{"id":61,"date":"2025-10-31T00:25:51","date_gmt":"2025-10-31T00:25:51","guid":{"rendered":"https:\/\/vibromera.eu\/glossary\/bpfi\/"},"modified":"2026-05-23T22:55:48","modified_gmt":"2026-05-23T22:55:48","slug":"bpfi","status":"publish","type":"glossary","link":"https:\/\/vibromera.eu\/bn\/glossary\/bpfi\/","title":{"rendered":"What is BPFI? Ball Pass Frequency Inner Race Explained"},"content":{"rendered":"<h1>Understanding BPFI \u2014 Ball Pass Frequency, Inner Race<\/h1>\n\t\t<section class=\"woocommerce hestia-shop products is-shortcode\" id=\"products\" data-sorder=\"hestia_shop\" >\n\t\t\t\t\t\t<div class=\"\">\n\t\t\t\t\t\t<div class=\"hestia-shop-content\">\n\t\t\t<div class=\"row\" data-aos=\"fade-up\" >\t\t\t\t\t<div class=\"col-ms-6 col-sm-6 col-md-3 shop-item\">\n\t\t\t\t\t\t<a href=\"https:\/\/vibromera.eu\/bn\/product\/balanset-1\/\" class=\"woocommerce-LoopProduct-link woocommerce-loop-product__link\">\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<div class=\"card-image\">\n\t\t\t\t\t\t\t\t\t<a href=\"https:\/\/vibromera.eu\/bn\/product\/balanset-1\/\" title=\"Portable balancer &#038; Vibration analyzer Balanset-1A\">\n\t\t\t\t\t\t\t\t\t\t<img loading=\"lazy\" decoding=\"async\" width=\"230\" height=\"153\" src=\"https:\/\/vibromera.eu\/wp-content\/uploads\/2023\/09\/77-e1693745667801-230x153.webp\" class=\"attachment-woocommerce_thumbnail size-woocommerce_thumbnail\" alt=\"Balanset-1A full kit portable balancer and vibration analyzer\" srcset=\"https:\/\/vibromera.eu\/wp-content\/uploads\/2023\/09\/77-e1693745667801-230x153.webp 230w, https:\/\/vibromera.eu\/wp-content\/uploads\/2023\/09\/77-e1693745667801-18x12.webp 18w, https:\/\/vibromera.eu\/wp-content\/uploads\/2023\/09\/77-e1693745667801-360x240.webp 360w, https:\/\/vibromera.eu\/wp-content\/uploads\/2023\/09\/77-e1693745667801-272x182.webp 272w\" sizes=\"auto, (max-width: 230px) 100vw, 230px\" \/>\t\t\t\t\t\t\t\t\t<\/a>\n\t\t\t\t\t\t\t\t\t<div class=\"ripple-container\"><\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<div class=\"content\">\n\t\t\t\t\t\t\t\t<span class=\"category\"><a href=\"https:\/\/vibromera.eu\/bn\/product-category\/devices\/\" rel=\"tag\">Devices<\/a><\/span>\n\t\t\t\t\t\t\t\t<h4 class=\"card-title\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<a class=\"shop-item-title-link\" href=\"https:\/\/vibromera.eu\/bn\/product\/balanset-1\/\" title=\"Portable balancer &#038; Vibration analyzer Balanset-1A\">Portable balancer &#038; Vibration analyzer Balanset-1A<\/a>\n\n\t\t\t\t\t\t\t\t<\/h4>\n\n\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t<div class=\"footer\">\n\n\t\t\t\t\t\t\t\t\t<div class=\"price\"><h4><span class=\"woocommerce-Price-amount amount\"><span class=\"woocommerce-Price-currencySymbol\">&euro;<\/span>1,975.00<\/span> + VAT (if applicable)<\/h4><\/div>\n\t\t\t\t\t\t\t\t\t<div class=\"stats\">\n\t\t\t\t\t\t\t\t\t\t<a rel=\"nofollow\" href=\"\/bn\/wp-json\/wp\/v2\/glossary\/61?add-to-cart=986\" data-quantity=\"1\" data-product_id=\"986\" data-product_sku=\"BS-1\" class=\"button product_type_simple add_to_cart_button ajax_add_to_cart btn btn-just-icon btn-simple btn-default\" title=\"\u0995\u09be\u09b0\u09cd\u099f\u09c7 \u09af\u09cb\u0997 \u0995\u09b0\u09c1\u09a8  \"><i rel=\"tooltip\" data-original-title=\"\u0995\u09be\u09b0\u09cd\u099f\u09c7 \u09af\u09cb\u0997 \u0995\u09b0\u09c1\u09a8  \" class=\"fas fa-cart-plus\"><\/i><\/a>\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/a><a href=\"\/bn\/wp-json\/wp\/v2\/glossary\/61?add-to-cart=986\" aria-describedby=\"woocommerce_loop_add_to_cart_link_describedby_986\" data-quantity=\"1\" class=\"button product_type_simple add_to_cart_button ajax_add_to_cart\" data-product_id=\"986\" data-product_sku=\"BS-1\" aria-label=\"\u0995\u09be\u09b0\u09cd\u099f\u09c7 \u09af\u09cb\u0997 \u0995\u09b0\u09c1\u09a8: &ldquo;Portable balancer &amp; Vibration analyzer Balanset-1A&rdquo;\" rel=\"nofollow\" data-success_message=\"\u0986\u09aa\u09a8\u09be\u09b0 \u0995\u09be\u09b0\u09cd\u099f\u09c7 &ldquo;Portable balancer &amp; Vibration analyzer Balanset-1A&rdquo; \u09af\u09cb\u0997 \u0995\u09b0\u09be \u09b9\u09af\u09bc\u09c7\u099b\u09c7\">\u0995\u09be\u09b0\u09cd\u099f\u09c7 \u09af\u09cb\u0997 \u0995\u09b0\u09c1\u09a8  <\/a>\t<span id=\"woocommerce_loop_add_to_cart_link_describedby_986\" class=\"screen-reader-text\">\n\t\t\t<\/span>\n\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t\t\t<div class=\"col-ms-6 col-sm-6 col-md-3 shop-item\">\n\t\t\t\t\t\t<a href=\"https:\/\/vibromera.eu\/bn\/product\/vibration-sensor\/\" class=\"woocommerce-LoopProduct-link woocommerce-loop-product__link\">\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<div class=\"card-image\">\n\t\t\t\t\t\t\t\t\t<a href=\"https:\/\/vibromera.eu\/bn\/product\/vibration-sensor\/\" title=\"Vibration sensor\">\n\t\t\t\t\t\t\t\t\t\t<img loading=\"lazy\" decoding=\"async\" width=\"230\" height=\"153\" src=\"https:\/\/vibromera.eu\/wp-content\/uploads\/2018\/05\/IMG-3-230x153.webp\" class=\"attachment-woocommerce_thumbnail size-woocommerce_thumbnail\" alt=\"Balanset-1A vibration sensor close-up\" srcset=\"https:\/\/vibromera.eu\/wp-content\/uploads\/2018\/05\/IMG-3-230x153.webp 230w, https:\/\/vibromera.eu\/wp-content\/uploads\/2018\/05\/IMG-3-600x400.webp 600w, https:\/\/vibromera.eu\/wp-content\/uploads\/2018\/05\/IMG-3-300x200.webp 300w, https:\/\/vibromera.eu\/wp-content\/uploads\/2018\/05\/IMG-3-768x512.webp 768w, https:\/\/vibromera.eu\/wp-content\/uploads\/2018\/05\/IMG-3-1024x682.webp 1024w, https:\/\/vibromera.eu\/wp-content\/uploads\/2018\/05\/IMG-3-272x182.webp 272w, https:\/\/vibromera.eu\/wp-content\/uploads\/2018\/05\/IMG-3.webp 1280w\" sizes=\"auto, (max-width: 230px) 100vw, 230px\" \/>\t\t\t\t\t\t\t\t\t<\/a>\n\t\t\t\t\t\t\t\t\t<div class=\"ripple-container\"><\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<div class=\"content\">\n\t\t\t\t\t\t\t\t<span class=\"category\"><a href=\"https:\/\/vibromera.eu\/bn\/product-category\/parts\/\" rel=\"tag\">Parts<\/a><\/span>\n\t\t\t\t\t\t\t\t<h4 class=\"card-title\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<a class=\"shop-item-title-link\" href=\"https:\/\/vibromera.eu\/bn\/product\/vibration-sensor\/\" title=\"Vibration sensor\">Vibration sensor<\/a>\n\n\t\t\t\t\t\t\t\t<\/h4>\n\n\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t<div class=\"footer\">\n\n\t\t\t\t\t\t\t\t\t<div class=\"price\"><h4><span class=\"woocommerce-Price-amount amount\"><span class=\"woocommerce-Price-currencySymbol\">&euro;<\/span>90.00<\/span> + VAT (if applicable)<\/h4><\/div>\n\t\t\t\t\t\t\t\t\t<div class=\"stats\">\n\t\t\t\t\t\t\t\t\t\t<a rel=\"nofollow\" href=\"\/bn\/wp-json\/wp\/v2\/glossary\/61?add-to-cart=1820\" data-quantity=\"1\" data-product_id=\"1820\" data-product_sku=\"VS-1\" class=\"button product_type_simple add_to_cart_button ajax_add_to_cart btn btn-just-icon btn-simple btn-default\" title=\"\u0995\u09be\u09b0\u09cd\u099f\u09c7 \u09af\u09cb\u0997 \u0995\u09b0\u09c1\u09a8  \"><i rel=\"tooltip\" data-original-title=\"\u0995\u09be\u09b0\u09cd\u099f\u09c7 \u09af\u09cb\u0997 \u0995\u09b0\u09c1\u09a8  \" class=\"fas fa-cart-plus\"><\/i><\/a>\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/a><a href=\"\/bn\/wp-json\/wp\/v2\/glossary\/61?add-to-cart=1820\" aria-describedby=\"woocommerce_loop_add_to_cart_link_describedby_1820\" data-quantity=\"1\" class=\"button product_type_simple add_to_cart_button ajax_add_to_cart\" data-product_id=\"1820\" data-product_sku=\"VS-1\" aria-label=\"\u0995\u09be\u09b0\u09cd\u099f\u09c7 \u09af\u09cb\u0997 \u0995\u09b0\u09c1\u09a8: &ldquo;Vibration sensor&rdquo;\" rel=\"nofollow\" data-success_message=\"\u0986\u09aa\u09a8\u09be\u09b0 \u0995\u09be\u09b0\u09cd\u099f\u09c7 &ldquo;Vibration sensor&rdquo; \u09af\u09cb\u0997 \u0995\u09b0\u09be \u09b9\u09af\u09bc\u09c7\u099b\u09c7\">\u0995\u09be\u09b0\u09cd\u099f\u09c7 \u09af\u09cb\u0997 \u0995\u09b0\u09c1\u09a8  <\/a>\t<span id=\"woocommerce_loop_add_to_cart_link_describedby_1820\" class=\"screen-reader-text\">\n\t\t\t<\/span>\n\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t\t\t<div class=\"col-ms-6 col-sm-6 col-md-3 shop-item\">\n\t\t\t\t\t\t<a href=\"https:\/\/vibromera.eu\/bn\/product\/optical-sensor-for-balanset-and-arbalance\/\" class=\"woocommerce-LoopProduct-link woocommerce-loop-product__link\">\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<div class=\"card-image\">\n\t\t\t\t\t\t\t\t\t<a href=\"https:\/\/vibromera.eu\/bn\/product\/optical-sensor-for-balanset-and-arbalance\/\" title=\"Optical Sensor (Laser Tachometer)\">\n\t\t\t\t\t\t\t\t\t\t<img loading=\"lazy\" decoding=\"async\" width=\"230\" height=\"153\" src=\"https:\/\/vibromera.eu\/wp-content\/uploads\/2022\/12\/ZKqzGXSCCBU-230x153.webp\" class=\"attachment-woocommerce_thumbnail size-woocommerce_thumbnail\" alt=\"Optical Sensor (Laser Tachometer)\" srcset=\"https:\/\/vibromera.eu\/wp-content\/uploads\/2022\/12\/ZKqzGXSCCBU-230x153.webp 230w, https:\/\/vibromera.eu\/wp-content\/uploads\/2022\/12\/ZKqzGXSCCBU-300x200.webp 300w, https:\/\/vibromera.eu\/wp-content\/uploads\/2022\/12\/ZKqzGXSCCBU-1024x682.webp 1024w, https:\/\/vibromera.eu\/wp-content\/uploads\/2022\/12\/ZKqzGXSCCBU-768x512.webp 768w, https:\/\/vibromera.eu\/wp-content\/uploads\/2022\/12\/ZKqzGXSCCBU-1536x1023.webp 1536w, https:\/\/vibromera.eu\/wp-content\/uploads\/2022\/12\/ZKqzGXSCCBU-18x12.webp 18w, https:\/\/vibromera.eu\/wp-content\/uploads\/2022\/12\/ZKqzGXSCCBU-360x240.webp 360w, https:\/\/vibromera.eu\/wp-content\/uploads\/2022\/12\/ZKqzGXSCCBU-460x306.webp 460w, https:\/\/vibromera.eu\/wp-content\/uploads\/2022\/12\/ZKqzGXSCCBU-600x400.webp 600w, https:\/\/vibromera.eu\/wp-content\/uploads\/2022\/12\/ZKqzGXSCCBU-272x182.webp 272w, https:\/\/vibromera.eu\/wp-content\/uploads\/2022\/12\/ZKqzGXSCCBU.webp 1600w\" sizes=\"auto, (max-width: 230px) 100vw, 230px\" \/>\t\t\t\t\t\t\t\t\t<\/a>\n\t\t\t\t\t\t\t\t\t<div class=\"ripple-container\"><\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<div class=\"content\">\n\t\t\t\t\t\t\t\t<span class=\"category\"><a href=\"https:\/\/vibromera.eu\/bn\/product-category\/parts\/\" rel=\"tag\">Parts<\/a><\/span>\n\t\t\t\t\t\t\t\t<h4 class=\"card-title\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<a class=\"shop-item-title-link\" href=\"https:\/\/vibromera.eu\/bn\/product\/optical-sensor-for-balanset-and-arbalance\/\" title=\"Optical Sensor (Laser Tachometer)\">Optical Sensor (Laser Tachometer)<\/a>\n\n\t\t\t\t\t\t\t\t<\/h4>\n\n\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t<div class=\"footer\">\n\n\t\t\t\t\t\t\t\t\t<div class=\"price\"><h4><span class=\"woocommerce-Price-amount amount\"><span class=\"woocommerce-Price-currencySymbol\">&euro;<\/span>124.00<\/span> + VAT (if applicable)<\/h4><\/div>\n\t\t\t\t\t\t\t\t\t<div class=\"stats\">\n\t\t\t\t\t\t\t\t\t\t<a rel=\"nofollow\" href=\"\/bn\/wp-json\/wp\/v2\/glossary\/61?add-to-cart=1832\" data-quantity=\"1\" data-product_id=\"1832\" data-product_sku=\"Tach-1\" class=\"button product_type_simple add_to_cart_button ajax_add_to_cart btn btn-just-icon btn-simple btn-default\" title=\"\u0995\u09be\u09b0\u09cd\u099f\u09c7 \u09af\u09cb\u0997 \u0995\u09b0\u09c1\u09a8  \"><i rel=\"tooltip\" data-original-title=\"\u0995\u09be\u09b0\u09cd\u099f\u09c7 \u09af\u09cb\u0997 \u0995\u09b0\u09c1\u09a8  \" class=\"fas fa-cart-plus\"><\/i><\/a>\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/a><a href=\"\/bn\/wp-json\/wp\/v2\/glossary\/61?add-to-cart=1832\" aria-describedby=\"woocommerce_loop_add_to_cart_link_describedby_1832\" data-quantity=\"1\" class=\"button product_type_simple add_to_cart_button ajax_add_to_cart\" data-product_id=\"1832\" data-product_sku=\"Tach-1\" aria-label=\"\u0995\u09be\u09b0\u09cd\u099f\u09c7 \u09af\u09cb\u0997 \u0995\u09b0\u09c1\u09a8: &ldquo;Optical Sensor (Laser Tachometer)&rdquo;\" rel=\"nofollow\" data-success_message=\"\u0986\u09aa\u09a8\u09be\u09b0 \u0995\u09be\u09b0\u09cd\u099f\u09c7 &ldquo;Optical Sensor (Laser Tachometer)&rdquo; \u09af\u09cb\u0997 \u0995\u09b0\u09be \u09b9\u09af\u09bc\u09c7\u099b\u09c7\">\u0995\u09be\u09b0\u09cd\u099f\u09c7 \u09af\u09cb\u0997 \u0995\u09b0\u09c1\u09a8  <\/a>\t<span id=\"woocommerce_loop_add_to_cart_link_describedby_1832\" class=\"screen-reader-text\">\n\t\t\t<\/span>\n\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t\t\t<div class=\"col-ms-6 col-sm-6 col-md-3 shop-item\">\n\t\t\t\t\t\t<a href=\"https:\/\/vibromera.eu\/bn\/product\/balanset-4\/\" class=\"woocommerce-LoopProduct-link woocommerce-loop-product__link\">\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<div class=\"card-image\">\n\t\t\t\t\t\t\t\t\t<a href=\"https:\/\/vibromera.eu\/bn\/product\/balanset-4\/\" title=\"Balanset-4\">\n\t\t\t\t\t\t\t\t\t\t<img loading=\"lazy\" decoding=\"async\" width=\"230\" height=\"153\" src=\"https:\/\/vibromera.eu\/wp-content\/uploads\/2022\/12\/balkom4-230x153.webp\" class=\"attachment-woocommerce_thumbnail size-woocommerce_thumbnail\" alt=\"Vibromera rotor balancing kit: carry case, multi-channel signal conditioner, handheld analyzer, magnetic base, vibration sensors, and coiled cables.\" srcset=\"https:\/\/vibromera.eu\/wp-content\/uploads\/2022\/12\/balkom4-230x153.webp 230w, https:\/\/vibromera.eu\/wp-content\/uploads\/2022\/12\/balkom4-300x200.webp 300w, https:\/\/vibromera.eu\/wp-content\/uploads\/2022\/12\/balkom4-18x12.webp 18w, https:\/\/vibromera.eu\/wp-content\/uploads\/2022\/12\/balkom4-360x240.webp 360w, https:\/\/vibromera.eu\/wp-content\/uploads\/2022\/12\/balkom4-460x306.webp 460w, https:\/\/vibromera.eu\/wp-content\/uploads\/2022\/12\/balkom4-600x400.webp 600w, https:\/\/vibromera.eu\/wp-content\/uploads\/2022\/12\/balkom4-272x182.webp 272w, https:\/\/vibromera.eu\/wp-content\/uploads\/2022\/12\/balkom4.webp 640w\" sizes=\"auto, (max-width: 230px) 100vw, 230px\" \/>\t\t\t\t\t\t\t\t\t<\/a>\n\t\t\t\t\t\t\t\t\t<div class=\"ripple-container\"><\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<div class=\"content\">\n\t\t\t\t\t\t\t\t<span class=\"category\"><a href=\"https:\/\/vibromera.eu\/bn\/product-category\/devices\/\" rel=\"tag\">Devices<\/a><\/span>\n\t\t\t\t\t\t\t\t<h4 class=\"card-title\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<a class=\"shop-item-title-link\" href=\"https:\/\/vibromera.eu\/bn\/product\/balanset-4\/\" title=\"Balanset-4\">Balanset-4<\/a>\n\n\t\t\t\t\t\t\t\t<\/h4>\n\n\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t<div class=\"footer\">\n\n\t\t\t\t\t\t\t\t\t<div class=\"price\"><h4><span class=\"woocommerce-Price-amount amount\"><span class=\"woocommerce-Price-currencySymbol\">&euro;<\/span>6,803.00<\/span> + VAT (if applicable)<\/h4><\/div>\n\t\t\t\t\t\t\t\t\t<div class=\"stats\">\n\t\t\t\t\t\t\t\t\t\t<a rel=\"nofollow\" href=\"\/bn\/wp-json\/wp\/v2\/glossary\/61?add-to-cart=1833\" data-quantity=\"1\" data-product_id=\"1833\" data-product_sku=\"BS-4\" class=\"button product_type_simple add_to_cart_button ajax_add_to_cart btn btn-just-icon btn-simple btn-default\" title=\"\u0995\u09be\u09b0\u09cd\u099f\u09c7 \u09af\u09cb\u0997 \u0995\u09b0\u09c1\u09a8  \"><i rel=\"tooltip\" data-original-title=\"\u0995\u09be\u09b0\u09cd\u099f\u09c7 \u09af\u09cb\u0997 \u0995\u09b0\u09c1\u09a8  \" class=\"fas fa-cart-plus\"><\/i><\/a>\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/a><a href=\"\/bn\/wp-json\/wp\/v2\/glossary\/61?add-to-cart=1833\" aria-describedby=\"woocommerce_loop_add_to_cart_link_describedby_1833\" data-quantity=\"1\" class=\"button product_type_simple add_to_cart_button ajax_add_to_cart\" data-product_id=\"1833\" data-product_sku=\"BS-4\" aria-label=\"\u0995\u09be\u09b0\u09cd\u099f\u09c7 \u09af\u09cb\u0997 \u0995\u09b0\u09c1\u09a8: &ldquo;Balanset-4&rdquo;\" rel=\"nofollow\" data-success_message=\"\u0986\u09aa\u09a8\u09be\u09b0 \u0995\u09be\u09b0\u09cd\u099f\u09c7 &ldquo;Balanset-4&rdquo; \u09af\u09cb\u0997 \u0995\u09b0\u09be \u09b9\u09af\u09bc\u09c7\u099b\u09c7\">\u0995\u09be\u09b0\u09cd\u099f\u09c7 \u09af\u09cb\u0997 \u0995\u09b0\u09c1\u09a8  <\/a>\t<span id=\"woocommerce_loop_add_to_cart_link_describedby_1833\" class=\"screen-reader-text\">\n\t\t\t<\/span>\n\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div><!-- \/.row --><div class=\"row\">\t\t\t\t\t<div class=\"col-ms-6 col-sm-6 col-md-3 shop-item\">\n\t\t\t\t\t\t<a href=\"https:\/\/vibromera.eu\/bn\/product\/magnet-stand\/\" class=\"woocommerce-LoopProduct-link woocommerce-loop-product__link\">\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<div class=\"card-image\">\n\t\t\t\t\t\t\t\t\t<a href=\"https:\/\/vibromera.eu\/bn\/product\/magnet-stand\/\" title=\"Magnetic Stand Insize-60-kgf\">\n\t\t\t\t\t\t\t\t\t\t<img loading=\"lazy\" decoding=\"async\" width=\"230\" height=\"153\" src=\"https:\/\/vibromera.eu\/wp-content\/uploads\/2018\/05\/IMG-36-230x153.webp\" class=\"attachment-woocommerce_thumbnail size-woocommerce_thumbnail\" alt=\"Magnet base.\" srcset=\"https:\/\/vibromera.eu\/wp-content\/uploads\/2018\/05\/IMG-36-230x153.webp 230w, https:\/\/vibromera.eu\/wp-content\/uploads\/2018\/05\/IMG-36-600x400.webp 600w, https:\/\/vibromera.eu\/wp-content\/uploads\/2018\/05\/IMG-36-300x200.webp 300w, https:\/\/vibromera.eu\/wp-content\/uploads\/2018\/05\/IMG-36-1024x682.webp 1024w, https:\/\/vibromera.eu\/wp-content\/uploads\/2018\/05\/IMG-36-768x512.webp 768w, https:\/\/vibromera.eu\/wp-content\/uploads\/2018\/05\/IMG-36-360x240.webp 360w, https:\/\/vibromera.eu\/wp-content\/uploads\/2018\/05\/IMG-36-272x182.webp 272w, https:\/\/vibromera.eu\/wp-content\/uploads\/2018\/05\/IMG-36.webp 1280w\" sizes=\"auto, (max-width: 230px) 100vw, 230px\" \/>\t\t\t\t\t\t\t\t\t<\/a>\n\t\t\t\t\t\t\t\t\t<div class=\"ripple-container\"><\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<div class=\"content\">\n\t\t\t\t\t\t\t\t<span class=\"category\"><a href=\"https:\/\/vibromera.eu\/bn\/product-category\/parts\/\" rel=\"tag\">Parts<\/a><\/span>\n\t\t\t\t\t\t\t\t<h4 class=\"card-title\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<a class=\"shop-item-title-link\" href=\"https:\/\/vibromera.eu\/bn\/product\/magnet-stand\/\" title=\"Magnetic Stand Insize-60-kgf\">Magnetic Stand Insize-60-kgf<\/a>\n\n\t\t\t\t\t\t\t\t<\/h4>\n\n\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t<div class=\"footer\">\n\n\t\t\t\t\t\t\t\t\t<div class=\"price\"><h4><span class=\"woocommerce-Price-amount amount\"><span class=\"woocommerce-Price-currencySymbol\">&euro;<\/span>46.00<\/span> + VAT (if applicable)<\/h4><\/div>\n\t\t\t\t\t\t\t\t\t<div class=\"stats\">\n\t\t\t\t\t\t\t\t\t\t<a rel=\"nofollow\" href=\"\/bn\/wp-json\/wp\/v2\/glossary\/61?add-to-cart=1852\" data-quantity=\"1\" data-product_id=\"1852\" data-product_sku=\"MS-1\" class=\"button product_type_simple add_to_cart_button ajax_add_to_cart btn btn-just-icon btn-simple btn-default\" title=\"\u0995\u09be\u09b0\u09cd\u099f\u09c7 \u09af\u09cb\u0997 \u0995\u09b0\u09c1\u09a8  \"><i rel=\"tooltip\" data-original-title=\"\u0995\u09be\u09b0\u09cd\u099f\u09c7 \u09af\u09cb\u0997 \u0995\u09b0\u09c1\u09a8  \" class=\"fas fa-cart-plus\"><\/i><\/a>\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/a><a href=\"\/bn\/wp-json\/wp\/v2\/glossary\/61?add-to-cart=1852\" aria-describedby=\"woocommerce_loop_add_to_cart_link_describedby_1852\" data-quantity=\"1\" class=\"button product_type_simple add_to_cart_button ajax_add_to_cart\" data-product_id=\"1852\" data-product_sku=\"MS-1\" aria-label=\"\u0995\u09be\u09b0\u09cd\u099f\u09c7 \u09af\u09cb\u0997 \u0995\u09b0\u09c1\u09a8: &ldquo;Magnetic Stand Insize-60-kgf&rdquo;\" rel=\"nofollow\" data-success_message=\"\u0986\u09aa\u09a8\u09be\u09b0 \u0995\u09be\u09b0\u09cd\u099f\u09c7 &ldquo;Magnetic Stand Insize-60-kgf&rdquo; \u09af\u09cb\u0997 \u0995\u09b0\u09be \u09b9\u09af\u09bc\u09c7\u099b\u09c7\">\u0995\u09be\u09b0\u09cd\u099f\u09c7 \u09af\u09cb\u0997 \u0995\u09b0\u09c1\u09a8  <\/a>\t<span id=\"woocommerce_loop_add_to_cart_link_describedby_1852\" class=\"screen-reader-text\">\n\t\t\t<\/span>\n\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t\t\t<div class=\"col-ms-6 col-sm-6 col-md-3 shop-item\">\n\t\t\t\t\t\t<a href=\"https:\/\/vibromera.eu\/bn\/product\/reflective-tape\/\" class=\"woocommerce-LoopProduct-link woocommerce-loop-product__link\">\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<div class=\"card-image\">\n\t\t\t\t\t\t\t\t\t<a href=\"https:\/\/vibromera.eu\/bn\/product\/reflective-tape\/\" title=\"Reflective tape\">\n\t\t\t\t\t\t\t\t\t\t<img loading=\"lazy\" decoding=\"async\" width=\"230\" height=\"153\" src=\"https:\/\/vibromera.eu\/wp-content\/uploads\/2023\/05\/s-l1600-230x153.webp\" class=\"attachment-woocommerce_thumbnail size-woocommerce_thumbnail\" alt=\"Reflective tape\" srcset=\"https:\/\/vibromera.eu\/wp-content\/uploads\/2023\/05\/s-l1600-230x153.webp 230w, https:\/\/vibromera.eu\/wp-content\/uploads\/2023\/05\/s-l1600-16x12.webp 16w, https:\/\/vibromera.eu\/wp-content\/uploads\/2023\/05\/s-l1600-360x240.webp 360w, https:\/\/vibromera.eu\/wp-content\/uploads\/2023\/05\/s-l1600-460x306.webp 460w, https:\/\/vibromera.eu\/wp-content\/uploads\/2023\/05\/s-l1600-272x182.webp 272w\" sizes=\"auto, (max-width: 230px) 100vw, 230px\" \/>\t\t\t\t\t\t\t\t\t<\/a>\n\t\t\t\t\t\t\t\t\t<div class=\"ripple-container\"><\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<div class=\"content\">\n\t\t\t\t\t\t\t\t<span class=\"category\"><a href=\"https:\/\/vibromera.eu\/bn\/product-category\/parts\/\" rel=\"tag\">Parts<\/a><\/span>\n\t\t\t\t\t\t\t\t<h4 class=\"card-title\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<a class=\"shop-item-title-link\" href=\"https:\/\/vibromera.eu\/bn\/product\/reflective-tape\/\" title=\"Reflective tape\">Reflective tape<\/a>\n\n\t\t\t\t\t\t\t\t<\/h4>\n\n\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t<div class=\"footer\">\n\n\t\t\t\t\t\t\t\t\t<div class=\"price\"><h4><span class=\"woocommerce-Price-amount amount\"><span class=\"woocommerce-Price-currencySymbol\">&euro;<\/span>10.00<\/span> + VAT (if applicable)<\/h4><\/div>\n\t\t\t\t\t\t\t\t\t<div class=\"stats\">\n\t\t\t\t\t\t\t\t\t\t<a rel=\"nofollow\" href=\"\/bn\/wp-json\/wp\/v2\/glossary\/61?add-to-cart=2329\" data-quantity=\"1\" data-product_id=\"2329\" data-product_sku=\"rt-1\" class=\"button product_type_simple add_to_cart_button ajax_add_to_cart btn btn-just-icon btn-simple btn-default\" title=\"\u0995\u09be\u09b0\u09cd\u099f\u09c7 \u09af\u09cb\u0997 \u0995\u09b0\u09c1\u09a8  \"><i rel=\"tooltip\" data-original-title=\"\u0995\u09be\u09b0\u09cd\u099f\u09c7 \u09af\u09cb\u0997 \u0995\u09b0\u09c1\u09a8  \" class=\"fas fa-cart-plus\"><\/i><\/a>\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/a><a href=\"\/bn\/wp-json\/wp\/v2\/glossary\/61?add-to-cart=2329\" aria-describedby=\"woocommerce_loop_add_to_cart_link_describedby_2329\" data-quantity=\"1\" class=\"button product_type_simple add_to_cart_button ajax_add_to_cart\" data-product_id=\"2329\" data-product_sku=\"rt-1\" aria-label=\"\u0995\u09be\u09b0\u09cd\u099f\u09c7 \u09af\u09cb\u0997 \u0995\u09b0\u09c1\u09a8: &ldquo;Reflective tape&rdquo;\" rel=\"nofollow\" data-success_message=\"\u0986\u09aa\u09a8\u09be\u09b0 \u0995\u09be\u09b0\u09cd\u099f\u09c7 &ldquo;Reflective tape&rdquo; \u09af\u09cb\u0997 \u0995\u09b0\u09be \u09b9\u09af\u09bc\u09c7\u099b\u09c7\">\u0995\u09be\u09b0\u09cd\u099f\u09c7 \u09af\u09cb\u0997 \u0995\u09b0\u09c1\u09a8  <\/a>\t<span id=\"woocommerce_loop_add_to_cart_link_describedby_2329\" class=\"screen-reader-text\">\n\t\t\t<\/span>\n\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t\t\t<div class=\"col-ms-6 col-sm-6 col-md-3 shop-item\">\n\t\t\t\t\t\t<a href=\"https:\/\/vibromera.eu\/bn\/product\/dynamic-balancer-balanset-1a\/\" class=\"woocommerce-LoopProduct-link woocommerce-loop-product__link\">\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<div class=\"card-image\">\n\t\t\t\t\t\t\t\t\t<a href=\"https:\/\/vibromera.eu\/bn\/product\/dynamic-balancer-balanset-1a\/\" title=\"Dynamic balancer \u201cBalanset-1A\u201d OEM\">\n\t\t\t\t\t\t\t\t\t\t<img loading=\"lazy\" decoding=\"async\" width=\"230\" height=\"153\" src=\"https:\/\/vibromera.eu\/wp-content\/uploads\/2021\/11\/\u0411\u0430\u043b\u043a\u043e\u043c\u041a\u0438\u0442-scaled-230x153.webp\" class=\"attachment-woocommerce_thumbnail size-woocommerce_thumbnail\" alt=\"Balanset-1A kit contents with interface unit, sensors, tachometer and accessories\" srcset=\"https:\/\/vibromera.eu\/wp-content\/uploads\/2021\/11\/\u0411\u0430\u043b\u043a\u043e\u043c\u041a\u0438\u0442-scaled-230x153.webp 230w, https:\/\/vibromera.eu\/wp-content\/uploads\/2021\/11\/\u0411\u0430\u043b\u043a\u043e\u043c\u041a\u0438\u0442-scaled-600x400.webp 600w, https:\/\/vibromera.eu\/wp-content\/uploads\/2021\/11\/\u0411\u0430\u043b\u043a\u043e\u043c\u041a\u0438\u0442-scaled-300x200.webp 300w, https:\/\/vibromera.eu\/wp-content\/uploads\/2021\/11\/\u0411\u0430\u043b\u043a\u043e\u043c\u041a\u0438\u0442-scaled-1024x683.webp 1024w, https:\/\/vibromera.eu\/wp-content\/uploads\/2021\/11\/\u0411\u0430\u043b\u043a\u043e\u043c\u041a\u0438\u0442-scaled-768x512.webp 768w, https:\/\/vibromera.eu\/wp-content\/uploads\/2021\/11\/\u0411\u0430\u043b\u043a\u043e\u043c\u041a\u0438\u0442-scaled-1536x1024.webp 1536w, https:\/\/vibromera.eu\/wp-content\/uploads\/2021\/11\/\u0411\u0430\u043b\u043a\u043e\u043c\u041a\u0438\u0442-scaled-2048x1366.webp 2048w, https:\/\/vibromera.eu\/wp-content\/uploads\/2021\/11\/\u0411\u0430\u043b\u043a\u043e\u043c\u041a\u0438\u0442-scaled-360x240.webp 360w, https:\/\/vibromera.eu\/wp-content\/uploads\/2021\/11\/\u0411\u0430\u043b\u043a\u043e\u043c\u041a\u0438\u0442-scaled-272x182.webp 272w, https:\/\/vibromera.eu\/wp-content\/uploads\/2021\/11\/\u0411\u0430\u043b\u043a\u043e\u043c\u041a\u0438\u0442-scaled-e1732998877834.webp 708w\" sizes=\"auto, (max-width: 230px) 100vw, 230px\" \/>\t\t\t\t\t\t\t\t\t<\/a>\n\t\t\t\t\t\t\t\t\t<div class=\"ripple-container\"><\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<div class=\"content\">\n\t\t\t\t\t\t\t\t<span class=\"category\"><a href=\"https:\/\/vibromera.eu\/bn\/product-category\/devices\/\" rel=\"tag\">Devices<\/a><\/span>\n\t\t\t\t\t\t\t\t<h4 class=\"card-title\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<a class=\"shop-item-title-link\" href=\"https:\/\/vibromera.eu\/bn\/product\/dynamic-balancer-balanset-1a\/\" title=\"Dynamic balancer \u201cBalanset-1A\u201d OEM\">Dynamic balancer \u201cBalanset-1A\u201d OEM<\/a>\n\n\t\t\t\t\t\t\t\t<\/h4>\n\n\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t<div class=\"footer\">\n\n\t\t\t\t\t\t\t\t\t<div class=\"price\"><h4><span class=\"woocommerce-Price-amount amount\"><span class=\"woocommerce-Price-currencySymbol\">&euro;<\/span>1,735.00<\/span> + VAT (if applicable)<\/h4><\/div>\n\t\t\t\t\t\t\t\t\t<div class=\"stats\">\n\t\t\t\t\t\t\t\t\t\t<a rel=\"nofollow\" href=\"\/bn\/wp-json\/wp\/v2\/glossary\/61?add-to-cart=4193\" data-quantity=\"1\" data-product_id=\"4193\" data-product_sku=\"BS-1OEM\" class=\"button product_type_simple add_to_cart_button ajax_add_to_cart btn btn-just-icon btn-simple btn-default\" title=\"\u0995\u09be\u09b0\u09cd\u099f\u09c7 \u09af\u09cb\u0997 \u0995\u09b0\u09c1\u09a8  \"><i rel=\"tooltip\" data-original-title=\"\u0995\u09be\u09b0\u09cd\u099f\u09c7 \u09af\u09cb\u0997 \u0995\u09b0\u09c1\u09a8  \" class=\"fas fa-cart-plus\"><\/i><\/a>\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/a><a href=\"\/bn\/wp-json\/wp\/v2\/glossary\/61?add-to-cart=4193\" aria-describedby=\"woocommerce_loop_add_to_cart_link_describedby_4193\" data-quantity=\"1\" class=\"button product_type_simple add_to_cart_button ajax_add_to_cart\" data-product_id=\"4193\" data-product_sku=\"BS-1OEM\" aria-label=\"\u0995\u09be\u09b0\u09cd\u099f\u09c7 \u09af\u09cb\u0997 \u0995\u09b0\u09c1\u09a8: &ldquo;Dynamic balancer \u201cBalanset-1A\u201d OEM&rdquo;\" rel=\"nofollow\" data-success_message=\"\u0986\u09aa\u09a8\u09be\u09b0 \u0995\u09be\u09b0\u09cd\u099f\u09c7 &ldquo;Dynamic balancer \u201cBalanset-1A\u201d OEM&rdquo; \u09af\u09cb\u0997 \u0995\u09b0\u09be \u09b9\u09af\u09bc\u09c7\u099b\u09c7\">\u0995\u09be\u09b0\u09cd\u099f\u09c7 \u09af\u09cb\u0997 \u0995\u09b0\u09c1\u09a8  <\/a>\t<span id=\"woocommerce_loop_add_to_cart_link_describedby_4193\" class=\"screen-reader-text\">\n\t\t\t<\/span>\n\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/section>\n\t\t\n<p><strong>BPFI<\/strong> (Ball Pass Frequency, Inner Race) is one of the four fundamental <a href=\"https:\/\/vibromera.eu\/glossary\/bearing-fault-frequencies\/\">bearing fault frequencies<\/a> and represents the rate at which rolling elements pass over a defect on the rotating inner race of a bearing. When a spall, crack, or pit forms on that inner raceway, every rolling element strikes the flaw as the race carries it past, generating periodic impacts that show up in the <a href=\"https:\/\/vibromera.eu\/glossary\/vibration\/\">vibration<\/a> signal at the BPFI frequency. What sets BPFI apart from the other characteristic frequencies is its near-constant escort of \u00b11\u00d7 <a href=\"https:\/\/vibromera.eu\/glossary\/sidebands\/\">sidebands<\/a> \u2014 a fingerprint that makes inner-race defects among the most confidently diagnosed faults in <a href=\"https:\/\/vibromera.eu\/glossary\/vibration-analysis\/\">vibration analysis<\/a>.<\/p>\n<h2>1. Definition: What is BPFI?<\/h2>\n<p>BPFI counts how many rolling-element passes occur over one point on the inner race per unit time. Because the inner race turns with the shaft while the elements orbit more slowly at cage speed, the relative motion between race and elements is high \u2014 and so is the frequency. The defect sits on the rotating race, so it is repeatedly hammered by each ball or roller that sweeps past. Together with the outer-race frequency (<a href=\"https:\/\/vibromera.eu\/glossary\/bpfo\/\">BPFO<\/a>), the cage frequency (<a href=\"https:\/\/vibromera.eu\/glossary\/ftf\/\">FTF<\/a>), and the rolling-element spin frequency (<a href=\"https:\/\/vibromera.eu\/glossary\/bsf\/\">BSF<\/a>), BPFI forms the standard set of frequencies an analyst calculates to localise damage within a bearing. The faults themselves belong to the wider topic of <a href=\"https:\/\/vibromera.eu\/glossary\/bearing-defects\/\">bearing defects<\/a>.<\/p>\n<h2>2. Mathematical Calculation<\/h2>\n<h3>Formula and variables<\/h3>\n<p>BPFI follows from bearing geometry and shaft speed:<\/p>\n<blockquote><p><strong>BPFI = (N \u00d7 n \/ 2) \u00d7 [1 \u2212 (Bd\/Pd) \u00b7 cos \u03b2]<\/strong><\/p><\/blockquote>\n<ul>\n<li><strong>N<\/strong> = number of rolling elements in the bearing.<\/li>\n<li><strong>n<\/strong> = shaft rotational frequency in Hz (or RPM \u00f7 60).<\/li>\n<li><strong>Bd<\/strong> = ball or roller diameter.<\/li>\n<li><strong>Pd<\/strong> = pitch diameter (the circle through the rolling-element centres).<\/li>\n<li><strong>\u03b2<\/strong> = contact angle.<\/li>\n<\/ul>\n<h3>Why BPFI is always higher than BPFO<\/h3>\n<p>For the same bearing, BPFI always exceeds BPFO, and the formula shows exactly why:<\/p>\n<ul>\n<li>The inner race rotates with the shaft, while the rolling elements orbit at roughly 0.4\u00d7 cage speed, so the relative velocity at the inner race is greater.<\/li>\n<li>BPFI uses the term [1 \u2212 Bd\/Pd], whereas BPFO uses [1 + Bd\/Pd].<\/li>\n<li>Subtracting a fraction from one keeps BPFI&#8217;s multiplier larger than BPFO&#8217;s.<\/li>\n<li>The typical ratio BPFI\/BPFO works out to about <strong>1.6\u20131.8<\/strong>.<\/li>\n<\/ul>\n<h3>Typical values<\/h3>\n<ul>\n<li>For common bearings, BPFI lands around <strong>5\u20137\u00d7 shaft speed<\/strong>.<\/li>\n<li><strong>Worked example:<\/strong> a 10-ball bearing at 1800 RPM (30 Hz) gives BPFI \u2248 173 Hz, about 5.8\u00d7 shaft speed.<\/li>\n<\/ul>\n<p>Rather than evaluate this by hand for every machine, most analysts read the value \u2014 alongside BPFO, BSF, and FTF \u2014 straight from the <a href=\"https:\/\/vibromera.eu\/calculators\/bearing-defect-frequencies\/\">Bearing Defect Frequency Calculator<\/a>, entering the bearing geometry and running speed once.<\/p>\n<h2>3. Physical Mechanism and Load-Zone Modulation<\/h2>\n<h3>The rotating defect<\/h3>\n<p>An inner-race flaw creates a situation the outer race never sees, because the defect itself moves:<\/p>\n<ol>\n<li>The defect rides on the rotating inner race.<\/li>\n<li>As the race turns, the flaw travels around the bearing circumference.<\/li>\n<li>Each rolling element strikes it on passing \u2014 that is the BPFI rate.<\/li>\n<li>But the force of each strike depends on where the defect sits relative to the load zone at that instant.<\/li>\n<\/ol>\n<h3>The load-zone effect<\/h3>\n<p>Every loaded bearing has a region \u2014 the load zone \u2014 where the rolling elements press hardest against the races. As the inner-race defect rotates through and out of this zone once per shaft turn, the impact strength rises and falls:<\/p>\n<ul>\n<li><strong>Defect inside the load zone:<\/strong> high contact force, a strong impact as each element strikes it.<\/li>\n<li><strong>Defect opposite the load zone:<\/strong> little or no contact force, a weak or absent impact.<\/li>\n<li><strong>Modulation frequency:<\/strong> the defect completes this cycle once per shaft revolution \u2014 i.e. at <a href=\"https:\/\/vibromera.eu\/glossary\/running-speed\/\">1\u00d7 running speed<\/a>.<\/li>\n<li><strong>Result:<\/strong> the BPFI impacts are amplitude-modulated at 1\u00d7 shaft speed.<\/li>\n<\/ul>\n<h3>Sideband generation<\/h3>\n<p>That amplitude modulation is what produces the diagnostic sideband comb:<\/p>\n<ul>\n<li><strong>Carrier frequency:<\/strong> BPFI.<\/li>\n<li><strong>Modulation frequency:<\/strong> 1\u00d7 shaft speed.<\/li>\n<li><strong>Sidebands:<\/strong> BPFI \u00b1 1\u00d7, BPFI \u00b1 2\u00d7, BPFI \u00b1 3\u00d7, symmetrically spaced about the carrier.<\/li>\n<li><strong>Diagnostic value:<\/strong> this regular 1\u00d7 sideband family is all but pathognomonic for an inner-race defect \u2014 and it is precisely what distinguishes BPFI from the FTF-spaced sidebands of a BSF fault.<\/li>\n<\/ul>\n<h2>4. Vibration Signature Characteristics<\/h2>\n<h3>Typical spectrum appearance<\/h3>\n<ul>\n<li><strong>Central peak<\/strong> at the BPFI frequency.<\/li>\n<li><strong>Sideband family<\/strong> of peaks at BPFI \u00b1 n\u00d7(1\u00d7).<\/li>\n<li><strong>Harmonic families<\/strong> at 2\u00d7BPFI and 3\u00d7BPFI, each carrying its own \u00b11\u00d7 sidebands.<\/li>\n<li><strong>Visual pattern:<\/strong> a &#8220;picket fence&#8221; or comb of evenly spaced peaks.<\/li>\n<\/ul>\n<h3>Why the envelope spectrum is decisive<\/h3>\n<p>Inner-race impacts excite high-frequency bearing resonances rather than depositing all their energy at BPFI directly, so a raw <a href=\"https:\/\/vibromera.eu\/glossary\/fft\/\">FFT<\/a> can look unremarkable in the early stages. <a href=\"https:\/\/vibromera.eu\/glossary\/envelope-analysis\/\">Envelope analysis<\/a> demodulates those resonant bursts, and in the resulting <a href=\"https:\/\/vibromera.eu\/glossary\/envelope-spectrum\/\">envelope spectrum<\/a> the BPFI peak dominates and the 1\u00d7 sidebands stand out with exceptional clarity \u2014 often months before the standard <a href=\"https:\/\/vibromera.eu\/glossary\/spectrum\/\">spectrum<\/a> shows anything. As the defect grows, the envelope amplitude climbs steeply.<\/p>\n<h2>5. Detection, Diagnosis, and Field Practice<\/h2>\n<h3>A reliable recognition sequence<\/h3>\n<ol>\n<li><strong>Calculate BPFI<\/strong> from the bearing model number or geometry.<\/li>\n<li><strong>Search the spectrum<\/strong> for a peak at the calculated frequency, allowing about \u00b15% tolerance.<\/li>\n<li><strong>Verify the \u00b11\u00d7 sidebands<\/strong> \u2014 the key confirming feature.<\/li>\n<li><strong>Check the harmonics<\/strong> (2\u00d7BPFI, 3\u00d7BPFI) for their own sidebands.<\/li>\n<li><strong>Assess amplitude<\/strong> against baseline or severity guidelines.<\/li>\n<li><strong>Confirm:<\/strong> BPFI plus 1\u00d7 sidebands equals an inner-race defect.<\/li>\n<\/ol>\n<p>In the field, the same workflow runs on a portable two-channel instrument. An analyst can mount an accelerometer on the bearing housing, capture the high-frequency vibration at operating speed, and screen the envelope on-site \u2014 the very kind of measure-it-where-it-runs task a tool such as the <a href=\"https:\/\/vibromera.eu\/product\/balanset-1\/\">Balanset-1A<\/a> is built for, doubling as a field vibration analyser alongside its rotor-balancing role.<\/p>\n<h3>BPFI versus BPFO at a glance<\/h3>\n<table border=\"1\" style=\"width:100%; border-collapse:collapse;\">\n<tr>\n<th>Feature<\/th>\n<th>BPFI (Inner Race)<\/th>\n<th>BPFO (Outer Race)<\/th>\n<\/tr>\n<tr>\n<td>Frequency<\/td>\n<td>Higher (5\u20137\u00d7 shaft speed)<\/td>\n<td>Lower (3\u20135\u00d7 shaft speed)<\/td>\n<\/tr>\n<tr>\n<td>Sidebands<\/td>\n<td>Almost always present (\u00b11\u00d7)<\/td>\n<td>May or may not be present<\/td>\n<\/tr>\n<tr>\n<td>Sideband pattern<\/td>\n<td>Very regular, clear spacing<\/td>\n<td>Less regular when present<\/td>\n<\/tr>\n<tr>\n<td>Occurrence<\/td>\n<td>Less common (~25% of failures)<\/td>\n<td>Most common (~40% of failures)<\/td>\n<\/tr>\n<\/table>\n<h2>6. Progression, Severity, and Remaining Life<\/h2>\n<h3>Defect development stages<\/h3>\n<ol>\n<li><strong>Initiation:<\/strong> a microscopic crack or pit forms; not yet detectable.<\/li>\n<li><strong>Incipient:<\/strong> a small BPFI peak emerges in the envelope spectrum (\u2248 0.1\u20130.5 g).<\/li>\n<li><strong>Early:<\/strong> a clear BPFI peak with one or two harmonics and sidebands (\u2248 0.5\u20132 g).<\/li>\n<li><strong>Moderate:<\/strong> multiple harmonics, prominent sidebands, a spall visible on inspection (\u2248 2\u201310 g).<\/li>\n<li><strong>Advanced:<\/strong> very high amplitude, numerous harmonics, a rising noise floor (> 10 g).<\/li>\n<li><strong>Severe:<\/strong> broadband noise dominates, the discrete peaks wash out, and catastrophic failure is imminent.<\/li>\n<\/ol>\n<h3>Remaining-life guidance<\/h3>\n<ul>\n<li><strong>Incipient to early:<\/strong> typically 6\u201318 months remaining.<\/li>\n<li><strong>Early to moderate:<\/strong> 3\u20136 months.<\/li>\n<li><strong>Moderate to advanced:<\/strong> 1\u20133 months.<\/li>\n<li><strong>Advanced to severe:<\/strong> days to weeks.<\/li>\n<li><strong>Caveat:<\/strong> the real timeline depends on load, speed, lubrication, and bearing size \u2014 figures are guides, not guarantees, and feed into any formal <a href=\"https:\/\/vibromera.eu\/glossary\/remaining-useful-life\/\">remaining useful life<\/a> estimate.<\/li>\n<\/ul>\n<h2>7. Causes and Corrective Actions<\/h2>\n<h3>Common causes of inner-race defects<\/h3>\n<ul>\n<li><strong>Fatigue:<\/strong> high-cycle subsurface fatigue from repetitive loading, the classic end-of-life mechanism.<\/li>\n<li><strong>Improper installation:<\/strong> mounting damage, such as driving the bearing on by striking the inner race.<\/li>\n<li><strong>Shaft damage:<\/strong> a rough or scored shaft seat causing fretting.<\/li>\n<li><strong>Excessive interference fit:<\/strong> over-tight press-fitting raising hoop stress.<\/li>\n<li><strong>Misalignment:<\/strong> non-uniform loading that accelerates fatigue.<\/li>\n<li><strong>Contamination:<\/strong> hard particles denting the raceway.<\/li>\n<li><strong>Lubrication failure:<\/strong> inadequate film leading to surface distress and <a href=\"https:\/\/vibromera.eu\/glossary\/spalling\/\">spalling<\/a>.<\/li>\n<\/ul>\n<h3>Response and replacement planning<\/h3>\n<p>On detection, step up the monitoring interval (monthly \u2192 weekly \u2192 daily as severity rises), schedule replacement for the next convenient outage, and trend the amplitude to forecast remaining life. Avoid lingering at <a href=\"https:\/\/vibromera.eu\/glossary\/critical-speed\/\">critical speeds<\/a> that could hasten failure. When planning the swap, order the correct bearing model, inspect the shaft (an advanced inner-race defect can score the seat), and run a root-cause review so the replacement does not fail the same way. Folded into a disciplined <a href=\"https:\/\/vibromera.eu\/glossary\/condition-monitoring\/\">condition monitoring<\/a> programme, BPFI detection becomes a cornerstone of bearing reliability \u2014 its unmistakable high-frequency peak with 1\u00d7 sidebands giving timely, unambiguous warning that prevents secondary damage to shafts and housings.<\/p>\n<hr>\n<p><a href=\"https:\/\/vibromera.eu\/glossary\/\">\u2190 Back to Main Index<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Learn about BPFI (Ball Pass Frequency Inner Race), the bearing fault frequency indicating inner race defects, characterized by high frequency and distinctive 1X sidebands.<\/p>","protected":false},"featured_media":0,"template":"","meta":{"ai_generated_summary":"","footnotes":""},"categories":[114,109],"tags":[],"class_list":["post-61","glossary","type-glossary","status-publish","hentry","category-analysis","category-glossary"],"_links":{"self":[{"href":"https:\/\/vibromera.eu\/bn\/wp-json\/wp\/v2\/glossary\/61","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/vibromera.eu\/bn\/wp-json\/wp\/v2\/glossary"}],"about":[{"href":"https:\/\/vibromera.eu\/bn\/wp-json\/wp\/v2\/types\/glossary"}],"version-history":[{"count":1,"href":"https:\/\/vibromera.eu\/bn\/wp-json\/wp\/v2\/glossary\/61\/revisions"}],"predecessor-version":[{"id":101426,"href":"https:\/\/vibromera.eu\/bn\/wp-json\/wp\/v2\/glossary\/61\/revisions\/101426"}],"wp:attachment":[{"href":"https:\/\/vibromera.eu\/bn\/wp-json\/wp\/v2\/media?parent=61"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/vibromera.eu\/bn\/wp-json\/wp\/v2\/categories?post=61"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/vibromera.eu\/bn\/wp-json\/wp\/v2\/tags?post=61"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}