{"id":72483,"date":"2026-08-11T09:04:18","date_gmt":"2026-08-11T06:04:18","guid":{"rendered":"https:\/\/unox.com.tr\/valve-selection-dn-misconception-how-to-determine-the-correct-valve-size\/"},"modified":"2026-08-11T10:28:38","modified_gmt":"2026-08-11T07:28:38","slug":"valve-selection-dn-misconception-how-to-determine-the-correct-valve-size","status":"publish","type":"post","link":"https:\/\/unox.com.tr\/en\/valve-selection-dn-misconception-how-to-determine-the-correct-valve-size\/","title":{"rendered":"The DN Misconception in Valve Selection: How to Determine the Correct Valve Size"},"content":{"rendered":"\n<p class=\"wp-block-wd-paragraph wd-a4f52392\">Industrial <a href=\"https:\/\/unox.com.tr\/en\/valve-group\/\" data-type=\"link\" data-id=\"https:\/\/unox.com.tr\/vana\/\">valve <\/a>selection often begins with the DN (Nominal Diameter) value. When the pipeline diameter is known, it may seem sufficient to select a valve with the same DN rating. However, this approach can lead to incorrect valve selection, especially in systems where flow rate, pressure, and process conditions vary.  <\/p>\n\n<p class=\"wp-block-wd-paragraph wd-7c6ba7ae\">Because proper valve sizing depends on much more than the pipe diameter. It should be evaluated based on several parameters, including the type of fluid, flow rate, inlet and outlet pressure, pressure differential, temperature, flow velocity, and the valve\u2019s flow capacity.<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-0e516a92\">So, what does the DN value represent, and how is the correct valve size determined?<\/p>\n\n<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_86 counter-hierarchy ez-toc-counter ez-toc-grey ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">Sayfa \u0130\u00e7eri\u011fi<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Toggle Table of Content\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/unox.com.tr\/en\/valve-selection-dn-misconception-how-to-determine-the-correct-valve-size\/#What_Is_the_DN_Value\" >What Is the DN Value?<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/unox.com.tr\/en\/valve-selection-dn-misconception-how-to-determine-the-correct-valve-size\/#Do_the_Pipe_Diameter_and_Valve_Diameter_Have_to_Be_the_Same\" >Do the Pipe Diameter and Valve Diameter Have to Be the Same?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/unox.com.tr\/en\/valve-selection-dn-misconception-how-to-determine-the-correct-valve-size\/#What_Parameters_Should_Be_Considered_When_Sizing_a_Valve\" >What Parameters Should Be Considered When Sizing a Valve?<\/a><ul class='ez-toc-list-level-4' ><li class='ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/unox.com.tr\/en\/valve-selection-dn-misconception-how-to-determine-the-correct-valve-size\/#1_Flow_Rate\" >1. Flow Rate<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/unox.com.tr\/en\/valve-selection-dn-misconception-how-to-determine-the-correct-valve-size\/#2_Inlet_and_Outlet_Pressure\" >2. Inlet and Outlet Pressure<\/a><\/li><\/ul><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/unox.com.tr\/en\/valve-selection-dn-misconception-how-to-determine-the-correct-valve-size\/#Why_Is_the_Kv_Value_Important\" >Why Is the Kv Value Important?<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/unox.com.tr\/en\/valve-selection-dn-misconception-how-to-determine-the-correct-valve-size\/#How_Is_Kv_Determined\" >How Is Kv Determined?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"https:\/\/unox.com.tr\/en\/valve-selection-dn-misconception-how-to-determine-the-correct-valve-size\/#Is_It_Correct_to_Select_an_Oversized_Valve\" >Is It Correct to Select an Oversized Valve?<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-9\" href=\"https:\/\/unox.com.tr\/en\/valve-selection-dn-misconception-how-to-determine-the-correct-valve-size\/#What_Are_the_Risks_of_Selecting_an_Undersized_Valve\" >What Are the Risks of Selecting an Undersized Valve?<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-10\" href=\"https:\/\/unox.com.tr\/en\/valve-selection-dn-misconception-how-to-determine-the-correct-valve-size\/#Why_Is_the_Type_of_Fluid_Important_in_Valve_Sizing\" >Why Is the Type of Fluid Important in Valve Sizing?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-11\" href=\"https:\/\/unox.com.tr\/en\/valve-selection-dn-misconception-how-to-determine-the-correct-valve-size\/#Why_Should_Flow_Velocity_Be_Considered_in_Valve_Sizing\" >Why Should Flow Velocity Be Considered in Valve Sizing?<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-12\" href=\"https:\/\/unox.com.tr\/en\/valve-selection-dn-misconception-how-to-determine-the-correct-valve-size\/#How_Are_DN_Flow_Rate_and_Kv_Related\" >How Are DN, Flow Rate, and Kv Related?<\/a><ul class='ez-toc-list-level-4' ><li class='ez-toc-heading-level-4'><ul class='ez-toc-list-level-4' ><li class='ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-13\" href=\"https:\/\/unox.com.tr\/en\/valve-selection-dn-misconception-how-to-determine-the-correct-valve-size\/#7-Step_Checklist_for_Proper_Valve_Sizing\" >7-Step Checklist for Proper Valve Sizing<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-14\" href=\"https:\/\/unox.com.tr\/en\/valve-selection-dn-misconception-how-to-determine-the-correct-valve-size\/#The_Most_Common_Mistake_in_Valve_Selection\" >The Most Common Mistake in Valve Selection<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-15\" href=\"https:\/\/unox.com.tr\/en\/valve-selection-dn-misconception-how-to-determine-the-correct-valve-size\/#Preliminary_Sizing_with_the_UNOX_Kv_Cv_Calculator\" >Preliminary Sizing with the UNOX Kv &amp; Cv Calculator<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-16\" href=\"https:\/\/unox.com.tr\/en\/valve-selection-dn-misconception-how-to-determine-the-correct-valve-size\/#Conclusion_The_Right_Valve_Is_More_Than_Just_the_Right_DN\" >Conclusion: The Right Valve Is More Than Just the Right DN<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-17\" href=\"https:\/\/unox.com.tr\/en\/valve-selection-dn-misconception-how-to-determine-the-correct-valve-size\/#Lets_Briefly_Recap\" >Let\u2019s Briefly Recap<\/a><\/li><\/ul><\/li><\/ul><\/nav><\/div>\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"What_Is_the_DN_Value\"><\/span>What Is the DN Value?<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n<p class=\"wp-block-wd-paragraph wd-0e84ab6c\">DN is a sizing designation that indicates the nominal diameter of a valve or pipeline. Terms such as DN50, DN80, DN100, and DN150 are used to define the product\u2019s connection and nominal size classification. <\/p>\n\n<p class=\"wp-block-wd-paragraph wd-19f31656\">However, there is an important distinction to be made here:<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-e659b58a\"><strong>DN alone does not indicate how much fluid the valve can handle.<\/strong><\/p>\n\n<p class=\"wp-block-wd-paragraph wd-967cd94e\">For example, two different valves with the same DN rating can exhibit different flow performance depending on their design, valve type, internal geometry, and flow characteristics.<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-418bbcdc\">Therefore, the approach of \u201cIf the pipe is DN100, the valve should also be DN100\u201d may serve as a starting point in some applications, but it is not, by itself, a technical sizing method.<\/p>\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Do_the_Pipe_Diameter_and_Valve_Diameter_Have_to_Be_the_Same\"><\/span>Do the Pipe Diameter and Valve Diameter Have to Be the Same?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n<p class=\"wp-block-wd-paragraph wd-ed8406de\">It is not correct to say that the pipe and valve must have the same DN rating in every system.<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-d5b7cce0\">When sizing a valve, the primary objective is to select a valve that can reliably and effectively handle the flow rate required by the system. In addition to the pipe diameter, the operating flow rate and the pressure differential across the valve must also be taken into consideration. <\/p>\n\n<p class=\"wp-block-wd-paragraph wd-76c93ee4\">Especially in control valves, selecting a valve based solely on the line size;<\/p>\n\n<ul class=\"wp-block-list\">\n<li>can result in the valve being oversized,<\/li>\n\n\n\n<li>reduced control accuracy,<\/li>\n\n\n\n<li>unnecessary pressure losses,<\/li>\n\n\n\n<li>increased energy consumption,<\/li>\n\n\n\n<li>inefficient use of the valve\u2019s operating range,<\/li>\n<\/ul>\n\n<p class=\"wp-block-wd-paragraph wd-7e9aa2bb\">can cause.<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-e82015c3\">Similarly, selecting a valve that is too small can result in high flow velocities, excessive pressure loss, noise, vibration, and increased loads on the equipment.<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-c7aab3e8\">Therefore, the right approach is to answer the question, \u201cWhat flow rate does the system require under its operating conditions?\u201d before asking, \u201cWhat is the pipe DN?\u201d<\/p>\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"What_Parameters_Should_Be_Considered_When_Sizing_a_Valve\"><\/span>What Parameters Should Be Considered When Sizing a Valve?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n<p class=\"wp-block-wd-paragraph wd-055bc3c5\">To determine the correct <a href=\"https:\/\/www.unoxonline.com.tr\/urun-kategori\/vana\/\" data-type=\"link\" data-id=\"https:\/\/www.unoxonline.com.tr\/urun-kategori\/vana\/\" rel=\"nofollow noopener\" target=\"_blank\">valve <\/a>size, as much technical data as possible about the system should be collected.<\/p>\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"1_Flow_Rate\"><\/span>1. Flow Rate<span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n<p class=\"wp-block-wd-paragraph wd-a91c5906\">One of the first and most important parameters is the flow rate required by the system.<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-bcc6a967\">In liquid systems, flow rate is typically expressed in units such as m\u00b3\/h, while different units such as Nm\u00b3\/h may be used in gas applications. In steam systems, flow may instead be evaluated based on mass flow rate, such as kg\/h. <\/p>\n\n<p class=\"wp-block-wd-paragraph wd-f2f8e8ca\">As the flow rate increases, the valve\u2019s required flow capacity also changes.<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-896554eb\">Therefore, knowing only the pipe diameter is not sufficient to determine the correct valve size.<\/p>\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"2_Inlet_and_Outlet_Pressure\"><\/span>2. Inlet and Outlet Pressure<span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n<p class=\"wp-block-wd-paragraph wd-bbbfc75d\">The pressure values at the valve inlet and outlet also play a critical role in valve sizing.<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-677fd7cf\">The difference between these two values is one of the key parameters that determines the valve\u2019s operating conditions.<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-1b04e3ce\"><strong>\u0394P = P\u2081 \u2212 P\u2082<\/strong><\/p>\n\n<p class=\"wp-block-wd-paragraph wd-c9a2f9f6\">Where:<\/p>\n\n<ul class=\"wp-block-list\">\n<li>P\u2081: Valve inlet pressure<\/li>\n\n\n\n<li>P\u2082: Valve outlet pressure<\/li>\n\n\n\n<li>\u0394P: Pressure differential across the valve<\/li>\n<\/ul>\n\n<p class=\"wp-block-wd-paragraph wd-157719cf\">Especially in control valves, this value is directly used to determine the required flow coefficient.<\/p>\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Why_Is_the_Kv_Value_Important\"><\/span>Why Is the Kv Value Important?<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n<p class=\"wp-block-wd-paragraph wd-268e8c45\">One of the most important reasons why the DN value alone is not sufficient is the Kv value.<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-d7d09db5\">Kv is the flow coefficient that indicates how much flow capacity a valve has under a given pressure differential. UNOX\u2019s Kv\/Cv calculation tool also allows the Kv and Cv values required for a valve to be calculated using the relevant parameters for liquids, gases, and steam. <\/p>\n\n<p class=\"wp-block-wd-paragraph wd-6cd9c5eb\">Simply put:<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-80dee6c3\"><strong>As the Kv value increases, the valve\u2019s flow capacity also increases.<\/strong><\/p>\n\n<p class=\"wp-block-wd-paragraph wd-7d859bd6\">For example, two valves with the same DN rating may have different internal designs and flow coefficients. Therefore, it should not be assumed that these two valves will deliver the same performance based solely on their DN values. <\/p>\n\n<p class=\"wp-block-wd-paragraph wd-5e5ed66e\">Therefore, especially when selecting control valves, DN, Kv, and operating conditions should be evaluated together.<\/p>\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"How_Is_Kv_Determined\"><\/span>How Is Kv Determined?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n<p class=\"wp-block-wd-paragraph wd-4ec7f7b6\">The key parameters used in Kv calculations may vary depending on the application; however, in liquid systems, the following are particularly important:<\/p>\n\n<ul class=\"wp-block-list\">\n<li>Fluid density,<\/li>\n\n\n\n<li>Flow rate,<\/li>\n\n\n\n<li>Pressure differential across the valve<\/li>\n<\/ul>\n\n<p class=\"wp-block-wd-paragraph wd-111eccb8\">are taken into consideration.<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-40d5ebab\">In gas applications, additional parameters such as temperature and compressibility become important. In steam applications, other parameters, such as system pressure and mass flow rate, also need to be taken into consideration. <\/p>\n\n<p class=\"wp-block-wd-paragraph wd-f02038ea\">Therefore, a valve with the same DN rating cannot be sized in the same way for different fluids.<\/p>\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Is_It_Correct_to_Select_an_Oversized_Valve\"><\/span>Is It Correct to Select an Oversized Valve?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n<p class=\"wp-block-wd-paragraph wd-b71d7ffe\">At first glance, selecting a larger valve may seem like a safer choice.<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-25545189\">However, the assumption that \u201ca larger valve is a better valve\u201d is not correct.<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-bb5824ef\">An oversized valve, especially in control applications requiring modulation, may operate outside its ideal operating range. The valve may be forced to operate at a very low opening percentage, which can negatively affect control accuracy. <\/p>\n\n<p class=\"wp-block-wd-paragraph wd-265afa37\">In addition, unnecessarily selecting a high-capacity valve can also be economically inefficient in system design.<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-fcb094a8\">Therefore, the goal is not to select the largest valve possible, but to determine the correctly sized valve that meets the process requirements.<\/p>\n\n<h2 class=\"wp-block-wd-title title wd-0f222205\"><span class=\"ez-toc-section\" id=\"What_Are_the_Risks_of_Selecting_an_Undersized_Valve\"><\/span>What Are the Risks of Selecting an Undersized Valve?<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n<p class=\"wp-block-wd-paragraph wd-dcc47615\">At the other end of the spectrum is the selection of an undersized valve.<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-ea2f5dec\">When the valve capacity is insufficient to meet the system\u2019s required flow rate, a higher pressure differential may be required to achieve the necessary flow.<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-83ebecd2\">As a result, depending on the application:<\/p>\n\n<ul class=\"wp-block-list\">\n<li>Pressure loss may increase,<\/li>\n\n\n\n<li>Flow velocity may increase,<\/li>\n\n\n\n<li>Noise may occur,<\/li>\n\n\n\n<li>Vibration may occur,<\/li>\n\n\n\n<li>The valve and piping components may be subjected to greater stress,<\/li>\n\n\n\n<li>Energy consumption may increase.<\/li>\n<\/ul>\n\n<p class=\"wp-block-wd-paragraph wd-6bf78a5a\">Therefore, rather than making generalizations such as \u201cif the line is DN100, a DN80 valve will definitely be sufficient\u201d or \u201ca DN150 valve is safer,\u201d an engineering calculation should be carried out based on the actual operating conditions.<\/p>\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Why_Is_the_Type_of_Fluid_Important_in_Valve_Sizing\"><\/span>Why Is the Type of Fluid Important in Valve Sizing?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n<p class=\"wp-block-wd-paragraph wd-33c81b46\">The fluid flowing through the valve is one of the fundamental factors in the sizing process.<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-5266f2e7\">Water, oil, chemical liquids, air, natural gas, and steam do not exhibit the same flow behavior.<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-85ebbc08\">Especially in gas and steam applications, parameters such as fluid compressibility, temperature, and pressure conditions can directly affect the sizing calculation.<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-f0d5103b\">Therefore, when selecting a valve, it is important not to consider only:<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-35e14a5d\"><strong>\u201cWhat is the flow rate?\u201d<\/strong><\/p>\n\n<p class=\"wp-block-wd-paragraph wd-0fb61e2e\">rather than just asking,<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-d9677de6\"><strong>\u201cWhat fluid is flowing, at what temperature, and under what pressure conditions?\u201d<\/strong><\/p>\n\n<p class=\"wp-block-wd-paragraph wd-43939579\">must also be answered.<\/p>\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Why_Should_Flow_Velocity_Be_Considered_in_Valve_Sizing\"><\/span>Why Should Flow Velocity Be Considered in Valve Sizing?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n<p class=\"wp-block-wd-paragraph wd-05f2a334\">The flow velocity through the valve is another important parameter that affects system performance.<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-b23d11ff\">Excessively high flow velocity can contribute to issues such as increased pressure loss, noise, and vibration, depending on the application.<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-48f37301\">On the other hand, excessively low flow velocities can also prevent the process from operating efficiently in some applications.<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-df7dd675\">Therefore, proper valve selection should not be based solely on the criterion of \u201cbeing able to handle the maximum flow rate.\u201d The valve\u2019s behavior at its normal operating point should also be evaluated. <\/p>\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"How_Are_DN_Flow_Rate_and_Kv_Related\"><\/span>How Are DN, Flow Rate, and Kv Related?<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n<p class=\"wp-block-wd-paragraph wd-091dc216\">We can think of proper valve sizing as a simple chain:<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-8ea00baa\"><strong>Process requirement \u2192 Flow rate \u2192 Pressure conditions \u2192 Required Kv \u2192 Suitable valve type and DN<\/strong><\/p>\n\n<p class=\"wp-block-wd-paragraph wd-63bf32ca\">This approach is much more reliable than selecting a valve based solely on the pipe diameter.<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-6da01eb8\">For example, the presence of a DN100 pipe in a system does not automatically mean that a DN100 valve is the most appropriate choice. First, the required flow rate and the valve\u2019s operating conditions are determined. Then, the required flow capacity is evaluated to select the appropriate valve.  <\/p>\n\n<p class=\"wp-block-wd-paragraph wd-3b7a5582\">Here, DN is an important part of the sizing process, but it is not the final determining factor.<\/p>\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"7-Step_Checklist_for_Proper_Valve_Sizing\"><\/span>7-Step Checklist for Proper Valve Sizing<span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n<p class=\"wp-block-wd-paragraph wd-208508f2\">Before selecting an industrial valve, the following information should be checked:<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-ed188e5f\"><strong>1. Identify the fluid.<\/strong><br\/>Such as water, gas, steam, oil, or a chemical fluid.<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-5b8309f4\"><strong>2. Determine the design and operating flow rates.<br\/>Evaluate the normal and maximum flow rates separately whenever possible.<br\/><\/strong><\/p>\n\n<p class=\"wp-block-wd-paragraph wd-392547ad\"><strong>3. Determine the inlet and outlet pressures.<\/strong><br\/>Calculate the pressure differential across the valve under operating conditions.<br\/><\/p>\n\n<p class=\"wp-block-wd-paragraph wd-81192387\"><strong>4. Check the operating temperature.<\/strong><br\/>The suitability of the valve body and sealing components for the application should be evaluated.<br\/><\/p>\n\n<p class=\"wp-block-wd-paragraph wd-33fd907c\"><strong>5. Calculate the required Kv value.<br\/>Determine the required flow capacity based on the flow rate and pressure differential.<br\/><\/strong><\/p>\n\n<p class=\"wp-block-wd-paragraph wd-3aae09cc\"><strong>6. Select the appropriate valve type.<\/strong><br\/>Butterfly valves, ball valves, control valves, gate valves, knife gate valves, or other valve types should be evaluated based on the process requirements.<br\/><\/p>\n\n<p class=\"wp-block-wd-paragraph wd-11761733\"><strong>7. Evaluate the DN value together with the final selection criteria.<\/strong><br\/>The pipe diameter, connection standard, pressure class, and valve capacity should be checked together.<br\/><\/p>\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"The_Most_Common_Mistake_in_Valve_Selection\"><\/span>The Most Common Mistake in Valve Selection<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n<p class=\"wp-block-wd-paragraph wd-b38ecb3f\">One of the most common mistakes in valve selection is equating the pipe diameter with the valve size and considering the selection complete at that point.<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-ef7820f0\">DN, on the other hand, is only one part of the sizing process.<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-7aff4680\">For the correct selection, the flow rate, pressure differential, temperature, fluid properties, Kv value, valve type, and operating conditions should all be evaluated together.<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-4a38d88e\">Especially in critical industrial applications, an incorrectly sized valve can lead not only to performance issues but also to additional costs over time in terms of energy losses, maintenance requirements, and process continuity.<\/p>\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Preliminary_Sizing_with_the_UNOX_Kv_Cv_Calculator\"><\/span>Preliminary Sizing with the UNOX Kv &amp; Cv Calculator<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n<p class=\"wp-block-wd-paragraph wd-b7e28b31\">In the early stages of the valve selection process, UNOX provides a Kv &amp; Cv Calculator to help determine the required Kv\/Cv values.<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-b214b7c7\">For liquids, the tool can use density, inlet and outlet pressure, and flow rate; for gases, temperature and gas properties can also be entered; and for steam, the relevant pressure and mass flow rate values can be used.<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-37bf018b\"><a href=\"https:\/\/unox.com.tr\/en\/kv-cv-calculator\/?utm_source=chatgpt.com\">UNOX Kv &amp; Cv Calculator<\/a><\/p>\n\n<p class=\"wp-block-wd-paragraph wd-fe7baab7\">The results obtained here should be considered as a guide for preliminary sizing. Especially in critical processes, the final product selection should be made through expert engineering evaluation, taking all operating conditions of the system into account. UNOX also recommends treating the calculator results as guidance and consulting a qualified or authorized engineer for reliable final results. <\/p>\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Conclusion_The_Right_Valve_Is_More_Than_Just_the_Right_DN\"><\/span>Conclusion: The Right Valve Is More Than Just the Right DN<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n<p class=\"wp-block-wd-paragraph wd-1b549d55\">In industrial valve selection, DN is an important starting parameter. However, determining the correct valve size requires more than simply considering the pipe diameter. <\/p>\n\n<p class=\"wp-block-wd-paragraph wd-d2addc87\">The actual requirement;<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-8f0960e5\"><strong>Flow rate + pressure differential + fluid + temperature + Kv\/Cv + valve type + operating conditions<\/strong><\/p>\n\n<p class=\"wp-block-wd-paragraph wd-3ee35e14\">is determined by evaluating all these factors together.<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-fd73cc27\">Therefore, instead of approaching valve selection with the assumption that \u201cthe pipe is DN100, so the valve must be DN100,\u201d the right question to ask is: \u201cWhat flow capacity does this process require, and which valve will provide the most suitable operating performance under these conditions?\u201d<\/p>\n\n<p class=\"wp-block-wd-paragraph wd-4dfd5dcd\">A properly sized valve can contribute to more controlled, efficient, and reliable system operation. Especially in industrial facilities, selecting the right valve is not merely a purchasing decision; it is an engineering decision that can affect the system\u2019s long-term performance. <\/p>\n\n<h3 class=\"wp-block-wd-title title wd-4ebe1415\"><span class=\"ez-toc-section\" id=\"Lets_Briefly_Recap\"><\/span>Let\u2019s Briefly Recap<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n<p class=\"wp-block-wd-paragraph wd-200bf26c\"><strong>DN refers to the valve\u2019s nominal size; it does not, by itself, determine the valve\u2019s flow capacity.<\/strong><\/p>\n\n<p class=\"wp-block-wd-paragraph wd-bfb91c9b\"><strong>Kv is one of the critical parameters used to evaluate a valve\u2019s flow capacity.<\/strong><\/p>\n\n<p class=\"wp-block-wd-paragraph wd-5c788267\"><strong>Flow rate and pressure differential are fundamental inputs for valve sizing.<\/strong><\/p>\n\n<p class=\"wp-block-wd-paragraph wd-d84c62ae\"><strong>Selecting a valve that is either oversized or undersized can negatively affect system performance.<\/strong><\/p>\n\n<p class=\"wp-block-wd-paragraph wd-3602f671\"><strong>The most appropriate selection is made by evaluating all of the process\u2019s operating conditions together.<\/strong><\/p>\n\n<p class=\"wp-block-wd-paragraph wd-50660efd\"><\/p>\n\n<div class=\"wp-block-wd-gallery wd-grid-g wd-caption-mask wd-cb3bfc52\" style=\"--wd-col-lg:4;--wd-col-md:4;--wd-col-sm:1;--wd-gap-lg:20px;--wd-gap-sm: 10px;\">\n<div class=\"wp-block-wd-gallery-item wd-col wd-b40da7aa\"><div class=\"wd-block-image\"><img decoding=\"async\" width=\"1600\" height=\"1600\" class=\"wp-image-71853\" src=\"https:\/\/unox.com.tr\/wp-content\/themes\/woodmart\/images\/lazy.svg\" data-src=\"https:\/\/unox.com.tr\/wp-content\/uploads\/2026\/05\/pnomatik-aktuatorlu-u-pvc-kelebek-vana-1.webp\" alt=\"Pn&#xF6;matik Akt&#xFC;at&#xF6;rl&#xFC; U-PVC Kelebek Vana\" title=\"\" srcset=\"\" data-srcset=\"https:\/\/unox.com.tr\/wp-content\/uploads\/2026\/05\/pnomatik-aktuatorlu-u-pvc-kelebek-vana-1.webp 1600w, https:\/\/unox.com.tr\/wp-content\/uploads\/2026\/05\/pnomatik-aktuatorlu-u-pvc-kelebek-vana-1-400x400.webp 400w, https:\/\/unox.com.tr\/wp-content\/uploads\/2026\/05\/pnomatik-aktuatorlu-u-pvc-kelebek-vana-1-150x150.webp 150w, https:\/\/unox.com.tr\/wp-content\/uploads\/2026\/05\/pnomatik-aktuatorlu-u-pvc-kelebek-vana-1-768x768.webp 768w, https:\/\/unox.com.tr\/wp-content\/uploads\/2026\/05\/pnomatik-aktuatorlu-u-pvc-kelebek-vana-1-1536x1536.webp 1536w, https:\/\/unox.com.tr\/wp-content\/uploads\/2026\/05\/pnomatik-aktuatorlu-u-pvc-kelebek-vana-1-300x300.webp 300w, https:\/\/unox.com.tr\/wp-content\/uploads\/2026\/05\/pnomatik-aktuatorlu-u-pvc-kelebek-vana-1-600x600.webp 600w\" sizes=\"(max-width: 1600px) 100vw, 1600px\" \/><\/div><\/div>\n\n\n\n<div class=\"wp-block-wd-gallery-item wd-col wd-a21de480\"><div class=\"wd-block-image\"><img decoding=\"async\" width=\"1600\" height=\"1600\" class=\"wp-image-71800\" src=\"https:\/\/unox.com.tr\/wp-content\/themes\/woodmart\/images\/lazy.svg\" data-src=\"https:\/\/unox.com.tr\/wp-content\/uploads\/2026\/05\/pnomatik-aktuatorlu-u-pvc-kuresel-vana-3.webp\" alt=\"Pn&#xF6;matik Akt&#xFC;at&#xF6;rl&#xFC; U-PVC K&#xFC;resel Vana\" title=\"\" srcset=\"\" data-srcset=\"https:\/\/unox.com.tr\/wp-content\/uploads\/2026\/05\/pnomatik-aktuatorlu-u-pvc-kuresel-vana-3.webp 1600w, https:\/\/unox.com.tr\/wp-content\/uploads\/2026\/05\/pnomatik-aktuatorlu-u-pvc-kuresel-vana-3-400x400.webp 400w, https:\/\/unox.com.tr\/wp-content\/uploads\/2026\/05\/pnomatik-aktuatorlu-u-pvc-kuresel-vana-3-150x150.webp 150w, https:\/\/unox.com.tr\/wp-content\/uploads\/2026\/05\/pnomatik-aktuatorlu-u-pvc-kuresel-vana-3-768x768.webp 768w, https:\/\/unox.com.tr\/wp-content\/uploads\/2026\/05\/pnomatik-aktuatorlu-u-pvc-kuresel-vana-3-1536x1536.webp 1536w, https:\/\/unox.com.tr\/wp-content\/uploads\/2026\/05\/pnomatik-aktuatorlu-u-pvc-kuresel-vana-3-300x300.webp 300w, https:\/\/unox.com.tr\/wp-content\/uploads\/2026\/05\/pnomatik-aktuatorlu-u-pvc-kuresel-vana-3-600x600.webp 600w\" sizes=\"(max-width: 1600px) 100vw, 1600px\" \/><\/div><\/div>\n\n\n\n<div class=\"wp-block-wd-gallery-item wd-col wd-8669af05\"><div class=\"wd-block-image\"><img decoding=\"async\" width=\"1600\" height=\"1600\" class=\"wp-image-71752\" src=\"https:\/\/unox.com.tr\/wp-content\/themes\/woodmart\/images\/lazy.svg\" data-src=\"https:\/\/unox.com.tr\/wp-content\/uploads\/2026\/05\/pnomatik-aktuatorlu-lug-tip-kelebek-vana-4.webp\" alt=\"Pn&#xF6;matik Akt&#xFC;at&#xF6;rl&#xFC; Lug Tip Kelebek Vana\" title=\"\" srcset=\"\" data-srcset=\"https:\/\/unox.com.tr\/wp-content\/uploads\/2026\/05\/pnomatik-aktuatorlu-lug-tip-kelebek-vana-4.webp 1600w, https:\/\/unox.com.tr\/wp-content\/uploads\/2026\/05\/pnomatik-aktuatorlu-lug-tip-kelebek-vana-4-400x400.webp 400w, https:\/\/unox.com.tr\/wp-content\/uploads\/2026\/05\/pnomatik-aktuatorlu-lug-tip-kelebek-vana-4-150x150.webp 150w, https:\/\/unox.com.tr\/wp-content\/uploads\/2026\/05\/pnomatik-aktuatorlu-lug-tip-kelebek-vana-4-768x768.webp 768w, https:\/\/unox.com.tr\/wp-content\/uploads\/2026\/05\/pnomatik-aktuatorlu-lug-tip-kelebek-vana-4-1536x1536.webp 1536w, https:\/\/unox.com.tr\/wp-content\/uploads\/2026\/05\/pnomatik-aktuatorlu-lug-tip-kelebek-vana-4-300x300.webp 300w, https:\/\/unox.com.tr\/wp-content\/uploads\/2026\/05\/pnomatik-aktuatorlu-lug-tip-kelebek-vana-4-600x600.webp 600w\" sizes=\"(max-width: 1600px) 100vw, 1600px\" \/><\/div><\/div>\n\n\n\n<div class=\"wp-block-wd-gallery-item wd-col wd-fb3f09dc\"><div class=\"wd-block-image\"><img decoding=\"async\" class=\"wp-image-70112\" src=\"https:\/\/unox.com.tr\/wp-content\/themes\/woodmart\/images\/lazy.svg\" data-src=\"https:\/\/unox.com.tr\/wp-content\/uploads\/\" alt=\"\" title=\"\"><\/div><\/div>\n\n\n\n<div class=\"wp-block-wd-gallery-item wd-col wd-08d901be\"><div class=\"wd-block-image\"><img decoding=\"async\" width=\"1600\" height=\"1600\" class=\"wp-image-70163\" src=\"https:\/\/unox.com.tr\/wp-content\/themes\/woodmart\/images\/lazy.svg\" data-src=\"https:\/\/unox.com.tr\/wp-content\/uploads\/2020\/09\/batwech_wafer-tip-kelebek-vana-2.webp\" alt=\"Wafer Tip Kelebek Vana\" title=\"\" srcset=\"\" data-srcset=\"https:\/\/unox.com.tr\/wp-content\/uploads\/2020\/09\/batwech_wafer-tip-kelebek-vana-2.webp 1600w, https:\/\/unox.com.tr\/wp-content\/uploads\/2020\/09\/batwech_wafer-tip-kelebek-vana-2-400x400.webp 400w, https:\/\/unox.com.tr\/wp-content\/uploads\/2020\/09\/batwech_wafer-tip-kelebek-vana-2-150x150.webp 150w, https:\/\/unox.com.tr\/wp-content\/uploads\/2020\/09\/batwech_wafer-tip-kelebek-vana-2-768x768.webp 768w, https:\/\/unox.com.tr\/wp-content\/uploads\/2020\/09\/batwech_wafer-tip-kelebek-vana-2-1536x1536.webp 1536w, https:\/\/unox.com.tr\/wp-content\/uploads\/2020\/09\/batwech_wafer-tip-kelebek-vana-2-300x300.webp 300w, https:\/\/unox.com.tr\/wp-content\/uploads\/2020\/09\/batwech_wafer-tip-kelebek-vana-2-600x600.webp 600w\" sizes=\"(max-width: 1600px) 100vw, 1600px\" \/><\/div><\/div>\n\n\n\n<div class=\"wp-block-wd-gallery-item wd-col wd-0b71b291\"><div class=\"wd-block-image\"><img decoding=\"async\" width=\"1600\" height=\"1600\" class=\"wp-image-69827\" src=\"https:\/\/unox.com.tr\/wp-content\/themes\/woodmart\/images\/lazy.svg\" data-src=\"https:\/\/unox.com.tr\/wp-content\/uploads\/2020\/09\/batwech_Urun3-2.webp\" alt=\"Elektrik Akt&#xFC;at&#xF6;rl&#xFC; Wafer Tip Kelebek Vana\" title=\"\" srcset=\"\" data-srcset=\"https:\/\/unox.com.tr\/wp-content\/uploads\/2020\/09\/batwech_Urun3-2.webp 1600w, https:\/\/unox.com.tr\/wp-content\/uploads\/2020\/09\/batwech_Urun3-2-400x400.webp 400w, https:\/\/unox.com.tr\/wp-content\/uploads\/2020\/09\/batwech_Urun3-2-150x150.webp 150w, https:\/\/unox.com.tr\/wp-content\/uploads\/2020\/09\/batwech_Urun3-2-768x768.webp 768w, https:\/\/unox.com.tr\/wp-content\/uploads\/2020\/09\/batwech_Urun3-2-1536x1536.webp 1536w, https:\/\/unox.com.tr\/wp-content\/uploads\/2020\/09\/batwech_Urun3-2-300x300.webp 300w, https:\/\/unox.com.tr\/wp-content\/uploads\/2020\/09\/batwech_Urun3-2-600x600.webp 600w\" sizes=\"(max-width: 1600px) 100vw, 1600px\" \/><\/div><\/div>\n\n\n\n<div class=\"wp-block-wd-gallery-item wd-col wd-31c9d07e\"><div class=\"wd-block-image\"><img decoding=\"async\" width=\"1600\" height=\"1600\" class=\"wp-image-69855\" src=\"https:\/\/unox.com.tr\/wp-content\/themes\/woodmart\/images\/lazy.svg\" data-src=\"https:\/\/unox.com.tr\/wp-content\/uploads\/2020\/09\/batwech_2.webp\" alt=\"\" title=\"\" srcset=\"\" data-srcset=\"https:\/\/unox.com.tr\/wp-content\/uploads\/2020\/09\/batwech_2.webp 1600w, https:\/\/unox.com.tr\/wp-content\/uploads\/2020\/09\/batwech_2-400x400.webp 400w, https:\/\/unox.com.tr\/wp-content\/uploads\/2020\/09\/batwech_2-150x150.webp 150w, https:\/\/unox.com.tr\/wp-content\/uploads\/2020\/09\/batwech_2-768x768.webp 768w, https:\/\/unox.com.tr\/wp-content\/uploads\/2020\/09\/batwech_2-1536x1536.webp 1536w, https:\/\/unox.com.tr\/wp-content\/uploads\/2020\/09\/batwech_2-300x300.webp 300w, https:\/\/unox.com.tr\/wp-content\/uploads\/2020\/09\/batwech_2-600x600.webp 600w\" sizes=\"(max-width: 1600px) 100vw, 1600px\" \/><\/div><\/div>\n\n\n\n<div class=\"wp-block-wd-gallery-item wd-col wd-97716aa5\"><div class=\"wd-block-image\"><img decoding=\"async\" width=\"1600\" height=\"1600\" class=\"wp-image-69749\" src=\"https:\/\/unox.com.tr\/wp-content\/themes\/woodmart\/images\/lazy.svg\" data-src=\"https:\/\/unox.com.tr\/wp-content\/uploads\/2020\/09\/batwech_IKI1FL.webp\" alt=\"\" title=\"\" srcset=\"\" data-srcset=\"https:\/\/unox.com.tr\/wp-content\/uploads\/2020\/09\/batwech_IKI1FL.webp 1600w, https:\/\/unox.com.tr\/wp-content\/uploads\/2020\/09\/batwech_IKI1FL-400x400.webp 400w, https:\/\/unox.com.tr\/wp-content\/uploads\/2020\/09\/batwech_IKI1FL-150x150.webp 150w, https:\/\/unox.com.tr\/wp-content\/uploads\/2020\/09\/batwech_IKI1FL-768x768.webp 768w, https:\/\/unox.com.tr\/wp-content\/uploads\/2020\/09\/batwech_IKI1FL-1536x1536.webp 1536w, https:\/\/unox.com.tr\/wp-content\/uploads\/2020\/09\/batwech_IKI1FL-300x300.webp 300w, https:\/\/unox.com.tr\/wp-content\/uploads\/2020\/09\/batwech_IKI1FL-600x600.webp 600w\" sizes=\"(max-width: 1600px) 100vw, 1600px\" \/><\/div><\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>What Is the DN Value? Do the Pipe Diameter and Valve Diameter Have to Be the Same? What Parameters Should<\/p>\n","protected":false},"author":1,"featured_media":70179,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1715],"tags":[],"class_list":["post-72483","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-unox-blog"],"_links":{"self":[{"href":"https:\/\/unox.com.tr\/en\/wp-json\/wp\/v2\/posts\/72483","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/unox.com.tr\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/unox.com.tr\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/unox.com.tr\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/unox.com.tr\/en\/wp-json\/wp\/v2\/comments?post=72483"}],"version-history":[{"count":1,"href":"https:\/\/unox.com.tr\/en\/wp-json\/wp\/v2\/posts\/72483\/revisions"}],"predecessor-version":[{"id":72484,"href":"https:\/\/unox.com.tr\/en\/wp-json\/wp\/v2\/posts\/72483\/revisions\/72484"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/unox.com.tr\/en\/wp-json\/wp\/v2\/media\/70179"}],"wp:attachment":[{"href":"https:\/\/unox.com.tr\/en\/wp-json\/wp\/v2\/media?parent=72483"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/unox.com.tr\/en\/wp-json\/wp\/v2\/categories?post=72483"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/unox.com.tr\/en\/wp-json\/wp\/v2\/tags?post=72483"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}