On generating boilers as well as in heat exchange tubes, a scale deposit might occur on heat transfer surfaces. This deposit occurs when soluble matter reacts in the boiler water to form a layer of material on the waterside of the boiler exchange tubes.
Scale creates a problem because it typically possesses a thermal conductivity with an order of magnitude less than the corresponding value for bare steel. When a deposit of a certain thickness and given composition is formed on the heat exchange surface, the heat transfer through surfaces is reduced as a function of the scale thickness. Even small deposits might thus serve as an effective heat insulator and consequently reduce heat transfer. The result is overheating of boiler tube metal, tube failures and loss of energy efficiency. By removing the deposit, operators can easily save on energy use and on the annual operating costs.
Fuel waste due to boiler scale may be 2 % for water-tube boilers and up to 5 % in fire-tube boilers.
At boiler level, a regular removal of this scale deposit can produce substantial energy savings.

無論蒸汽鍋爐或熱交換器，其爐管內的傳熱面可能發生結垢現象，其原因是當鍋爐水中的溶解物質起變化，形成一層物質附著在爐管接觸水的表面。
結垢產生的問題在於其熱傳導係數相對於表面光滑的鐵器表面小好幾倍，如果結垢堆積到某一厚度，結垢形成在熱交換粗糙的表面，就會減損熱傳導能力，即使是些微的積垢也會使隔熱效果降低。
積垢會導致爐管金屬過熱、爐管堵塞失效而致能效減損。如果能將結垢去除就可以節能及節省操作成本。
鍋爐爐垢的生成對於水管式鍋爐及火管式鍋爐分別造成約2%及5%燃料浪費，將鍋爐結垢去除可有節能效果。

By treating feed-water to prevent scale deposits, the use of chemicals may increase.

為了處理飼水以防止積垢須使用的化學藥劑會增加。

Whether scale deposits need to be removed can be ascertained by a simple visual inspection during maintenance. As a rule of thumb, maintenance several times per year may be effective for appliances at high pressure ( 50 bar). For appliances at low pressure ( 2 bar) annual maintenance is recommended.
It is possible to avoid deposits by improving the water quality (e.g. by switching to soft water or demineralised water). An acid treatment for deposit removal has to be carefully as sessed, particularly for high pressure steam boilers.

在定期維護保養時以目視檢查方式可以決定結垢是否需要清除。一般規則是高操作壓力的裝置(50 bar)每年會有幾次的維保安排；至於低壓裝置(2 bar)則維持每年一次維保。
改良飼水水質，如改用軟水或除礦水也可以避免積垢。如要執行酸洗除垢必須小心評鑑，尤其是高壓蒸汽鍋爐。
 

Depends on the method used, and other factors, such as raw feed-water chemistry, boiler type, etc. Payback in fuel savings, increased reliability of the steam system and increased operating life of the boiler system ( giving savings on lost production time and capital costs) are all achievable.

See examples, in Annex 7.10.1.

視所採取方法及其他因素而定， 如原水的化學性質、鍋爐型態、種類等。
可以達到包括燃料節省的回收年限、增加蒸汽系統可靠度、延長鍋爐系統使用年限、減少停產時間及資本支出等經濟性。相關案例請參閱附件 7.10.1。

Energy Efficiency (2009) 3.2.6