Seals,Packings,Backup Rings,Gaskets,Wipers

Seals

密封

Seals are used to prevent fluid from passing a certain point, as well as to keep air and dirt out of the system in which they are used. The increased use of hydraulics and pneumatics in aircraft systems has created a need for packings and gaskets of varying characteristics and design to meet the many variations of operating speeds and temperatures to which they are subjected. No one style or type of seal is satisfactory for all installations. Some of the reasons for this are:

(1) pressure at which the system operates,

(2) the type fluid used in the system,

(3) the metal finish and the clearance between adjacent parts, and

(4) the type motion (rotary or reciprocating), if any.

Seals are divided into three main classes:

(1) packings,

(2) gaskets, and

(3) wipers.

密封件用于防止流体通过某一点，以及防止空气和灰尘进入所使用的系统。随着液压和气动技术在飞机系统中的应用越来越广泛，因此需要不同特性和设计的密封和密封垫，以满足不同的运行速度和温度要求。没有一种密封件的样式或类型可以满足所有的安装要求。造成这种情况的原因有 ：

(1) 系统运行的压力，

(2) 系统中使用的流体类型，

(3) 金属表面处理（粗糙度）和相邻部件之间的间隙，以及

(4) 运动类型（旋转或往复）（如果有的话）。

密封件主要分为三类：

(1) 密封、

(2) 密封垫和

(3) 刮油环。

 

Packings

密封

Packings are made of synthetic or natural rubber. They are generally used as “running seals,” that is, in units that contain moving parts, such as actuating cylinders, pumps, selector valves, and so forth. Packings are made in the form of O-rings, V-rings, and U-rings, each designed for a specific purpose. [Figure 5-16]

密封由合成橡胶或天然橡胶制成，通常用作“运行密封件”，即用于包含运动部件的装置中，例如驱动气缸、泵、选择阀等。密封有O型密封圈、V型密封圈和U型密封圈三种形式，每种都专为特定用途设计。[图5-16]

O-Ring Packings

O型密封圈

O-ring packings are used to prevent both internal and external leakage. This type of packing ring seals effectively in both directions and is the type most commonly used. In installations subject to pressures above 1,500 psi, backup rings are used with O-rings to prevent extrusion.

O型密封圈用于防止内外泄漏。这种密封环在双向作用下都能有效密封，是应用最广泛的类型。在承受超过1500磅/平方英寸压力的安装环境中，需配合支撑环使用以防止O型密封圈被挤出。

When an O-ring packing is subjected to pressure from both sides, as in actuating cylinders, two backup rings must be used (one on either side of the O-ring). When an O-ring is subject to pressure on only one side, a single backup ring is generally used. In this case, the backup ring is always placed on the side of the O-ring away from the pressure.

当O型密封圈需要承受双侧压力时（如执行气缸），必须在O型密封圈两侧各加装一个支撑环；若仅承受单侧压力，则通常只需一个支撑环。此时背压环应始终安装在O型密封圈远离压力源的一侧。

 

The materials from which O-rings are manufactured have been compounded for various operating conditions, temperatures, and fluids. An O-ring designed specifically for use as a static (stationary) seal probably will not do the job when installed on a moving part, such as a hydraulic piston. Most O-rings are similar in appearance and texture, but their characteristics may differ widely. An O-ring is useless if it is not compatible with the system fluid and operating temperature.

O型圈的制造材料经过特殊配比，可适应不同工况、温度和流体环境。专为静态（固定）密封设计的O型圈，若安装在液压活塞等运动部件上，很可能无法正常工作。虽然大多数O型圈外观和质地相似，但其性能参数可能大相径庭。如果O型圈与系统流体及工作温度不匹配，就完全无法发挥作用。

Advances in aircraft design have necessitated new O-ring compositions to meet changed operating conditions. Hydraulic O-rings were originally established under AN specification numbers (6227, 6230, and 6290) for use in MIL-H-5606 fluid at temperatures ranging from −65 °F to +160 °F. When new designs raised operating temperatures to a possible 275 °F, more compounds were developed and perfected.

随着飞机设计技术的进步，新型O型环材料应运而生以适应不断变化的运行工况。液压O型环最初是根据美国军用标准（AN）编号（6227、6230和6290）开发的，适用于MIL-H-5606标准规定的流体环境，工作温度范围为−65°F至+160°F。当新型设计将工作温度提升至可能达到275°F时，更多复合材料的研发与优化工作随之展开。

Recently, a compound was developed that offered improved low temperature performance without sacrificing high temperature performance, rendering the other series obsolete. This superior material was adopted in the MS28775 series. This series is now the standard for MIL-H-5606 systems in which the temperature may vary from −65 °F to +275 °F.

近期研发出一种新型化合物，在保持高温性能的同时提升了低温表现，使得原有系列产品被淘汰。该优质材料被应用于MS28775系列，现已成为MIL-H-5606系统标准配置，适用于温度范围从−65°F到+275°F的环境。

Manufacturers provide color coding on some O-rings, but this is not a reliable or complete means of identification. The color coding system does not identify sizes, but only system fluid or vapor compatibility and in some cases the manufacturer.

制造商在某些O型环上提供了颜色编码，但这不是一种可靠或完整的识别手段。颜色编码系统不能识别尺寸，只能识别系统流体或蒸汽相容性，有时还能识别制造商。

Color codes on O-rings that are compatible with MIL-H-5606 fluid will always contain blue, but may also contain red or other colors. Packings and gaskets suitable for use with Skydrol fluid will always be coded with a green stripe, but may also have a blue, grey, red, green, or yellow dot as a part of the color code.

与MIL-H-5606液压油兼容的O型环颜色代码始终包含蓝色，但可能也包含红色或其他颜色。适用于Skydrol液压油的密封件和垫片始终带有绿色条纹，但可能还包含蓝色、灰色、红色、绿色或黄色圆点作为颜色代码的一部分。

Color codes on O-rings that are compatible with hydrocarbon fluid will always contain red, but will never contain blue. A colored stripe around the circumference indicates that the O-ring is a boss gasket seal. The color of the stripe indicates fluid compatibility: red for fuel, blue for hydraulic fluid.

与碳氢化合物流体兼容的O型环上的颜色代码将始终包含红色，但永远不会包含蓝色。圆周上的彩色条纹表示O型环是凸缘垫片密封件。条纹的颜色指示流体兼容性：红色用于燃料，蓝色用于液压油。

The coding on some rings is not permanent. On others it may be omitted due to manufacturing difficulties or interference with operation. Furthermore, the color coding system provides no means to establish the age of the O-ring or its temperature limitations.

某些密封环的编码不是永久性的，其他密封环的编码可能由于制造困难或对操作的干扰而被省略。此外，颜色编码系统不能确定O型环的年龄或其温度限制。

Because of the difficulties with color coding, O-rings are available in individual hermetically sealed envelopes, labeled with all pertinent data. When selecting an O-ring for installation, the basic part number on the sealed envelope provides the most reliable compound identification.

由于颜色编码存在困难，O型密封环可单独密封包装，包装上标有所有相关数据。在选择安装用O型密封环时，包装上的件号提供了最可靠的化合物识别。

Although an O-ring may appear perfect at first glance, slight surface flaws may exist. These flaws are often capable of preventing satisfactory O-ring performance under the variable operating pressures of aircraft systems; therefore, O-rings should be rejected for flaws that will affect their performance. Such flaws are difficult to detect, and one aircraft manufacturer recommends using a 4 power magnifying glass with adequate lighting to inspect each ring before it is installed.

虽然O型密封环乍看之下似乎完美无缺，但表面可能暗藏瑕疵。这些微小缺陷往往会影响其在飞机系统多变工作压力下的性能表现，因此存在影响性能的缺陷时应直接报废该O型密封环。这类瑕疵往往难以察觉，有飞机制造商建议使用配备充足照明的四倍放大镜，在安装前对每个O型环进行细致检查。

By rolling the ring on an inspection cone or dowel, the inner diameter surface can also be checked for small cracks, particles of foreign material, or other irregularities that will cause leakage or shorten the life of the O-ring. The slight stretching of the ring when it is rolled inside out will help to reveal some defects not otherwise visible.

通过在检查锥或定位柱上滚动密封环，可以检查内径表面是否存在小裂纹、异物颗粒或其他不规则性，这些缺陷会导致泄漏或缩短O型密封环的寿命。当环在内部翻转时，轻微的拉伸有助于发现其他情况下无法看到的缺陷。

Backup Rings

支撑环

Backup rings (MS28782) made of Teflon™ do not deteriorate with age, are unaffected by any system fluid or vapor, and can tolerate temperature extremes in excess of those encountered in high pressure hydraulic systems. Their dash numbers indicate not only their size but also relate directly to the dash number of the O-ring for which they are dimensionally suited. They are procurable under a number of basic part numbers, but they are interchangeable; that is, any Teflon™ backup ring may be used to replace any other Teflon™ backup ring if it is of proper overall dimension to support the applicable O-ring. Backup rings are not color coded or otherwise marked and must be identified from package labels.The inspection of backup rings should include a check to ensure that surfaces are free from irregularities, that the edges are clean cut and sharp, and that scarf cuts are parallel. When checking Teflon™ spiral backup rings, make sure that the coils do not separate more than inch when unrestrained.

由特氟龙™材料制成的支撑环（MS28782）不会随时间老化，不受任何系统流体或蒸汽影响，并能承受比高压液压系统更高的极端温度。其破折号编号不仅标明尺寸，还直接对应与其尺寸匹配的O型密封环破折号编号。这些支撑环可通过多个件号采购，且具有互换性——即任何特氟龙™支撑环均可替换其他特氟龙™支撑环，只要其整体尺寸足以支持适用的O型环。支撑环不采用颜色编码或其他标识方式，必须通过包装标签进行识别。检查支撑环时应确保表面无异常不规则，边缘切割整齐锋利，切口平行。在检查特氟龙™螺旋支撑环时，需确认未受约束状态下线圈间距不超过一英寸。

V-Ring Packings

V型密封圈

V-ring packings (AN6225) are one-way seals and are always installed with the open end of the “V” facing the pressure. V-ring packings must have a male and female adapter to hold them in the proper position after installation. It is also necessary to torque the seal retainer to the value specified by the manufacturer of the component being serviced, or the seal may not give satisfactory service. An installation using V-rings is shown in Figure 5-17.

V型密封环（AN6225）属于单向密封件，安装时必须确保“V”形开口端始终朝向压力方向。安装后需使用公母适配器将密封环固定到位，同时需按照被维护部件制造商指定的扭矩值对密封保持架进行紧固，否则可能导致密封效果不理想。图5-17展示了采用V型密封环的安装示意图。

U-Ring Packings

U型密封圈

U-ring packings (AN6226) and U-cup packings are used in brake assemblies and brake master cylinders. The U-ring and U-cup will seal pressure in only one direction; therefore, the lip of the packings must face toward the pressure. U-ring packings are primarily low pressure packings to be used with pressures of less than 1,000 psi.

U型密封环（AN6226）和U型杯密封环用于制动器组件和制动主缸。U型密封环和U型杯只能在一个方向上密封压力，因此，密封环的唇缘必须朝向压力方向。U型密封环主要是低压密封件，适用于压力小于1000psi的情况。

 

Gaskets

密封垫

Gaskets are used as static (stationary) seals between two flat surfaces. Some of the more common gasket materials are asbestos, copper, cork, and rubber. Asbestos sheeting is used wherever a heat resistant gasket is needed. It is used extensively for exhaust system gaskets. Most asbestos exhaust gaskets have a thin sheet of copper edging to prolong their life.

密封垫是用于两个平面之间作为静态（固定）密封件的装置。常见的垫片材料有石棉、铜、软木和橡胶等。石棉板材适用于所有需要耐热垫片的场合，尤其在排气系统密封垫中应用广泛。大多数石棉排气密封垫边缘都有一层薄铜片，以延长其使用寿命。

A solid copper washer is used for spark plug gaskets where it is essential to have a noncompressible, yet semisoft gasket.

在火花塞垫片中使用实心铜垫圈，因为必须具有不可压缩但半软质的垫片。

Cork gaskets can be used as an oil seal between the engine crankcase and accessories, and where a gasket is required that is capable of occupying an uneven or varying space caused by a rough surface or expansion and contraction.

软木垫片可用作发动机曲轴箱和附件之间的油封，也可用作需要能够占据由粗糙表面或膨胀收缩造成的不均匀或变化空间的垫片。

Rubber sheeting can be used where there is a need for a compressible gasket. It should not be used in any place where it may come in contact with gasoline or oil because the rubber will deteriorate very rapidly when exposed to these substances. Gaskets are used in fluid systems around the end caps of actuating cylinders, valves, and other units. The gasket generally used for this purpose is in the shape of an O-ring, similar to O-ring packings.

橡胶密封垫适用于需要使用可压缩密封件的场合。但需注意，若接触汽油或机油等腐蚀性介质，橡胶材料会迅速劣化，因此严禁在这些区域使用。在液压系统中，密封垫主要安装于执行气缸、阀门等部件的端盖周围。这类密封件通常采用O型环结构，其形状与常规O型填料相似。

Wipers

刮油环

Wipers are used to clean and lubricate the exposed portions of piston shafts. They prevent dirt from entering the system and help protect the piston shaft against scoring. Wipers may be either metallic or felt. They are sometimes used together, a felt wiper installed behind a metallic wiper.

刮油环用于清洁和润滑活塞轴的暴露部分。它们可防止污物进入系统，并有助于保护活塞轴免受划痕。刮油环可以是金属的或毛毡的。有时会将两者一起使用，即在金属刮油环后面安装一个毛毡刮油环。