{"id":72807,"date":"2025-12-09T19:03:48","date_gmt":"2025-12-09T19:03:48","guid":{"rendered":"https:\/\/discover.restek.com\/?p=72807"},"modified":"2026-01-09T21:42:07","modified_gmt":"2026-01-09T21:42:07","slug":"fittings-and-connections-part-2-compression-fitting-installation-and-tightening","status":"publish","type":"post","link":"https:\/\/discover.restek.com\/de\/blogs-de\/gnot5401\/fittings-and-connections-part-2-compression-fitting-installation-and-tightening","title":{"rendered":"Fittings and Connections Part 2: Compression Fitting Installation and Tightening"},"content":{"rendered":"\n<p>In the first part of this blog series I opened with a brief introduction into how compression fittings work, with a promise to dig into proper installation. Having used compression fittings for years and even helped plan and plumb out a lab renovation, I was pretty confident in my knowledge of compression fitting installation. A bit of research showed I was making some basic mistakes, so hopefully this blog will help you avoid them.<\/p>\n\n\n\n<p>First, a brief reminder that the gas seal on compression fittings is between the front ferrule, fitting body, and tube wall, as shown in Figure 1. This means that the threads do not contribute to the gas seal and using PTFE tape or other thread sealants can interfere with proper use of the fittings.<\/p>\n\n\n<div class=\"wp-block-custom-chromatogram-article-top\"><div class=\"chromatogram-article-placeholder\"><div class=\"figure-heading\"><strong>Figure 1:<\/strong> Compression Fitting Seal<\/div><div class='chromatogram-article-inner-full'><div class=\"chromatogram-article-inner\">\n\n<figure class=\"wp-block-image size-medium is-resized\"><img loading=\"lazy\" decoding=\"async\" width=\"300\" height=\"186\" src=\"https:\/\/discover.restek.com\/wp-content\/uploads\/blog-fittings-connections-2-fig-1--300x186.png\" alt=\"\" class=\"wp-image-75323\" style=\"width:506px;height:auto\" title=\"-\" srcset=\"https:\/\/discover.restek.com\/wp-content\/uploads\/blog-fittings-connections-2-fig-1--300x186.png 300w, https:\/\/discover.restek.com\/wp-content\/uploads\/blog-fittings-connections-2-fig-1--768x475.png 768w, https:\/\/discover.restek.com\/wp-content\/uploads\/blog-fittings-connections-2-fig-1-.png 979w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/figure>\n\n<\/div><\/div><\/div>\n\n\n<div style=\"height:30px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<p>With that out of the way, let\u2019s talk about the tools needed. The most basic things you\u2019ll need are wrenches, of course. Below are the most common wrench sizes needed for GC labs.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>9\/16\u201d \u2013 \u00bc\u201d compression fittings (used for main gas lines)<\/li>\n\n\n\n<li>7\/16\u201d \u2013 1\/8\u201d compression fittings (GC gas lines)<\/li>\n\n\n\n<li>\u00bd\u201d \u2013 Fitting unions (check size)<\/li>\n\n\n\n<li>\u00bc\u201d \u2013 1\/16\u201d fittings (sample valves and other sample introduction devices)<\/li>\n<\/ul>\n\n\n\n<p>It might be tempting to get an adjustable or crescent wrench since that will give you one wrench that will fit everything, but they often don\u2019t give you tight fits and can slip and strip fittings, especially brass ones. Fixed-size, open-ended wrenches are generally a better choice.<\/p>\n\n\n\n<p>Once you have the proper wrenches and fittings, you\u2019re ready for installation. Swagelok has a good guide for fitting installation but I\u2019ll give the highlights and some tips. (<a href=\"https:\/\/www.swagelok.com\/downloads\/webcatalogs\/EN\/MS-13-151.PDF\" target=\"_blank\" rel=\"noopener\">https:\/\/www.swagelok.com\/downloads\/webcatalogs\/EN\/MS-13-151.PDF<\/a>) <\/p>\n\n\n\n<p>First, lightly screw the nut into the body with the back ferrule and front ferrule in place, as shown in figure 2. The back ferrule should have its widest end toward the nut, and the front ferrule should taper towards the body.<\/p>\n\n\n<div class=\"wp-block-custom-chromatogram-article-top\"><div class=\"chromatogram-article-placeholder\"><div class=\"figure-heading\"><strong>Figure 2: <\/strong>Nut and ferrule install into body of compression fitting.<\/div><div class='chromatogram-article-inner-full'><div class=\"chromatogram-article-inner\">\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"436\" height=\"180\" src=\"https:\/\/discover.restek.com\/wp-content\/uploads\/blog-fittings-connections-2-fig-2.png\" alt=\"\" class=\"wp-image-75329\" title=\"-\" srcset=\"https:\/\/discover.restek.com\/wp-content\/uploads\/blog-fittings-connections-2-fig-2.png 436w, https:\/\/discover.restek.com\/wp-content\/uploads\/blog-fittings-connections-2-fig-2-300x124.png 300w\" sizes=\"auto, (max-width: 436px) 100vw, 436px\" \/><\/figure>\n\n<\/div><\/div><\/div>\n\n\n<div style=\"height:30px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<p>Next, push the tubing fully into the fitting until it bottoms out, as shown in figure 3. Make sure that the end of the tubing is cut evenly.<\/p>\n\n\n<div class=\"wp-block-custom-chromatogram-article-top\"><div class=\"chromatogram-article-placeholder\"><div class=\"figure-heading\"><strong>Figure 3: <\/strong>Tubing Installation<\/div><div class='chromatogram-article-inner-full'><div class=\"chromatogram-article-inner\">\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"462\" height=\"340\" src=\"https:\/\/discover.restek.com\/wp-content\/uploads\/blog-fittings-connections-2-fig-3.png\" alt=\"\" class=\"wp-image-75335\" title=\"-\" srcset=\"https:\/\/discover.restek.com\/wp-content\/uploads\/blog-fittings-connections-2-fig-3.png 462w, https:\/\/discover.restek.com\/wp-content\/uploads\/blog-fittings-connections-2-fig-3-300x221.png 300w\" sizes=\"auto, (max-width: 462px) 100vw, 462px\" \/><\/figure>\n\n<\/div><\/div><\/div>\n\n\n<div style=\"height:25px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<p>If the fitting is mounted on something sturdy, like an instrument, it\u2019s then easy to tighten. If you\u2019re using a union to tie 2 bits of tubing together it can be more difficult to hold things straight. My preferred way is to hold a wrench vertically in my hand with my thumb up, like I\u2019m the Fonz. Then I place the fitting into the wrench and drop my thumb down to hold it in place. I then use my other hand with the second wrench to tighten the fittings, as shown in figure 4.<\/p>\n\n\n<div class=\"wp-block-custom-chromatogram-article-top\"><div class=\"chromatogram-article-placeholder\"><div class=\"figure-heading\"><strong>Figure 4: Two-Wrench Setup for Tightening Union Fittings<\/strong><\/div><div class='chromatogram-article-inner-full'><div class=\"chromatogram-article-inner\">\n\n<figure class=\"wp-block-image size-full is-resized\"><img loading=\"lazy\" decoding=\"async\" width=\"186\" height=\"184\" src=\"https:\/\/discover.restek.com\/wp-content\/uploads\/blog-fittings-connections-2-fig-4b.png\" alt=\"\" class=\"wp-image-75362\" style=\"width:274px;height:auto\" title=\"-\"><\/figure>\n\n\n\n<figure class=\"wp-block-image size-full is-resized\"><img loading=\"lazy\" decoding=\"async\" width=\"198\" height=\"184\" src=\"https:\/\/discover.restek.com\/wp-content\/uploads\/blog-fittings-connections-2-fig-4c.png\" alt=\"\" class=\"wp-image-75368\" style=\"width:274px;height:auto\" title=\"-\"><\/figure>\n\n<\/div><\/div><\/div>\n\n\n<div style=\"height:25px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<p>If you\u2019re using a Tee fitting, it can be difficult to hold it in place and tighten the top fitting. While you can angle the wrench across the body to hold it steady, a better option is to use a Tee wrench (cat.# 22623).<\/p>\n\n\n<div class=\"wp-block-custom-chromatogram-article-top\"><div class=\"chromatogram-article-placeholder\"><div class=\"figure-heading\"><strong>Figure 5: <\/strong>Angled Wrench and Tee Wrench on Tee Fittings<\/div><div class='chromatogram-article-inner-full'><div class=\"chromatogram-article-inner\">\n\n<p>Angled Wrench<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"328\" height=\"222\" src=\"https:\/\/discover.restek.com\/wp-content\/uploads\/blog-fittings-connections-2-fig-5a.png\" alt=\"\" class=\"wp-image-75377\" title=\"-\" srcset=\"https:\/\/discover.restek.com\/wp-content\/uploads\/blog-fittings-connections-2-fig-5a.png 328w, https:\/\/discover.restek.com\/wp-content\/uploads\/blog-fittings-connections-2-fig-5a-300x203.png 300w\" sizes=\"auto, (max-width: 328px) 100vw, 328px\" \/><\/figure>\n\n\n\n<p>Tee Wrench<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"276\" height=\"222\" src=\"https:\/\/discover.restek.com\/wp-content\/uploads\/blog-fittings-connections-2-fig-5b.png\" alt=\"\" class=\"wp-image-75384\" title=\"-\"><\/figure>\n\n<\/div><\/div><\/div>\n\n\n<p>From there, the amount to tighten the fitting is important, and is something that I found I didn\u2019t understand as well as I thought. Swagelok\u2019s recommendation is to tighten 1\/16\u201d and 1\/8\u201d fittings by \u00be of a turn, and 1\/4\u201d fittings by 1 and \u00bc turns (see figure 5). I have been installing compression fittings by feel, and while I\u2019ve been pretty close on the smaller sizes, I definitely haven\u2019t been going more than a full turn for most \u00bc\u201d fittings.<\/p>\n\n\n<div class=\"wp-block-custom-chromatogram-article-top\"><div class=\"chromatogram-article-placeholder\"><div class=\"figure-heading\"><strong>Figure 6: <\/strong>Proper Tightening for Compression Fittings &gt;3\/16\u201d<\/div><div class='chromatogram-article-inner-full'><div class=\"chromatogram-article-inner\">\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"362\" height=\"294\" src=\"https:\/\/discover.restek.com\/wp-content\/uploads\/blog-fittings-connections-2-fig-6.png\" alt=\"\" class=\"wp-image-75390\" title=\"-\" srcset=\"https:\/\/discover.restek.com\/wp-content\/uploads\/blog-fittings-connections-2-fig-6.png 362w, https:\/\/discover.restek.com\/wp-content\/uploads\/blog-fittings-connections-2-fig-6-300x244.png 300w\" sizes=\"auto, (max-width: 362px) 100vw, 362px\" \/><\/figure>\n\n<\/div><\/div><\/div>\n\n\n<div style=\"height:25px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<p>Another way to ensure proper tightening is to use a gap inspection gauge, which can be used to measure how close the nut is to the fitting. We offer a gauge that works for \u00bc\u201d, \u00bd\u201d, and 3\/8\u201d (cat.# 22624), but other sizes can be purchased from Swagelok. I went and checked some \u00bc\u201d fittings I\u2019d installed with the gap inspection gauge and sure enough several of them were under-tightened. Even though they were all leak free, better tightening will likely make future connections seal more consistently.<\/p>\n\n\n\n<p>It can be tempting to overtighten fittings if leaks are found, but that can cause several issues. On the fitting side, it can flare out the fitting where it meets the ferrule, making it difficult or impossible to remove or reinstall fittings. An example is shown in figures 6 and 7.<\/p>\n\n\n<div class=\"wp-block-custom-chromatogram-article-top\"><div class=\"chromatogram-article-placeholder\"><div class=\"figure-heading\"><strong>Figure 7<\/strong>: Comparison of a Damaged, Flared Fitting to a Normal One<\/div><div class='chromatogram-article-inner-full'><div class=\"chromatogram-article-inner\">\n\n<p>Flared Fitting<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"492\" height=\"320\" src=\"https:\/\/discover.restek.com\/wp-content\/uploads\/blog-fittings-connections-2-fig-7.png\" alt=\"\" class=\"wp-image-75396\" title=\"-\" srcset=\"https:\/\/discover.restek.com\/wp-content\/uploads\/blog-fittings-connections-2-fig-7.png 492w, https:\/\/discover.restek.com\/wp-content\/uploads\/blog-fittings-connections-2-fig-7-300x195.png 300w\" sizes=\"auto, (max-width: 492px) 100vw, 492px\" \/><\/figure>\n\n\n\n<p>Normal Fitting<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"492\" height=\"340\" src=\"https:\/\/discover.restek.com\/wp-content\/uploads\/blog-fittings-connections-2-fig-7b.png\" alt=\"\" class=\"wp-image-75402\" title=\"-\" srcset=\"https:\/\/discover.restek.com\/wp-content\/uploads\/blog-fittings-connections-2-fig-7b.png 492w, https:\/\/discover.restek.com\/wp-content\/uploads\/blog-fittings-connections-2-fig-7b-300x207.png 300w\" sizes=\"auto, (max-width: 492px) 100vw, 492px\" \/><\/figure>\n\n<\/div><\/div><\/div>\n\n\n<div style=\"height:25px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<p>Another issue that can happen is the compression of the tube itself. Since the end of the tubing should be bottomed out when installing, overtightening can squeeze the tubing and cause it to bulge out ahead of the ferrule, especially with softer tubing like copper. This can cause the tubing to get stuck in the fitting, making it difficult to remove. The fitting itself can be deformed as well, making it difficult to re-seal it if new fittings are installed. An example is shown in figures 8 and 9.<\/p>\n\n\n<div class=\"wp-block-custom-chromatogram-article-top\"><div class=\"chromatogram-article-placeholder\"><div class=\"figure-heading\"><strong>Figure 8: <\/strong>Tubing Stuck in Fitting Due to Overtightening<\/div><div class='chromatogram-article-inner-full'><div class=\"chromatogram-article-inner\">\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"524\" height=\"248\" src=\"https:\/\/discover.restek.com\/wp-content\/uploads\/blog-fittings-connections-2-fig-8.png\" alt=\"\" class=\"wp-image-75408\" title=\"-\" srcset=\"https:\/\/discover.restek.com\/wp-content\/uploads\/blog-fittings-connections-2-fig-8.png 524w, https:\/\/discover.restek.com\/wp-content\/uploads\/blog-fittings-connections-2-fig-8-300x142.png 300w\" sizes=\"auto, (max-width: 524px) 100vw, 524px\" \/><\/figure>\n\n<\/div><\/div><\/div>\n\n\n<div style=\"height:25px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n<div class=\"wp-block-custom-chromatogram-article-top\"><div class=\"chromatogram-article-placeholder\"><div class=\"figure-heading\"><strong>Figure 9: <\/strong>Correctly Tightened Tubing (Left) and Overtightened Tubing (Right) Showing Bulging Due to Over-Compression of the Ferrule<\/div><div class='chromatogram-article-inner-full'><div class=\"chromatogram-article-inner\">\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"560\" height=\"376\" src=\"https:\/\/discover.restek.com\/wp-content\/uploads\/blog-fittings-connections-2-fig-9.png\" alt=\"\" class=\"wp-image-75414\" title=\"-\" srcset=\"https:\/\/discover.restek.com\/wp-content\/uploads\/blog-fittings-connections-2-fig-9.png 560w, https:\/\/discover.restek.com\/wp-content\/uploads\/blog-fittings-connections-2-fig-9-300x201.png 300w\" sizes=\"auto, (max-width: 560px) 100vw, 560px\" \/><\/figure>\n\n<\/div><\/div><\/div>\n\n\n<div style=\"height:25px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<p>Tune in for the next blog where I cover compression fitting repair techniques.<\/p>\n\n\n        <div class=\"cpb\">\n            <h3 class=\"cpb-heading\">Products Mentioned<\/h3>\n            <hr class=\"cpb-heading-underline\" \/>\n            <div class=\"cpb-list\">\n                                    <div class=\"cpb-item\">\n                        <div class=\"cpb-col cpb-col--left\">\n                            <a class=\"cpb-catalog\" target=\"_blank\" rel=\"noopener noreferrer\" href=\"https:\/\/de.restek.com\/p\/22623\">                                Catalog No. 22623                            <\/a>                        <\/div>\n                        <div class=\"cpb-col cpb-col--middle\">\n                            <div class=\"cpb-title\">&quot;T&quot;-Schl\u00fcssel, f\u00fcr 1\/4&quot; oder 6 mm &quot;T&quot;- oder Cross Fittings, nur f\u00fcr Swagelok Fittings<\/div>\n                        <\/div>\n                        <div class=\"cpb-col cpb-col--right\">\n                                                            <a class=\"cpb-view-btn\" target=\"_blank\" rel=\"noopener noreferrer\" href=\"https:\/\/de.restek.com\/p\/22623\">Produkt anzeigen<\/a>\n                                                    <\/div>\n                    <\/div>\n                            <\/div>\n        <\/div>\n        \n\n\n<div style=\"height:100px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n","protected":false},"excerpt":{"rendered":"<p>Proper installation of compression fittings ensures reliable gas seals between ferrules, fitting body, and tube wall. Correct wrench selection, tightening techniques, and inspection tools prevent leaks, deformation, and overtightening damage in GC systems.<\/p>\n","protected":false},"author":27,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_kad_blocks_custom_css":"","_kad_blocks_head_custom_js":"","_kad_blocks_body_custom_js":"","_kad_blocks_footer_custom_js":"","_kadence_starter_templates_imported_post":false,"_kad_post_transparent":"","_kad_post_title":"","_kad_post_layout":"","_kad_post_sidebar_id":"","_kad_post_content_style":"","_kad_post_vertical_padding":"","_kad_post_feature":"","_kad_post_feature_position":"","_kad_post_header":false,"_kad_post_footer":false,"footnotes":""},"categories":[792],"tags":[],"industries-application":[2231,2230],"post-badge":[29],"resource-type":[],"product-library":[],"resource-technique":[2323,2324],"hf_cat_post":[],"ppma_author":[447],"class_list":["post-72807","post","type-post","status-publish","format-standard","hentry","category-blogs-de","industries-application-luftprufung","industries-application-umweltbereich","post-badge-new","resource-technique-luftprobenahme","resource-technique-gaschromatographie-gc"],"acf":[],"taxonomy_info":{"category":[{"value":792,"label":"Blogs"}],"industries-application":[{"value":2231,"label":"Luftpr\u00fcfung"},{"value":2230,"label":"Umweltbereich"}],"post-badge":[{"value":29,"label":"New"}],"resource-technique":[{"value":2323,"label":"Luftprobenahme"},{"value":2324,"label":"Gaschromatographie (GC)"}]},"featured_image_src_large":false,"author_info":{"display_name":"Jason Hoisington","author_link":"https:\/\/discover.restek.com\/de\/author\/jason-hoisington\/"},"comment_info":0,"category_info":[{"term_id":792,"name":"Blogs","slug":"blogs-de","term_group":0,"term_taxonomy_id":792,"taxonomy":"category","description":"","parent":0,"count":442,"filter":"raw","cat_ID":792,"category_count":442,"category_description":"","cat_name":"Blogs","category_nicename":"blogs-de","category_parent":0}],"tag_info":false,"authors":[{"term_id":447,"user_id":27,"is_guest":0,"slug":"jason-hoisington","display_name":"Jason Hoisington","avatar_url":{"url":"https:\/\/discover.restek.com\/wp-content\/uploads\/people-hoisington-jason-01.jpg","url2x":"https:\/\/discover.restek.com\/wp-content\/uploads\/people-hoisington-jason-01.jpg"},"0":null,"1":"","2":"","3":"","4":"","5":"","6":"","7":"","8":""}],"_links":{"self":[{"href":"https:\/\/discover.restek.com\/de\/wp-json\/wp\/v2\/posts\/72807","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/discover.restek.com\/de\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/discover.restek.com\/de\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/discover.restek.com\/de\/wp-json\/wp\/v2\/users\/27"}],"replies":[{"embeddable":true,"href":"https:\/\/discover.restek.com\/de\/wp-json\/wp\/v2\/comments?post=72807"}],"version-history":[{"count":22,"href":"https:\/\/discover.restek.com\/de\/wp-json\/wp\/v2\/posts\/72807\/revisions"}],"predecessor-version":[{"id":80111,"href":"https:\/\/discover.restek.com\/de\/wp-json\/wp\/v2\/posts\/72807\/revisions\/80111"}],"wp:attachment":[{"href":"https:\/\/discover.restek.com\/de\/wp-json\/wp\/v2\/media?parent=72807"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/discover.restek.com\/de\/wp-json\/wp\/v2\/categories?post=72807"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/discover.restek.com\/de\/wp-json\/wp\/v2\/tags?post=72807"},{"taxonomy":"industries-application","embeddable":true,"href":"https:\/\/discover.restek.com\/de\/wp-json\/wp\/v2\/industries-application?post=72807"},{"taxonomy":"post-badge","embeddable":true,"href":"https:\/\/discover.restek.com\/de\/wp-json\/wp\/v2\/post-badge?post=72807"},{"taxonomy":"resource-type","embeddable":true,"href":"https:\/\/discover.restek.com\/de\/wp-json\/wp\/v2\/resource-type?post=72807"},{"taxonomy":"product-library","embeddable":true,"href":"https:\/\/discover.restek.com\/de\/wp-json\/wp\/v2\/product-library?post=72807"},{"taxonomy":"resource-technique","embeddable":true,"href":"https:\/\/discover.restek.com\/de\/wp-json\/wp\/v2\/resource-technique?post=72807"},{"taxonomy":"hf_cat_post","embeddable":true,"href":"https:\/\/discover.restek.com\/de\/wp-json\/wp\/v2\/hf_cat_post?post=72807"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/discover.restek.com\/de\/wp-json\/wp\/v2\/ppma_author?post=72807"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}