A Comparison of Fittings For Use with Plastic & Rubber Tubing

A Comparison of Fittings For Use with Plastic & Rubber Tubing NewAge® Industries, Inc. A Comparison of Fittings 2 Introduction When you’re using plastic tubing or rubber hose, you will, in most cases, need to attach it to something . . . a piece of equipment or another section of tubing. Fittings or connectors are a common means to accomplish this and come in many different materials — polyethylene, nylon, PVDF, fluoropolymer, stainless steel, brass — so you can select the best match for your application. There are many styles of fittings, from simple barbed varieties to multi-component compression types to heavy duty cam couplings. This paper examines each style, what materials are offered, what tubing materials each works best with, how complicated (or not) installation is, and usage tips. Clamps are also reviewed. This document explores products available from NewAge Industries, Inc. Barbed Fittings As the name states, barbed fittings have a single barb or multiple barbs on at least one end. The barbed end is inserted into the tubing. The function of the barbs is to grip the interior wall of the tubing, without damaging the wall, to hold the fitting in place. Barbed fittings work best with soft tubing (flexible PVC, polyurethane, silicone, thermoplastic rubber), as the tubing must give a bit to fit around the barbed end. Leaks can occur when there isn't a good fit, i.e. the fitting is too small. In fact, the O.D. (outer diameter) of the barbed area on the fitting must be larger than the I.D. (inner diameter) of the tubing, and there should be some resistance when the fitting is inserted into the tubing. As an example, .250" (1/4") I.D. tubing should use a barbed fitting with a barb O.D. of at least .270". A Comparison of Fittings 3 Barbed fittings are usually applied by hand without tools, and typically clamps or cable ties are used to securely attach the fitting to the tubing and ensure a good seal. Sometimes on lower pressure applications, clamps may not be necessary, but that is the exception rather than the rule and should always be deter- mined by testing the connections as they will be used in the actual application. Tubing and fitting materials must mate well with each other as well as to the application. For instance, a brass barbed fitting may not be a good match for silicone tubing. The barb could be too sharp for the silicone material and could cut into the wall, resulting in a failure. Polyurethane tubing, which is much more resilient and resist- ant to tearing than silicone, may be a better choice for a brass barbed fitting. Less aggressive barb designs are recommended for silicone tubing, along with plastic clamps or lined metal clamps. Push-To-Connect Fittings Push-to-connect fittings attach to tubing by simply pushing the tubing into the fitting to connect the two items. But how exactly does this work, and how do they stay attached? Each port or opening in a push-to-connect fitting typically has a collet (or collar), a gripper, and an O-ring, surrounded by a body. The collet and the gripper may be integrated into a single component, depending on the manufacturer. But whether they're two pieces or one, their job is to keep the tubing secured within the fitting's body. The gripper does just what it says — it literally grips the tubing. The O-ring forms a seal between the exterior of the tubing and the interior of the fitting body to prevent leaks. The body's job is to provide a smooth interior for fluid or air flow between sections of tubing and to hold everything in place. A Comparison of Fittings 4 Unlike barbed fittings where the barbs are on the inte- rior of the tubing, push-to-connect fittings hold onto the tubing's O.D., thereby having much less effect on the interior flow. But push-to-connect styles can have an end that's threaded, barbed, or straight (called a stem), and swivel types are available as well. Your application and tubing material will help determine what's needed. Push-to-connect fittings work best with rigid and semi-rigid tubing such as nylon, poly- ethylene, polypropylene and hard durometer polyurethane. They may be used with some softer tubing materials — PVC, for instance — when a tube support is employed. The fittings perform best when the end of the tubing going into the fitting is round, cleanly cut and free of exterior scratches. Tubing may need to be recut if removed from the fitting and reinserted. Covers for collets are available to help prevent accidental depression of the collet and tubing disconnection. Collet covers come in colors, making coding and line identification quick and easy. Compression Fittings Compression fittings use three or four components per fitting to put pressure on the tubing's O.D. to create a secure seal. These fittings are commonly used in applications involving fluids but may also be used for gas. Because the interior of the tubing is unencumbered by inserts like barbs, compression fittings offer good flow characteris- tics. Depending on the application and materials involved (plastic, metal), the fittings may be reused. They’re a good choice for rigid and semi-rigid tubing materials. A Comparison of Fittings 5 Compression fittings consist of a fitting body (E), an outer compres- sion nut (B), an inner compression ring or ferrule (D), and in some cases a gripper (C). When the nut is tightened onto the fitting body, the ferrule compresses around the O.D. of the tubing (A) creating a secure seal. The nut is normally finger tightened, and then further tightened one additional turn using a wrench. It is important to avoid over-tightening, as the ferrule may deform and cause the seal to fail. Cam Operated Couplings Besides the term “cam operated couplings,” these connectors are known by several names including cam and groove, cam groove, cam op, cam lever, cam lock, cam couplings or cam fittings. Cam operated couplings are intended for quick and easy connection and disconnection. No tools or special skills are needed. The design involves a coupler and a grooved adapter. Each coupler has two cams — movable pieces that fit into the groove, then rotate and lock the two fitting components into place. This ensures a proper fit and a tight seal against the gasket inside. Many cam couplings have a retaining pin that can be used to make sure the cams remain locked in place. Clamps are typically used with barbed versions. Cam couplings are available in the following universal styles: A ↓ C D ↓ E ↓ B ↓ ↓ A Comparison of Fittings 6 Type A: male adapter on one end with a FNPT (Female National Pipe Thread) on the other Type B: female coupler and MNPT (Male National Pipe Thread) Type C: female coupler and hose barb Type D: female coupler and FNPT Type E: male adapter and hose barb Type F: male adapter and MNPT Type DP: plug (also called a dust plug) Type DC: cap (also called a dust cap) Materials used in cam coupling manufacture include aluminum, stainless steel, brass, other metals, and various plastics such as polypropylene, PVDF and nylon. Sizes can range from as small as 1/4" to as large as 8". The application will determine which cam coupling material and size is needed. One important thing to keep in mind is that cam couplings generally have a much larger body as compared to barbed, push-to-connect or compression fittings. This should be care- fully considered with the overall fluid transfer system design. Cam operated coupling uses include positive pressure fluid and dry product handling such as petroleum, chemicals, agricultural commodi- ties, water and other liquids. The couplings should not be used for steam or compressed air applications. Type A Type B Type C Type D Type E Type F Type DP Type DC A Comparison of Fittings 7 Clamps When tubing needs to be securely attached to another piece of equipment by use of a fitting, most manufacturers of the tubing recommend using a clamp to help hold the tubing and the fitting together. Without a securely-fastened clamp, the potential for the two compo- nents to separate exists, and that can result in costly and time-consuming leaks. There are several types of hose clamps, and each has its place depending on the application. Three popular styles are ear type, worm gear and double bond. They're used in industries such as food and beverage, chemical, laboratory, medical, pharmaceutical, OEM, MRO, pool and spa, automotive, appliance, marine and others. Ear type clamps are tightened around tubing when part of the clamp is crimped using a special tool called a pincer. They're known as breathable clamps, because they adapt to expansion and contraction — a benefit when varying temperatures are involved. Ear type clamps are lightweight and typically made from steel (stainless, galvanized or zinc-plated carbon). One ear, two ear and one ear stepless styles offer options for different tubing materials. The clamps provide a compact design, making them well suited for limited-space applications. Worm gear clamps, which are also known as screw or band clamps, are easily installed with a standard screwdriver or ratcheting socket. Tightening the screw pulls a band through a housing, thereby tighten- ing the band around the hose or tubing. Like ear type clamps, they are constructed of steel. Styles designed to work with soft tubing, such as silicone, and with harder tubing are available. Worm gear clamps may be reused. When a non-metallic clamp is needed, double bond clamps, com- monly made of nylon, may be used. Double bond (also called double grip) clamps offer two rows of teeth to ensure a strong hold and can be easily adjusted for a tighter fit around tubing. These clamps are non-conductive and will not rust or corrode. They are typically hand applied, although pliers or channel locks can be used to tighten the clamp. Like worm gear clamps, double bond clamps may be reused. A Comparison of Fittings 8 Comparison Chart 1: Appearance, Styles, Function What It A single barb or Each port typically has Three-to-four Two components: Looks Like multiple barbs on at a collet (collar), gripper, components (body, nut, a coupler with handles least one end & O-ring, surrounded ferrule, sometimes a & a grooved adapter by a body gripper) combined during installation Example Styles Tees (T's), wyes (Y's), Tees (T's), wyes (Y's), Tees (T's), elbows, Adapters & couplers Available elbows, adapters, elbows, adapters, adapters, straight with barbed or National swivels, single use/ straight connectors, connectors Pipe Thread ends; disposable reducers, three-way plugs & caps & four-way connectors, end stops, check valves How It Works Insert a barbed end into The fitting’s gripper The nut of the fitting is A coupler is attached to a section of tubing. The tightly grasps the tightened onto the fitting one end of a hose using barbs function to grip exterior of the tubing. body, & a ferrule com- a clamp; an adapter is the interior wall of the An O-ring forms a seal presses around the O.D. attached to another tubing, without damage, between the exterior of of the tubing to create hose. A coupler’s two to assist with holding the tubing & the interior a seal. cams – movable pieces the fitting in place. of the fitting body to that fit into a groove in prevent leaks. The body an adapter – rotate & provides a smooth lock the two pieces into interior & holds all place. components in place. Ba rb ed Fit tin g T yp e Pu sh -to -C on ne ct Co mp res sio n Ca m Op era ted Co up lin g▼ A Comparison of Fittings 9 Comparison Chart 2: Tubing Compatibility, Installation Requirements, Tips, Materials, Brand Names Ba rb ed Fit tin g T yp e Pu sh -to -C on ne ct Co mp res sio n Ca m Op era ted Co up lin g▼ Tubing/Hose Soft tubing such as Rigid & semi-rigid Rigid tubing such as Softer hose such as It Works Best flexible PVC, silicone, tubing like nylon, fluoropolymer flexible PVC & With polyurethane, TPR polyethylene, polyurethane; typically (thermoplastic rubber), polypropylene & hard used with reinforced latex & Viton™ durometer polyurethane hose Tools Needed None, except those None Wrench None, except those for Installation that may be needed that may be needed for clamp installation for clamp installation Clamps Yes, except in very low No No Yes Required? pressure applications Tips The O.D. of the barbed Covers for collets are Well suited for corrosive Also known as cam & area on the fitting must available to help prevent environments & groove, cam groove, be larger than the I.D. accidental depression of chemicals & for ultra- cam op, cam lever, of the tubing, & there the collet, resulting in pure fluid applications cam lock, cam couplings should be some resist- tubing disconnection. where contamination- or cam fittings. ance when the fitting is Collets come in colors free systems are inserted into the tubing. for coding & needed. A complete identification. fluid transfer system made of fluoropolymer is possible. Fitting Nylon, polyethylene, Acetal, brass PFA fluoropolymer Nylon & polypropylene Materials PVDF, polypropylene, Offered by brass NewAge NewAge’s Thermobarb® Newloc® Pureloc® n/a Brand Name A Comparison of Fittings 10 Conclusions The determining factor for what type of fitting and clamp to use depends on the specifics of your application. Evaluate needs based on tubing material and hardness, temperatures involved, the product being transferred through the tubing and fitting, harsh or mild environments, performance expectations, durability requirements and styles needed (elbows, tees, etc.). When you need help deciding what to use, give the Fluid Transfer Specialists® a call. We’ll help. Contact us at 800-506-3924 (U.S. only), 215-526-2300, info@newageindustries or visit www.newageindustries.com. Be sure to check out NewAge Industries’ other white papers at www.newageindustries.com/whitepaper-request.asp. The Top 20 Tubing and Hose Buying Tips, #s 1-10 The Top 20 Tubing and Hose Buying Tips, #s 11-20 Sign up for our eNewsletter at www.newageindustries.com/extrusions 145 James Way • Southampton, Pennsylvania 18966 USA 888-506-3924 • 215-526-2300 www.newageindustries.com • info@newageindustries.com Thermobarb®, Newloc®, Pureloc®, NewAge® and “Fluid Transfer Specialists®” are registered trademarks of NewAge® Industries, Inc. Viton™ trademark The Chemours Company. © Copyright 2017 All Rights Reserved. 12/19/17 Reproduction of this document or any part thereof, in any form whatsoever, is prohibited without express written permission of NewAge® Industries, Inc. 123c Fluid Transfer Specialists®
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