Engineering English
Operating Line
Chemical Engineering · Last updated: July 30, 2026 · How this entry was written
Definition: A straight line on a McCabe-Thiele diagram that represents the mass balance relationship between vapor and liquid compositions in a section of a distillation column. It defines the operating conditions for a given reflux ratio.
Example in context
“By plotting the operating line on the McCabe-Thiele diagram, the designer can visually determine the required number of theoretical stages.”
“McCabe-Thiele diyagramında işletme çizgisini çizerek, tasarımcı gerekli teorik kademe sayısını görsel olarak belirleyebilir.”
Where engineers use it
The operating line appears in the rectifying and stripping sections of a distillation column. Engineers use it together with the equilibrium curve to perform stage-by-stage calculations. Understanding it is key to optimizing reflux and product purity.
Practice: can you use “Operating Line” at work?
A junior engineer is reviewing a McCabe-Thiele diagram and must explain why the operating line shifts when the reflux ratio is increased.
Show a model answer
“Check the slope of the operating line to verify the reflux ratio condition.”
“Operating Line” in 21 languages
| English | Operating Line |
|---|---|
| Turkish | işletme çizgisi |
| French | ligne d'opération |
| German | Arbeitslinie |
| Spanish | línea de operación |
| Chinese | 操作线 |
| Arabic | خط التشغيل |
| Portuguese | linha de operação |
| Russian | рабочая линия |
| Japanese | 操作線 |
| Italian | retta di operazione |
| Vietnamese | đường vận hành |
| Hindi | संचालन रेखा |
| Thai | เส้นปฏิบัติการ |
| Indonesian | garis operasi |
| Korean | 조작선 |
| Bengali | পরিচালনা রেখা |
| Dutch | werkingslijn |
| Swedish | operationslinje |
| Finnish | käyttölinja |
| Ukrainian | робоча лінія |
Frequently asked questions
What does Operating Line mean in engineering?
A straight line on a McCabe-Thiele diagram that represents the mass balance relationship between vapor and liquid compositions in a section of a distillation column. It defines the operating conditions for a given reflux ratio. In Chemical Engineering, the term carries a usage-frequency rating of 10/10 in the Engineering English library.
How do you pronounce Operating Line?
Operating Line is pronounced /ˈɒpəreɪtɪŋ laɪn/ (IPA). The Engineering English app plays audio for the term and checks your pronunciation with speech recognition.
How is Operating Line used in a sentence?
Example from an engineering context: “By plotting the operating line on the McCabe-Thiele diagram, the designer can visually determine the required number of theoretical stages.”
This entry is one of 7,806 terms in the Engineering English iOS app — with quizzes, spaced repetition and pronunciation checking.
Get the app on the App Store