{"id":1383,"date":"2018-07-17T15:23:23","date_gmt":"2018-07-17T13:23:23","guid":{"rendered":"http:\/\/sibam89.fr\/?p=1383"},"modified":"2018-07-17T15:46:02","modified_gmt":"2018-07-17T13:46:02","slug":"net-positive-suction-head","status":"publish","type":"post","link":"https:\/\/sibam89.fr\/?p=1383","title":{"rendered":"Net Positive Suction Head"},"content":{"rendered":"<p style=\"text-align: justify;\"><span style=\"font-family: arial, helvetica, sans-serif; font-size: 13pt;\">La <span style=\"color: #005db4;\"><strong>tension de vapeur<\/strong><\/span> d\u2019un liquide correspond \u00e0 la pression absolue n\u00e9cessaire \u00e0 la surface de ce liquide pour \u00e9viter qu\u2019il ne se vaporise. Si la pression absolue \u00e0 la surface de ce dernier est inf\u00e9rieure \u00e0 cette tension de vapeur, il en r\u00e9sulte une vaporisation imm\u00e9diate donnant naissance \u00e0 des \u00ab\u00a0bulles\u00a0\u00bb qui vont aller se r\u00e9sorber dans les zones de plus haute pression\u00a0; c\u2019est le <span style=\"color: #005db4;\"><strong>ph\u00e9nom\u00e8ne de cavitation<\/strong><\/span> qui provoque\u00a0:<\/span><\/p>\n<ul style=\"text-align: justify;\">\n<li><span style=\"font-family: arial, helvetica, sans-serif; font-size: 13pt;\">la chute de la hauteur manom\u00e9trique,<\/span><\/li>\n<li><span style=\"font-family: arial, helvetica, sans-serif; font-size: 13pt;\">des bruits de cr\u00e9pitements dus \u00e0 la r\u00e9sorption des bulles,<\/span><\/li>\n<li><span style=\"font-family: arial, helvetica, sans-serif; font-size: 13pt;\">des vibrations de la pompe pouvant entra\u00eener une d\u00e9t\u00e9rioration m\u00e9canique,<\/span><\/li>\n<li><span style=\"font-family: arial, helvetica, sans-serif; font-size: 13pt;\">une usure de la roue par \u00e9rosion due aux variations de pressions locales tr\u00e8s importantes.<\/span><\/li>\n<\/ul>\n<p style=\"text-align: justify;\"><span style=\"font-family: arial, helvetica, sans-serif; font-size: 13pt;\">Afin d\u2019\u00e9viter ce ph\u00e9nom\u00e8ne, il faut prendre garde \u00e0 respecter la r\u00e8gle du <span style=\"color: #005db4;\"><strong>NPSH<\/strong><\/span> (Net Positive Suction Head).<\/span><\/p>\n<p style=\"text-align: justify;\"><span style=\"font-family: arial, helvetica, sans-serif; font-size: 13pt;\">Le <span style=\"color: #005db4;\"><strong>NPSH requis<\/strong><\/span> ou <span style=\"color: #005db4;\"><strong>constructeur<\/strong><\/span> d\u2019une pompe, exprim\u00e9 en m\u00e8tre de colonne d\u2019eau (mCE), indique la charge nette absolue minimum qui doit \u00eatre assur\u00e9e \u00e0 l\u2019entr\u00e9e de la pompe pour un fonctionnement correct. Laquelle valeur fait partie des caract\u00e9ristiques constructeur, elle est fournie par une courbe croissante en fonction du d\u00e9bit.<\/span><\/p>\n<p style=\"text-align: justify;\"><span style=\"font-family: arial, helvetica, sans-serif; font-size: 13pt;\">Le <span style=\"color: #005db4;\"><strong>NPSH disponible<\/strong><\/span> ou <span style=\"color: #005db4;\"><strong>r\u00e9seau<\/strong><\/span> est \u00e9gale \u00e0 la limite physique d\u2019aspiration du liquide corrig\u00e9e en fonction de l\u2019altitude et de la temp\u00e9rature (10,33 mCE pour de l\u2019eau \u00e0 temp\u00e9rature ambiante au niveau de la mer), \u00e0 laquelle sont soustraites les hauteur g\u00e9om\u00e9trique et pertes de charge du r\u00e9seau \u00e0 l\u2019aspiration de la pompe.<\/span><\/p>\n<p style=\"text-align: justify;\"><span style=\"font-family: arial, helvetica, sans-serif; font-size: 13pt;\">Il est indispensable que\u00a0:<\/span><\/p>\n<p style=\"text-align: center;\"><span style=\"font-family: arial, helvetica, sans-serif; font-size: 13pt;\"><span style=\"color: #005db4;\"><strong>NPSH disponible (r\u00e9seau) &gt; NPSH requis (constructeur) + 0,5 \u00e0 1 mCE<\/strong><\/span><\/span><\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify;\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-1385\" src=\"http:\/\/sibam89.fr\/wp-content\/uploads\/2018\/07\/NSPH-Wilo-495x400.jpg\" alt=\"\" width=\"600\" height=\"371\" srcset=\"https:\/\/sibam89.fr\/wp-content\/uploads\/2018\/07\/NSPH-Wilo-300x185.jpg 300w, https:\/\/sibam89.fr\/wp-content\/uploads\/2018\/07\/NSPH-Wilo-768x475.jpg 768w, https:\/\/sibam89.fr\/wp-content\/uploads\/2018\/07\/NSPH-Wilo-1030x637.jpg 1030w, https:\/\/sibam89.fr\/wp-content\/uploads\/2018\/07\/NSPH-Wilo-705x436.jpg 705w, https:\/\/sibam89.fr\/wp-content\/uploads\/2018\/07\/NSPH-Wilo-450x278.jpg 450w, https:\/\/sibam89.fr\/wp-content\/uploads\/2018\/07\/NSPH-Wilo.jpg 1273w\" sizes=\"auto, (max-width: 600px) 100vw, 600px\" \/><\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: center;\"><strong><span style=\"font-family: arial, helvetica, sans-serif; font-size: 13pt; color: #005db4;\">Attention, lorsque le d\u00e9bit de la pompe augmente\u00a0: le NSPH requis augmente et le NPSH disponible diminue.<\/span><\/strong><\/p>\n<p style=\"text-align: center;\"><strong><span style=\"font-family: arial, helvetica, sans-serif; font-size: 13pt; color: #005db4;\">Si NSPH dispo &lt; NSPH requis alors il y a cavitation.<\/span><\/strong><\/p>\n<p style=\"text-align: center;\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-1386 size-full aligncenter\" src=\"http:\/\/sibam89.fr\/wp-content\/uploads\/2018\/07\/NPSH.jpg\" alt=\"\" width=\"549\" height=\"361\" srcset=\"https:\/\/sibam89.fr\/wp-content\/uploads\/2018\/07\/NPSH.jpg 549w, https:\/\/sibam89.fr\/wp-content\/uploads\/2018\/07\/NPSH-300x197.jpg 300w, https:\/\/sibam89.fr\/wp-content\/uploads\/2018\/07\/NPSH-450x296.jpg 450w\" sizes=\"auto, (max-width: 549px) 100vw, 549px\" \/><\/p>\n","protected":false},"excerpt":{"rendered":"<p>La tension de vapeur d\u2019un liquide correspond \u00e0 la pression absolue n\u00e9cessaire \u00e0 la surface de ce liquide pour \u00e9viter qu\u2019il ne se vaporise. Si la pression absolue \u00e0 la surface de ce dernier est inf\u00e9rieure \u00e0 cette tension de vapeur, il en r\u00e9sulte une vaporisation imm\u00e9diate donnant naissance \u00e0 des \u00ab\u00a0bulles\u00a0\u00bb qui vont aller [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":1386,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4],"tags":[],"class_list":["post-1383","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-theorie-appliquee"],"_links":{"self":[{"href":"https:\/\/sibam89.fr\/index.php?rest_route=\/wp\/v2\/posts\/1383","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/sibam89.fr\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/sibam89.fr\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/sibam89.fr\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/sibam89.fr\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1383"}],"version-history":[{"count":5,"href":"https:\/\/sibam89.fr\/index.php?rest_route=\/wp\/v2\/posts\/1383\/revisions"}],"predecessor-version":[{"id":1391,"href":"https:\/\/sibam89.fr\/index.php?rest_route=\/wp\/v2\/posts\/1383\/revisions\/1391"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/sibam89.fr\/index.php?rest_route=\/wp\/v2\/media\/1386"}],"wp:attachment":[{"href":"https:\/\/sibam89.fr\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1383"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/sibam89.fr\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1383"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/sibam89.fr\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1383"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}