The reduction of compressed air system ( CAS) leaks has by far the highest potential gain on energy. Leakage is directly proportional to the system pressure (gauge). Leakages are present in every CAS and they are effective 24 hours a day, not only during production.
The percentage of compressor capacity lost to leakage should be less than 10 % in a well maintained large system. For small systems, leakage rates of less than 5 % are recommended. The amount of leakage in a poorly maintained 'historically grown' CAS can be up to 25 %.
Preventive maintenance programmes for compressed air systems should therefore include leak prevention measures and periodic leak tests. Once the leaks are found and repaired, the system should be re-evaluated. Tests should include the following:
●estimating the amount of leakage: all methods of estimating the amount of leakage in a CAS require no demands on the system, which means that all devices consuming air are turned off and therefore all air consumption is only due to leakage:，
●direct measurement is possible if a compressed air consumption measurement device is installed
●in a CAS with compressors that use start/stop controls, the estimation of the amount of leakage is possible by determination of the running time (on-load time) of the compressor in relation to the total time of the measurement. In order to get a representative value, the measurement time should include at least five starts of the compressor. Leakage expressed as a percentage of the compressor capacity is then calculated as follows:
               Leakage (%) = 100 x running time/measurement time
in a CAS with other control strategies, leakage can be estimated if a valve is installed between the compressor and the system. An estimation of the total system volume downstream of that valve and a pressure gauge downstream of the valve are also required.
the system is then brought to operating pressure (P1), the compressor is switched off and the valve shut. The time (t) it takes for the system to drop from P1 to a lower pressure P2 is measured. P2 should be about 50 % of the operating pressure (P1). The leakage flow can then be calculated as follows:
●Leakage (m³/min) = system volume (m³) x (P1 (bar) − P2 ( bar)) x 1.25/t (min)
●The 1.25 multiplier is a correction for the reduced leakage with falling system pressure 
●Leakage expressed as a percentage of the compressor capacity is then calculated as follows:
●Leakage (%) = 100 x leakage (m³/min)/compressor inlet volume flow (m³/min)
reducing the leakage: stopping leaks can be as simple a s tightening a connection or as complex as replacing faulty equipment such as couplings, fittings, pipe sections, hoses, joints, drains, and traps. In many cases, leaks are caused by badly or improperly applied thread sealant. Equipment or whole parts of the system no longer in use should be isolated from the active part of the CAS.
An additional way to reduce leakage is to lower the operating pressure of the system. With lower differential pressure across a leak, the leakage flowrate is reduced.

降低壓縮空氣系統的洩漏在節能方面有很高的潛能。些漏率與系統的表壓力是成正比的，而且其洩漏時機是24小時都存在，而不光是在生產作業期間。
一套維護保養良好的系統壓縮空氣漏損率必須小於壓縮機容量的10%以下。更小的系統應在5%以下。維護不良的壓縮空氣系統，其漏損率會隨時間的累積到達25%。
所以壓縮空氣系統維護保養實施計畫應要包含有洩漏預防及定期測漏檢查。一旦發現又洩漏經修復後必須重新評鑑。測試方法包括下列：
●估計洩漏量:作壓縮空氣系統洩漏量估算時所有系統內的需求都必須關閉不用，測得的消耗量就是來自於洩漏
●如果系統內各使用量都可以以量具量到，則可以直接量測洩漏量。
●以啟動/停止控制的壓縮機要估算洩漏量可以用其運轉時間(負荷時間)相對於其總量測時間的關係。為了要取得代表值量測時間要至少有五次以上的啟動次數。壓縮機容量的洩漏率可以用下面公式來計算：:

                洩漏率%= 100 x 運轉時間 / 量測時間
以其他控制方式的壓縮空氣系統，其洩漏率的估算可在壓縮機和系統間裝設一套閥門。閥門後端要裝一只壓力表，然後估算閥門後整個系統的容積。將系統建壓操作壓力P1關閉壓縮機和閥門，量測系統壓力從P1到P2的時間(P2=P1壓力的50%)，於是系統洩漏量即可計算：:
●系統洩漏量=系統容積(m3) x P1壓力(大氣壓力) - P2(大氣壓力) x 1.25/公噸-分鐘
●1.25是系統因壓力降而減少的洩漏率調整係數 (譯註：壓力逐漸降低洩漏量逐漸減少)
●壓縮機容量的洩漏率可以以下列公式表示:
●洩漏率=100x 洩漏量(m³/分) / 壓縮機進氣空氣量 ((m_³/分)
(譯註：壓縮機進氣空氣量 ((m³/分)可自壓縮機銘牌上取得)
減少洩漏的方法：止漏的方法可從簡單的鎖緊接頭到複雜的更換系統中缺損設備，如接頭、管件、管段、皮管、皮管接頭、排放口、排洩器等。有些洩漏的情況是使用不當的管線絲口止漏材料。
設備或整個壓縮空氣系統的某些部分停止使用時，應將之與系統使用中的部分隔離。
另外一個減少洩漏的辦法是將系統操作壓力降低，壓力降低後通過洩漏處的壓差小了，洩漏量就會減少。

None reported.

無資料。

Generally applicable to all CASs (see Table 3.23).

一般適用於所有壓縮空氣系統。（請參閱表3.23）

The costs of leak detection and repair depend on the individual CAS and on the expertise of the maintenance crew of the plant. Typical savings in a medium size CAS of 50 kW are:
50 kW x 3000 h/yr x EUR 0.08/kWh x 20 % = EUR 2400/yr The typical costs for regular leakage detection and repair is EUR 1000/yr.
As leakage reduction is widely applicable (80 %) and gives the highest gains (20 %), it is the most important measure for reducing CAS energy consumption.

一座壓縮空氣系統的洩漏偵測和修復成本要看系統及工廠內維護人員的專業而定。一座中型50kW規模的正常節省如下計算，正常洩漏成本約2400歐元/年，其中偵測與修復費用約等於1000歐元。
洩漏率降低的做法廣泛被採用(80%)，且獲益最高可達20%，所以是壓縮空氣系統中減少能源消耗重要的方法。

Energy Efficiency (2009) 3.7.6