[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"detail-sidebar-cat-1-en-105":3,"doc-seo-564083-105":53,"doc-detail-564083-en":120},{"code":4,"msg":5,"data":6},0,"success",[7,14,19,24,29,34,39,44,49],{"id":8,"doc_module":9,"doc_module_name":10,"category_name":11,"show_sort_weight":12,"slug":13},11,1,"Template","Presentations",90,"presentations",{"id":15,"doc_module":9,"doc_module_name":10,"category_name":16,"show_sort_weight":17,"slug":18},12,"Resumes",80,"resumes",{"id":20,"doc_module":9,"doc_module_name":10,"category_name":21,"show_sort_weight":22,"slug":23},14,"Invoices",70,"invoices",{"id":25,"doc_module":9,"doc_module_name":10,"category_name":26,"show_sort_weight":27,"slug":28},15,"Posters",60,"posters",{"id":30,"doc_module":9,"doc_module_name":10,"category_name":31,"show_sort_weight":32,"slug":33},16,"Social Media",50,"social-media",{"id":35,"doc_module":9,"doc_module_name":10,"category_name":36,"show_sort_weight":37,"slug":38},17,"Forms",40,"forms",{"id":40,"doc_module":9,"doc_module_name":10,"category_name":41,"show_sort_weight":42,"slug":43},18,"Letters",30,"letters",{"id":45,"doc_module":9,"doc_module_name":10,"category_name":46,"show_sort_weight":47,"slug":48},21,"Paper Templates",5,"papers-templates",{"id":50,"doc_module":9,"doc_module_name":10,"category_name":51,"show_sort_weight":4,"slug":52},158,"General","general-158",{"code":4,"msg":54,"data":55},"ok",{"site_id":56,"language":57,"slug":58,"title":59,"keywords":60,"description":61,"schema_data":62,"social_meta":113,"head_meta":115,"extra_data":117,"updated_unix":119},105,"en","a-study-of-tension-and-jamming-when-pulling-cable-around-bends","A Study of Tension and Jamming When Pulling Cable Around Bends","","Existing theory and research on pulling and jamming of three cables through conduit bends are reviewed. Pulling tension through bends is measured for three cable pulls with jam ratios spanning 2.4 to 4.3, and these cases are compared with single-cable pulls. Cable feed position and lubrication effects in the three-cable pulls are analyzed. Jam Ratio is calculated using J=1.05 ID/OD, including conduit ovalization at the bend, and literature-reported likely jam ranges are synthesized.",{"@graph":63,"@context":112},[64,80,95],{"@type":65,"itemListElement":66},"BreadcrumbList",[67,71,74,77],{"item":68,"name":69,"@type":70,"position":9},"https://docshare.wps.com","Home","ListItem",{"item":72,"name":10,"@type":70,"position":73},"https://docshare.wps.com/template/",2,{"item":75,"name":46,"@type":70,"position":76},"https://docshare.wps.com/template/paper-templates/",3,{"item":78,"name":59,"@type":70,"position":79},"https://docshare.wps.com/template/a-study-of-tension-and-jamming-when-pulling-cable-around-bends/564083/",4,{"url":78,"name":59,"@type":81,"author":82,"headline":59,"publisher":85,"fileFormat":88,"inLanguage":57,"description":61,"dateModified":89,"datePublished":89,"encodingFormat":88,"isAccessibleForFree":90,"interactionStatistic":91},"DigitalDocument",{"name":83,"@type":84},"jay","Person",{"url":68,"name":86,"@type":87},"DocShare","Organization","application/pdf","2026-10-12",true,{"@type":92,"interactionType":93,"userInteractionCount":4},"InteractionCounter",{"@type":94},"ViewAction",{"@type":96,"mainEntity":97},"FAQPage",[98,104,108],{"name":99,"@type":100,"acceptedAnswer":101},"What is meant by “jamming” when pulling cables around bends?","Question",{"text":102,"@type":103},"Jamming refers to three cables becoming wedged against the conduit wall as they are forced toward the inside of a bend, making the cables “stuck.”","Answer",{"name":105,"@type":100,"acceptedAnswer":106},"How is Jam Ratio calculated in this study?",{"text":107,"@type":103},"Jam Ratio is calculated with J=1.05 ID/OD, where ID is the conduit interior diameter and OD is the cable outer diameter; the 1.05 factor accounts for conduit ovalization at the bend.",{"name":109,"@type":100,"acceptedAnswer":110},"Why can pulling three cables sometimes require higher tension than predicted?",{"text":111,"@type":103},"Recent studies address this by using a higher coefficient of friction for three cables than for a single cable, recommending a three-cable COF that is 10% to 100% higher under low sidewall pressure conditions.","https://schema.org",{"og:url":78,"og:type":114,"og:title":59,"og:site_name":86,"og:description":61},"article",{"robots":116,"canonical":78},"index,follow",{"doc_id":118,"site_id":56},564083,1791840162,{"code":4,"msg":5,"data":121},{"doc_id":118,"user_id":122,"nickname":83,"user_avatar":123,"doc_module":9,"category_id":45,"category_name":46,"doc_title":59,"doc_description":61,"doc_content":124,"file_id":125,"file_url":126,"file_type":127,"file_size":128,"view_count":4,"is_deleted":4,"is_public":9,"is_downloadable":9,"audit_status":9,"page_count":129,"language":130,"language_code":57,"site_id":56,"html_lang":57,"table_of_contents":131,"faqs":132,"seo_title":133,"seo_description":61,"update_tm":119,"read_time":73},3985747858866,"https://ap-avatar.wpscdn.com/davatar_a8503ba1806abce46bf441b54a3ca4cd","# A Study of Tension and Jamming When Pulling Cable Around Bends\n\nKeywords:  Cable Pulling;Jamming;Jam Ratio;Lubricants;Tension;Conduit Bend;Weight CorrectionFactor;Triangular;Cradled;Conduit Fill  \n## 1.INTRODUCTION\n\nThe “jamming”of three cables as they are pulledthrough a bend is well described in the literature.When the combined diameters of three cables roughlyequal the interior diameter of the conduit,the cablescan line up linearly as they are pulled around the bend.The cables then wedge against the conduit wall as theyare forced towards the inside of the bend.The wedged(or jammed)cables are“stuck”.To pull jammed cableswith enough force to get them through a bend usuallyruins the cable by ripping off the jacket or crushing theinsulation.  \nThe common technique to avoid jamming is to avoidpulling cables with an unfavorable ratio of cable OD toconduit ID(called Jam Ratio).However,unfavorablejam ratios cover a wide range,and to avoid themcompletely is not always possible.  \nJohn M.FeeAmerican Polywater CorpPO Box 53Stillwater,MN 55082 USA  \nAbstract:Existing theory and research on the pulling(and jamming)of three cables through bends are reviewed.Pulling tension through bends is measuredfor three cable pulls with jam ratios from 2.4 to 4.3.These three cable pulls are compared to single cablepulls.Cable feed position and lubrication in three cable pulls are also analyzed.  \nMichael J.FeeAmerican Polywater CorpPO Box 53Stillwater,MN 55082 USA  \nEquation(1)presents the usual calculation of Jam Ratio:  \nJ=1.05 ID/OD  \n(1)  \nWhere  \nJ=Jam Ratio (dimensionless)  \nID=Interior diameter of conduit in mm(in)OD=Outer diameter of the cable in mm(in)  \nNote that a 1.05 factor is included to estimate the\"ovalization\"of the conduit at the bend.  \nWhile the literature is consistent that jamming canoccur with a jam ratio around 3,there is inconsistencyon the exact range of jam ratios that pose a problem.References [1],[2],[3],and [4]indicate the highestprobability of jamming at jam ratios of 2.6 to 2.9;2.9to 3.3;2.8 to 3.0;and 2.7 to 3.0.  \nReference[1]uses a probability approach to assessjamming.This is reproduced in Table 1.Table 1provides a good target range of jam ratios for thepulling through bends study.Table 1 indicatesthere is some probability of 3 cables jamming from29%to 52%conduit fill.This broad range of conduitfills includes those common in electrical construction.  \nJa4 -2tio  \nProbabilityof Jamming  \n2.5-2.6  \nMedium  \n2.6-2.9  \nHigh  \n2.9-3.0  \nMedium  \n3.0-3.2  \nLow  \nTable 1.Probability of Jamming  \nAnother peculiarity in pulling three cables isdescribed in recent studies of cable pulling [Ref.3].Three cables pull with higher tension than expectedbased on physical theory and how a single cable pulls.Reference [3]handles this issue by defining a highercoefficient of friction(COF)for three cables than a  \nsingle cable.The reference recommends that the \"\"three cable COF”,which is 10%to 100%higher than thesingle cable COF,be used whenever three cables arepulled at sidewall pressures less than 2,180 N/m(150lbs/ft).  \nExperienced cable pulling crews use a “trifurcater” or similar device in three cable pulls to maintain thefeed of the cables in a consistent triangular position.Presumably,this prevents the cables from being forcedto roll over each other and jam because they wereallowed to change positions during the feed.But sthere an optimal feed position?  \nThe research in this paper provides data andinformation on some of the three cable pulling issuesraised above.  \n## II.BODY\n\nExperimental Method and Measurement Apparatus  \nThe test apparatus used in this work is described inReference [5].The apparatus was set up to pull cablearound two 90 degree conduit bends.The incoming(orback)tension was varied and the pulling tension wasmeasured.From this data,a coefficient of frictioncould be calculated,and effects from jamming,cableadjustment,cable jacket type,conduit type,lubrication,etc.could be measured.  \nSize  \n2/0  \n3/0  \n4/0  \n25","cbCaihLQyBoLY6iB","https://ap.wps.com/l/cbCaihLQyBoLY6iB","pdf",337455,6,"English","# 1. INTRODUCTION\n## Jam ratio, wedge/jamming behavior, and motivation\n## Jam Ratio equation and probability ranges\n## Experimental study scope and feeding position question\n# II. BODY\n## Experimental method and measurement apparatus\n## Cable selection and controlled variables","[{\"question\":\"What is meant by “jamming” when pulling cables around bends?\",\"answer\":\"Jamming refers to three cables becoming wedged against the conduit wall as they are forced toward the inside of a bend, making the cables “stuck.”\"},{\"question\":\"How is Jam Ratio calculated in this study?\",\"answer\":\"Jam Ratio is calculated with J=1.05 ID/OD, where ID is the conduit interior diameter and OD is the cable outer diameter; the 1.05 factor accounts for conduit ovalization at the bend.\"},{\"question\":\"Why can pulling three cables sometimes require higher tension than predicted?\",\"answer\":\"Recent studies address this by using a higher coefficient of friction for three cables than for a single cable, recommending a three-cable COF that is 10% to 100% higher under low sidewall pressure conditions.\"}]","A Study of Tension and Jamming When Pulling Cable Around Bends | PDF"]