How to choose the right connector for low-pressure fluid handling
如何正确选择低压流体处理的快速接头
Posted by Connector Tips Editor on Wednesday, April 15, 2015
by Grant Wilhelm, Senior Design Engineer, Colder Products Co.

选择理想的管道连接器可以确保产品性能、增加易用性并为您的产品设计增加功能。这是一个三步指南。Selecting the ideal tubing connector can ensure product performance, increase ease of use and add functionality to your product designs. Here’s a three-step guide.

一系列产品的功能是通过小直径管道传输液体或气体——从医疗市场中的病床和体外诊断、打印机中的墨水管理系统和服务器机架中的液体冷却系统到食品应用和燃料管线中的调味品输送在船舶和发动机系统中。每个应用中的主要需求是将流体从 A 点移动到 B 点。 虽然这听起来很简单，但流体处理过程可能会因介质特性、流速或压力要求、物理空间限制、空气夹杂和溢出问题而变得复杂，用户或环境安全问题等等。

管道连接器是解决这些流体处理挑战的关键组件。您选择的连接器通常会在后一刻做出设计决定，从而对产品可靠性、性能和用户接受度产生重大影响。有数以千计的连接器选项可供选择，在不同的功能、材料和类型中进行选择可能是一项艰巨的任务。为简化此过程，连接器选择可分为三个步骤。遵循下面概述的每个步骤将有助于确保为任何需要使用管道处理流体的产品设计成功选择连接器。

The tubing connector is a critical component in solving these fluid-handling challenges. Often bumped to a last-minute design decision, the connector you choose can make a big difference in product reliability, performance and user acceptance. There are thousands of connector options available, and choosing among the differing capabilities, materials and types can be an overwhelming task. To simplify this process, connector selection can be broken down into three steps. Following each step outlined below will help ensure successful connector choices for any product design requiring fluid handling with tubing.

A range of products function by transferring liquids or gasses through small-diameter tubing—from patient beds and in vitro diagnostics in the medical market, ink management systems in printers, and liquid cooling systems in server racks to condiment delivery in food applications and fuel lines in marine and engine systems. The primary need in each application is to move fluid from point A to point B. While this sounds simple, the fluid-handling process can be complicated by media characteristics, flow rate or pressure requirements, physical space limitations, air inclusion and spillage concerns, user or environmental safety issues, and much more.

colder-produts-connector
图 1：带有内置阀门的连接器有助于防止溢出。Figure 1: Connectors with built-in valves help prevent spills.

步骤 1：定义应用的功能需求
1: Define the functional needs of the application

应用的操作需求决定了管道和连接器的参数。接头、鲁尔接头和快速断开接头是低压环境中常见的管道连接器。虽然每种都适用于某些应用程序，但它们不一定可以互换。例如，在需要防止溢出的应用中，带阀的连接器是比鲁尔接头更好的选择（见图 1 和图 2）。如果应用涉及频繁的连接和断开，设计用于长期可靠性的快速断开是一个不错的选择。The operative demands of your application determine the parameters for tubing and connectors. Fittings, luers and quick disconnect couplings are the most common tubing connectors used in low-pressure environments. While each is appropriate for certain applications, they are not necessarily interchangeable. For example, in applications where spill prevention is desired, a valved connector is a better choice than a luer (see figures 1 and 2). If the application involves frequent connecting and disconnecting, a quick disconnect designed for long-term reliability is a good choice.

Luer-connectors
图 2：Luer 连接器的设计没有截止阀。Figure 2: Luer connectors are designed without a shutoff valve.

总体而言，在分析您的应用程序时，请考虑以下设计选项：
Overall, consider the following design options when analyzing your application:

- 管材——您使用的是什么尺寸的管材，包括内径和外径？管子的内径 (ID) 尺寸通常是连接器尺寸的首要考虑因素。
- 端接类型——常见的端接类型是软管倒钩、压缩接头和推入式连接（见图 3）。

- Tubing—What size tubing, both inner and outer diameter, are you using? The inner diameter (ID) size of the tubing is generally the first consideration for the size of the connector.
- Termination type—The most common termination styles are hose barb, compression fittings and push-to-connect (see figure 3).

Hose-barb-compression-fittings
图 3：软管倒钩、压缩接头或按压式连接终端适合您的低压流体处理应用。
Figure 3: Hose barb, compression fittings or push-to-connect terminations can be suitable for your low-pressure fluid-handling application.

- 软管倒钩端头安装在管道内，并在一系列管道样式和材料上提供安全连接。
- 单软管倒钩适用于较软的管子，例如硅橡胶。带有多个制作精良的倒钩（具有锋利边缘且没有分型线）的连接器提供了一种牢固的连接，在管道样式和材料上不易断开。
- 压缩接头安装在管子的外侧，并使用螺母和套圈进行连接。
- 按压连接终端允许将管子推入接头。
- 流量要求— 所需的流量和流量压力是多少？允许的压降是多少？连接器和阀门的压降因制造商而异，有些设计比其他设计表现出更少的湍流和流动阻力。请务必在计算中考虑截止阀和管道连接的影响。
- 尺寸——您需要知道软管倒钩的内径、推入式接头的外径以及管内径和压缩外径。
- 阀门选项——阀门的款式很多，流量和压降各不相同。带有集成阀的连接器可防止断开连接时溢出并防止空气在连接过程中进入系统。与提升阀式阀门相比，带有精密齐平阀的连接器被认为是真正的“干断”或“非溢出”连接器，应在迫切需要避免任何溢出、污染或引入时选择连接时空气进入系统（见图 4）。

- Hose barb terminations fit inside tubing and provide a secure connection over a range of tubing styles and materials.
- Single-hose barbs work well with softer tubing, such as silicone rubber. Connectors with multiple well-made barbs (featuring sharp edges and free of parting lines) provide a secure connection that is not easily disconnected over tubing styles and materials.
- Compression fittings fit over the outside of tubing and use a nut and ferrule to make the connection.
- Push-to-connect terminations allow tubing to be pushed into the fitting.
- Flow requirements—What is the required flow rate and flow pressure? How much pressure drop is allowable? Pressure drops across connectors and valves vary greatly by manufacturer, and some designs exhibit less turbulence and resistance to flow than others. Be sure to allow for the effect of shutoff valves and tubing connections in your calculations.
- Size—You will need to know ID for hose barbs, OD for push-in-fittings and tube ID and OD for compression.
- Valve options—There are many styles of valves, and their flow rates and pressure drops vary. Connectors with integral valves prevent spills upon disconnection and prevent air from entering the system during connection. Connectors with precision flush-face valves, compared to a poppet-style valve, are considered true “dry-break” or “non-spill” connectors and should be selected when there is a critical need to avoid any spills, contamination or the introduction of air into the system upon connection (see figure 4).

Poppet-style-valves
图 4：带有齐平阀的连接器将溢出减少到接近零。由于其设计，提升式阀门可能会溢出。
Figure 4: Connectors featuring flush-faced valves reduce spills to near zero. Poppet-style valves, by virtue of their design, can spill.

- 安装选项——如何将连接配置到您的应用程序中？常见的安装选项包括面板安装或直接安装到 NPT 螺纹或端口。
- 连接器质量——连接器的制造质量水平会极大地影响其性能，也会影响美观。在模制塑料接头上，连接器主体上的分型线和模具缺陷（模具的两半聚集在一起）应该小，并且不会出现在第一个软管倒钩上。倒钩或螺纹上的缺陷会导致泄漏。模制连接器的浇口（塑料注入模具的点）应该没有锯齿状边缘，这些边缘会卡住或撕裂手套或管道。

- Mounting options—How is the connection going to be configured into your application? Common mounting options include panel mount, or direct mounting into NPT thread or ports.
- Connector quality—The level of manufacturing quality of a connector dramatically affects its performance and can also play a role in aesthetics. On molded plastic couplings, parting lines and mold defects (where two halves of the mold come together) should be minimal on the connector body and absent from the first hose barb. Imperfections on barbs or threads can lead to leaks. The molded connector’s gate (the point where the plastic was injected into the mold) should be free of jagged edges that can catch or tear gloves or tubing.

第 2 步：将材料与应用相匹配
Step 2: Match materials to the application

介质类型会影响连接器的选择。选择的连接器和管道材料需要与所使用的流体兼容。幸运的是，连接器有多种塑料和金属可供选择（见图 5）。除了考虑介质兼容性之外，通过连接的流体的粘度和腐蚀性也应该考虑到任何材料的决定。
The type of media influences the selection of a connector. The connector and tubing materials selected need to be compatible with the fluid being used. Fortunately, connectors are available in a ranges of both plastics and metals (see figure 5). In addition to considering media compatibility, the viscosity and corrosiveness of the fluid going through the connection should also be factored in to any materials decision.

流体处理连接器 fluid-handling-connectors

图 5：连接器有热塑性塑料、含氟聚合物、金属和各种材料组合可供选择，以满足低压流体处理应用的性能和成本要求。
Figure 5: Connectors are available in thermoplastics, fluoropolymers, metals and various materials combinations to meet the performance and cost requirements of low-pressure fluid-handling applications.

连接器快速接头还可能包括诸如 O 形圈和面板螺母之类的组件，以及诸如弹簧之类的内部组件。还应考虑这些部件与介质的化学兼容性。例如，涉及漂白溶液的应用将需要在流路中使用耐化学腐蚀的材料。Couplings may also include components such as O-rings and panel nuts, as well as internal components such as springs. The chemical compatibility of these parts with your media should also be considered. For example, applications involving bleach solutions will require a chemically resistant material in the flow path.

下面列出了通常可用的连接器和 O 形圈材料，以及使用这些材料的指南。
The following lists generally available connector and O-ring materials, plus guidelines for using these materials.

热塑性塑料

- ABS —经济型医用级热塑性塑料，可承受伽马射线和电子束灭菌
- 乙缩醛 —坚固、轻便且经济的材料，在很宽的温度范围内具有良好的刚性，具有韧性和耐用性
- 聚酰胺（尼龙）—抗磨损，在高温下具有良好的机械性能
- PEEK（聚醚醚酮） ——一种工程热塑性塑料，具有耐高温、耐化学性和抗疲劳性
- 聚碳酸酯——耐某些化学品，透明且经得起医疗应用的消毒。
- 聚乙烯— 低成本、耐化学性、不透明的热塑性塑料
- 聚丙烯 —优异的通用树脂，对溶剂和其他化学品的侵蚀具有很强的抵抗力
- 聚砜 —刚性、强度和耐化学性，它比大多数热塑性塑料更能承受反复消毒和更高的温度

Thermoplastics

- ABS—Economical medical-grade thermoplastic that withstands gamma and E-beam sterilization
- Acetal—Strong, lightweight and economical material that has good rigidity over a broad temperature range, with toughness and durability
- Polyamide (nylon)—Resists wear and abrasion, with good mechanical properties at elevated temperatures
- PEEK (polyetheretherketone)—An engineered thermoplastic with high-temperature, chemical and fatigue resistance
- Polycarbonate—Resistant to some chemicals, transparent and withstands sterilization for medical applications.
- Polyethylene—Low-cost, chemically resistant, opaque thermoplastic
- Polypropylene—Excellent general-purpose resin that is highly resistant to attack from solvents and other chemicals
- Polysulfone—Rigid, strong and chemically resistant, it withstands repeated sterilization and higher temperatures better than most thermoplastics

含氟聚合物
- PVDF（聚偏二氟乙烯） ——一种坚韧的工程热塑性塑料，具有平衡的物理和化学特性，使其适用于高性能应用

Fluoropolymers
- PVDF (polyvinylidene difluoride)—A tough engineered thermoplastic with a balance of physical and chemical properties that makes it suitable for high-performance applications

合金
- 铝— 具有高强度重量比的轻质金属，可提供经久耐用的阳极氧化处理
- 镀铬黄铜 —坚固且美观，这种金属非常适合高压和高温应用
- 压铸锌 —重量比黄铜轻 20%，这种耐用且轻便的材料可承受高压和高温
- 不锈钢— 具有出色的防锈性，常用于连接器组件，例如气门弹簧

Alloys
- Aluminum—Lightweight metal with a high strength-to-weight ratio that is available with a durable anodized finish
- Chrome-plated brass—Rugged and attractive, this metal is excellent for high- pressure and high-temperature applications
- Die-cast zinc—Weighing about 20% less than brass, this durable and lightweight material withstands high pressure and high temperature
- Stainless steel—Offers excellent rust resistance and is often used for connector components such as valve springs

O 型圈选择
- Buna-N —这是常见的 O 型圈材料，因为它具有耐溶剂性、耐油性和耐水性
- EPDM（乙烯-丙烯-二烯单体橡胶）—也称为 EPR，这种材料具有出色的化学性能电阻
- FKM（氟烃） -已知其对热，氧化，耐候性和耐臭氧性出色
- 硅都具有一个一样好或更好的耐热性为FKM; 医用级有机硅还满足 FDA 对生命科学应用中生物相容性的 VI 级要求。

O-Ring selection
- Buna-N—This is the most common O-ring material due to its solvent, oil and water resistance
- EPDM (ethylene-propylene-diene- monomer rubber)—Also known as EPR, this material offers excellent chemical resistance
- FKM (fluorocarbon)—Known for its outstanding resistance to heat, oxidation, weathering and ozone
- Silicone—Has as good or better temperature resistance as FKM; medical- grade silicones also meet FDA Class VI requirements for biocompatibility in life science applications.

其他介质考虑因素包括温度范围（-40 至 93o C）和连接器在应用、存储和运输过程中可能受到的压力，以及可能使用的清洁溶液或其他环境暴露。测试潜在的产品材料总是一个好主意，以评估实际应用中的材料性能。

Other media considerations include the range of temperatures (-40 to 93o C) and pressures the connectors might be subjected to in the application, in storage and during shipping, as well as cleaning solutions that may be used or other environmental exposure. Testing potential product materials is always a good idea in order to evaluate material performance in the actual application.

第 3 步：考虑增强的连接器功能
Step 3: Consider enhanced connector function

除了连接管道以促进和控制流体流动之外，当今的连接器技术还可以为产品设计带来更多的功能和性能属性。例如，配备射频识别 (RFID) 技术的智能连接器（见图 6）允许在连接点进行数据交换。通信耦合器传输的信息可以保护设备、改进流程甚至挽救生命。

In addition to connecting tubing to facilitate and control fluid flow, today’s connector technologies can bring increased functionality and performance attributes to product designs. For example, intelligent connectors equipped with radio frequency identification (RFID) technology (see figure 6) allow data exchange at the point of connection. Communicating couplers transmit information that can protect equipment, improve processes and even save lives.

CPCs-IdentiQuik-line-connector

图 6：支持 RFID 的连接器，例如 CPC 的 IdentiQuik 系列，可以通过将数据传输与流体处理相结合，为众多产品设计增加价值。Figure 6: RFID-enabled connectors, such as CPC’s IdentiQuik line, can add value to numerous product designs by combining data transmission with fluid handling.

这些智能连接器通过在两个分离的连接器之间发送 RFID 信号进行通信。数据存储在嵌入连接器或插件无源部分的 RFID 标签上。寻找标签的是一个 RFID 阅读器，该阅读器位于连接器或主体的有源部分。当两个半耦合器彼此相距几厘米时，阅读器会检测到标签，读取它，并将标签数据发送到运行系统的控制单元。控制单元还可以告诉阅读器将新信息写入标签。

支持 RFID 的耦合器的一种应用是通过确认使用正确的墨水颜色来进行商业打印机的墨水管理。

智能耦合还可用于确保产品在其使用寿命结束时退役，防止劣质介质损坏设备，强制使用一次性或有限使用的耗材设备，并确保在多端口环境中正确连接。

另一种为产品增加价值的连接器方法是多功能快速断开装置（见图 7）。这些连接器通过单个设备处理电力、信号和流体（液体和空气）的传输。

These intelligent couplings communicate by sending RFID signals between the two separated coupling halves. Data is stored on an RFID tag embedded in the passive half of the coupling or insert. Looking for the tag is an RFID reader housed in the active half of the coupling or body. When the two coupling halves are brought within a few centimeters of each other, the reader detects the tag, reads it, and sends the tag data to the control unit running the system. The control unit can also tell the reader to write new information to the tag.

One application of RFID-enabled couplers is for ink management in commercial printers by confirming that the correct ink color is used.

Intelligent couplings can also be used to ensure a product is retired at the end of its useful life, to prevent inferior media from damaging equipment, to enforce single- or limited-use consumable devices, and to ensure correct connections in multiport environments.

Another connector approach that adds value to products is the multifunction quick disconnect (see figure 7). These connectors handle the transfer of power, signal and fluids (liquids and air) through a single device.

CPC-混合连接器 CPC-Hybrid-Connector

图 7：多功能连接器，例如 CPC 的混合连接器，可以将媒体、气体和电信号的连接整合到一个单元中。Figure 7: Multifunction connectors, such as CPC’s Hybrid Connectors, can consolidate the connections for media, gasses and electrical signal, into a single unit.

多功能连接器无需多次连接并有助于防止错误连接。它们还简化了远程工具和设备之间的用户界面。在医疗应用中，这些连接器使技术人员能够快速、安全地更换或更换模块化工具、脐带缆或手持件。

具有增强功能的连接器可为您的产品在市场上提供竞争优势。通过选定的制造商提供，具有高级功能的定制连接器可以使您的产品更易于制造和使用。

尽管连接器在大多数产品中似乎是一个次要组件，但在您的设计过程中，它们不应该是事后的考虑。连接器通常是用户与您的产品的主要接口，它们可以在满足产品性能和易用性目标方面发挥关键作用。通过在连接器选择中遵循上述步骤，您不仅可以成功地将流体从 A 点移动到 B 点，而且还可以将您的产品移动到更直观、引人注目和功能性的设计。

Multifunction connectors eliminate the need for multiple connections and help prevent misconnection. They also simplify the user interface between remote tools and a device. In medical applications, these connectors enable technicians to quickly and safely change or replace modular tools, umbilicals or hand pieces.

Connectors with enhanced functions can provide competitive advantages for your product in the marketplace. Available through select manufacturers, custom connectors with advanced capabilities can make your product easier to manufacture and easier to use.

Although connectors seem like a minor component in most products, they deserve more than an afterthought in your design process. Connectors are often a user’s primary interface with your product, and they can they play a key role in meeting product performance and ease of use goals. By following the preceding steps in your connector selection, you will not only successfully move fluids from point A to point B—but you could also move your product to a more intuitive, compelling and functional design.

CPC