在選(xuan)擇型號(hao)之前(qian)，我們必須(xu)弄清楚真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)泵(beng)的(de)(de)(de)(de)(de)一些(xie)基本概念(nian)。真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)度(du)(du):真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)下氣(qi)(qi)(qi)體的(de)(de)(de)(de)(de)稀(xi)薄程(cheng)度(du)(du)，通常用真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)度(du)(du)來表(biao)(biao)示(shi)(shi)(shi)。從真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)計上讀取的(de)(de)(de)(de)(de)值(zhi)(zhi)(zhi)(zhi)稱為(wei)真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)度(du)(du)。真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)值(zhi)(zhi)(zhi)(zhi)是指系(xi)統(tong)壓(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)力(li)(li)(li)(li)(li)(li)(li)(li)的(de)(de)(de)(de)(de)實際值(zhi)(zhi)(zhi)(zhi)低(di)于大(da)氣(qi)(qi)(qi)壓(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)力(li)(li)(li)(li)(li)(li)(li)(li)的(de)(de)(de)(de)(de)值(zhi)(zhi)(zhi)(zhi)。表(biao)(biao)上顯示(shi)(shi)(shi)的(de)(de)(de)(de)(de)值(zhi)(zhi)(zhi)(zhi)也稱為(wei)表(biao)(biao)壓(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)，行業也稱為(wei)極(ji)限(xian)相對(dui)壓(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)力(li)(li)(li)(li)(li)(li)(li)(li)，即真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)=大(da)氣(qi)(qi)(qi)壓(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)-絕對(dui)壓(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)力(li)(li)(li)(li)(li)(li)(li)(li)(大(da)氣(qi)(qi)(qi)壓(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)一般為(wei)101325帕，水環(huan)真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)泵(beng)的(de)(de)(de)(de)(de)極(ji)限(xian)絕對(dui)壓(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)力(li)(li)(li)(li)(li)(li)(li)(li)為(wei)3300帕;旋轉葉片式真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)泵(beng)的(de)(de)(de)(de)(de)極(ji)限(xian)絕對(dui)壓(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)力(li)(li)(li)(li)(li)(li)(li)(li)約為(wei)10Pa)極(ji)限(xian)相對(dui)壓(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)力(li)(li)(li)(li)(li)(li)(li)(li):相對(dui)壓(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)力(li)(li)(li)(li)(li)(li)(li)(li)是測量(liang)的(de)(de)(de)(de)(de)內(nei)部壓(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)力(li)(li)(li)(li)(li)(li)(li)(li)比“大(da)氣(qi)(qi)(qi)壓(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)力(li)(li)(li)(li)(li)(li)(li)(li)”低(di)多(duo)少(shao)。表(biao)(biao)示(shi)(shi)(shi)系(xi)統(tong)壓(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)力(li)(li)(li)(li)(li)(li)(li)(li)的(de)(de)(de)(de)(de)實際值(zhi)(zhi)(zhi)(zhi)低(di)于大(da)氣(qi)(qi)(qi)壓(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)力(li)(li)(li)(li)(li)(li)(li)(li)。因為(wei)容器(qi)(qi)內(nei)的(de)(de)(de)(de)(de)空(kong)(kong)氣(qi)(qi)(qi)是泵(beng)送(song)的(de)(de)(de)(de)(de)，所以容器(qi)(qi)內(nei)的(de)(de)(de)(de)(de)壓(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)力(li)(li)(li)(li)(li)(li)(li)(li)總是低(di)于容器(qi)(qi)外的(de)(de)(de)(de)(de)壓(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)力(li)(li)(li)(li)(li)(li)(li)(li)。因此，當用相對(dui)壓(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)力(li)(li)(li)(li)(li)(li)(li)(li)或表(biao)(biao)壓(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)表(biao)(biao)示(shi)(shi)(shi)時，該(gai)值(zhi)(zhi)(zhi)(zhi)前(qian)面必須(xu)有一個負號(hao)，表(biao)(biao)示(shi)(shi)(shi)容器(qi)(qi)內(nei)部的(de)(de)(de)(de)(de)壓(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)力(li)(li)(li)(li)(li)(li)(li)(li)低(di)于外部的(de)(de)(de)(de)(de)壓(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)力(li)(li)(li)(li)(li)(li)(li)(li)。極(ji)限(xian)絕對(dui)壓(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)力(li)(li)(li)(li)(li)(li)(li)(li):絕對(dui)壓(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)力(li)(li)(li)(li)(li)(li)(li)(li)是指測量(liang)的(de)(de)(de)(de)(de)內(nei)部壓(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)力(li)(li)(li)(li)(li)(li)(li)(li)比“理論(lun)真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)(理論(lun)真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)壓(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)力(li)(li)(li)(li)(li)(li)(li)(li)值(zhi)(zhi)(zhi)(zhi)為(wei)0Pa)”高多(duo)少(shao)。它比較(jiao)的(de)(de)(de)(de)(de)對(dui)象是理論(lun)狀態下的(de)(de)(de)(de)(de)絕對(dui)真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)壓(ya)(ya)(ya)(ya)(ya)(ya)(ya)(ya)力(li)(li)(li)(li)(li)(li)(li)(li)。

　　由(you)于(yu)工藝限制，我們(men)在任何情況下(xia)都不能(neng)(neng)(neng)將內部(bu)壓力提升至絕對真空(kong)(kong)(kong)(kong)值0Pa。因此(ci)，由(you)真空(kong)(kong)(kong)(kong)泵(beng)(beng)(beng)抽吸(xi)的(de)(de)(de)真空(kong)(kong)(kong)(kong)值高于(yu)理論真空(kong)(kong)(kong)(kong)值。因此(ci)，當用絕對真空(kong)(kong)(kong)(kong)表示時(shi)，其(qi)前面(mian)沒有負號。泵(beng)(beng)(beng)送(song)(song)能(neng)(neng)(neng)力:泵(beng)(beng)(beng)送(song)(song)能(neng)(neng)(neng)力是(shi)真空(kong)(kong)(kong)(kong)泵(beng)(beng)(beng)泵(beng)(beng)(beng)送(song)(song)速度(du)(du)的(de)(de)(de)衡量(liang)(liang)因素。一般(ban)單位用L/S和m /h h表示。這(zhe)是(shi)一個(ge)彌補漏氣(qi)(qi)率(lv)的(de)(de)(de)參數。不難(nan)理解為什(shen)么(me)泵(beng)(beng)(beng)送(song)(song)量(liang)(liang)大(da)的(de)(de)(de)真空(kong)(kong)(kong)(kong)泵(beng)(beng)(beng)可以(yi)很(hen)容易地泵(beng)(beng)(beng)出(chu)(chu)我們(men)需要的(de)(de)(de)真空(kong)(kong)(kong)(kong)度(du)(du)，而(er)(er)泵(beng)(beng)(beng)送(song)(song)量(liang)(liang)小的(de)(de)(de)真空(kong)(kong)(kong)(kong)泵(beng)(beng)(beng)卻很(hen)慢，甚至不能(neng)(neng)(neng)泵(beng)(beng)(beng)出(chu)(chu)我們(men)想要的(de)(de)(de)真空(kong)(kong)(kong)(kong)度(du)(du)。由(you)于(yu)管道或容器不可能(neng)(neng)(neng)絕對密閉，而(er)(er)吸(xi)入(ru)的(de)(de)(de)大(da)量(liang)(liang)空(kong)(kong)(kong)(kong)氣(qi)(qi)可以(yi)彌補因空(kong)(kong)(kong)(kong)氣(qi)(qi)泄漏而(er)(er)造成的(de)(de)(de)真空(kong)(kong)(kong)(kong)度(du)(du)下(xia)降的(de)(de)(de)因素，因此(ci)很(hen)容易得(de)出(chu)(chu)理想的(de)(de)(de)大(da)氣(qi)(qi)體(ti)積真空(kong)(kong)(kong)(kong)度(du)(du)值。建議在計算(suan)理論泵(beng)(beng)(beng)送(song)(song)能(neng)(neng)(neng)力時(shi)，盡(jin)量(liang)(liang)選擇泵(beng)(beng)(beng)送(song)(song)能(neng)(neng)(neng)力較(jiao)高的(de)(de)(de)真空(kong)(kong)(kong)(kong)泵(beng)(beng)(beng)。泵(beng)(beng)(beng)送(song)(song)能(neng)(neng)(neng)力的(de)(de)(de)具體(ti)計算(suan)公式將在下(xia)面(mian)描述。

　　在(zai)了解真(zhen)空泵(beng)的基本參數、絕對壓力和相對壓力后(hou)，我們可以進(jin)入(ru)正式選擇真(zhen)空泵(beng)。

　　1.過程所需(xu)的真空度

　　真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)泵(beng)(beng)的工(gong)(gong)作壓力(li)(li)應滿足(zu)工(gong)(gong)藝工(gong)(gong)作壓力(li)(li)的要(yao)求，選(xuan)(xuan)擇(ze)時的真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)度應比(bi)真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)設(she)備的真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)度高一(yi)(yi)半(ban)至一(yi)(yi)個數量(liang)級。(例如，真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)過程要(yao)求真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)度為(wei)(wei)100帕(pa)(絕(jue)對(dui)(dui)壓力(li)(li))，真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)泵(beng)(beng)的真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)度至少應為(wei)(wei)50帕(pa)-10帕(pa))。一(yi)(yi)般來(lai)說，如果要(yao)求絕(jue)對(dui)(dui)壓力(li)(li)高于3300帕(pa)，水環真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)泵(beng)(beng)是(shi)首選(xuan)(xuan)的真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)裝置。如果要(yao)求絕(jue)對(dui)(dui)壓力(li)(li)低于3300帕(pa)，則(ze)不(bu)能選(xuan)(xuan)擇(ze)水環真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)泵(beng)(beng)，選(xuan)(xuan)擇(ze)旋(xuan)葉(xie)真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)泵(beng)(beng)或(huo)真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)度較高的真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)泵(beng)(beng)作為(wei)(wei)真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)獲取裝置。

　　2、工藝對提(ti)取率的要求(提(ti)取率)

　　真空(kong)泵(beng)(beng)需要(yao)泵(beng)(beng)送速率(即真空(kong)泵(beng)(beng)在其(qi)工(gong)作壓(ya)力下(xia)排出(chu)氣體(ti)、液體(ti)和固(gu)體(ti)的能力)，一般單位為(wei)m3/h、L/S、m3/min。具體(ti)計算(suan)方法(fa)可參照以(yi)下(xia)公式計算(suan)并(bing)選(xuan)擇(ze)類型。當然(ran)，真空(kong)泵(beng)(beng)的選(xuan)擇(ze)是(shi)一個綜(zong)合(he)的過(guo)程，涉(she)及到相關(guan)的經驗和其(qi)他因素。

　　S=(V/t)×ln(P1/P2)

　　式中:s為真空泵的抽速(升/秒)

　　v是真(zhen)空室容積(l)

　　t是達(da)到所需真空度所需的(de)時間

　　P1是(shi)初始壓(ya)力(li)(帕)

　　P2是所需的壓(ya)力(帕)

　　3.確定要泵(beng)送的(de)物(wu)體的(de)成分

　　首(shou)先，被泵(beng)送的(de)物體(ti)是氣體(ti)、液體(ti)還是粒(li)子。如(ru)果要(yao)(yao)泵(beng)送的(de)氣體(ti)含有水蒸氣或少量雜質(zhi)，如(ru)顆(ke)粒(li)和灰塵(chen)，應仔(zi)細選擇(ze)旋(xuan)轉葉片(pian)式真空(kong)泵(beng)。如(ru)果要(yao)(yao)求真空(kong)度高，在旋(xuan)葉式真空(kong)泵(beng)用(yong)作真空(kong)獲取設備之前(qian)，應增加一個過(guo)濾裝(zhuang)置進行過(guo)濾。

　　第二，有必要知道泵送的(de)物體是否被(bei)腐(fu)蝕(酸性(xing)或(huo)堿(jian)性(xing)，酸堿(jian)值是多少?)，如果氣體含(han)有酸和堿(jian)腐(fu)蝕或(huo)有機