf-pl-ficha-producto is-layout-flow wp-block-group-is-layout-flow\"><nav class=\"wp-block-group vf-breadcrumbs vfa-aria-label--Breadcrumbs is-layout-flow wp-block-group-is-layout-flow\"><p class=\"vf-envolt wp-block-paragraph\"><a href=\"\/en\/\">Home<\/a><span class=\"vf-sep\" aria-hidden=\"true\">\u203a<\/span><a href=\"https:\/\/www.valfonta.com\/en\/pressure-relief-valve\/\">Pressure relief valves<\/a><span class=\"vf-sep\" aria-hidden=\"true\">\u203a<\/span><span aria-current=\"page\">S3 pressure relief valve<\/span><\/p><\/nav><article class=\"wp-block-group vf-pdp vfd-model--S3 is-layout-flow wp-block-group-is-layout-flow\"><div class=\"wp-block-group vf-pdp-hero is-layout-flow wp-block-group-is-layout-flow\"><div class=\"wp-block-group vf-pdp-title is-layout-flow wp-block-group-is-layout-flow\"><p class=\"vf-pdp-eyebrow wp-block-paragraph\">Pressure relief valve \u00b7 Spring-loaded<\/p><h1 class=\"wp-block-heading\">S3 pressure relief valve<\/h1><\/div><div class=\"wp-block-group vf-pdp-media vf-photo is-layout-flow wp-block-group-is-layout-flow\"><p class=\"vf-envolt wp-block-paragraph\"><span class=\"vf-pdp-badge\">Up to 220 \u00b0C<\/span><\/p><figure class=\"wp-block-image vf-img-suelta\"><img decoding=\"async\" src=\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/valvula-alivio-presion-s3-s4-perspectiva.webp\" alt=\"Valfonta S3 pressure relief valve with spring loading and flanged connection, perspective view\" class=\"wp-image-10229\" width=\"900\" height=\"900\" fetchpriority=\"high\"><\/figure><div class=\"wp-block-group vf-pdp-thumbs is-layout-flow wp-block-group-is-layout-flow\"><p class=\"vf-envolt wp-block-paragraph\"><button type=\"button\" aria-pressed=\"true\" aria-label=\"Show perspective view\" data-vf-thumb=\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/valvula-alivio-presion-s3-s4-perspectiva.webp\" data-alt=\"Valfonta S3 pressure relief valve with spring loading and flanged connection, perspective view\"><img decoding=\"async\" src=\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/valvula-alivio-presion-s3-s4-perspectiva-400.webp\" alt=\"\" class=\"wp-image-10230\" width=\"58\" height=\"58\" loading=\"lazy\"><\/button><button type=\"button\" aria-pressed=\"false\" aria-label=\"Show front view\" data-vf-thumb=\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/valvula-alivio-presion-s3-s4-frontal.webp\" data-alt=\"Valfonta S3 pressure relief valve with spring loading and flanged connection, front view\"><img decoding=\"async\" src=\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/valvula-alivio-presion-s3-s4-frontal-400.webp\" alt=\"\" class=\"wp-image-10231\" width=\"58\" height=\"58\" loading=\"lazy\"><\/button><\/p><\/div><\/div><div class=\"wp-block-group vf-pdp-body is-layout-flow wp-block-group-is-layout-flow\"><p class=\"vf-lead wp-block-paragraph\">The S3 is a direct-acting, spring-loaded pressure relief valve with a guided plug. It holds the upstream pressure at the set value, from 0.5 to 20 barg, on steam, Group 1 and 2 gases, and liquids, up to 220 \u00b0C.<\/p><ul class=\"vf-pdp-keys wp-block-list\"><li><span>Sizes<\/span><b>DN15 to DN150 <small>DN125 and DN150 on request<\/small><\/b><\/li><li><span>Pressure rating<\/span><b>PN25 \u2013 PN40 <small>Class 150 \u2013 300<\/small><\/b><\/li><li><span>Set pressure<\/span><b>0.5 to 20 barg<\/b><\/li><li><span>Temperature<\/span><b>up to 220 \u00b0C <small>250 \u00b0C with special gaskets<\/small><\/b><\/li><li><span>Kv<\/span><b>3.5 to 130 m\u00b3\/h<\/b><\/li><li><span>Leakage class<\/span><b>IV (metal-to-metal) or VI (PTFE+GR)<\/b><\/li><\/ul><div class=\"wp-block-group vf-pdp-cta is-layout-flow wp-block-group-is-layout-flow\"><p class=\"vf-envolt wp-block-paragraph\"><a class=\"vf-btn vf-btn--pri\" href=\"#solicitar\">Request a quote<\/a><a class=\"vf-btn vf-btn--sec\" href=\"\/wp-content\/uploads\/2026\/10\/S3-17A-ESP.pdf\" target=\"_blank\" rel=\"noopener\">Download datasheet <small>PDF<\/small><\/a><\/p><\/div><p class=\"vf-pdp-contact wp-block-paragraph\">Questions about set pressure or sizing? Call <a href=\"tel:+34933720888\">933 720 888<\/a> or email <a href=\"mailto:valfonta@valfonta.com\">valfonta@valfonta.com<\/a>.<\/p><\/div><\/div><ul class=\"vf-pdp-trust wp-block-list\"><li>In-house design and manufacturing in Badalona<\/li><li>ISO 9001 quality system<\/li><li>Guided plug for greater stability<\/li><li>Recommended spare parts identified in the exploded view<\/li><\/ul><nav class=\"wp-block-group vf-pdp-nav vfa-aria-label--Datasheet%20contents is-layout-flow wp-block-group-is-layout-flow\"><ul class=\"wp-block-list\"><li><a href=\"#aplicaciones\">Applications<\/a><\/li><li><a href=\"#especificaciones\">Specifications<\/a><\/li><li><a href=\"#funcionamiento\">Operation<\/a><\/li><li><a href=\"#instalacion\">Installation<\/a><\/li><li><a href=\"#documentacion\">Documentation<\/a><\/li><li><a href=\"#comparar\">Compare<\/a><\/li><li><a href=\"#preguntas\">FAQ<\/a><\/li><li><a href=\"#solicitar\">Request a quote<\/a><\/li><\/ul><\/nav><section id=\"aplicaciones\" class=\"wp-block-group is-layout-flow wp-block-group-is-layout-flow\"><div class=\"wp-block-group vf-pdp-two is-layout-flow wp-block-group-is-layout-flow\"><div class=\"wp-block-group is-layout-flow wp-block-group-is-layout-flow\"><h2 class=\"wp-block-heading\">What the S3 relief valve is used for<\/h2><p class=\"wp-block-paragraph\">The <strong>S3<\/strong> is a <a href=\"https:\/\/www.valfonta.com\/en\/pressure-relief-valve\/\">pressure relief valve<\/a> that holds the upstream pressure at the set value: when the inlet pressure exceeds it, the valve opens gradually, in proportion to the pressure rise, and closes again when the pressure returns to normal. It is direct-acting: no auxiliary power, diaphragm, or control line.<\/p><p class=\"wp-block-paragraph\">The set pressure is determined by a spring, and the <strong>guided plug<\/strong> provides stability. It has AISI 316L stainless steel internals and is available with Class VI leakage using a PTFE + graphite seat. If you work with water, read our article on the <a href=\"https:\/\/www.valfonta.com\/en\/blog\/water-pressure-relief-valve\/\">pressure relief valve for water<\/a>.<\/p><ul class=\"vf-pdp-apps wp-block-list\"><li><b>Pump bypass<\/b><span>Returns excess flow to the suction side or to the tank.<\/span><\/li><li><b>Line and equipment protection<\/b><span>Limits the upstream pressure to the set value.<\/span><\/li><li><b>Steam<\/b><span>Up to 220 \u00b0C with PTFE + graphite plug and gaskets.<\/span><\/li><li><b>Group 1 and 2 gases<\/b><span>Proportional relief of excess pressure.<\/span><\/li><li><b>Water, oil, and other liquids<\/b><span>With PTFE + graphite, stainless steel, EPDM, NBR, FKM, or PEEK plug.<\/span><\/li><\/ul><\/div><aside class=\"wp-block-group vf-pdp-fit is-layout-flow wp-block-group-is-layout-flow\"><h3 class=\"wp-block-heading\">Choose the S3 if\u2026<\/h3><ul class=\"vf-si wp-block-list\"><li>You are looking for a direct-acting valve with no diaphragm or control line.<\/li><li>Your set pressure is between 0.5 and 20 barg.<\/li><li>You work with steam, gases, or liquids up to 220 \u00b0C.<\/li><li>You need Class VI leakage or a special design, such as super duplex.<\/li><\/ul><h3 class=\"wp-block-heading\">Choose another model if\u2026<\/h3><ul class=\"vf-no wp-block-list\"><li>You need a set pressure below 0.5 barg: the <a href=\"https:\/\/www.valfonta.com\/en\/product\/pressure-excess-valve-s2\/\">S2<\/a> adjusts from 0.02 barg and the <a href=\"https:\/\/www.valfonta.com\/en\/product\/excess-pressure-valve-model-prv55\/\">PRV55<\/a> from 0.01 barg.<\/li><li>Regulations require a certified safety valve: the S3 does not replace one; see our <a href=\"https:\/\/www.valfonta.com\/en\/safety-valves\/\">safety valves<\/a>.<\/li><li>You want the stem sealed by a stainless steel bellows: see the <a href=\"https:\/\/www.valfonta.com\/en\/product\/pressure-excess-valve-s1\/\">S1<\/a>.<\/li><li>You only need DN15 to DN25 in stainless steel: see the <a href=\"https:\/\/www.valfonta.com\/en\/product\/pressure-excess-valve-prv53\/\">PRV53<\/a> or the <a href=\"https:\/\/www.valfonta.com\/en\/product\/pressure-excess-valve-prv54\/\">PRV54<\/a> (steam up to 210 \u00b0C).<\/li><\/ul><\/aside><\/div><\/section><section id=\"especificaciones\" class=\"wp-block-group is-layout-flow wp-block-group-is-layout-flow\"><h2 class=\"wp-block-heading\">S3 relief valve technical specifications<\/h2><div class=\"wp-block-group vf-tbl-wrap is-layout-flow wp-block-group-is-layout-flow\"><figure class=\"wp-block-table vf-tbl\"><table><tbody><tr><th scope=\"row\">Type<\/th><td>Direct-acting, spring-loaded, with guided plug<\/td><\/tr><tr><th scope=\"row\">Sizes<\/th><td>DN15 to DN100; DN125 and DN150 on request<\/td><\/tr><tr><th scope=\"row\">Connections<\/th><td>EN and ANSI flanges \u00b7 BSP or NPT thread from \u00bd\u2033 to 2\u2033 \u00b7 Weld ends (BW, SW) on request<\/td><\/tr><tr><th scope=\"row\">Pressure rating<\/th><td>PN16 \u2013 PN25 \u2013 PN40 \u00b7 ANSI Class 150 \u2013 Class 300<\/td><\/tr><tr><th scope=\"row\">Set pressure<\/th><td>0.5 to 20 barg, with different spring ranges<\/td><\/tr><tr><th scope=\"row\">Kv coefficient<\/th><td>From 3.5 m\u00b3\/h (DN15) to 130 m\u00b3\/h (DN100). Full bore as standard; reduced bore on request<\/td><\/tr><tr><th scope=\"row\">Body temperature<\/th><td>Carbon steel: \u221210 to 220 \u00b0C \u00b7 CF3M stainless: \u221230 to 220 \u00b0C \u00b7 Up to 250 \u00b0C with special gaskets<\/td><\/tr><tr><th scope=\"row\">Temperature depending on plug<\/th><td>NBR: 80 \u00b0C \u00b7 EPDM or FPM: 150 \u00b0C \u00b7 PTFE + graphite: 220 \u00b0C \u00b7 PEEK: 250 \u00b0C<\/td><\/tr><tr><th scope=\"row\">Gaskets and packing<\/th><td>Virgin PTFE up to 180 \u00b0C \u00b7 PTFE + graphite up to 220 \u00b0C<\/td><\/tr><tr><th scope=\"row\">Leakage class<\/th><td>Class IV (metal-to-metal) \u00b7 Class VI (PTFE + graphite seat)<\/td><\/tr><tr><th scope=\"row\">Fluids<\/th><td>Steam, Group 1 and 2 gases, water, oil, and other liquids<\/td><\/tr><tr><th scope=\"row\">Body material<\/th><td>GP240GH (1.0619) carbon steel or A351 CF3M stainless. On request: RG10 bronze, duplex, or super duplex<\/td><\/tr><tr><th scope=\"row\">Internals<\/th><td>Stainless steel AISI 316L<\/td><\/tr><tr><th scope=\"row\">Options<\/th><td>Handwheel adjustment \u00b7 PEEK, NBR, EPDM, or stellited plug \u00b7 Special gaskets<\/td><\/tr><tr><th scope=\"row\">Standards<\/th><td>ISO 9001 quality system \u00b7 PED 2014\/68\/EU: the nameplate indicates whether CE marking is required<\/td><\/tr><\/tbody><\/table><\/figure><\/div><h3 class=\"wp-block-heading\">Dimensions and weight<\/h3><div class=\"wp-block-group vf-tbl-wrap is-layout-flow wp-block-group-is-layout-flow\"><figure class=\"wp-block-table vf-tbl vf-tbl--grid\"><table><thead><tr><th scope=\"col\"><\/th><th scope=\"col\">DN15<\/th><th scope=\"col\">DN20<\/th><th scope=\"col\">DN25<\/th><th scope=\"col\">DN32<\/th><th scope=\"col\">DN40<\/th><th scope=\"col\">DN50<\/th><th scope=\"col\">DN65<\/th><th scope=\"col\">DN80<\/th><th scope=\"col\">DN100<\/th><\/tr><\/thead><tbody><tr><th scope=\"row\">Kv (m\u00b3\/h)<\/th><td>3,5<\/td><td>5<\/td><td>9<\/td><td>15<\/td><td>22<\/td><td>35<\/td><td>60<\/td><td>85<\/td><td>130<\/td><\/tr><tr><th scope=\"row\">Cv (gpm)<\/th><td>4<\/td><td>5,8<\/td><td>10,4<\/td><td>17,5<\/td><td>25<\/td><td>41<\/td><td>70<\/td><td>100<\/td><td>152<\/td><\/tr><tr><th scope=\"row\">Length A (EN 558-1)<\/th><td>130<\/td><td>150<\/td><td>160<\/td><td>180<\/td><td>200<\/td><td>230<\/td><td>290<\/td><td>310<\/td><td>350<\/td><\/tr><tr><th scope=\"row\">Length A (ANSI 150)<\/th><td>On request<\/td><td>On request<\/td><td>184<\/td><td>\u2013<\/td><td>222<\/td><td>254<\/td><td>276<\/td><td>298,5<\/td><td>352,5<\/td><\/tr><tr><th scope=\"row\">Length A (ANSI 300)<\/th><td>On request<\/td><td>On request<\/td><td>197<\/td><td>\u2013<\/td><td>235<\/td><td>267<\/td><td>292<\/td><td>317,5<\/td><td>\u2013<\/td><\/tr><tr><th scope=\"row\">Weight (kg)<\/th><td>10<\/td><td>10<\/td><td>12<\/td><td>13<\/td><td>16<\/td><td>18<\/td><td>30<\/td><td>40<\/td><td>50<\/td><\/tr><\/tbody><\/table><\/figure><\/div><p class=\"vf-note wp-block-paragraph\">Dimensions in millimeters. Heights, with or without handwheel, are shown in the PDF drawings.<\/p><h3 class=\"wp-block-heading\">Recommended set pressure ranges<\/h3><div class=\"wp-block-group vf-tbl-wrap is-layout-flow wp-block-group-is-layout-flow\"><figure class=\"wp-block-table vf-tbl vf-tbl--grid\"><table><thead><tr><th scope=\"col\">Range (barg)<\/th><th scope=\"col\">DN15 and DN20<\/th><th scope=\"col\">DN25 and DN32<\/th><th scope=\"col\">DN40 and DN50<\/th><th scope=\"col\">DN65<\/th><th scope=\"col\">DN80<\/th><th scope=\"col\">DN100<\/th><\/tr><\/thead><tbody><tr><th scope=\"row\">1 \u2013 4<\/th><td>\u2013<\/td><td>\u2013<\/td><td>Standard<\/td><td>Standard<\/td><td>Standard<\/td><td>Standard<\/td><\/tr><tr><th scope=\"row\">1 \u2013 6<\/th><td>Standard<\/td><td>Standard<\/td><td>\u2013<\/td><td>\u2013<\/td><td>\u2013<\/td><td>\u2013<\/td><\/tr><tr><th scope=\"row\">3 \u2013 8<\/th><td>\u2013<\/td><td>\u2013<\/td><td>Standard<\/td><td>Standard<\/td><td>Standard<\/td><td>Standard<\/td><\/tr><tr><th scope=\"row\">4 \u2013 12<\/th><td>Standard<\/td><td>Standard<\/td><td>Standard<\/td><td>Standard<\/td><td>Standard<\/td><td>On request<\/td><\/tr><tr><th scope=\"row\">8 \u2013 16<\/th><td>Standard<\/td><td>Standard<\/td><td>Standard<\/td><td>On request<\/td><td>\u2013<\/td><td>\u2013<\/td><\/tr><tr><th scope=\"row\">15 \u2013 25<\/th><td>On request<\/td><td>On request<\/td><td>On request<\/td><td>\u2013<\/td><td>\u2013<\/td><td>\u2013<\/td><\/tr><\/tbody><\/table><\/figure><\/div><h3 class=\"wp-block-heading\">Allowable working pressure by temperature (bar, EN 12516-1 and EN 1092-2)<\/h3><div class=\"wp-block-group vf-tbl-wrap is-layout-flow wp-block-group-is-layout-flow\"><figure class=\"wp-block-table vf-tbl vf-tbl--grid\"><table><thead><tr><th scope=\"col\">Body<\/th><th scope=\"col\">\u221210 \u00b0C<\/th><th scope=\"col\">50 \u00b0C<\/th><th scope=\"col\">100 \u00b0C<\/th><th scope=\"col\">150 \u00b0C<\/th><th scope=\"col\">200 \u00b0C<\/th><th scope=\"col\">250 \u00b0C<\/th><\/tr><\/thead><tbody><tr><th scope=\"row\">PN40 \u00b7 GP240GH carbon steel<\/th><td>40<\/td><td>40<\/td><td>36<\/td><td>35<\/td><td>34<\/td><td>33<\/td><\/tr><tr><th scope=\"row\">PN40 \u00b7 CF3M stainless<\/th><td>40<\/td><td>38<\/td><td>33<\/td><td>30<\/td><td>28<\/td><td>26<\/td><\/tr><\/tbody><\/table><\/figure><\/div><details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary>Exploded view and materials (19 parts)<\/summary><div class=\"wp-block-group is-layout-flow wp-block-group-is-layout-flow\"><div class=\"wp-block-group vf-tbl-wrap is-layout-flow wp-block-group-is-layout-flow\"><figure class=\"wp-block-table vf-tbl vf-tbl--grid\"><table><thead><tr><th scope=\"col\">No.<\/th><th scope=\"col\">Part<\/th><th scope=\"col\">Material<\/th><\/tr><\/thead><tbody><tr><th scope=\"row\">1<\/th><td>Body<\/td><td>Carbon steel or A351 CF3M stainless (316L)<\/td><\/tr><tr><th scope=\"row\">2, 3, 5, 6<\/th><td>Seat, guide, plug holder, and stem<\/td><td>AISI 316L stainless<\/td><\/tr><tr><th scope=\"row\">4<\/th><td>Plug<\/td><td>PTFE + graphite or 316L stainless; EPDM, NBR, FKM, or PEEK on request<\/td><\/tr><tr><th scope=\"row\">7, 24<\/th><td>Screws and washer<\/td><td>Zinc-plated steel 8.8 or A2-70 stainless<\/td><\/tr><tr><th scope=\"row\">8, 17<\/th><td>O-rings<\/td><td>FKM (or NBR, EPDM)<\/td><\/tr><tr><th scope=\"row\">9<\/th><td>Spring cover<\/td><td>A351 CF3M stainless (316L)<\/td><\/tr><tr><th scope=\"row\">10<\/th><td>Adjusting spring<\/td><td>Spring steel with epoxy paint<\/td><\/tr><tr><th scope=\"row\">11, 20<\/th><td>Lower and upper spring supports<\/td><td>Zinc-plated steel 1.1191<\/td><\/tr><tr><th scope=\"row\">12<\/th><td>Bearings<\/td><td>PTFE + graphite<\/td><\/tr><tr><th scope=\"row\">13<\/th><td>Adjusting stem A<\/td><td>AISI 316L stainless<\/td><\/tr><tr><th scope=\"row\">14, 19, 27, 28<\/th><td>Washer, adjusting stem B, pin, and nut<\/td><td>A2-70 stainless<\/td><\/tr><tr><th scope=\"row\">15<\/th><td>Cap plug<\/td><td>Zinc-plated steel 1.1191 or 316L stainless<\/td><\/tr><tr><th scope=\"row\">16<\/th><td>O-ring<\/td><td>FKM (or NBR, EPDM, PTFE)<\/td><\/tr><tr><th scope=\"row\">21<\/th><td>Flat gasket<\/td><td>PTFE<\/td><\/tr><tr><th scope=\"row\">22<\/th><td>Flat gasket<\/td><td>Graphite (or PTFE)<\/td><\/tr><tr><th scope=\"row\">23<\/th><td>Bonnet<\/td><td>AISI 316L stainless<\/td><\/tr><tr><th scope=\"row\">25<\/th><td>Insulating gasket<\/td><td>PTFE + graphite + 302 stainless<\/td><\/tr><tr><th scope=\"row\">26<\/th><td>Stem guide<\/td><td>Bronze or 316L stainless + Ni<\/td><\/tr><tr><th scope=\"row\">110 \u2013 116<\/th><td>Handwheel option components<\/td><td>Painted steel handwheel, 316L stem, plug, and gaskets<\/td><\/tr><\/tbody><\/table><\/figure><\/div><\/div><\/details><details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary>Recommended spare parts<\/summary><div class=\"wp-block-group is-layout-flow wp-block-group-is-layout-flow\"><div class=\"wp-block-group vf-tbl-wrap is-layout-flow wp-block-group-is-layout-flow\"><figure class=\"wp-block-table vf-tbl vf-tbl--grid\"><table><thead><tr><th scope=\"col\">Reference<\/th><th scope=\"col\">Description<\/th><th scope=\"col\">Parts<\/th><\/tr><\/thead><tbody><tr><th scope=\"row\">\u2014<\/th><td>Plug<\/td><td>4<\/td><\/tr><tr><th scope=\"row\">\u2014<\/th><td>O-rings<\/td><td>8, 16, and 17<\/td><\/tr><tr><th scope=\"row\">\u2014<\/th><td>Bearings<\/td><td>12<\/td><\/tr><tr><th scope=\"row\">\u2014<\/th><td>Flat and insulating gaskets<\/td><td>21, 22, and 25<\/td><\/tr><\/tbody><\/table><\/figure><\/div><\/div><\/details><\/section><section id=\"funcionamiento\" class=\"wp-block-group is-layout-flow wp-block-group-is-layout-flow\"><h2 class=\"wp-block-heading\">How the S3 relief valve works<\/h2><p class=\"wp-block-paragraph\">The inlet pressure and the spring force balance each other on the plug, with no auxiliary power.<\/p><ol class=\"vf-steps wp-block-list\"><li><b>Valve closed.<\/b> As long as the force of the inlet pressure (p1) is lower than the spring force, the plug stays on the seat.<\/li><li><b>Proportional opening.<\/b> When the pressure exceeds it, the valve opens in proportion to the pressure rise and relieves the excess fluid.<\/li><li><b>Stable regulation.<\/b> The valve modulates so that the upstream pressure does not exceed the set pressure; the guided plug gives it stability.<\/li><li><b>Closing.<\/b> When the pressure returns to normal, the spring closes the valve again.<\/li><li><b>Set pressure.<\/b> The spring force is adjusted with the adjusting stem (13) or, on the handwheel version, with the handwheel.<\/li><\/ol><p class=\"wp-block-paragraph\">A relief valve is not a safety valve; if you need overpressure protection, install both. See the <a href=\"https:\/\/www.valfonta.com\/en\/blog\/what-difference-between-safety-valve-and-relief-valve\/\">difference between a safety valve and a relief valve<\/a>.<\/p><\/section><section id=\"instalacion\" class=\"wp-block-group is-layout-flow wp-block-group-is-layout-flow\"><h2 class=\"wp-block-heading\">S3 relief valve installation<\/h2><p class=\"wp-block-paragraph\">In a typical installation, the S3 is mounted on a branch off the main line, for example on a pump bypass, so that the relieved flow returns to the suction side or to the tank. An upstream pressure gauge lets you check the set pressure.<\/p><div class=\"wp-block-group vf-diagram vf-s-7307c0 vf-t-figure is-layout-flow wp-block-group-is-layout-flow\"><div class=\"wp-block-group vf-svgw is-layout-flow wp-block-group-is-layout-flow\"><p class=\"vf-envolt wp-block-paragraph\"><svg viewbox=\"0 0 900 240\" role=\"img\" aria-label=\"Installation diagram of a pressure relief or excess pressure valve on a branch line\"><path d=\"M20 90 H880\" stroke=\"#9aa0a6\" stroke-width=\"6\" fill=\"none\"><\/path><path d=\"M865 90 l14 0 -10 -7 m10 7 -10 7\" stroke=\"#1e2123\" stroke-width=\"3\" fill=\"none\"><\/path><rect x=\"60\" y=\"62\" width=\"90\" height=\"56\" rx=\"4\" fill=\"#fff\" stroke=\"#1e2123\" stroke-width=\"2\"><\/rect><circle cx=\"105\" cy=\"90\" r=\"16\" fill=\"none\" stroke=\"#1e2123\" stroke-width=\"2\"><\/circle><path d=\"M97 90 l18 0\" stroke=\"#1e2123\" stroke-width=\"2\"><\/path><path d=\"M420 90 V150\" stroke=\"#9aa0a6\" stroke-width=\"5\"><\/path><rect x=\"385\" y=\"150\" width=\"70\" height=\"46\" rx=\"4\" fill=\"#fdecf1\" stroke=\"#e6305d\" stroke-width=\"2\"><\/rect><path d=\"M420 160 v24 m-7 -8 7 8 7 -8\" stroke=\"#e6305d\" stroke-width=\"2.5\" fill=\"none\"><\/path><path d=\"M455 173 H640 V215\" stroke=\"#9aa0a6\" stroke-width=\"5\" fill=\"none\"><\/path><path d=\"M632 205 l8 12 8 -12\" stroke=\"#1e2123\" stroke-width=\"2.5\" fill=\"none\"><\/path><g><circle cx=\"300\" cy=\"51\" r=\"13\" fill=\"#fff\" stroke=\"#1e2123\" stroke-width=\"2\"><\/circle><line x1=\"300\" y1=\"64\" x2=\"300\" y2=\"90\" stroke=\"#1e2123\" stroke-width=\"2\"><\/line><line x1=\"300\" y1=\"51\" x2=\"307\" y2=\"44\" stroke=\"#e6305d\" stroke-width=\"2\"><\/line><\/g><rect x=\"720\" y=\"65\" width=\"110\" height=\"50\" rx=\"4\" fill=\"#fff\" stroke=\"#1e2123\" stroke-width=\"2\"><\/rect><circle cx=\"105\" cy=\"138\" r=\"11\" fill=\"#1e2123\"><\/circle><text x=\"105\" y=\"142\" font-size=\"12\" font-weight=\"700\" fill=\"#fff\" text-anchor=\"middle\" font-family=\"Montserrat,Arial\">1<\/text><circle cx=\"324\" cy=\"38\" r=\"11\" fill=\"#1e2123\"><\/circle><text x=\"324\" y=\"42\" font-size=\"12\" font-weight=\"700\" fill=\"#fff\" text-anchor=\"middle\" font-family=\"Montserrat,Arial\">2<\/text><circle cx=\"420\" cy=\"218\" r=\"11\" fill=\"#e6305d\"><\/circle><text x=\"420\" y=\"222\" font-size=\"12\" font-weight=\"700\" fill=\"#fff\" text-anchor=\"middle\" font-family=\"Montserrat,Arial\">3<\/text><circle cx=\"640\" cy=\"232\" r=\"11\" fill=\"#1e2123\"><\/circle><text x=\"640\" y=\"236\" font-size=\"12\" font-weight=\"700\" fill=\"#fff\" text-anchor=\"middle\" font-family=\"Montserrat,Arial\">4<\/text><circle cx=\"775\" cy=\"136\" r=\"11\" fill=\"#1e2123\"><\/circle><text x=\"775\" y=\"140\" font-size=\"12\" font-weight=\"700\" fill=\"#fff\" text-anchor=\"middle\" font-family=\"Montserrat,Arial\">5<\/text><\/svg><\/p><\/div><div class=\"wp-block-group vf-t-figcaption is-layout-flow wp-block-group-is-layout-flow\"><ol class=\"wp-block-list\"><li>Pump or equipment that generates the pressure<\/li><li>Upstream pressure gauge<\/li><li>S3 relief valve<\/li><li>Return to the suction side or to the tank<\/li><li>Main line to the point of use<\/li><\/ol><\/div><\/div><h3 class=\"wp-block-heading\">Installation and start-up<\/h3><ol class=\"vf-steps wp-block-list\"><li><b>Protect the valve<\/b> from dirt and impacts. If you use lifting gear, attach it to the body, never to the adjusting screw.<\/li><li><b>Clean the pipe and install a strainer<\/b> upstream of the valve to protect the seat.<\/li><li><b>Follow the arrow on the body<\/b> and install the valve in a horizontal pipe, which is the recommended position (with a slight slope if condensate is present).<\/li><li><b>Support the pipe, not the valve:<\/b> place supports close to the flanges.<\/li><li><b>Start up slowly:<\/b> open the isolation valves gradually, inlet first, to avoid water hammer.<\/li><li><b>Adjust the set pressure<\/b> if necessary (Valfonta supplies the valve set to the specified pressure): remove the cap plug (15) and the O-ring (16) and turn the adjusting stem (13), or turn the handwheel. Turning clockwise compresses the spring and raises the set pressure. Refit the O-ring and the cap plug.<\/li><\/ol><p class=\"wp-block-paragraph\">It must be installed by specialized personnel, without exceeding the design pressure and temperature. See our guide on relief valve set pressure.<\/p><\/section><section id=\"documentacion\" class=\"wp-block-group is-layout-flow wp-block-group-is-layout-flow\"><h2 class=\"wp-block-heading\">S3 technical documentation<\/h2><div class=\"wp-block-group vf-docs is-layout-flow wp-block-group-is-layout-flow\"><div class=\"wp-block-group vf-doc vf-amb-enllac is-layout-flow wp-block-group-is-layout-flow\"><p class=\"vf-envolt wp-block-paragraph\"><i>PDF<\/i><\/p><div class=\"wp-block-group is-layout-flow wp-block-group-is-layout-flow\"><p class=\"vf-envolt wp-block-paragraph\"><b>S3 datasheet<\/b><span>PDF \u00b7 6 pages \u00b7 features, exploded view, dimensions, and spring ranges<\/span><\/p><\/div><p class=\"vf-enllac wp-block-paragraph\"><a class=\"vf-enllac-estirat\" href=\"\/wp-content\/uploads\/2026\/10\/S3-17A-ESP.pdf\" aria-label=\"PDF S3 datasheet PDF \u00b7 6 pages \u00b7 features, exploded view, dimensions, and spring ranges\" target=\"_blank\" rel=\"noopener\"><\/a><\/p><\/div><div class=\"wp-block-group vf-doc vf-amb-enllac is-layout-flow wp-block-group-is-layout-flow\"><p class=\"vf-envolt wp-block-paragraph\"><i>PDF<\/i><\/p><div class=\"wp-block-group is-layout-flow wp-block-group-is-layout-flow\"><p class=\"vf-envolt wp-block-paragraph\"><b>Operation and installation manual<\/b><span>PDF \u00b7 12 pages \u00b7 installation, adjustment, troubleshooting, and receiving<\/span><\/p><\/div><p class=\"vf-enllac wp-block-paragraph\"><a class=\"vf-enllac-estirat\" href=\"\/wp-content\/uploads\/2026\/10\/Manual-S3-17A-ESP.pdf\" aria-label=\"PDF Operation and installation manual PDF \u00b7 12 pages \u00b7 installation, adjustment, troubleshooting, and receiving\" target=\"_blank\" rel=\"noopener\"><\/a><\/p><\/div><\/div><p class=\"wp-block-paragraph\">To order spare parts, give the serial number (S\/N) shown on the nameplate. Order certificates: see our <a href=\"https:\/\/www.valfonta.com\/en\/certificates\/\">quality certificates<\/a>.<\/p><\/section><section id=\"comparar\" class=\"wp-block-group is-layout-flow wp-block-group-is-layout-flow\"><h2 class=\"wp-block-heading\">S3 vs. other relief and excess pressure valves<\/h2><p class=\"wp-block-paragraph\">The range covers DN15 to DN150 and set pressures from 0.01 to 20 barg.<\/p><div class=\"wp-block-group vf-tbl-wrap is-layout-flow wp-block-group-is-layout-flow\"><figure class=\"wp-block-table vf-tbl vf-tbl--grid\"><table><thead><tr><th scope=\"col\">Model<\/th><th scope=\"col\">DN<\/th><th scope=\"col\">PN<\/th><th scope=\"col\">Set pressure (barg)<\/th><th scope=\"col\">Max. T (\u00b0C)<\/th><th scope=\"col\">Steam<\/th><th scope=\"col\">Standard body<\/th><\/tr><\/thead><tbody><tr><th scope=\"row\"><a href=\"https:\/\/www.valfonta.com\/en\/product\/pressure-excess-valve-prv53\/\">PRV53<\/a><\/th><td>15 \u2013 25<\/td><td>25<\/td><td>0,5 \u2013 15<\/td><td>150<\/td><td>No<\/td><td>CF3M stainless<\/td><\/tr><tr><th scope=\"row\"><a href=\"https:\/\/www.valfonta.com\/en\/product\/pressure-excess-valve-prv54\/\">PRV54<\/a><\/th><td>15 \u2013 25<\/td><td>25<\/td><td>0,5 \u2013 12<\/td><td>210<\/td><td>Yes<\/td><td>CF3M stainless<\/td><\/tr><tr><th scope=\"row\"><a href=\"https:\/\/www.valfonta.com\/en\/product\/excess-pressure-valve-model-prv55\/\">PRV55<\/a><\/th><td>15 \u2013 25<\/td><td>25<\/td><td>0,01 \u2013 8<\/td><td>150<\/td><td>Yes<\/td><td>CF3M stainless<\/td><\/tr><tr><th scope=\"row\"><a href=\"https:\/\/www.valfonta.com\/en\/product\/pressure-excess-valve-s1\/\">S1<\/a><\/th><td>15 \u2013 150<\/td><td>40<\/td><td>0,5 \u2013 15<\/td><td>220<\/td><td>Yes<\/td><td>Carbon steel or CF3M stainless<\/td><\/tr><tr><th scope=\"row\"><a href=\"https:\/\/www.valfonta.com\/en\/product\/pressure-excess-valve-s2\/\">S2<\/a><\/th><td>15 \u2013 100<\/td><td>40<\/td><td>0,02 \u2013 10<\/td><td>180<\/td><td>Yes<\/td><td>Carbon steel or CF3M stainless<\/td><\/tr><tr><th scope=\"row\"><span class=\"vf-dato vf-dato-fila\" hidden data-vf-class=\"vf-cur\"><\/span>S3<\/th><td>15 \u2013 150<\/td><td>40<\/td><td>0,5 \u2013 20<\/td><td>220<\/td><td>Yes<\/td><td>Carbon steel or CF3M stainless<\/td><\/tr><tr><th scope=\"row\">S4<\/th><td>15 \u2013 100<\/td><td>40<\/td><td>0,5 \u2013 20<\/td><td>220<\/td><td>Yes<\/td><td>Carbon steel or CF3M stainless<\/td><\/tr><\/tbody><\/table><\/figure><\/div><p class=\"vf-note wp-block-paragraph\">Data from the Valfonta summary catalog (2025); S2 set pressure from its datasheet. All accept water, oil, air, and non-flammable gases.<\/p><\/section><section id=\"preguntas\" class=\"wp-block-group is-layout-flow wp-block-group-is-layout-flow\"><h2 class=\"wp-block-heading\">Frequently asked questions about the S3<\/h2><details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary>Does a pressure relief valve replace a safety valve?<\/summary><div class=\"wp-block-group is-layout-flow wp-block-group-is-layout-flow\"><p class=\"wp-block-paragraph\">No. The S3 relieves excess pressure proportionally, but it is not a safety valve. If the installation needs overpressure protection, a <a href=\"https:\/\/www.valfonta.com\/en\/safety-valves\/\">safety valve<\/a> must also be installed.<\/p><\/div><\/details><details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary>What set pressure does the S3 accept?<\/summary><div class=\"wp-block-group is-layout-flow wp-block-group-is-layout-flow\"><p class=\"wp-block-paragraph\">From 0.5 to 20 barg, with different springs. For example, for DN15 and DN20 the standard ranges are 1 to 6, 4 to 12, and 8 to 16 barg; the 15 to 25 barg range is available on request.<\/p><\/div><\/details><details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary>How do you adjust the set pressure?<\/summary><div class=\"wp-block-group is-layout-flow wp-block-group-is-layout-flow\"><p class=\"wp-block-paragraph\">Remove the cap plug (15) and the O-ring (16) and turn the adjusting stem (13): turning clockwise raises the set pressure and counterclockwise lowers it. With a handwheel, simply turn it.<\/p><\/div><\/details><details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary>Can it be used with steam?<\/summary><div class=\"wp-block-group is-layout-flow wp-block-group-is-layout-flow\"><p class=\"wp-block-paragraph\">Yes. With a PTFE + graphite plug and gaskets it works up to 220 \u00b0C, and up to 250 \u00b0C with special gaskets or a PEEK plug.<\/p><\/div><\/details><details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary>Is it suitable for fire protection systems?<\/summary><div class=\"wp-block-group is-layout-flow wp-block-group-is-layout-flow\"><p class=\"wp-block-paragraph\">Yes. The S3 has specific approval for fire protection systems, where it is installed on the pump bypass. Ask us for the certificate along with the quote.<\/p><\/div><\/details><details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary>How is it installed on a pump bypass?<\/summary><div class=\"wp-block-group is-layout-flow wp-block-group-is-layout-flow\"><p class=\"wp-block-paragraph\">On a branch off the discharge line that returns to the suction side or to the tank, with an upstream pressure gauge. If the pressure exceeds the set pressure, the S3 opens and returns the excess flow.<\/p><\/div><\/details><\/section><section id=\"relacionados\" class=\"wp-block-group is-layout-flow wp-block-group-is-layout-flow\"><h2 class=\"wp-block-heading\">Other pressure relief valve models<\/h2><ul class=\"vf-rel wp-block-list\"><li><a href=\"https:\/\/www.valfonta.com\/en\/product\/pressure-excess-valve-s1\/\"><img decoding=\"async\" src=\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/ok-M1-S1-3D.jpg\" alt=\"S1 excess pressure valve\" class=\"wp-image-205\" width=\"300\" height=\"300\" loading=\"lazy\"><b>S1 excess pressure valve<\/b><span>Diaphragm and bellows, up to DN150 and 220 \u00b0C.<\/span><\/a><\/li><li><a href=\"https:\/\/www.valfonta.com\/en\/product\/pressure-excess-valve-s2\/\"><img decoding=\"async\" src=\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/ok-M2-PROVISIONAL.jpg\" alt=\"S2 excess pressure valve\" class=\"wp-image-206\" width=\"300\" height=\"300\" loading=\"lazy\"><b>S2 excess pressure valve<\/b><span>Diaphragm with internal sensing, set pressure from 0.02 barg.<\/span><\/a><\/li><li><a href=\"https:\/\/www.valfonta.com\/en\/product\/pressure-excess-valve-prv53\/\"><img decoding=\"async\" src=\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/ok-PRV30-44.jpg\" alt=\"PRV53 excess pressure valve\" class=\"wp-image-207\" width=\"300\" height=\"300\" loading=\"lazy\"><b>PRV53 excess pressure valve<\/b><span>CF3M stainless, DN15 to DN25, set pressure from 0.5 to 15 barg.<\/span><\/a><\/li><li><a href=\"https:\/\/www.valfonta.com\/en\/product\/pressure-excess-valve-prv54\/\"><img decoding=\"async\" src=\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/ok-PRV30-44.jpg\" alt=\"PRV54 excess pressure valve\" class=\"wp-image-207\" width=\"300\" height=\"300\" loading=\"lazy\"><b>PRV54 excess pressure valve<\/b><span>CF3M stainless, DN15 to DN25, steam up to 210 \u00b0C.<\/span><\/a><\/li><li><a href=\"https:\/\/www.valfonta.com\/en\/product\/excess-pressure-valve-model-prv55\/\"><img decoding=\"async\" src=\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/ok-PRV45-55.jpg\" alt=\"PRV55 excess pressure valve\" class=\"wp-image-208\" width=\"300\" height=\"300\" loading=\"lazy\"><b>PRV55 excess pressure valve<\/b><span>Set pressures from 0.01 barg, DN15 to DN25.<\/span><\/a><\/li><\/ul><\/section><section id=\"solicitar\" class=\"wp-block-group is-layout-flow wp-block-group-is-layout-flow\"><div class=\"wp-block-group vf-quote is-layout-flow wp-block-group-is-layout-flow\"><div class=\"wp-block-group is-layout-flow wp-block-group-is-layout-flow\"><h2 class=\"wp-block-heading\">Request a quote for the S3<\/h2><p class=\"wp-block-paragraph\">Give us your installation details and we will recommend the right size, spring range, and plug material for your set pressure.<\/p><ul class=\"wp-block-list\"><li>Fluid and operating temperature<\/li><li>Set pressure and normal operating pressure<\/li><li>Flow rate the valve must relieve<\/li><li>Size, body material, and connection type<\/li><\/ul><p class=\"vf-pdp-contact wp-block-paragraph\">You can also call <a href=\"tel:+34933720888\">933 720 888<\/a>.<\/p><\/div>\n<div class=\"wpcf7 no-js\" id=\"wpcf7-f551-o1\" lang=\"en-US\" dir=\"ltr\" data-wpcf7-id=\"551\">\n<div class=\"screen-reader-response\"><p role=\"status\" aria-live=\"polite\" aria-atomic=\"true\"><\/p> <ul><\/ul><\/div>\n<form action=\"\/en\/wp-json\/wp\/v2\/product\/651#wpcf7-f551-o1\" method=\"post\" class=\"wpcf7-form init vf-form wpcf7-acceptance-as-validation\" aria-label=\"Contact form\" novalidate=\"novalidate\" data-status=\"init\" toolname=\"solicitar_oferta\" tooldescription=\"Request a quote from Valfonta for the models on this page (model, size, fluid and pressures); a member of the team will reply.\">\n<fieldset class=\"hidden-fields-container\"><input type=\"hidden\" name=\"_wpcf7\" value=\"551\" \/><input type=\"hidden\" name=\"_wpcf7_version\" value=\"6.2.3\" \/><input type=\"hidden\" name=\"_wpcf7_locale\" value=\"en_US\" \/><input type=\"hidden\" name=\"_wpcf7_unit_tag\" value=\"wpcf7-f551-o1\" \/><input type=\"hidden\" name=\"_wpcf7_container_post\" value=\"0\" \/><input type=\"hidden\" name=\"_wpcf7_posted_data_hash\" value=\"\" \/><input type=\"hidden\" name=\"_vf_t\" value=\"1792698985.da101b714643e598\" \/>\n<\/fieldset>\n<input class=\"wpcf7-form-control wpcf7-hidden\" value=\"S3\" type=\"hidden\" name=\"modelo\" \/><label>Name *<span class=\"wpcf7-form-control-wrap\" data-name=\"nombre\"><input size=\"40\" maxlength=\"400\" class=\"wpcf7-form-control wpcf7-text wpcf7-validates-as-required\" autocomplete=\"name\" aria-required=\"true\" aria-invalid=\"false\" value=\"\" type=\"text\" name=\"nombre\" \/><\/span><\/label><label>Company<span class=\"wpcf7-form-control-wrap\" data-name=\"empresa\"><input size=\"40\" maxlength=\"400\" class=\"wpcf7-form-control wpcf7-text\" autocomplete=\"organization\" aria-invalid=\"false\" value=\"\" type=\"text\" name=\"empresa\" \/><\/span><\/label><label>Email *<span class=\"wpcf7-form-control-wrap\" data-name=\"email\"><input size=\"40\" maxlength=\"400\" class=\"wpcf7-form-control wpcf7-email wpcf7-validates-as-required wpcf7-text wpcf7-validates-as-email\" autocomplete=\"email\" aria-required=\"true\" aria-invalid=\"false\" value=\"\" type=\"email\" name=\"email\" \/><\/span><\/label><label>Phone<span class=\"wpcf7-form-control-wrap\" data-name=\"telefono\"><input size=\"40\" maxlength=\"400\" class=\"wpcf7-form-control wpcf7-tel wpcf7-text wpcf7-validates-as-tel\" autocomplete=\"tel\" aria-invalid=\"false\" value=\"\" type=\"tel\" name=\"telefono\" \/><\/span><\/label><fieldset><legend>Application data (optional)<\/legend><label>Size<span class=\"wpcf7-form-control-wrap\" data-name=\"dn\"><select class=\"wpcf7-form-control wpcf7-select\" aria-invalid=\"false\" name=\"dn\"><option value=\"\">Select<\/option><option value=\"DN15 (\u00bd\u2033)\">DN15 (\u00bd\u2033)<\/option><option value=\"DN20 (\u00be\u2033)\">DN20 (\u00be\u2033)<\/option><option value=\"DN25 (1\u2033)\">DN25 (1\u2033)<\/option><option value=\"DN32 (1\u00bc\u2033)\">DN32 (1\u00bc\u2033)<\/option><option value=\"DN40 (1\u00bd\u2033)\">DN40 (1\u00bd\u2033)<\/option><option value=\"DN50 (2\u2033)\">DN50 (2\u2033)<\/option><option value=\"DN65\">DN65<\/option><option value=\"DN80\">DN80<\/option><option value=\"DN100\">DN100<\/option><option value=\"DN125\">DN125<\/option><option value=\"DN150\">DN150<\/option><option value=\"I don&#039;t know\">I don&#039;t know<\/option><\/select><\/span><\/label><label>Fluid<span class=\"wpcf7-form-control-wrap\" data-name=\"fluido\"><input size=\"40\" maxlength=\"400\" class=\"wpcf7-form-control wpcf7-text\" aria-invalid=\"false\" placeholder=\"water, steam, oil\u2026\" value=\"\" type=\"text\" name=\"fluido\" \/><\/span><\/label><label>Set pressure (barg)<span class=\"wpcf7-form-control-wrap\" data-name=\"tarado\"><input size=\"40\" maxlength=\"400\" class=\"wpcf7-form-control wpcf7-text\" aria-invalid=\"false\" value=\"\" type=\"text\" name=\"tarado\" \/><\/span><\/label><label>Operating pressure (barg)<span class=\"wpcf7-form-control-wrap\" data-name=\"p_servicio\"><input size=\"40\" maxlength=\"400\" class=\"wpcf7-form-control wpcf7-text\" aria-invalid=\"false\" value=\"\" type=\"text\" name=\"p_servicio\" \/><\/span><\/label><label>Flow rate to discharge<span class=\"wpcf7-form-control-wrap\" data-name=\"caudal\"><input size=\"40\" maxlength=\"400\" class=\"wpcf7-form-control wpcf7-text\" aria-invalid=\"false\" placeholder=\"e.g. 15 m\u00b3\/h\" value=\"\" type=\"text\" name=\"caudal\" \/><\/span><\/label><label>Temperature (\u00b0C)<span class=\"wpcf7-form-control-wrap\" data-name=\"temperatura\"><input size=\"40\" maxlength=\"400\" class=\"wpcf7-form-control wpcf7-text\" aria-invalid=\"false\" value=\"\" type=\"text\" name=\"temperatura\" \/><\/span><\/label><\/fieldset><label class=\"vf-full\">Message<span class=\"wpcf7-form-control-wrap\" data-name=\"mensaje\"><textarea cols=\"40\" rows=\"4\" maxlength=\"2000\" class=\"wpcf7-form-control wpcf7-textarea\" aria-invalid=\"false\" name=\"mensaje\"><\/textarea><\/span><\/label><label class=\"vf-chk vf-full\"><span class=\"wpcf7-form-control-wrap\" data-name=\"privacidad\"><span class=\"wpcf7-form-control wpcf7-acceptance\"><span class=\"wpcf7-list-item\"><input type=\"checkbox\" name=\"privacidad\" value=\"1\" aria-invalid=\"false\" \/><\/span><\/span><\/span> <span>I have read and accept the <a href=\"\/en\/privacy-policy\/\">privacy policy<\/a> *<\/span><\/label><input class=\"wpcf7-form-control wpcf7-submit has-spinner vf-btn vf-btn--pri\" type=\"submit\" value=\"Send request\" \/><span class=\"vf-hp\" aria-hidden=\"true\"><label>Web <input type=\"text\" name=\"vf_web\" value=\"\" tabindex=\"-1\" autocomplete=\"off\" toolparamdescription=\"Campo de control: d\u00e9jalo vac\u00edo\"><\/label><\/span><div class=\"wpcf7-response-output\" aria-hidden=\"true\"><\/div>\n<\/form>\n<\/div>\n\n<\/div><\/section><div class=\"wp-block-group vf-pdp-bar is-layout-flow wp-block-group-is-layout-flow\"><p class=\"vf-envolt wp-block-paragraph\"><a class=\"vf-btn vf-btn--sec\" href=\"tel:+34933720888\">Call<\/a><a class=\"vf-btn vf-btn--pri\" href=\"#solicitar\">Request a quote<\/a><\/p><\/div><\/article><\/div>","protected":false},"excerpt":{"rendered":"<p>Home\u203aPressure relief valves\u203aS3 pressure relief valve Pressure relief valve \u00b7 Spring-loaded S3 pressure relief valve Up to 220 \u00b0C The S3 is a direct-acting, spring-loaded pressure relief valve with a guided plug. It holds the upstream pressure at the set value, from 0.5 to 20 barg, on steam, Group 1 and 2 gases, and liquids, ... <a title=\"S3 pressure relief valve\" class=\"read-more\" href=\"https:\/\/www.valfonta.com\/en\/product\/pressure-relief-valve-s3\/\" aria-label=\"Read more about S3 pressure relief valve\">Read more<\/a><\/p>\n","protected":false},"featured_media":0,"template":"","meta":{"_acf_changed":false,"_generate-full-width-content":"true","_generate-disable-headline":"true","rank_math_title":"S3 spring-loaded pressure relief valve | Valfonta","rank_math_description":"Direct-acting, spring-loaded S3 pressure relief valve. DN15 to DN150, PN40, set pressure from 0.5 to 20 barg, steam, gases, and liquids up to 220 \u00b0C.","rank_math_focus_keyword":"","vf_jsonld":"[{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"Organization\",\"@id\":\"https:\/\/www.valfonta.com\/#organization\",\"name\":\"Valfonta\",\"legalName\":\"Val Fonta, S.L.\",\"taxID\":\"B59935718\",\"url\":\"https:\/\/www.valfonta.com\/en\/\",\"logo\":{\"@type\":\"ImageObject\",\"url\":\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/valfonta-logo.webp\"},\"foundingDate\":\"1962\",\"email\":\"valfonta@valfonta.com\",\"telephone\":\"+34 933 720 888\",\"address\":{\"@type\":\"PostalAddress\",\"streetAddress\":\"C\/ Bronze 26, Pol. Ind. Les Guixeres\",\"postalCode\":\"08915\",\"addressLocality\":\"Badalona\",\"addressRegion\":\"Barcelona\",\"addressCountry\":\"ES\"},\"description\":\"Design, manufacture, and sale of pressure reducing valves, pressure relief valves, and control valves.\"},{\"@type\":\"WebSite\",\"@id\":\"https:\/\/www.valfonta.com\/#website\",\"url\":\"https:\/\/www.valfonta.com\/en\/\",\"name\":\"Valfonta\",\"publisher\":{\"@id\":\"https:\/\/www.valfonta.com\/#organization\"},\"inLanguage\":\"en\"},{\"@type\":\"ItemPage\",\"@id\":\"https:\/\/www.valfonta.com\/en\/product\/pressure-relief-valve-s3\/#webpage\",\"url\":\"https:\/\/www.valfonta.com\/en\/product\/pressure-relief-valve-s3\/\",\"name\":\"S3 spring-loaded pressure relief valve | Valfonta\",\"description\":\"Direct-acting, spring-loaded S3 pressure relief valve. DN15 to DN150, PN40, set pressure from 0.5 to 20 barg, steam, gases, and liquids up to 220 \u00b0C.\",\"isPartOf\":{\"@id\":\"https:\/\/www.valfonta.com\/#website\"},\"about\":{\"@id\":\"https:\/\/www.valfonta.com\/#organization\"},\"inLanguage\":\"en\",\"datePublished\":\"2020-02-05T12:52:21+02:00\",\"dateModified\":\"2026-03-19T14:11:04+02:00\",\"primaryImageOfPage\":{\"@id\":\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/ok-S3-2017.jpg\"},\"breadcrumb\":{\"@id\":\"https:\/\/www.valfonta.com\/en\/product\/pressure-relief-valve-s3\/#breadcrumb\"},\"mainEntity\":{\"@id\":\"https:\/\/www.valfonta.com\/en\/product\/pressure-relief-valve-s3\/#product\"}},{\"@type\":\"ImageObject\",\"@id\":\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/ok-S3-2017.jpg\",\"url\":\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/ok-S3-2017.jpg\",\"width\":\"1000\",\"height\":\"1000\",\"caption\":\"Pressure relief valve\",\"inLanguage\":\"en\"},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\/\/www.valfonta.com\/en\/product\/pressure-relief-valve-s3\/#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\/\/www.valfonta.com\/en\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"Pressure relief valves\",\"item\":\"https:\/\/www.valfonta.com\/en\/pressure-relief-valve\/\"},{\"@type\":\"ListItem\",\"position\":3,\"name\":\"S3 pressure relief valve\",\"item\":\"https:\/\/www.valfonta.com\/en\/product\/pressure-relief-valve-s3\/\"}]},{\"@type\":\"Product\",\"@id\":\"https:\/\/www.valfonta.com\/en\/product\/pressure-relief-valve-s3\/#product\",\"name\":\"S3 pressure relief valve\",\"url\":\"https:\/\/www.valfonta.com\/en\/product\/pressure-relief-valve-s3\/\",\"description\":\"The S3 is a direct-acting, spring-loaded pressure relief valve with a guided plug. It holds the upstream pressure at the set value, from 0.5 to 20 barg, on steam, Group 1 and 2 gases, and liquids, up to 220 \u00b0C.\",\"brand\":{\"@type\":\"Brand\",\"name\":\"Valfonta\"},\"manufacturer\":{\"@id\":\"https:\/\/www.valfonta.com\/#organization\"},\"model\":\"S3\",\"image\":\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/ok-S3-2017.jpg\",\"material\":\"Carbon steel or stainless steel CF3M\",\"additionalProperty\":[{\"@type\":\"PropertyValue\",\"name\":\"Type\",\"value\":\"Direct-acting, spring-loaded, with guided plug\"},{\"@type\":\"PropertyValue\",\"name\":\"Sizes\",\"value\":\"DN15 to DN100; DN125 and DN150 on request\"},{\"@type\":\"PropertyValue\",\"name\":\"Connections\",\"value\":\"EN and ANSI flanges \u00b7 BSP or NPT thread from \u00bd\u2033 to 2\u2033 \u00b7 Weld ends (BW, SW) on request\"},{\"@type\":\"PropertyValue\",\"name\":\"Pressure rating\",\"value\":\"PN16 \u2013 PN25 \u2013 PN40 \u00b7 ANSI Class 150 \u2013 Class 300\"},{\"@type\":\"PropertyValue\",\"name\":\"Set pressure\",\"value\":\"0.5 to 20 barg, with different spring ranges\"},{\"@type\":\"PropertyValue\",\"name\":\"Kv coefficient\",\"value\":\"From 3.5 m\u00b3\/h (DN15) to 130 m\u00b3\/h (DN100). Full bore as standard; reduced bore on request\"},{\"@type\":\"PropertyValue\",\"name\":\"Body temperature\",\"value\":\"Carbon steel: \u221210 to 220 \u00b0C \u00b7 CF3M stainless: \u221230 to 220 \u00b0C \u00b7 Up to 250 \u00b0C with special gaskets\"},{\"@type\":\"PropertyValue\",\"name\":\"Temperature depending on plug\",\"value\":\"NBR: 80 \u00b0C \u00b7 EPDM or FPM: 150 \u00b0C \u00b7 PTFE + graphite: 220 \u00b0C \u00b7 PEEK: 250 \u00b0C\"},{\"@type\":\"PropertyValue\",\"name\":\"Gaskets and packing\",\"value\":\"Virgin PTFE up to 180 \u00b0C \u00b7 PTFE + graphite up to 220 \u00b0C\"},{\"@type\":\"PropertyValue\",\"name\":\"Leakage class\",\"value\":\"Class IV (metal-to-metal) \u00b7 Class VI (PTFE + graphite seat)\"},{\"@type\":\"PropertyValue\",\"name\":\"Fluids\",\"value\":\"Steam, Group 1 and 2 gases, water, oil, and other liquids\"},{\"@type\":\"PropertyValue\",\"name\":\"Body material\",\"value\":\"GP240GH (1.0619) carbon steel or A351 CF3M stainless. On request: RG10 bronze, duplex, or super duplex\"},{\"@type\":\"PropertyValue\",\"name\":\"Internals\",\"value\":\"Stainless steel AISI 316L\"},{\"@type\":\"PropertyValue\",\"name\":\"Options\",\"value\":\"Handwheel adjustment \u00b7 PEEK, NBR, EPDM, or stellited plug \u00b7 Special gaskets\"},{\"@type\":\"PropertyValue\",\"name\":\"Standards\",\"value\":\"ISO 9001 quality system \u00b7 PED 2014\/68\/EU: the nameplate indicates whether CE marking is required\"}],\"category\":\"Pressure relief valves\",\"subjectOf\":[{\"@type\":\"DigitalDocument\",\"name\":\"S3 datasheet\",\"url\":\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/S3-17A-ESP.pdf\",\"encodingFormat\":\"application\/pdf\"},{\"@type\":\"DigitalDocument\",\"name\":\"Operation and installation manual\",\"url\":\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/Manual-S3-17A-ESP.pdf\",\"encodingFormat\":\"application\/pdf\"}]},{\"@type\":\"FAQPage\",\"@id\":\"https:\/\/www.valfonta.com\/en\/product\/pressure-relief-valve-s3\/#faq\",\"mainEntity\":[{\"@type\":\"Question\",\"name\":\"Does a pressure relief valve replace a safety valve?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"No. The S3 relieves excess pressure proportionally, but it is not a safety valve. If the installation needs overpressure protection, a safety valve must also be installed.\"}},{\"@type\":\"Question\",\"name\":\"What set pressure does the S3 accept?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"From 0.5 to 20 barg, with different springs. For example, for DN15 and DN20 the standard ranges are 1 to 6, 4 to 12, and 8 to 16 barg; the 15 to 25 barg range is available on request.\"}},{\"@type\":\"Question\",\"name\":\"How do you adjust the set pressure?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Remove the cap plug (15) and the O-ring (16) and turn the adjusting stem (13): turning clockwise raises the set pressure and counterclockwise lowers it. With a handwheel, simply turn it.\"}},{\"@type\":\"Question\",\"name\":\"Can it be used with steam?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Yes. With a PTFE + graphite plug and gaskets it works up to 220 \u00b0C, and up to 250 \u00b0C with special gaskets or a PEEK plug.\"}},{\"@type\":\"Question\",\"name\":\"Is it suitable for fire protection systems?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Yes. The S3 has specific approval for fire protection systems, where it is installed on the pump bypass. Ask us for the certificate along with the quote.\"}},{\"@type\":\"Question\",\"name\":\"How is it installed on a pump bypass?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"On a branch off the discharge line that returns to the suction side or to the tank, with an upstream pressure gauge. If the pressure exceeds the set pressure, the S3 opens and returns the excess flow.\"}}]}]}]"},"product_brand":[],"product_cat":[79],"product_tag":[],"class_list":["post-651","product","type-product","status-publish","product_cat-sin-categorizar","first","instock","shipping-taxable","product-type-simple"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.valfonta.com\/en\/wp-json\/wp\/v2\/product\/651","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.valfonta.com\/en\/wp-json\/wp\/v2\/product"}],"about":[{"href":"https:\/\/www.valfonta.com\/en\/wp-json\/wp\/v2\/types\/product"}],"wp:attachment":[{"href":"https:\/\/www.valfonta.com\/en\/wp-json\/wp\/v2\/media?parent=651"}],"wp:term":[{"taxonomy":"product_brand","embeddable":true,"href":"https:\/\/www.valfonta.com\/en\/wp-json\/wp\/v2\/product_brand?post=651"},{"taxonomy":"product_cat","embeddable":true,"href":"https:\/\/www.valfonta.com\/en\/wp-json\/wp\/v2\/product_cat?post=651"},{"taxonomy":"product_tag","embeddable":true,"href":"https:\/\/www.valfonta.com\/en\/wp-json\/wp\/v2\/product_tag?post=651"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}