{"id":40,"date":"2026-10-05T20:12:06","date_gmt":"2026-10-05T12:12:06","guid":{"rendered":"http:\/\/runda-hitech.com\/?page_id=40"},"modified":"2026-10-05T21:09:38","modified_gmt":"2026-10-05T13:09:38","slug":"high-purity-weld-fittings","status":"publish","type":"page","link":"https:\/\/runda-hitech.com\/index.php\/products\/tube-fittings\/high-purity-weld-fittings\/","title":{"rendered":"High-Purity Weld Fittings: Butt-Weld &#038; VCR"},"content":{"rendered":"\n<div class=\"wp-block-cover alignfull rlok-hero\" style=\"min-height:430px;aspect-ratio:unset;\"><span aria-hidden=\"true\" class=\"wp-block-cover__background has-background-dim\"><\/span><img decoding=\"async\" class=\"wp-block-cover__image-background\" alt=\"\" src=\"http:\/\/runda-hitech.com\/wp-content\/uploads\/2026\/10\/r-lok-high-purity-weld-fittings-1-1.jpg\" data-object-fit=\"cover\"\/><div class=\"wp-block-cover__inner-container has-global-padding is-layout-constrained wp-block-cover-is-layout-constrained\">\n<h1 class=\"wp-block-heading\">High-Purity Weld Fittings: Butt-Weld &amp; VCR<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">High-purity weld fittings join tubing by butt welding, so no elastomer or threaded joint sits in the fluid path. RUNDA HITECH supplies two lines: miniature weld connectors from 1\/8 in to 1\/2 in (6-12 mm) and full-size butt-weld connectors from 1\/4 in to 1 in (6-18 mm). Working pressures reach 8,500 psi (586 bar) and flow passages are electropolished.<\/p>\n\n\n\n<div class=\"wp-block-buttons is-layout-flex wp-block-buttons-is-layout-flex\">\n<div class=\"wp-block-button\"><a class=\"wp-block-button__link wp-element-button\" href=\"\/index.php\/contact\/\">Request a quote<\/a><\/div>\n\n<div class=\"wp-block-button is-style-outline\"><a class=\"wp-block-button__link wp-element-button\" href=\"\/index.php\/products\/\">Browse products<\/a><\/div>\n<\/div>\n<\/div><\/div>\n\n\n\n<div class=\"wp-block-group rlok-body has-global-padding is-layout-constrained wp-container-core-group-is-layout-b8954cbe wp-block-group-is-layout-constrained\" style=\"border-radius:0px\">\n<p class=\"wp-block-paragraph\"><span class=\"rlok-fallback-nav\"><a href=\"\/index.php\/products\/\">Products<\/a> &nbsp;&middot;&nbsp; <a href=\"\/index.php\/applications\/\">Applications<\/a> &nbsp;&middot;&nbsp; <a href=\"\/index.php\/quality\/\">Quality<\/a> &nbsp;&middot;&nbsp; <a href=\"\/index.php\/resources\/\">Resources<\/a> &nbsp;&middot;&nbsp; <a href=\"\/index.php\/about\/\">About<\/a> &nbsp;&middot;&nbsp; <a href=\"\/index.php\/contact\/\">Contact<\/a><\/span><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><span class=\"rlok-bc\"><a href=\"\/index.php\/\">Home<\/a> &rsaquo; <a href=\"\/index.php\/products\/\">Products<\/a> &rsaquo; <a href=\"\/index.php\/products\/tube-fittings\/\">Tube Fittings<\/a> &rsaquo; <strong>Weld Fittings<\/strong><\/span><\/p>\n\n\n\n<div class=\"wp-block-columns is-layout-flex wp-container-core-columns-is-layout-6ac5c474 wp-block-columns-is-layout-flex\">\n<div class=\"wp-block-column is-layout-flow wp-block-column-is-layout-flow\">\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" src=\"http:\/\/runda-hitech.com\/wp-content\/uploads\/2026\/10\/r-lok-high-purity-weld-fittings-2-1.jpg\" alt=\"ME series micro 90 degree elbow weld fitting in 316 stainless steel\" width=\"760\"\/><\/figure>\n<\/div>\n<\/div>\n\n\n\n<div class=\"wp-block-columns is-layout-flex wp-container-core-columns-is-layout-6ac5c474 wp-block-columns-is-layout-flex\">\n<div class=\"wp-block-column is-layout-flow wp-block-column-is-layout-flow\">\n<h3 class=\"wp-block-heading\">Key features<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Butt-weld joints with flat, square, burr-free weld ends dimensioned to the tube<\/li>\n\n<li>Miniature line 1\/8 in to 1\/2 in (6-12 mm); full-size to 1 in<\/li>\n\n<li>Working pressures: 8,500 psi (586 bar) to 2,400 psi (165 bar)<\/li>\n\n<li>Flow passages electropolished to Ra 0.25 \u00b5m (10 \u00b5in.) for high-purity service<\/li>\n\n<li>VCR metal gasket connectors 1\/8 in to 1 in, nut with leak-test hole<\/li>\n\n<li>Extended-weld bodies machined from forgings with uniform wall thickness<\/li>\n<\/ul>\n<\/div>\n\n<div class=\"wp-block-column is-layout-flow wp-block-column-is-layout-flow\">\n<h3 class=\"wp-block-heading\">Specifications<\/h3>\n\n\n\n<figure class=\"wp-block-table is-style-stripes\"><table><thead><tr><th>Parameter<\/th><th>Value<\/th><\/tr><\/thead><tbody><tr><td>Body material<\/td><td>316 \/ 316L stainless steel<\/td><\/tr><tr><td>Tube wall<\/td><td>0.028 in to 0.065 in (1.0-1.5 mm)<\/td><\/tr><tr><td>Pressure<\/td><td>8,500 psi (586 bar) on 1\/8 in; 5,100 psi (351 bar) 1\/4 in<\/td><\/tr><tr><td>Pressure<\/td><td>3,300 psi (227 bar) 3\/8 in; 3,700 psi (254 bar) 1\/2 in<\/td><\/tr><tr><td>Pressure<\/td><td>2,400 psi (165 bar) on 1 in and 3\/4 in<\/td><\/tr><tr><td>Metric pressure<\/td><td>6,095 psi (420 bar) on 6 mm; 2,902 psi on 12 mm<\/td><\/tr><tr><td>VCR<\/td><td>1\/8 in to 1 in; TSG short-leg and TLG long-leg; 6L, NI gaskets<\/td><\/tr><tr><td>VCR pressure<\/td><td>1\/2 in VCR to 1\/4 in, 4,300 psi or 3,500 psi<\/td><\/tr><\/tbody><\/table><\/figure>\n<\/div>\n<\/div>\n\n\n\n<h2 class=\"wp-block-heading\">How a weld joint seals<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">A mechanical tube fitting seals on a ferrule driven into the tube wall. A weld fitting seals on the weld itself: the fitting end is machined flat and square, and the tube is fused around the circumference, so the joint holds torque and leak rate.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The joint is permanent, so weld fittings suit gas panels, analyser sample systems, dosing skids and high-vacuum or ultra-high-purity manifolds. Removable connections stay at the instrument or regulator needing service. Manual TIG and orbital welding apply, and drawings give flat, square weld ends per size.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Miniature weld connectors<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">The miniature line covers compact piping: EP straight connector, MR and LR reducing connectors, ME 90\u00b0 elbow, MEL 90\u00b0 elbow with one extended leg, MEF 45\u00b0 elbow, MT tee, MTB cross-plane tee and MCT cross. Full-size LE, LT and LCT use the same naming.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Tube outside diameters run 1\/8 in, 1\/4 in, 3\/8 in and 1\/2 in (6, 8, 10 and 12 mm). Part numbers name both ends: MR6S4S joins 3\/8 in to 1\/4 in, MEL4S-2 is a 1\/4 in elbow, and MT10M6MS is a 10 mm run.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Full-size and VCR lines<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">The full-size series (catalogue 2-09 to 2-14) covers 1\/4 in to 1 in (6-18 mm) tube at L 29-33.5 mm. Reducing tees include LT12M6MS and LT8M6MS. Extended-weld bodies are machined from forgings, with uniform wall thickness for weld repeatability.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The VCR face seal uses a metal gasket between flat faces and is leak-tight from vacuum to high pressure. No polymer contacts the media. The male nut has a test hole, female threads are silver plated, and TSG and TLG adapters differ in leg length.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Standards referenced:<\/strong> Pressure ratings follow ASME B31.3 process piping practice, derated for tube size, wall thickness and temperature; Imperial and metric tube outside diameters follow the standard instrument tubing series.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Typical duties:<\/strong> Semiconductor and ultra-high-purity gas distribution panels; Analyser and sample systems in refineries; High-vacuum and UHP lines in pharmaceutical production; Hydrogen, nitrogen and specialty gas skids; Dosing and metering lines on chemical injection packages; Instrument tubing on oil and gas wellhead facilities.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">High-purity weld fitting model selection guide<\/h2>\n\n\n\n<figure class=\"wp-block-table is-style-stripes\"><table><thead><tr><th>Series \/ model<\/th><th>Size<\/th><th>Connection<\/th><th>Working pressure<\/th><th>Body material<\/th><th>Notes<\/th><\/tr><\/thead><tbody><tr><td>MR4S<\/td><td>1\/4 in. tube OD x 1\/8 in. tube OD<\/td><td>tube weld<\/td><td>5100 psig (351 bar)<\/td><td>not published<\/td><td>micro reducing straight union (\u82f1\u5236)<\/td><\/tr><tr><td>MR6S<\/td><td>1\/2 in. tube OD x 3\/8 in. tube OD<\/td><td>tube weld<\/td><td>3300 psig (227 bar)<\/td><td>not published<\/td><td>micro reducing straight union (\u82f1\u5236)<\/td><\/tr><tr><td>ME2S<\/td><td>1\/8 in. tube OD<\/td><td>tube weld<\/td><td>8500 psig (586 bar)<\/td><td>not published<\/td><td>micro 90 deg elbow<\/td><\/tr><tr><td>ME4S<\/td><td>1\/4 in. tube OD<\/td><td>tube weld<\/td><td>5100 psig (351 bar)<\/td><td>not published<\/td><td>micro 90 deg elbow<\/td><\/tr><tr><td>ME6S<\/td><td>3\/8 in. tube OD<\/td><td>tube weld<\/td><td>3300 psig (227 bar)<\/td><td>not published<\/td><td>micro 90 deg elbow<\/td><\/tr><tr><td>ME8S<\/td><td>1\/2 in. tube OD<\/td><td>tube weld<\/td><td>3700 psig (254 bar)<\/td><td>not published<\/td><td>micro 90 deg elbow<\/td><\/tr><tr><td>MEL4S<\/td><td>1\/4 in. tube OD<\/td><td>tube weld<\/td><td>5100 psig (351 bar)<\/td><td>not published<\/td><td>micro single-end extended 90 deg elbow; MEL4S-1\/-2\/-3\/-4 differ in Lx, B1, F dimensions at the same rating<\/td><\/tr><tr><td>MEF4S<\/td><td>1\/4 in. tube OD<\/td><td>tube weld<\/td><td>5100 psig (351 bar)<\/td><td>not published<\/td><td>micro 45 deg elbow; MEF6S 3\/8 in. 3300 psig (227 bar), MEF8S 1\/2 in. 3700 psig (254 bar)<\/td><\/tr><tr><td>MT4S<\/td><td>3\/8 in. tube OD x 1\/4 in. tube OD<\/td><td>tube weld<\/td><td>3300 psig (227 bar)<\/td><td>not published<\/td><td>micro reducing tee (outlet 1\/4 in.) (\u82f1\u5236)<\/td><\/tr><tr><td>MT8S<\/td><td>1\/2 in. tube OD x 1\/4 in. tube OD<\/td><td>tube weld<\/td><td>3700 psig (254 bar)<\/td><td>not published<\/td><td>micro reducing tee (outlet 1\/4 in.) (\u82f1\u5236)<\/td><\/tr><tr><td>MCT4S<\/td><td>1\/4 in. tube OD<\/td><td>tube weld<\/td><td>5100 psig (351 bar)<\/td><td>not published<\/td><td>micro four-way cross<\/td><\/tr><tr><td>MCT6S<\/td><td>3\/8 in. tube OD<\/td><td>tube weld<\/td><td>3300 psig (227 bar)<\/td><td>not published<\/td><td>micro four-way cross<\/td><\/tr><tr><td>LT8S<\/td><td>1\/2 in. tube OD<\/td><td>tube weld<\/td><td>3700 psig (254 bar)<\/td><td>not published<\/td><td>tee (\u82f1\u5236)<\/td><\/tr><tr><td>LT12S<\/td><td>3\/4 in. tube OD<\/td><td>tube weld<\/td><td>2400 psig (165 bar)<\/td><td>not published<\/td><td>tee (\u82f1\u5236)<\/td><\/tr><tr><td>LT12M6S<\/td><td>12 mm x 6 mm tube OD<\/td><td>tube weld<\/td><td>2902 psig (200 bar)<\/td><td>not published<\/td><td>reducing tee, metric table (\u516c\u5236)<\/td><\/tr><tr><td>LT12S (reducing)<\/td><td>3\/4 in. tube OD x 3\/8 in. tube OD<\/td><td>tube weld<\/td><td>2400 psig (165 bar)<\/td><td>not published<\/td><td>reducing tee, \u53d8\u5f84\u4e09\u901a table; same value printed for LT12M6S and LT12M8S in the metric table<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Selection notes:<\/strong> Working pressure is printed as psig with the bar equivalent in brackets; the catalogue pages used do not state a temperature basis, so the owner should confirm the reference temperature (for example 100 degF) before publishing. Body material is not printed anywhere on pages 2-01 to 2-12; every Body material cell is left as &#8220;not published&#8221; and the material grade (for example 316 SS \/ 316L) must be supplied by the owner.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><em>Catalogue reference 2-01, 2-02, 2-03, 2-04, 2-07, 2-08, 2-11, 2-12. Confirm the final rating against the data sheet issued with your order.<\/em><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>See also:<\/strong> <a href=\"\/index.php\/products\/tube-fittings\/double-ferrule-fittings\/\">Double Ferrule Fittings<\/a> &middot; <a href=\"\/index.php\/products\/tube-fittings\/threaded-fittings\/\">Threaded Fittings<\/a> &middot; <a href=\"\/index.php\/products\/tube-fittings\/\">Tube Fittings<\/a><\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Frequently asked questions<\/h2>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary>Can you supply material certificates and dimensional reports?<\/summary>\n<p class=\"wp-block-paragraph\">Yes. Material certificates for the wetted parts are supplied with the goods, and dimensional inspection reports are issued on request. Tell us at enquiry stage which document set your QA department needs, so we prepare it with the shipment.<\/p>\n<\/details>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary>When is a VCR face seal used instead of a weld end?<\/summary>\n<p class=\"wp-block-paragraph\">Use a VCR face seal where a joint must be reopened. It seals on a metal gasket between two flat faces. Weld ends are permanent and hold torque and leak rate through vibration and thermal cycling.<\/p>\n<\/details>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary>Which pressure rating applies to my tube size?<\/summary>\n<p class=\"wp-block-paragraph\">The rating follows the tube, not the fitting. A 1\/8 in tube with 0.028 in wall is listed at 8,500 psi (586 bar), 1\/4 in at 5,100 psi (351 bar), 3\/8 in at 3,300 psi (227 bar) and 1\/2 in at 3,700 psi (254 bar).<\/p>\n<\/details>\n<\/div>\n\n\n\n<div class=\"wp-block-group alignfull rlok-cta has-global-padding is-layout-constrained wp-container-core-group-is-layout-c4390f02 wp-block-group-is-layout-constrained\" style=\"border-radius:0px\">\n<div class=\"wp-block-group has-global-padding is-layout-constrained wp-container-core-group-is-layout-b097105c wp-block-group-is-layout-constrained\" style=\"border-radius:0px\">\n<h2 class=\"wp-block-heading\">Request a quote or technical clarification<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Send us the model, size, material and quantity you need &mdash; or a photo of the existing part. We reply with a quotation, availability and the applicable documents, usually within one working day.<\/p>\n\n\n\n<div class=\"wp-block-buttons is-layout-flex wp-block-buttons-is-layout-flex\">\n<div class=\"wp-block-button\"><a class=\"wp-block-button__link wp-element-button\" href=\"mailto:nimo@runda-hitech.com\">Email nimo@runda-hitech.com<\/a><\/div>\n\n<div class=\"wp-block-button is-style-outline\"><a class=\"wp-block-button__link wp-element-button\" href=\"https:\/\/wa.me\/8613657416007\">WhatsApp +86 136 5741 6007<\/a><\/div>\n<\/div>\n\n\n\n<p class=\"wp-block-paragraph\">Tel \/ WhatsApp: +86 136 5741 6007 &middot; Email: nimo@runda-hitech.com<\/p>\n<\/div>\n<\/div>\n\n\n\n<style>img{max-width:100%;height:auto}.wp-block-table{max-width:100%}.rlok-bc{display:block;font-size:13px;letter-spacing:.01em;color:#5a6b7d;margin:0 0 26px}.rlok-bc a{color:#0b2545;text-decoration:none}.rlok-bc a:hover{color:#c8102e;text-decoration:underline}.rlok-bc strong{color:#0b2545}.rlok-fallback-nav{display:block;border-bottom:1px solid #dde3ea;padding-bottom:12px;margin:0 0 18px;font-size:14.5px;font-weight:600}.rlok-fallback-nav a{color:#0b2545;text-decoration:none}.rlok-fallback-nav a:hover{color:#c8102e;text-decoration:underline}@media (max-width:782px){.rlok-hero{min-height:330px!important;padding-left:18px!important;padding-right:18px!important}.rlok-hero h1{font-size:26px;line-height:1.22}.rlok-hero p{font-size:15.5px}.rlok-body{padding:30px 18px 12px!important}.rlok-cta{padding:38px 18px!important}.rlok-cta h2{font-size:22px}.rlok-bc{font-size:12.5px;margin-bottom:18px}.wp-block-table{display:block;overflow-x:auto;-webkit-overflow-scrolling:touch}.wp-block-table table{min-width:520px;font-size:13px}.wp-block-table th,.wp-block-table td{padding:7px 9px}.wp-block-columns{gap:1.1rem;margin-bottom:1.3rem}.wp-block-button{width:100%}.wp-block-button__link{width:100%;text-align:center}h2.wp-block-heading{font-size:22px}h3.wp-block-heading{font-size:19px}.wp-block-details{padding:12px 14px}}<\/style><script type=\"application\/ld+json\">{\"@context\": \"https:\/\/schema.org\", \"@type\": \"BreadcrumbList\", \"itemListElement\": [{\"@type\": \"ListItem\", \"position\": 1, \"name\": \"Home\", \"item\": \"http:\/\/runda-hitech.com\/\"}, {\"@type\": \"ListItem\", \"position\": 2, \"name\": \"Products\", \"item\": \"http:\/\/runda-hitech.com\/products\/\"}, {\"@type\": \"ListItem\", \"position\": 3, \"name\": \"Tube Fittings\", \"item\": \"http:\/\/runda-hitech.com\/products\/tube-fittings\/\"}, {\"@type\": \"ListItem\", \"position\": 4, \"name\": \"Weld Fittings\", \"item\": \"http:\/\/runda-hitech.com\/products\/tube-fittings\/high-purity-weld-fittings\/\"}]}<\/script>\n\n\n<!-- VERIFY BEFORE PUBLISHING: Confirm the exact body material grades offered for each series (316, 316L or dual-certified 316\/316L) before the spec line is published; the catalogue tables give dimensions and pressures but the material grade must be confirmed with the supplier. | Confirm whether electropolishing to Ra 0.25 \u00b5m (10 \u00b5in.) is standard for all series or is available only on the VCR connectors and selected weld fittings. | Confirm the gasket material codes shown as 6L and NI in the VCR adapter tables (catalogue 2-15 and 2-16) \u2014 most likely a 316L gasket and a nickel gasket, but this must be verified before publication, along with which code applies to which pressure column. | Confirm the maximum service temperature of the fittings and of the VCR metal gasket so a temperature limit can be quoted; no temperature rating appears in this catalogue section. | Confirm that material certificates traceable to the mill heat number and dimensional inspection reports can be issued for every shipment, and state the lead time for documentation. | Confirm which fittings in this family are held in stock in imperial sizes and which in metric, and the typical lead time for forged bodies in 3\/4 in and 1 in sizes. | Confirm the applicable design reference for the pressure ratings \u2014 the catalogue lists per-size pressures but does not name the standard they are derived from; the brief permits referencing ASME B31.3 only as a design\/manufacturing reference. -->\n\n<!-- build: slug=high-purity-weld-fittings type=category keywords=high purity weld fittings supplier, butt weld tube fittings 316L, VCR gasket face seal fittings exporter, miniature weld connector 1\/8 inch, electropolished weld fittings Ra 0.25, TSG TLG VCR to tube weld adapter, instrument tube weld fittings 6mm 12mm, UHP gas panel weld fittings China supplier, weld fittings for semiconductor gas lines, long leg weld elbow tee cross 1 inch -->","protected":false},"excerpt":{"rendered":"<p>High-purity weld fittings 1\/8\u20131 in (6\u201318 mm) to 8,500 psi (586 bar), electropolished to Ra 0.25 \u00b5m. Export supply with material certificates.<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":64,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-40","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/runda-hitech.com\/index.php\/wp-json\/wp\/v2\/pages\/40","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/runda-hitech.com\/index.php\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/runda-hitech.com\/index.php\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/runda-hitech.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/runda-hitech.com\/index.php\/wp-json\/wp\/v2\/comments?post=40"}],"version-history":[{"count":12,"href":"https:\/\/runda-hitech.com\/index.php\/wp-json\/wp\/v2\/pages\/40\/revisions"}],"predecessor-version":[{"id":429,"href":"https:\/\/runda-hitech.com\/index.php\/wp-json\/wp\/v2\/pages\/40\/revisions\/429"}],"up":[{"embeddable":true,"href":"https:\/\/runda-hitech.com\/index.php\/wp-json\/wp\/v2\/pages\/64"}],"wp:attachment":[{"href":"https:\/\/runda-hitech.com\/index.php\/wp-json\/wp\/v2\/media?parent=40"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}