For hazardous liquid (toxic, flammable); controlled removal of Inboard seal leakage. Seal operates on process fluid on inboard seal; buffer fluid on outboard seal. Inboard seal handle full pressure; outboard seal runs at atmospheric or low pressure. Outboard seal can handle the same conditions as inboard seal.
shutdown for repair. 外密封只作短时间备用密封， 即用于短时间的停车维修.
Operating long term on the outboard seal will defeat the purpose
of installing dual seal. 外密封长时间的运转将失去安装双密封的意义和目的.
In such cases, a single seal is unacceptable, either a Pressurised or Non-pressurised dual seal is employed.
在这些情况下，一般不采用单封，而采用带压或不Fra bibliotek压双封5
Dual Seal Arrangements 双封排列方式
双封指不管在什么方向上，密封腔中密封数超过一个的密封排列 式.它或者使用不带压的缓冲液，或者使用带压的隔离液作为封 液。
Classical “Tandem”
典型串联密封
Classical “Double”
典型双封
Process sea Backup seal l介质侧密封 备用密封
Back to back 背对背
Process seal Barrier fluid seal 介质侧密封 缓冲液侧密封
4
What is Dual Seal ?双封指的是什么 ?
Non-pressurized (Tandem) 不带压双封 (串联双封)
Pressurized (double) 带压双封
Process 介质
Buffer Atmosphere
优点
可承受一些不对中因素，没有摇摆 ，没有振动，密封面磨损小，同时 可减少泄漏 减少操作应力和O形圈磨损 较好的冷却效果 可应用于高速运转工况
What is Dual Seal ?双封指的是什么 ?
A seal arrangement using more than one seal in the same seal chamber in any orientation which can utilise either a non-pressurised buffer fluid or a pressurised barrier fluid for sealing.
John Crane
Mechanical Seal Training
机械密封培训
Programme Overview 目录简介
Mechanical Seal Operating Principles 机械密封操作原理
• How a Seal Works 密封是如何操作的 • Basic Component of Mechanical Seal 构成机械密封的基本零部
Non pressurized or Pressurized ? 不带压或带压 ?
How to select ? 如何选择 ?
Type 2648
Type 3648
> Seal Chamber Pressure 密封腔压力
Buffer Fluid Pressure 缓冲液压力
Seal Chamber Pressure 密封腔压力
API 682 piping plan (API 682 管道方案)
• Differentiate flushing & quenching 冲洗与吹扫的 • Common Single seal piping plan 常用单密封管道方案 • Dual Seal piping system and components functionality 双密封
决方案 Monitor equipment conditions for good sealing system
reliability 检测设备运转情况.提高密封系统运行的可靠性
Paragraph 1
Introduction about mechanical seal 机械密封介绍
Seal Arrangements密封排列方式
缓冲液
大气侧
Process 介质
Barrier 隔离液
Atmosphere 大气侧
Pressure 压力 Pressure 压力
Why Dual Seal ? 为什么采用双封 ?
Dual seal is not used just because ” two must be better than one". 采用双封并不是简单地因为“两个一定比一个好” Their increased complexity, cost and maintenance over single seal must be justified. 和单封相比，双封比较复杂，成本高且维护起来不如单 封简单 The usual justifications are : 通常采用双封的工况是:
Dual Seal Arrangements 双封排列方式 Non pressurized or Pressurized ? 不带压或带压 ?
Type 2648
> Seal Chamber Pressure 密封腔压力
Buffer Fluid Pressure 缓冲液压力
Non pressurized Application
单封优点：
成本低 可靠性较高 零件数少 没有封液系统
1
Single Seal Arrangements单封排列方式
Inside or Outside Mounted?内装式或外装式?
Inside Mounted 内装式
Advantages
优点
Better cooling- Seal surrounded by product flushing. Pressure acts to close the seal face. Parts in compression,which is preferable to tension. Can be use for high pressure application Self cleaning- centrifuge particles away from seal. Less space required outside housing. Seal leakage containment is simpler. Lower leakage due to centrifugal action.
2
Rotating Head or Rotating Seat Arrangement ?动环旋转或静环旋转 ?
Advantages Self Cleaning Less Radial & Axial Space Requirements Lower Cost (Seal head is normally one or two size smaller than stationary seal head version.)
件
Seal Types Classifications 机械密封的分类
• Seal Types 密封类型分类
Seal Arrangements and Systems 密封排列形式
• Dual seal arrangements, operating principles, benefits & limitations 双密封排列形式,操作原理,优点与局限
旋转密封头可适用的范围:
对大弹簧结构可达到3500 fpm 对多弹簧结构可达到5000 fpm
3
Rotating Head or Rotating Seat Arrangement ?动环旋转或静环旋转 ?
Advantages
Tolerates misalignment better. Improved tracking ,no wobble, no vibration, less face wear & reduced emissions. Reduces operating stresses & O-ring fretting. Better cooling. Higher speed capability.
较好的冷却效果 - 密封全部处 于冲洗状态下 压力有利于密封面的贴合 零件处于压缩状态，这更有利 于压紧 可适用于高压工况 自冲洗- 将颗粒与密封分离开 腔体外需要较小的空间即可 对密封泄漏的处理比较简单 在离心力作用下，泄漏量较小
Single Seal Arrangements单封排列方式
Inside or Outside Mounted?内装式或外装式?
管道系统和部件的功能
Handling of mechanical seal 安装密封注意事项 Seal installation alignment 安装密封的公差检查需求 Commissioning and venting 开车与排气须知 Causes of seal failure and solutions 密封失效的原因及解
Inside or Outside Mounted?内装式或外装式?