{"id":743,"date":"2024-06-20T08:56:28","date_gmt":"2024-06-20T06:56:28","guid":{"rendered":"https:\/\/www.valfonta.com\/blog\/self-regulating-excess-pressure-valves\/"},"modified":"2026-10-15T12:12:52","modified_gmt":"2026-10-15T10:12:52","slug":"self-regulating-excess-pressure-valves","status":"publish","type":"post","link":"https:\/\/www.valfonta.com\/en\/blog\/self-regulating-excess-pressure-valves\/","title":{"rendered":"Features of the S1 and S2 self-regulating excess pressure valves"},"content":{"rendered":"<div class=\"wp-block-group vf-raiz vf-pl-articulo is-layout-flow wp-block-group-is-layout-flow\"><div class=\"wp-block-group vf-cat-wrap is-layout-flow wp-block-group-is-layout-flow\"><article class=\"wp-block-group vf-pdp vf-post 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\">\u203a<\/span><a href=\"\/en\/blog\/\">Blog<\/a><span class=\"vf-sep\">\u203a<\/span><span aria-current=\"page\">Features of the S1 and S2 self-regulating excess pressure valves<\/span><\/p><\/nav><header class=\"wp-block-group vf-post-head is-layout-flow wp-block-group-is-layout-flow\"><p class=\"vf-pdp-eyebrow wp-block-paragraph\"><a href=\"\/en\/pressure-relief-valve\/\">Pressure relief valves<\/a><\/p><h1 class=\"wp-block-heading\">Features of the S1 and S2 self-regulating excess pressure valves<\/h1><p class=\"vf-post-meta wp-block-paragraph\"><span>By Valfonta<\/span><span><time datetime=\"2026-09-30\">Updated September 30, 2026<\/time><\/span><span>9 min read<\/span><\/p><\/header><figure class=\"wp-block-image size-full vf-post-hero is-resized\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/valvulas-de-exceso-de-presion-autorreguladora-1.jpg\" alt=\"Features of the S1 and S2 self-regulating excess pressure valves\" class=\"wp-image-244\" width=\"1200\" height=\"514\"\/><\/figure><div class=\"wp-block-group vf-post-grid is-layout-flow wp-block-group-is-layout-flow\"><div class=\"wp-block-group vf-post-body is-layout-flow wp-block-group-is-layout-flow\"><aside class=\"wp-block-group vf-post-summary vfa-aria-label--In%20summary is-layout-flow wp-block-group-is-layout-flow\"><p class=\"vf-t wp-block-paragraph\">In summary<\/p><p class=\"wp-block-paragraph\">A self-regulating excess pressure valve stays closed while the inlet pressure is below the set pressure and opens proportionally when it is exceeded, discharging the excess flow to a return line, a tank, or a lower-pressure zone. The Valfonta S1, with diaphragm and bellows, has set pressures from 0.5 to 15 barg and handles steam up to 220 \u00b0C; the S2, with diaphragm, has set pressures from 0.02 to 10 barg. Both require a condensate pot with steam or liquids above 125 \u00b0C. Neither replaces a safety valve.<\/p><\/aside><details class=\"wp-block-details vf-post-toc-m is-layout-flow wp-block-details-is-layout-flow\"><summary>Article contents<\/summary><ol class=\"wp-block-list\"><li><a href=\"#como-funciona-una-valvula-de-exceso-de-presion\">How an excess pressure valve works<\/a><\/li><li><a href=\"#exceso-de-presion-reductora-y-valvula-de-seguridad\">Excess pressure valve, reducing valve, and safety valve<\/a><\/li><li><a href=\"#que-podemos-ofrecerle-desde-valfonta\">What can Valfonta offer you?<\/a><\/li><li><a href=\"#los-modelos-de-exceso-de-presion-de-un-vistazo\">The excess pressure models at a glance<\/a><\/li><li><a href=\"#como-elegir-la-valvula-de-exceso-de-presion\">How to choose an excess pressure valve<\/a><\/li><li><a href=\"#preguntas\">Frequently asked questions<\/a><\/li><\/ol><\/details><h2 class=\"wp-block-heading\" id=\"como-funciona-una-valvula-de-exceso-de-presion\">How an excess pressure valve works<\/h2><p class=\"wp-block-paragraph\">The valve stays closed while the inlet pressure is below the set pressure. When it is exceeded, the valve opens gradually, in proportion to the pressure rise, and lets the excess flow pass to a return line, a tank, or a lower-pressure zone. When the pressure returns to its value, it closes.<\/p><p class=\"wp-block-paragraph\">All Valfonta valves of this type are <strong>self-operated<\/strong>: an adjusting spring opposes the inlet pressure, with no air or electricity. What changes is the element that senses the pressure: a piston (PRV53), a diaphragm (S2 and PRV55), a bellows (PRV54), a diaphragm and bellows (S1), or the spring-loaded guided plug itself (S3).<\/p><h2 class=\"wp-block-heading\" id=\"exceso-de-presion-reductora-y-valvula-de-seguridad\">Excess pressure valve, reducing valve, and safety valve<\/h2><ul class=\"wp-block-list\"><li>The <strong>excess pressure valve<\/strong> (or relief valve) holds the <strong>upstream<\/strong> pressure: it opens when there is excess pressure.<\/li><li>The <strong>pressure reducing valve<\/strong> holds the <strong>downstream<\/strong> pressure: it closes when the outlet pressure rises. See our <a href=\"\/en\/pressure-reducing-valves\/\">pressure reducing valves<\/a>.<\/li><li>The <strong>safety valve<\/strong> is a safety accessory that protects tanks, boilers, or piping against overpressure. An excess pressure valve does not replace it. We explain this in <a href=\"\/en\/blog\/what-difference-between-safety-valve-and-relief-valve\/\">the difference between a safety valve and a relief valve<\/a>.<\/li><\/ul><h2 class=\"wp-block-heading\" id=\"que-podemos-ofrecerle-desde-valfonta\"><strong>What can Valfonta offer you?<\/strong><\/h2><p class=\"wp-block-paragraph\">At Valfonta, we are dedicated to <strong>manufacturing and developing pressure control mechanisms<\/strong>, ensuring greater effectiveness and efficiency in distribution systems and installations carrying fluids of different characteristics.\u00a0<\/p><p class=\"wp-block-paragraph\">We specialize in the design, manufacture, and customization of<a href=\"\/en\/pressure-reducing-valves\/\"><strong> pressure reducing valves<\/strong> <\/a>and <a href=\"\/en\/pressure-relief-valve\/\"><strong>excess pressure and pressure relief valves.<\/strong><\/a> Our ability to produce custom solutions is based on a deep understanding of the varied and sometimes complex needs of different systems and installations.<\/p><p class=\"wp-block-paragraph\">Regulating valves are essential for the efficient and safe management of any fluid system. They not only control pressure, but also prevent damage to the piping and minimize fluid and gas losses and leaks. In this way, they contribute to operational efficiency, machinery safety, and environmental protection.<\/p><p class=\"wp-block-paragraph\">Distribution networks, especially in the industrial sector, are often complex and may have zones where <strong>the pressure is higher than the piping or equipment can safely withstand<\/strong>. This can happen for several reasons, such as proximity to pumping stations or location in low-elevation geographic areas, where pressure can build up.<\/p><p class=\"wp-block-paragraph\">In these situations, pressure reducing valves become absolutely critical. They are able to <strong>reduce the pressure inside the system to a safe level, avoiding the risk of pipe ruptures,<\/strong> caused by excess pressure. They also help prevent leaks of any fluid or gas flowing through the system, protecting both the integrity of the system and the surrounding environment. If what you need is to discharge overpressure, see our guide to excess pressure valves.<\/p><p class=\"wp-block-paragraph\">In short, at Valfonta we strive to produce valves of the highest quality that provide precise and reliable pressure regulation, ensuring the efficiency and safety of your systems and installations.<\/p><h3 class=\"wp-block-heading\" id=\"que-valvulas-de-exceso-de-presion-te-mostramos-en-este-artic\"><strong>Which excess pressure valves do we show you in this article?<\/strong><\/h3><div class=\"wp-block-group vf-post-gallery vf-n2 is-layout-flow wp-block-group-is-layout-flow\"><figure class=\"wp-block-image size-full is-resized\"><img decoding=\"async\" src=\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/S1-valvula-reescaled.webp\" alt=\"Pressure relief valve\" class=\"wp-image-251\" width=\"512\" height=\"512\" loading=\"lazy\"\/><\/figure><figure class=\"wp-block-image size-full is-resized\"><img decoding=\"async\" src=\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/Valvula-industrial-M2.jpg\" alt=\"Pressure relief valve\" class=\"wp-image-252\" width=\"512\" height=\"512\" loading=\"lazy\"\/><\/figure><\/div><h3 class=\"wp-block-heading\" id=\"cual-es-la-funcion-de-la-valvula-reductora-de-presion\"><strong>What is the function of a pressure reducing valve? <\/strong><\/h3><figure class=\"wp-block-image size-full is-resized\"><img decoding=\"async\" src=\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/empresa-07.jpg\" alt=\"company 07 - Valfonta\" class=\"wp-image-309\" width=\"800\" height=\"600\" loading=\"lazy\"\/><\/figure><p class=\"wp-block-paragraph\">The answer to this question lies at the very core of the efficiency and safety of fluid systems. As a control valve, the pressure reducing valve plays a crucial role in adjusting the outlet pressure of the system. It does so consistently and reliably, unaffected by variations in inlet pressure or by changes in demand on the flow line.<\/p><p class=\"wp-block-paragraph\">At Valfonta, <strong>we specialize in the manufacture and design of this type of pressure regulating valve,<\/strong> with more than fifty years of experience in the fluid systems industry. This long track record allows us to say with pride that pressure reducing valves are our specialty and our passion.<\/p><p class=\"wp-block-paragraph\">The knowledge accumulated over more than half a century of service gives us a solid, rich foundation to guarantee each of our customers the solution best suited to their needs.<\/p><p class=\"wp-block-paragraph\">We don\u2019t just manufacture valves; at Valfonta, every project is a challenge we approach in a personalized way. <strong>We carefully analyze each installation, consider all the needs and requests our customers bring to us<\/strong>, and work meticulously to find the optimal solution and the most suitable valve.<\/p><h3 class=\"wp-block-heading\" id=\"caracteristicas-de-las-valvulas-de-exceso-de-presion-autorre\"><strong>Features of the S1 and S2 self-regulating excess pressure valves<\/strong><\/h3><p class=\"wp-block-paragraph\">In this post, we will show you the features of and differences between two of our most common pressure relief valve models, the S1 and S2. They are just two options from our wide catalog of valves; do not hesitate to request more information, as well as personalized advice to choose your valve, if you need it.<\/p><h3 class=\"wp-block-heading\" id=\"valvula-s1\"><strong>S1 valve<\/strong><\/h3><p class=\"wp-block-paragraph\">It is a self-operated excess pressure valve. This series of regulating valves is suitable for steam, compressed air, non-hazardous gases, and liquids. It responds very quickly to demand. It has a single-seat globe valve. The stem is sealed by the double-layer bellows.<\/p><p class=\"wp-block-paragraph\">It is made of stainless steel; to prevent any damage to the bellows, the S1 series is fitted with an anti-rotation system. The diaphragm is reinforced with an intermediate fabric layer. Regulation range from 0.5 to 15 barg with different actuators. The valve opens when the upstream pressure increases. Maximum inlet pressure 15 barg.<\/p><p class=\"wp-block-paragraph\"><strong>Other configurations: <\/strong><\/p><div class=\"wp-block-group vf-t-ul is-layout-flow wp-block-group-is-layout-flow\"><div class=\"wp-block-group vf-t-li is-layout-flow wp-block-group-is-layout-flow\"><p class=\"vf-envolt wp-block-paragraph\"><i><\/i><\/p><p class=\"wp-block-paragraph\">Reduced Kv or Cv. <\/p><\/div><div class=\"wp-block-group vf-t-li is-layout-flow wp-block-group-is-layout-flow\"><p class=\"vf-envolt wp-block-paragraph\"><i><\/i><\/p><p class=\"wp-block-paragraph\">A control line kit to sense the pressure directly at the body (optionally with or without a condensate pot) for set points &gt; 1 bar. <\/p><\/div><div class=\"wp-block-group vf-t-li is-layout-flow wp-block-group-is-layout-flow\"><p class=\"vf-envolt wp-block-paragraph\"><i><\/i><\/p><p class=\"wp-block-paragraph\">The condensate pot is available and is required for steam or fluids with a temperature above 125 \u00b0C, in order to protect the diaphragm against excessive temperatures.<\/p><\/div><\/div><figure class=\"wp-block-image size-full is-resized\"><img decoding=\"async\" src=\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/ok-M1-S1-3D-400x400-1.jpg\" alt=\"self-regulating excess pressure valve\" class=\"wp-image-284\" width=\"400\" height=\"400\" loading=\"lazy\"\/><\/figure><h3 class=\"wp-block-heading\" id=\"valvula-s2\"><strong>S2 valve<\/strong><\/h3><p class=\"wp-block-paragraph\">Self-regulating excess pressure valve. Its main function is to hold the inlet pressure at a set maximum value\u2013relieving the excess pressure downstream\u2013by means of the adjusting stem. <\/p><p class=\"wp-block-paragraph\">When the inlet pressure exceeds the set value, the valve opens in proportion to the pressure rise detected.<\/p><p class=\"wp-block-paragraph\">This S2 pressure regulator model is suitable for low-temperature steam (with a condensate pot), compressed air, gases, and liquids.<\/p><p class=\"wp-block-paragraph\">The actuator is fitted with a diaphragm with a high-quality intermediate reinforcing fabric. Its inlet pressure regulation range goes from 0.02 to 10 barg with the different actuator sizes. <\/p><figure class=\"wp-block-image size-full is-resized\"><img decoding=\"async\" src=\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/Valvula-industrial-M2-400x400-1.jpg\" alt=\"self-regulating excess pressure valves\" class=\"wp-image-310\" width=\"400\" height=\"400\" loading=\"lazy\"\/><\/figure><p class=\"wp-block-paragraph\">The condensate pot is available and is required when the fluid is steam or for liquids with a temperature above 125 \u00baC, to protect the diaphragm from overheating.\u00a0<\/p><p class=\"wp-block-paragraph\">It is important to note that an excess pressure valve is not a safety valve and, where necessary, overpressure protection must be installed.<\/p><p class=\"wp-block-paragraph\">This type of valve is used to let a zone with excess pressure feed another lower-pressure zone without starving the main line. In the event of excessive consumption, it prevents overpressure.<\/p><p class=\"wp-block-paragraph\">As we can see, pressure valves are designed to reduce and stabilize the pressure of a fluid. <\/p><p class=\"wp-block-paragraph\">They are mainly conceived as a pressure compensation system that seeks to minimize variation in the outlet pressure.<\/p><p class=\"wp-block-paragraph\"><strong>The benefits of these self-regulating pressure valves include stabilizing pressure in all types of systems and preventing high pressures from causing cracks, vibration, and noise in the piping, pressure variations at different times of day\u2026<\/strong><\/p><p class=\"wp-block-paragraph\">Control valves, if properly selected and maintained, increase efficiency, safety, and profitability.<\/p><p class=\"wp-block-paragraph\">To contact our sales department, simply fill in the form below, call <a href=\"tel:+34933720888\"><strong>933 72 08 88<\/strong><\/a>, or send an email to <a href=\"mailto:valfonta@valfonta.com\"><strong>valfonta@valfonta.com<\/strong><\/a><strong>. <\/strong><\/p><p class=\"wp-block-paragraph\">Together, we will find the most suitable valve for your system or installation!<\/p><h2 class=\"wp-block-heading\" id=\"los-modelos-de-exceso-de-presion-de-un-vistazo\">The excess pressure models at a glance<\/h2><div class=\"wp-block-group vf-tbl-wrap is-layout-flow wp-block-group-is-layout-flow\"><figure class=\"wp-block-table vf-post-table\"><table><thead><tr><th>Model<\/th><th>Construction<\/th><th>DN<\/th><th>Set pressure (barg)<\/th><th>Max. T (\u00b0C)<\/th><th>Steam<\/th><\/tr><\/thead><tbody><tr><th><a href=\"\/en\/product\/pressure-relief-valve-s3\/\">S3<\/a><\/th><td>Spring, guided plug<\/td><td>15 \u2013 150<\/td><td>0,5 \u2013 20<\/td><td>220<\/td><td>Yes<\/td><\/tr><tr><th><a href=\"\/en\/product\/pressure-excess-valve-s1\/\">S1<\/a><\/th><td>Diaphragm and bellows<\/td><td>15 \u2013 150<\/td><td>0,5 \u2013 15<\/td><td>220<\/td><td>Yes<\/td><\/tr><tr><th><a href=\"\/en\/product\/pressure-excess-valve-s2\/\">S2<\/a><\/th><td>Diaphragm, internal sensing<\/td><td>15 \u2013 100<\/td><td>0,02 \u2013 10<\/td><td>180<\/td><td>Yes, with external sensing<\/td><\/tr><tr><th><a href=\"\/en\/product\/pressure-excess-valve-prv53\/\">PRV53<\/a><\/th><td>Piston<\/td><td>15 \u2013 25<\/td><td>0,5 \u2013 10<\/td><td>150<\/td><td>No<\/td><\/tr><tr><th><a href=\"\/en\/product\/pressure-excess-valve-prv54\/\">PRV54<\/a><\/th><td>Bellows<\/td><td>15 \u2013 25<\/td><td>0,5 \u2013 12<\/td><td>210<\/td><td>Yes<\/td><\/tr><tr><th><a href=\"\/en\/product\/excess-pressure-valve-model-prv55\/\">PRV55<\/a><\/th><td>Diaphragm<\/td><td>15 \u2013 25<\/td><td>0,01 \u2013 8<\/td><td>150<\/td><td>Yes<\/td><\/tr><\/tbody><\/table><\/figure><\/div><p class=\"vf-anote wp-block-paragraph\">Data from the Valfonta excess pressure summary catalog (2025) and the datasheets. S3: DN125 and DN150, on request. PRV53: up to 15 barg on request. There is also a seventh model, the S4, with no datasheet on the website.<\/p><p class=\"wp-block-paragraph\">You will find the datasheets, spring ranges, and documentation for each model on our <a href=\"\/en\/pressure-relief-valve\/\">pressure relief and excess pressure valves<\/a> page.<\/p><h2 class=\"wp-block-heading\" id=\"como-elegir-la-valvula-de-exceso-de-presion\">How to choose an excess pressure valve<\/h2><ul class=\"wp-block-list\"><li><strong>Very low set pressures.<\/strong> The PRV55 has set pressures from 0.01 barg (10 mbar) and the S2, from 0.02 barg.<\/li><li><strong>High set pressures.<\/strong> The S3 reaches 20 barg and the S1, 15 barg.<\/li><li><strong>Flow.<\/strong> For small flows, the PRV53, PRV54, and PRV55 (DN15 to DN25, Kv from 2 to 3.5 m\u00b3\/h). For large lines, the S1 (Kv up to 240 m\u00b3\/h) or the S3 (up to 130 m\u00b3\/h in DN100).<\/li><li><strong>Steam.<\/strong> S3 and S1 up to 220 \u00b0C, PRV54 up to 210 \u00b0C, and PRV55 up to 150 \u00b0C. The PRV53 is for liquids, compressed air, and inert gases.<\/li><li><strong>Construction.<\/strong> The PRV models are made of AISI 316L stainless steel; the S1, S2, and S3 are made of carbon steel or CF3M stainless, and in duplex or super duplex on request.<\/li><\/ul><section id=\"preguntas\" class=\"wp-block-group vf-post-faq is-layout-flow wp-block-group-is-layout-flow\"><h2 class=\"wp-block-heading\">Frequently asked questions<\/h2><details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary>What is set pressure?<\/summary><div class=\"wp-block-group is-layout-flow wp-block-group-is-layout-flow\"><p class=\"wp-block-paragraph\">It is the pressure at which the valve begins to open. It is set by the compression of the adjusting spring: compressing it raises it. Valfonta supplies the valves adjusted to the value specified in the order.<\/p><\/div><\/details><details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary>Does an excess pressure 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. It modulates to hold the upstream pressure, but it is not a safety accessory. If the installation needs overpressure protection, a <a href=\"\/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>Which model do I use for steam?<\/summary><div class=\"wp-block-group is-layout-flow wp-block-group-is-layout-flow\"><p class=\"wp-block-paragraph\">The <a href=\"\/en\/product\/pressure-relief-valve-s3\/\">S3<\/a> or the <a href=\"\/en\/product\/pressure-excess-valve-s1\/\">S1<\/a> up to 220 \u00b0C, the <a href=\"\/en\/product\/pressure-excess-valve-prv54\/\">PRV54<\/a> up to 210 \u00b0C, and the <a href=\"\/en\/product\/excess-pressure-valve-model-prv55\/\">PRV55<\/a> up to 150 \u00b0C. The S2 handles low-temperature steam with an external pressure sensing point and a condensate pot.<\/p><\/div><\/details><details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary>Which valve is suitable for pressures of a few millibars?<\/summary><div class=\"wp-block-group is-layout-flow wp-block-group-is-layout-flow\"><p class=\"wp-block-paragraph\">The <a href=\"\/en\/product\/excess-pressure-valve-model-prv55\/\">PRV55<\/a>, with set pressures from 0.01 barg (10 mbar), and the <a href=\"\/en\/product\/pressure-excess-valve-s2\/\">S2<\/a>, from 0.02 barg.<\/p><\/div><\/details><details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary>Where is the excess flow discharged?<\/summary><div class=\"wp-block-group is-layout-flow wp-block-group-is-layout-flow\"><p class=\"wp-block-paragraph\">To a return or recirculation line, to the tank or the pump suction, or to another lower-pressure zone. The S2, for example, lets a zone with excess pressure feed another lower-pressure zone without starving the main line.<\/p><\/div><\/details><\/section><\/div><aside class=\"wp-block-group vf-post-aside is-layout-flow wp-block-group-is-layout-flow\"><div class=\"wp-block-group vf-post-sticky is-layout-flow wp-block-group-is-layout-flow\"><nav class=\"wp-block-group vf-post-toc vfa-aria-label--Article%20contents is-layout-flow wp-block-group-is-layout-flow\"><p class=\"wp-block-paragraph\">In this article<\/p><ol class=\"wp-block-list\"><li><a href=\"#como-funciona-una-valvula-de-exceso-de-presion\">How an excess pressure valve works<\/a><\/li><li><a href=\"#exceso-de-presion-reductora-y-valvula-de-seguridad\">Excess pressure valve, reducing valve, and safety valve<\/a><\/li><li><a href=\"#que-podemos-ofrecerle-desde-valfonta\">What can Valfonta offer you?<\/a><\/li><li><a href=\"#los-modelos-de-exceso-de-presion-de-un-vistazo\">The excess pressure models at a glance<\/a><\/li><li><a href=\"#como-elegir-la-valvula-de-exceso-de-presion\">How to choose an excess pressure valve<\/a><\/li><li><a href=\"#preguntas\">Frequently asked questions<\/a><\/li><\/ol><\/nav><div class=\"wp-block-group vf-post-cta is-layout-flow wp-block-group-is-layout-flow\"><p class=\"vf-t wp-block-paragraph\">Do you need a pressure relief or excess pressure valve?<\/p><p class=\"wp-block-paragraph\">We help you choose the right model and size for your installation.<\/p><p class=\"vf-envolt wp-block-paragraph\"><a class=\"vf-btn vf-btn--pri\" href=\"#contactar\">Request a quote<\/a><\/p><p class=\"vf-envolt wp-block-paragraph\"><a class=\"vf-btn vf-btn--sec\" href=\"\/en\/pressure-relief-valve\/\">View pressure relief valves<\/a><\/p><p class=\"vf-tel wp-block-paragraph\">Or call <a href=\"tel:+34933720888\">933 720 888<\/a><\/p><\/div><\/div><\/aside><\/div><section id=\"valvulas\" class=\"wp-block-group is-layout-flow wp-block-group-is-layout-flow\"><h2 class=\"wp-block-heading\">Related valves<\/h2><ul class=\"vf-rel wp-block-list\"><li><a href=\"\/en\/product\/pressure-relief-valve-s3\/\"><img decoding=\"async\" src=\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/valvula-alivio-presion-s3-s4-perspectiva-400.webp\" alt=\"S3 pressure relief valve\" class=\"wp-image-10230\" width=\"300\" height=\"300\" loading=\"lazy\"><b>S3 pressure relief valve<\/b><span>From DN15 to DN150, PN40, set pressure up to 20 barg and 220 \u00b0C.<\/span><\/a><\/li><li><a href=\"\/en\/product\/pressure-excess-valve-s1\/\"><img decoding=\"async\" src=\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/ok-M1-S1-3D-700x700-1.jpg\" alt=\"S1 excess pressure valve\" class=\"wp-image-192\" width=\"300\" height=\"300\" loading=\"lazy\"><b>S1 excess pressure valve<\/b><span>From DN15 to DN150 and PN40, for steam up to 220 \u00b0C.<\/span><\/a><\/li><li><a href=\"\/en\/product\/pressure-excess-valve-s2\/\"><img decoding=\"async\" src=\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/ok-M2-PROVISIONAL-700x700-1.jpg\" alt=\"S2 excess pressure valve\" class=\"wp-image-193\" width=\"300\" height=\"300\" loading=\"lazy\"><b>S2 excess pressure valve<\/b><span>From DN15 to DN100, PN40, and set pressure from 0.02 barg.<\/span><\/a><\/li><\/ul><p class=\"vf-post-more wp-block-paragraph\"><a href=\"\/en\/pressure-relief-valve\/\">View all pressure relief valves \u2192<\/a><\/p><\/section><section id=\"articulos\" class=\"wp-block-group is-layout-flow wp-block-group-is-layout-flow\"><h2 class=\"wp-block-heading\">Related articles<\/h2><div class=\"wp-block-group vf-post-cards vf-t-ul is-layout-flow wp-block-group-is-layout-flow\"><div class=\"wp-block-group vf-t-li is-layout-flow wp-block-group-is-layout-flow\"><div class=\"wp-block-group vf-amb-enllac is-layout-flow wp-block-group-is-layout-flow\"><figure class=\"wp-block-image vf-img-suelta\"><img decoding=\"async\" src=\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/valvula-alivio-presion.png\" alt=\"\" class=\"wp-image-233\" width=\"400\" height=\"225\" loading=\"lazy\"><\/figure><div class=\"wp-block-group vf-in is-layout-flow wp-block-group-is-layout-flow\"><p class=\"vf-envolt wp-block-paragraph\"><small>Pressure relief valves<\/small><b>What are the main features of a pneumatic pressure relief valve?<\/b><span>5 min read<\/span><\/p><\/div><p class=\"vf-enllac wp-block-paragraph\"><a class=\"vf-enllac-estirat\" href=\"\/en\/blog\/pneumatic-pressure-relief-valve\/\" aria-label=\"Pressure relief valves What are the main features of a pneumatic pressure relief valve? 5 min read\"><\/a><\/p><\/div><\/div><div class=\"wp-block-group vf-t-li is-layout-flow wp-block-group-is-layout-flow\"><div class=\"wp-block-group vf-amb-enllac is-layout-flow wp-block-group-is-layout-flow\"><figure class=\"wp-block-image vf-img-suelta\"><img decoding=\"async\" src=\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/gas.jpg\" alt=\"\" class=\"wp-image-243\" width=\"400\" height=\"225\" loading=\"lazy\"><\/figure><div class=\"wp-block-group vf-in is-layout-flow wp-block-group-is-layout-flow\"><p class=\"vf-envolt wp-block-paragraph\"><small>Pressure relief valves<\/small><b>Valfonta pressure relief valves for fire protection<\/b><span>7 min read<\/span><\/p><\/div><p class=\"vf-enllac wp-block-paragraph\"><a class=\"vf-enllac-estirat\" href=\"\/en\/blog\/fire-protection-pressure-relief-valves\/\" aria-label=\"Pressure relief valves Valfonta pressure relief valves for fire protection 7 min read\"><\/a><\/p><\/div><\/div><div class=\"wp-block-group vf-t-li is-layout-flow wp-block-group-is-layout-flow\"><div class=\"wp-block-group vf-amb-enllac is-layout-flow wp-block-group-is-layout-flow\"><figure class=\"wp-block-image vf-img-suelta\"><img decoding=\"async\" src=\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/chattering-valvulas-alivio.webp\" alt=\"\" class=\"wp-image-222\" width=\"400\" height=\"225\" loading=\"lazy\"><\/figure><div class=\"wp-block-group vf-in is-layout-flow wp-block-group-is-layout-flow\"><p class=\"vf-envolt wp-block-paragraph\"><small>Pressure relief valves<\/small><b>How to prevent \u201cchattering\u201d (vibration) in pressure relief valves<\/b><span>13 min read<\/span><\/p><\/div><p class=\"vf-enllac wp-block-paragraph\"><a class=\"vf-enllac-estirat\" href=\"\/en\/blog\/chattering-in-pressure-relief-valves\/\" aria-label=\"Pressure relief valves How to prevent \u201cchattering\u201d (vibration) in pressure relief valves 13 min read\"><\/a><\/p><\/div><\/div><\/div><\/section><section id=\"contactar\" 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\">Can we help with your installation?<\/h2><p class=\"wp-block-paragraph\">Tell us the fluid, the inlet and outlet pressures, the temperature, and the flow rate, and we will recommend the right valve.<\/p><p class=\"vf-pdp-contact wp-block-paragraph\">You can also call <a href=\"tel:+34933720888\">933 720 888<\/a> or email <a href=\"mailto:valfonta@valfonta.com\">valfonta@valfonta.com<\/a>.<\/p><\/div>\n<div class=\"wpcf7 no-js\" id=\"wpcf7-f535-o1\" lang=\"en-US\" dir=\"ltr\" data-wpcf7-id=\"535\">\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\/posts\/743#wpcf7-f535-o1\" method=\"post\" class=\"wpcf7-form init vf-form wpcf7-acceptance-as-validation\" aria-label=\"Contact form\" novalidate=\"novalidate\" data-status=\"init\" toolname=\"consulta_contacto\" tooldescription=\"Send an enquiry to Valfonta, industrial valve manufacturer; a member of the team will reply.\">\n<fieldset class=\"hidden-fields-container\"><input type=\"hidden\" name=\"_wpcf7\" value=\"535\" \/><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-f535-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=\"1792703007.8df660707e6f541f\" \/>\n<\/fieldset>\n<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><label class=\"vf-full\">Reason for your inquiry<span class=\"wpcf7-form-control-wrap\" data-name=\"motivo\"><select class=\"wpcf7-form-control wpcf7-select\" aria-invalid=\"false\" name=\"motivo\"><option value=\"\">Select<\/option><option value=\"Request a quote\">Request a quote<\/option><option value=\"Technical advice on choosing a valve\">Technical advice on choosing a valve<\/option><option value=\"Spare parts or repair\">Spare parts or repair<\/option><option value=\"Documentation or certificates\">Documentation or certificates<\/option><option value=\"Other\">Other<\/option><\/select><\/span><\/label><label class=\"vf-full\">Message *<span class=\"wpcf7-form-control-wrap\" data-name=\"mensaje\"><textarea cols=\"40\" rows=\"5\" maxlength=\"2000\" class=\"wpcf7-form-control wpcf7-textarea wpcf7-validates-as-required\" aria-required=\"true\" aria-invalid=\"false\" placeholder=\"Tell us what you need: fluid, pressures, flow rate, model, or serial number\u2026\" 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 message\" \/><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=\"#contactar\">Request a quote<\/a><\/p><\/div><\/article><\/div><\/div>","protected":false},"excerpt":{"rendered":"<p>A self-regulating excess pressure valve stays closed while the inlet pressure is below the set pressure and opens proportionally when it is exceeded, discharging the excess flow to a return line, a tank, or a lower-pressure area.<\/p>\n","protected":false},"author":1,"featured_media":244,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_generate-full-width-content":"true","_generate-disable-headline":"true","rank_math_title":"Self-regulating excess pressure valves | Valfonta","rank_math_description":"Self-regulating excess pressure valves. Discover the features of the S1 and S2 models. Request information with no obligation.","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\":\"WebPage\",\"@id\":\"https:\/\/www.valfonta.com\/en\/blog\/self-regulating-excess-pressure-valves\/#webpage\",\"url\":\"https:\/\/www.valfonta.com\/en\/blog\/self-regulating-excess-pressure-valves\/\",\"name\":\"Self-regulating excess pressure valves | Valfonta\",\"description\":\"Self-regulating excess pressure valves. Discover the features of the S1 and S2 models. Request information with no obligation.\",\"isPartOf\":{\"@id\":\"https:\/\/www.valfonta.com\/#website\"},\"about\":{\"@id\":\"https:\/\/www.valfonta.com\/#organization\"},\"inLanguage\":\"en\",\"datePublished\":\"2024-06-20T08:56:28+02:00\",\"dateModified\":\"2026-09-30T10:00:00+02:00\",\"primaryImageOfPage\":{\"@id\":\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/valvulas-de-exceso-de-presion-autorreguladora-1.jpg\"},\"breadcrumb\":{\"@id\":\"https:\/\/www.valfonta.com\/en\/blog\/self-regulating-excess-pressure-valves\/#breadcrumb\"}},{\"@type\":\"ImageObject\",\"@id\":\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/valvulas-de-exceso-de-presion-autorreguladora-1.jpg\",\"url\":\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/valvulas-de-exceso-de-presion-autorreguladora-1.jpg\",\"caption\":\"Features of the S1 and S2 self-regulating excess pressure valves\",\"inLanguage\":\"en\"},{\"@type\":\"ImageObject\",\"@id\":\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/valvulas-de-exceso-de-presion-autorreguladora-1.jpg\",\"url\":\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/valvulas-de-exceso-de-presion-autorreguladora-1.jpg\",\"width\":\"1000\",\"height\":\"1000\",\"caption\":\"self-regulating excess pressure valves\",\"inLanguage\":\"en\"},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\/\/www.valfonta.com\/en\/blog\/self-regulating-excess-pressure-valves\/#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\/\/www.valfonta.com\/en\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"Blog\",\"item\":\"https:\/\/www.valfonta.com\/en\/blog\/\"},{\"@type\":\"ListItem\",\"position\":3,\"name\":\"Features of the S1 and S2 self-regulating excess pressure valves\",\"item\":\"https:\/\/www.valfonta.com\/en\/blog\/self-regulating-excess-pressure-valves\/\"}]},{\"@type\":\"BlogPosting\",\"keywords\":\"self-regulating excess pressure valves\",\"datePublished\":\"2024-06-20T08:56:28+02:00\",\"dateModified\":\"2026-09-30T10:00:00+02:00\",\"articleSection\":\"Pressure relief valves\",\"publisher\":{\"@id\":\"https:\/\/www.valfonta.com\/#organization\"},\"@id\":\"https:\/\/www.valfonta.com\/en\/blog\/self-regulating-excess-pressure-valves\/#richSnippet\",\"isPartOf\":{\"@id\":\"https:\/\/www.valfonta.com\/en\/blog\/self-regulating-excess-pressure-valves\/#webpage\"},\"image\":{\"@id\":\"https:\/\/www.valfonta.com\/wp-content\/uploads\/2026\/10\/valvulas-de-exceso-de-presion-autorreguladora-1.jpg\"},\"inLanguage\":\"en\",\"mainEntityOfPage\":{\"@id\":\"https:\/\/www.valfonta.com\/en\/blog\/self-regulating-excess-pressure-valves\/#webpage\"},\"headline\":\"Features of the S1 and S2 self-regulating excess pressure valves\",\"name\":\"Self-regulating excess pressure valves | Valfonta\",\"description\":\"Self-regulating excess pressure valves. Discover the features of the S1 and S2 models. Request information with no obligation.\",\"author\":{\"@id\":\"https:\/\/www.valfonta.com\/#organization\"},\"abstract\":\"A self-regulating excess pressure valve stays closed while the inlet pressure is below the set pressure and opens proportionally when it is exceeded, discharging the excess flow to a return line, a tank, or a lower-pressure zone. The Valfonta S1, with diaphragm and bellows, has set pressures from 0.5 to 15 barg and handles steam up to 220 \u00b0C; the S2, with diaphragm, has set pressures from 0.02 to 10 barg. Both require a condensate pot with steam or liquids above 125 \u00b0C. Neither replaces a safety valve.\"},{\"@type\":\"FAQPage\",\"@id\":\"https:\/\/www.valfonta.com\/en\/blog\/self-regulating-excess-pressure-valves\/#faq\",\"mainEntity\":[{\"@type\":\"Question\",\"name\":\"What is set pressure?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"It is the pressure at which the valve begins to open. It is set by the compression of the adjusting spring: compressing it raises it. Valfonta supplies the valves adjusted to the value specified in the order.\"}},{\"@type\":\"Question\",\"name\":\"Does an excess pressure valve replace a safety valve?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"No. It modulates to hold the upstream pressure, but it is not a safety accessory. If the installation needs overpressure protection, a safety valve must also be installed.\"}},{\"@type\":\"Question\",\"name\":\"Which model do I use for steam?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"The S3 or the S1 up to 220 \u00b0C, the PRV54 up to 210 \u00b0C, and the PRV55 up to 150 \u00b0C. The S2 handles low-temperature steam with an external pressure sensing point and a condensate pot.\"}},{\"@type\":\"Question\",\"name\":\"Which valve is suitable for pressures of a few millibars?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"The PRV55, with set pressures from 0.01 barg (10 mbar), and the S2, from 0.02 barg.\"}},{\"@type\":\"Question\",\"name\":\"Where is the excess flow discharged?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"To a return or recirculation line, to the tank or the pump suction, or to another lower-pressure zone. The S2, for example, lets a zone with excess pressure feed another lower-pressure zone without starving the main line.\"}}]}]}]","footnotes":"","_vg_translation_of":"507","_vg_lang":"en","_vg_wpml_state":"{\"lang\":\"en\",\"trid\":\"710\",\"src\":\"es\"}"},"categories":[37],"tags":[],"class_list":["post-743","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-relief-and-safety"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.valfonta.com\/en\/wp-json\/wp\/v2\/posts\/743","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.valfonta.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.valfonta.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.valfonta.com\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.valfonta.com\/en\/wp-json\/wp\/v2\/comments?post=743"}],"version-history":[{"count":4,"href":"https:\/\/www.valfonta.com\/en\/wp-json\/wp\/v2\/posts\/743\/revisions"}],"predecessor-version":[{"id":10295,"href":"https:\/\/www.valfonta.com\/en\/wp-json\/wp\/v2\/posts\/743\/revisions\/10295"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.valfonta.com\/en\/wp-json\/wp\/v2\/media\/244"}],"wp:attachment":[{"href":"https:\/\/www.valfonta.com\/en\/wp-json\/wp\/v2\/media?parent=743"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.valfonta.com\/en\/wp-json\/wp\/v2\/categories?post=743"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.valfonta.com\/en\/wp-json\/wp\/v2\/tags?post=743"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}