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如何延長軸承壽命
譯者 段開元
摘要: 自然界苛刻的工作條件會導(dǎo)致軸承的失效,但是如果遵循一些簡單的規(guī)則,軸承正常運轉(zhuǎn)的機會是能夠被提高的。在軸承的使用過程當(dāng)中,過分的忽視會導(dǎo)致軸承的過熱現(xiàn)象,也可能使軸承不能夠再被使用,甚至完全的破壞。但是一個被損壞的軸承,會留下它為什么被損壞的線索。通過一些細(xì)致的偵察工作,我們可以采取行動來避免軸承的再次失效。
關(guān)鍵詞: 軸承 失效 壽命
導(dǎo)致軸承失效的原因很多,但常見的是不正確的使用、污染、潤滑劑使用不當(dāng)、裝卸或搬運時的損傷及安裝誤差等。診斷失效的原因并不困難,因為根據(jù)軸承上留下的痕跡可以確定軸承失效的原因。
然而,當(dāng)事后的調(diào)查分析提供出寶貴的信息時,最好首先通過正確地選定軸承來完全避免失效的發(fā)生。為了做到這一點,再考察一下制造廠商的尺寸定位指南和所選軸承的使用特點是非常重要的。
1 軸承失效的原因
在球軸承的失效中約有40%是由灰塵、臟物、碎屑的污染以及腐蝕造成的。污染通常是由不正確的使用和不良的使用環(huán)境造成的,它還會引起扭矩和噪聲的問題。由環(huán)境和污染所產(chǎn)生的軸承失效是可以預(yù)防的,而且通過簡單的肉眼觀察是可以確定產(chǎn)生這類失效的原因。
通過失效后的分析可以得知對已經(jīng)失效的或?qū)⒁У妮S承應(yīng)該在哪些方面進行查看。弄清諸如剝蝕和疲勞破壞一類失效的機理,有助于消除問題的根源。
只要使用和安裝合理,軸承的剝蝕是容易避免的。剝蝕的特征是在軸承圈滾道上留有由沖擊載荷或不正確的安裝產(chǎn)生的壓痕。剝蝕通常是在載荷超過材料屈服極限時發(fā)生的。如果安裝不正確從而使某一載荷橫穿軸承圈也會產(chǎn)生剝蝕。軸承圈上的壓坑還會產(chǎn)生噪聲、振動和附加扭矩。
類似的一種缺陷是當(dāng)軸承不旋轉(zhuǎn)時由于滾珠在軸承圈間振動而產(chǎn)生的橢圓形壓痕。這種破壞稱為低荷振蝕。這種破壞在運輸中的設(shè)備和不工作時仍振動的設(shè)備中都會產(chǎn)生。此外,低荷振蝕產(chǎn)生的碎屑的作用就象磨粒一樣,會進一步損害軸承。與剝蝕不同,低荷振蝕的特征通常是由于微振磨損腐蝕在潤滑劑中會產(chǎn)生淡紅色。
消除振動源并保持良好的軸承潤滑可以防止低荷振蝕。給設(shè)備加隔離墊或?qū)Φ鬃M行隔離可以減輕環(huán)境的振動。另外在軸承上加一個較小的預(yù)載荷不僅有助于滾珠和軸承圈保持緊密的接觸,并且對防止在設(shè)備運輸中產(chǎn)生的低荷振蝕也有幫助。
造成軸承卡住的原因是缺少內(nèi)隙、潤滑不當(dāng)和載荷過大。在卡住之前,過大的摩擦和熱量使軸承鋼軟化。過熱的軸承通常會改變顏色,一般會變成藍黑色或淡黃色。摩擦還會使保持架受力,這會破壞支承架,并加速軸承的失效。
材料過早出現(xiàn)疲勞破壞是由重載后過大的預(yù)載引起的。如果這些條件不可避免,就應(yīng)仔細(xì)計算軸承壽命,以制定一個維護計劃。
另一個解決辦法是更換材料。若標(biāo)準(zhǔn)的軸承材料不能保證足夠的軸承壽命,就應(yīng)當(dāng)采用特殊的材料。另外,如果這個問題是由于載荷過大造成的,就應(yīng)該采用抗載能力更強或其他結(jié)構(gòu)的軸承。
蠕動不象過早疲勞那樣普遍。軸承的蠕動是由于軸和內(nèi)圈之間的間隙過大造成的。蠕動的害處很大,它不僅損害軸承,也破壞其他零件。
蠕動的明顯特征是劃痕、擦痕或軸與內(nèi)圈的顏色變化。為了防止蠕動,應(yīng)該先用肉眼檢查一下軸承箱件和軸的配件。
蠕動與安裝不正有關(guān)。如果軸承圈不正或翹起,滾珠將沿著一個非圓周軌道運動。這個問題是由于安裝不正確或公差不正確或軸承安裝現(xiàn)場的垂直度不夠造成的。如果偏斜超過0.25°,軸承就會過早地失效。
檢查潤滑劑的污染比檢查裝配不正或蠕動要困難得多。污染的特征是使軸承過早的出現(xiàn)磨損。潤滑劑中的固體雜質(zhì)就象磨粒一樣。如果滾珠和保持架之間潤滑不良也會磨損并削弱保持架。在這種情況下,潤滑對于完全加工形式的保持架來說是至關(guān)重要的。相比之下,帶狀或冠狀保持架能較容易地使?jié)櫥瑒┑竭_全部表面。
銹是濕氣污染的一種形式,它的出現(xiàn)常常表明材料選擇不當(dāng)。如果某一材料經(jīng)檢驗適合工作要求,那么防止生銹的最簡單的方法是給軸承包裝起來,直到安裝使用時才打開包裝。
2 避免失效的方法
解決軸承失效問題的最好辦法就是避免失效發(fā)生。這可以在選用過程中通過考慮關(guān)鍵性能特征來實現(xiàn)。這些特征包括噪聲、起動和運轉(zhuǎn)扭矩、剛性、非重復(fù)性振擺以及徑向和軸向間隙。
扭矩要求是由潤滑劑、保持架、軸承圈質(zhì)量(彎曲部分的圓度和表面加工質(zhì)量)以及是否使用密封或遮護裝置來決定。潤滑劑的粘度必須認(rèn)真加以選擇,因為不適宜的潤滑劑會產(chǎn)生過大的扭矩,這在小型軸承中尤其如此。另外,不同的潤滑劑的噪聲特性也不一樣。舉例來說,潤滑脂產(chǎn)生的噪聲比潤滑油大一些。因此,要根據(jù)不同的用途來選用潤滑劑。
在軸承轉(zhuǎn)動過程中,如果內(nèi)圈和外圈之間存在一個隨機的偏心距,就會產(chǎn)生與凸輪運動非常相似的非重復(fù)性振擺(NRR)。保持架的尺寸誤差和軸承圈與滾珠的偏心都會引起NRR。和重復(fù)性振擺不同的是,NRR是沒有辦法進行補償?shù)摹?
在工業(yè)中一般是根據(jù)具體的應(yīng)用來選擇不同類型和精度等級的軸承。例如,當(dāng)要求振擺最小時,軸承的非重復(fù)性振擺不能超過0.3微米。同樣,機床主軸只能容許最小的振擺,以保證切削精度。因此在機床的應(yīng)用中應(yīng)該使用非重復(fù)性振擺較小的軸承。
在許多工業(yè)產(chǎn)品中,污染是不可避免的,因此常用密封或遮護裝置來保護軸承,使其免受灰塵或臟物的侵蝕。但是,由于軸承內(nèi)外圈的運動,使軸承的密封不可能達到完美的程度,因此潤滑油的泄漏和污染始終是一個未能解決的問題。
一旦軸承受到污染,潤滑劑就要變質(zhì),運行噪聲也隨之變大。如果軸承過熱,它將會卡住。當(dāng)污染物處于滾珠和軸承圈之間時,其作用和金屬表面之間的磨粒一樣,會使軸承磨損。采用密封和遮護裝置來擋開臟物是控制污染的一種方法。
噪聲是反映軸承質(zhì)量的一個指標(biāo)。軸承的性能可以用不同的噪聲等級來表示。
噪聲的分析是用安德遜計進行的,該儀器在軸承生產(chǎn)中可用來控制質(zhì)量,也可對失效的軸承進行分析。將一傳感器連接在軸承外圈上,而內(nèi)圈在心軸以1800r/min的轉(zhuǎn)速旋轉(zhuǎn)。測量噪聲的單位為anderon。即用um/rad表示的軸承位移。
根據(jù)經(jīng)驗,觀察者可以根據(jù)聲音辨別出微小的缺陷。例如,灰塵產(chǎn)生的是不規(guī)則的劈啪聲;滾珠劃痕產(chǎn)生一種連續(xù)的爆破聲,確定這種劃痕最困難;內(nèi)圈損傷通常產(chǎn)生連續(xù)的高頻噪聲,而外圈損傷則產(chǎn)生一種間歇的聲音。
軸承缺陷可以通過其頻率特性進一步加以鑒定。通常軸承缺陷被分為低、中、高三個波段。缺陷還可以根據(jù)軸承每轉(zhuǎn)動一周出現(xiàn)的不規(guī)則變化的次數(shù)加以鑒定。
低頻噪聲是長波段不規(guī)則變化的結(jié)果。軸承每轉(zhuǎn)一周這種不規(guī)則變化可出現(xiàn)1.6~10次,它們是由各種干涉(例如 軸承圈滾道上的凹坑)引起的??刹煊X的凹坑是一種制造缺陷,它是在制造過程中由于多爪卡盤夾的太緊而形成的。
中頻噪聲的特征是軸承每旋轉(zhuǎn)一周不規(guī)則變化出現(xiàn)10~60次。這種缺陷是由在軸承圈和滾珠的磨削加工中出現(xiàn)的振動引起的。軸承每旋轉(zhuǎn)一周高頻不規(guī)則變化出現(xiàn)60~300次,它表明軸承上存在著密集的振痕或大面積的粗糙不平。
利用軸承的噪聲特性對軸承進行分類,用戶除了可以確定大多數(shù)廠商所使用的ABEC標(biāo)準(zhǔn)外,還可確定軸承的噪聲等級。ABEC標(biāo)準(zhǔn)只定義了諸如孔、外徑、振擺等尺寸公差。隨著ABEC級別的增加(從3增到9),公差逐漸變小。但ABEC等級并不能反映其他軸承特性,如軸承圈質(zhì)量、粗糙度、噪聲等。因此,噪聲等級的劃分有助于工業(yè)標(biāo)準(zhǔn)的改進。
畢業(yè)設(shè)計(論文)外文翻譯原文
EXTENDING BEARING LIFE
Abstract:Nature works hard to destroy bearings, but their chances of survival can be improved by following a few simple guidelines. Extreme neglect in a bearing leads to overheating and possibly seizure or, at worst, an explosion. But even a failed bearing leaves clues as to what went wrong. After a little detective work, action can be taken to avoid a repeat performance.
Keywords: bearings failures life
Bearings fail for a number of reasons,but the most common are misapplication,contamination,improper lubricant,shipping or handling damage,and misalignment. The problem is often not difficult to diagnose because a failed bearing usually leaves telltale signs about what went wrong.
However,while a postmortem yields good information,it is better to avoid the process altogether by specifying the bearing correctly in The first place.To do this,it is useful to review the manufacturers sizing guidelines and operating characteristics for the selected bearing.
Equally critical is a study of requirements for noise, torque, and runout, as well as possible exposure to contaminants, hostile liquids, and temperature extremes. This can provide further clues as to whether a bearing is right for a job.
1 Why bearings fail
About 40% of ball bearing failures are caused by contamination from dust, dirt, shavings, and corrosion. Contamination also causes torque and noise problems, and is often the result of improper handling or the application environment.Fortunately, a bearing failure caused by environment or handling contamination is preventable,and a simple visual examination can easily identify the cause.
Conducting a postmortem il1ustrates what to look for on a failed or failing bearing.Then,understanding the mechanism behind the failure, such as brinelling or fatigue, helps eliminate the source of the problem.
Brinelling is one type of bearing failure easily avoided by proper handing and assembly. It is characterized by indentations in the bearing raceway caused by shock loading-such as when a bearing is dropped-or incorrect assembly. Brinelling usually occurs when loads exceed the material yield point(350,000 psi in SAE 52100 chrome steel).It may also be caused by improper assembly, Which places a load across the races.Raceway dents also produce noise,vibration,and increased torque.
A similar defect is a pattern of elliptical dents caused by balls vibrating between raceways while the bearing is not turning.This problem is called false brinelling. It occurs on equipment in transit or that vibrates when not in operation. In addition, debris created by false brinelling acts like an abrasive, further contaminating the bearing. Unlike brinelling, false binelling is often indicated by a reddish color from fretting corrosion in the lubricant.
False brinelling is prevented by eliminating vibration sources and keeping the bearing well lubricated. Isolation pads on the equipment or a separate foundation may be required to reduce environmental vibration. Also a light preload on the bearing helps keep the balls and raceway in tight contact. Preloading also helps prevent false brinelling during transit.
Seizures can be caused by a lack of internal clearance, improper lubrication, or excessive loading. Before seizing, excessive, friction and heat softens the bearing steel. Overheated bearings often change color,usually to blue-black or straw colored.Friction also causes stress in the retainer,which can break and hasten bearing failure.
Premature material fatigue is caused by a high load or excessive preload.When these conditions are unavoidable,bearing life should be carefully calculated so that a maintenance scheme can be worked out.
Another solution for fighting premature fatigue is changing material.When standard bearing materials,such as 440C or SAE 52100,do not guarantee sufficient life,specialty materials can be recommended. In addition,when the problem is traced back to excessive loading,a higher capacity bearing or different configuration may be used.
Creep is less common than premature fatigue.In bearings.it is caused by excessive clearance between bore and shaft that allows the bore to rotate on the shaft.Creep can be expensive because it causes damage to other components in addition to the bearing.
0ther more likely creep indicators are scratches,scuff marks,or discoloration to shaft and bore.To prevent creep damage,the bearing housing and shaft fittings should be visually checked.
Misalignment is related to creep in that it is mounting related.If races are misaligned or cocked.The balls track in a noncircumferencial path.The problem is incorrect mounting or tolerancing,or insufficient squareness of the bearing mounting site.Misalignment of more than 1/4·can cause an early failure.
Contaminated lubricant is often more difficult to detect than misalignment or creep.Contamination shows as premature wear.Solid contaminants become an abrasive in the lubricant.In addition。insufficient lubrication between ball and retainer wears and weakens the retainer.In this situation,lubrication is critical if the retainer is a fully machined type.Ribbon or crown retainers,in contrast,allow lubricants to more easily reach all surfaces.
Rust is a form of moisture contamination and often indicates the wrong material for the application.If the material checks out for the job,the easiest way to prevent rust is to keep bearings in their packaging,until just before installation.
2 Avoiding failures
The best way to handle bearing failures is to avoid them.This can be done in the selection process by recognizing critical performance characteristics.These include noise,starting and running torque,stiffness,nonrepetitive runout,and radial and axial play.In some applications, these items are so critical that specifying an ABEC level alone is not sufficient.
Torque requirements are determined by the lubricant,retainer,raceway quality(roundness cross curvature and surface finish),and whether seals or shields are used.Lubricant viscosity must be selected carefully because inappropriate lubricant,especially in miniature bearings,causes excessive torque.Also,different lubricants have varying noise characteristics that should be matched to the application. For example,greases produce more noise than oil.
Nonrepetitive runout(NRR)occurs during rotation as a random eccentricity between the inner and outer races,much like a cam action.NRR can be caused by retainer tolerance or eccentricities of the raceways and balls.Unlike repetitive runout, no compensation can be made for NRR.
NRR is reflected in the cost of the bearing.It is common in the industry to provide different bearing types and grades for specific applications.For example,a bearing with an NRR of less than 0.3um is used when minimal runout is needed,such as in disk—drive spindle motors.Similarly,machine—tool spindles tolerate only minimal deflections to maintain precision cuts.Consequently, bearings are manufactured with low NRR just for machine-tool applications.
Contamination is unavoidable in many industrial products,and shields and seals are commonly used to protect bearings from dust and dirt.However,a perfect bearing seal is not possible because of the movement between inner and outer races.Consequently,lubrication migration and contamination are always problems.
Once a bearing is contaminated, its lubricant deteriorates and operation becomes noisier.If it overheats,the bearing can seize.At the very least,contamination causes wear as it works between balls and the raceway,becoming imbedded in the races and acting as an abrasive between metal surfaces.Fending off dirt with seals and shields illustrates some methods for controlling contamination.
Noise is as an indicator of bearing quality.Various noise grades have been developed to classify bearing performance capabilities.
Noise analysis is done with an Anderonmeter, which is used for quality control in bearing production and also when failed bearings are returned for analysis. A transducer is attached to the outer ring and the inner race is turned at 1,800rpm on an air spindle. Noise is measured in andirons, which represent ball displacement in μm/rad.
With experience, inspectors can identify the smallest flaw from their sound. Dust, for example, makes an irregular crackling. Ball scratches make a consistent popping and are the most difficult to identify. Inner-race damage is normally a constant high-pitched noise, while a damaged outer race makes an intermittent sound as it rotates.
Bearing defects are further identified by their frequencies. Generally, defects are separated into low, medium, and high wavelengths. Defects are also referenced to the number of irregularities per revolution.
Low-band noise is the effect of long-wavelength irregularities that occur about 1.6 to 10 times per revolution. These are caused by a variety of inconsistencies, such as pockets in the race. Detectable pockets are manufacturing flaws and result when the race is mounted too tightly in multiplejaw chucks.
Medium-hand noise is characterized by irregularities that occur 10 to 60 times per revolution. It is caused by vibration in the grinding operation that produces balls and raceways. High-hand irregularities occur at 60 to 300 times per revolution and indicate closely spaced chatter marks or widely spaced, rough irregularities.
Classifying bearings by their noise characteristics allows users to specify a noise grade in addition to the ABEC standards used by most manufacturers. ABEC defines physical tolerances such as bore, outer diameter, and runout. As the ABEC class number increase (from 3 to 9), tolerances are tightened. ABEC class, however, does not specify other bearing characteristics such as raceway quality, finish, or noise. Hence, a noise classification helps improve on the industry standard.
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工 學(xué) 院 畢 業(yè) 設(shè) 計( 論 文 )
題 目: 桃子去皮機設(shè)計
專 業(yè): 機械設(shè)計制造及其自動化
班 級: 五班
姓 名: 段開元
學(xué) 號: 2006664506
指導(dǎo)教師: 李 慧
日 期: 2010年6月7日
工 學(xué) 院 畢 業(yè) 設(shè) 計(開題報告)
題 目: 桃子去皮機設(shè)計
專 業(yè): 機械設(shè)計制造及其自動化
班 級: 06級(5)班
姓 名: 段開元
學(xué) 號: 2006664506
指導(dǎo)教師: 李 慧
日 期: 2010年3月
工 學(xué) 院 畢 業(yè) 設(shè) 計( 論文綜述)
題 目: 桃子去皮機設(shè)計
專 業(yè): 機械設(shè)計制造及其自動化
班 級: 06級(5)班
姓 名: 段開元
學(xué) 號: 2006664506
指導(dǎo)教師: 李 慧
日 期: 2010年6月7日
一、論文題目
桃子去皮機的設(shè)計
題目來源
生產(chǎn)實踐
二、研究(調(diào)查)目的意義:
我國是世界上最大的農(nóng)業(yè)生產(chǎn)國,近年來,我國的果蔬加工業(yè)取得了巨大的成就,果蔬速凍食品機械在我國農(nóng)產(chǎn)品貿(mào)易中占據(jù)了重要地位。目前,我國的果蔬加工業(yè)已具備了一定的技術(shù)水平和較大的生產(chǎn)規(guī)模,外向型果蔬加工產(chǎn)業(yè)布局已基本形成。但是,盡管高新技術(shù)在我國果蔬加工業(yè)得到了逐步應(yīng)用,加工裝備水平也得到了明顯提高,但由于缺乏具有自主知識產(chǎn)權(quán)的核心關(guān)鍵技術(shù)與關(guān)鍵制造技術(shù),造成了我國果蔬加工業(yè)總體加工技術(shù)與加工裝備制造技術(shù)水平偏低。本課題的提出就是基于上述的實際需要出發(fā),尤其是考慮到任何一種形式的果蔬原料加工,去皮都是其中一項必不可少且重要的操作環(huán)節(jié)。去皮效率的高低和安全衛(wèi)生性將直接影響果蔬原料加工的效益。針對這些特點所采取的設(shè)計方案不僅從實際產(chǎn)量要求出發(fā),而且還結(jié)合經(jīng)濟最優(yōu)化,以達到最低成本產(chǎn)生最大收益[1]。
三、國內(nèi)、外研究概況和應(yīng)用前景(附參考文獻):
近年來,我國的果蔬加工業(yè)取得了巨大的成就,果蔬速凍食品機械在我國農(nóng)產(chǎn)品貿(mào)易中占據(jù)了重要地位。目前,我國的果蔬加工業(yè)已具備了一定的技術(shù)水平和較大的生產(chǎn)規(guī)模,外向型果蔬加工產(chǎn)業(yè)布局已基本形成。
盡管我國的果蔬加工產(chǎn)業(yè)無論是加工能力、技術(shù)水平、裝備硬件以及國內(nèi)外市場都取得了較大的進步和快速的發(fā)展,但是與國外發(fā)達國家相比仍然存在一定的差距。
我國在果蔬加工原料的選育方面取得了一定的進步,但是適合加工的果蔬品種仍然很少,制約了果蔬加工業(yè)的良性發(fā)展。例如,濃縮蘋果汁加工長期以來以鮮食品種為原料進行加工,制約了產(chǎn)品質(zhì)量的進一步提高,產(chǎn)品的出口價格低,經(jīng)濟效益不高。又如,在脫水果蔬及速凍果蔬方面,加工企業(yè)多數(shù)沒有自己的優(yōu)質(zhì)蔬菜加工原料基地,如國際貿(mào)易中占主導(dǎo)地位的脫水馬鈴薯、洋蔥、胡蘿卜及速凍豌豆、馬鈴薯等大品種,我國加工量較少[2]。
盡管高新技術(shù)在我國果蔬加工業(yè)得到了逐步應(yīng)用,加工裝備水平也得到了明顯提高,但由于缺乏具有自主知識產(chǎn)權(quán)的核心關(guān)鍵技術(shù)與關(guān)鍵制造技術(shù),造成了我國果蔬加工業(yè)總體加工技術(shù)與加工裝備制造技術(shù)水平偏低。
中國已發(fā)展成為世界果蔬和加工品的最大出口國,但很多是以半成品的形式出口,到國外后仍要進行深加工或灌裝,產(chǎn)品附加值較低。高附加值產(chǎn)品少,特別是對原料的綜合利用程度低,皮渣中果膠、果蔬天然香精、膳食纖維、色素、籽油等精深加工產(chǎn)品的產(chǎn)業(yè)化核心技術(shù)沒有突破[3]。
果蔬加工行業(yè)通過資本運作,逐步進行企業(yè)的并購與重組,企業(yè)規(guī)模不斷擴大,行業(yè)集中度日益增高,產(chǎn)生了一批農(nóng)業(yè)產(chǎn)業(yè)化龍頭企業(yè),產(chǎn)業(yè)規(guī)模得以迅速擴張,但依然處于企業(yè)的加工規(guī)模小、抗風(fēng)險能力差、產(chǎn)品單一、產(chǎn)品銷路不暢、競爭力差的發(fā)展階段。
更重要的是,我國果蔬加工企業(yè)的研發(fā)與創(chuàng)新能力十分薄弱,核心競爭力實質(zhì)只是所謂的“低價格優(yōu)勢”。在國外,絕大部分企業(yè)都設(shè)有企業(yè)的研發(fā)部門或研發(fā)中心,進行新產(chǎn)品的開發(fā),一般企業(yè)的研發(fā)費用占銷售收入2%—3%以上。但是,國內(nèi)的大部分加工企業(yè)不重視產(chǎn)品的研發(fā)和科技投入,不注重企業(yè)人才培養(yǎng)與引進,造成企業(yè)研發(fā)人才和研發(fā)設(shè)施缺乏,從而導(dǎo)致企業(yè)研發(fā)與創(chuàng)新能力差、技術(shù)水平落后、產(chǎn)品難以滿足市場需求。
果蔬原料清洗的目的在于洗去果蔬表面附著的塵土、泥沙和大量的微生物以及部分的化學(xué)農(nóng)藥,保證產(chǎn)品的清潔衛(wèi)生,從而保證產(chǎn)品品質(zhì)。對于農(nóng)藥殘留的果蔬,洗滌時常在水中加化學(xué)洗滌劑,常用的有鹽堿地酸、醋酸,有時也用氫氧化鈉等強堿及漂白粉、高錳酸鉀等強氧化劑。果蔬清洗的方法須根據(jù)果蔬形狀、質(zhì)地、表面狀態(tài)、污染程度、夾帶泥土量以及加工方法而定。主要有手工清洗和機械清洗。后者需配置滾筒式、噴淋式、壓氣式、漿葉式等設(shè)備[4]。
國內(nèi)外桃子去皮方法大致有三種,即機械去皮、蒸汽去皮和化學(xué)去皮,三種去皮方法的工作原理為:
機械去皮:在圓筒形容器中,依靠帶有磨料的圓盤、滾輪或依靠特制的橡膠輥在中速或高速旋轉(zhuǎn)中摩擦塊莖的表面而達到去皮目的。
蒸汽去皮:在高壓容器內(nèi),通入高壓蒸汽使塊莖表面受熱,然后打開容器蓋,突然釋放壓力,塊莖的表皮和果肉即自行分離。
化學(xué)去皮:在耐堿容器內(nèi),加入強堿溶液并加溫,后加入塊莖,經(jīng)一段時間后塊莖的表皮被堿溶液腐蝕,經(jīng)高壓水反復(fù)沖洗干凈后,在將塊莖放入機械去皮機中剝?nèi)ケ砥3]。
根據(jù)以上情況,我們應(yīng)該將果蔬加工多樣化,深層次化,本課題的提出就是基于上述的實際需要出發(fā),尤其是考慮到任何一種形式的果蔬原料加工,去皮都是其中一項必不可少且重要的操作環(huán)節(jié)。去皮效率的高低和安全衛(wèi)生性將直接影響果蔬原料加工的效益。針對這些特點所采取的設(shè)計方案不僅從實際產(chǎn)量要求出發(fā),而且還結(jié)合經(jīng)濟最優(yōu)化,以達到最低成本產(chǎn)生最大收益。
參考文獻:
[1 (1)無錫輕工業(yè)學(xué)院,天津輕工業(yè)學(xué)院編著.食品工廠機械與設(shè)備[M].北京輕工業(yè)出版社,1981
(2)張淑娟等.立式半夏去皮機的設(shè)計與研究[J].農(nóng)機與食品機械.1997年第2期
王 (3)景彬等.試論國內(nèi)外果蔬脫皮方法與設(shè)備[J].農(nóng)牧與食品機械,1991(2)
(4)吳慶章.馬鈴薯食品加工技術(shù).農(nóng)牧與食品機械,1986(3)
四、設(shè)計內(nèi)容、設(shè)計方法和思路:
設(shè)計內(nèi)容:
1. 桃子去皮機特性及計算
2. 桃子去皮機的設(shè)計依據(jù)
3. 桃子去皮機熱風(fēng)采暖爐系統(tǒng)設(shè)計及計算
設(shè)計方法:
1)查閱桃子去皮機的相關(guān)資料;
2)對桃子去皮機的可能性進行了理論分析;
3)設(shè)計桃子去皮機各結(jié)構(gòu),并實現(xiàn)其功能;
4)對桃子去皮機做出結(jié)論分析
設(shè)計思路:
在完成設(shè)計要求和原理分析,查閱相關(guān)技術(shù)資料后,設(shè)計去皮機系統(tǒng)的整體框架和分析工作過程。然后搭建整個去皮機系統(tǒng)示意圖并進行參數(shù)分析,然后進行桃子去皮機的設(shè)計,并對去皮機做出結(jié)論和建議,從而完成整個桃子去皮機的設(shè)計。
指導(dǎo)教師意見(研究的意義、創(chuàng)新點、前期基礎(chǔ)工作、存在的難點和困難、建議等):
指導(dǎo)教師簽名: 年 月 日
學(xué)院領(lǐng)導(dǎo)組意見:
簽名: 年 月 日
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