液体过滤系统

如何挑选适合您的过滤？
-----过滤机理
液体从过滤袋内流向袋外，滤出的颗粒被截留在袋内，使袋式过滤的工作原理是压力过滤。整套袋式过滤系统包括三个部分：过滤容器、支撑网篮和过滤袋。
要过滤的液体从被支撑网篮支撑的过滤袋顶部注入，这使得液体在过滤表面均匀分布，以便整个介质中流动分布是一致的面，没有紊流的负效应。
液体从过滤袋内流向袋外，滤出的颗粒被截留在袋内，使得更换过滤袋时不致污染已经过滤的液体。在过滤袋内的提手设计使得过滤袋更换快速便捷。
上海赢森滤袋特点如下：
高流通能力. 
较长滤袋使用寿命. 
均匀的流动液体令颗粒杂质平均地分布在滤袋的滤层中
较高的过滤效率,成本最低. 
1.滤材的选用
首先按照所要过滤的流体化学名称，依化学配合禁忌找出可用的滤材，再针对其操作温度，操作压力，酸碱值，操作条件(如，是否须要耐受蒸汽，热水或化学品杀菌等)，逐一评估，并剔除不适用之滤材。 用途也是一个重要的考虑因素，比方药品、食品或化妆品用之滤材必须是FDA准许的材质；超纯水则须挑选纯净、不含有释出物会影响比阻抗的滤材；过滤气体则须挑选疏水性材质以及是否需要"卫生级过滤"设计等等。
2.过滤精密度
这是一个最令人困扰的问题。比方，要除去肉眼可见的颗粒，要选用25微米过滤器；要除去液体中云状物，要选用1或5微米过滤器；要滤除最小的细菌则需0.2微米的过滤器。问题在于有两种过滤精度单位：绝对精度／公称精度.
绝对精度／公称精度
绝对精度是指能100%滤除所标示精度之颗粒。对任何一种过滤器而言，这几乎是一个不可能达到，而且不实际的标准，因为100%是一个无穷大的值。市面上通称的绝对过滤器如薄膜等，严格地说，只能称"趋近于绝对"的过滤器,而其它则皆属于公称精度，公称精度，这才是主要的困扰所在:"公称精度并没有一个业者共同认定并遵行的标准"。也就是说甲公司可以把公称精度订在85-95%，而乙公司却宁可订在50-70%。换句话说，甲公司的25微米过滤精度可能等于乙公司的5微米，或者更细。对此问题，有经验的专业过滤器供应商会有助于过滤精度之选择，而根本解决之道是"试用"。
3. 依照过滤温度时的粘度，专业过滤设备供应商可以计算出需要多大的过滤器，滤袋承担多大的流速以及预测其初期压降若干。若能提供流体中杂质含量，甚至可以预估其过滤寿命。
4. 过滤系统之设计 
　这个标题牵涉范围较广，比方应该选用那一种压力来源，需要多大的压力，是否需要装两套过滤器并联，以适合连续性操作之系统，对粒径分布宽广的场合应如何搭配粗滤与精滤，系统中是否须要装逆止阀或其他装置等等。这些都需要使用单位与过滤器供应商密切配合，共同找出最恰当的设计。
5. 滤袋的使用方式 
滤器密闭过滤：滤袋与配套过滤器同时使用，利用系统流体压力，将液体挤压通过滤袋，以达到过滤的目的。具有流速快，处理能力大，滤袋使用寿命长的优点，特别适应大流量需密闭过滤的场合。自流开放过滤：滤袋通过适合接头直接与管道相连，得用流体重力压差进行过滤。其显著特点是无需设备投资，过滤简单可行，特别适用于小规格、多品种、间歇式的经济型液体过滤。
表面过滤与深度过滤的区别
表面过滤主要采用筛网材料，深度过滤则采用毛毡材料，它们的区别如下：
1．筛网材料（尼龙单丝、金属单丝）将过滤中杂质直接截留在材料表面。优点是单丝结构可反复清洗，消耗成本较低；而缺点是表面过滤模式，易造成滤袋表面堵塞，该类型产品最适用于精度较低的粗滤场合，过滤精度25-1200μm。
2．毛毡材料（针刺布、溶吹无纺布）是常见的深层三维过滤材料，其特点是纤维组织疏松，高空隙率增加了杂质的容截量，该种纤维材料系属复式截留模式，即较大的颗粒杂质被截留在纤维表面，而细微颗粒则被捕捉于滤材深层中，因此过滤具有较高过滤效率，此外高温表面热处理，即应用瞬间烧结技术，能有效地防止过滤时纤维受流体高速冲带而散失；毛毡材料是属于丢弃型的（一次性使用），过滤精度1-200μm。
过滤毡主要使用的材质性能如下：
聚脂--最普遍使用的滤材纤维，抗化学品佳，工作温度小于170-190℃
聚丙烯--用于化学工业的液体过滤，有极佳的抗酸、碱功能，工作温度小于100-110℃
羊毛--很好的抗溶剂功能，但不适用于抗酸、碱的过滤 
尼龙--有良好抗化学品功能（除抗酸以外），工作温度小于170-190℃ 
氟化物--具有******的抗温及抗化学品功能，工作温度小于250-270℃ 

How to select the filtration fit for your application
Principles of filtration
Liquid goes through the filter bag, particulars are trapped in the bag, the principles of the filter is pressure filtration. The bag type filtration system has filter container, support net basket and filter bag.
Liquid for filtration is feed from the top and evenly distributed in the filtration surface, the movement of the medium is at uniformed side, non negative effect of vortex flow. 
The particulars are trapped in the bag, and will not containment the filtered liquid while replacing the filter bag. 
Featurres: 
High flow capability. 
Long life time of the filter bag. 
Evenly distributed particulars in the filtration layer of the bag 
High filtration effect, low cost. 
1.Selection of filtration material
Select the applicable filtration material based upon the chemical nomination of the fluid chemical and the chemical composition; secondly, judged by the operating temperature, operating pressure, acid & caustic values, operating conditions (such as steam durable, hot water or chemical anti-bacteria etc) rejecting the non suitable filtration material. The usage is another important factor, such as medicine, food or cosmetics filtration material must be FDA compliance material. Filtration material used in the pure water must be purified, non releasing material which may impact the anti-resistance , air filtration must be hydro water material and whether need hygiene filtration design etc
2.Filtration mesh and density
This has been an annoying issue. For example, to remove the seeable particulars may need 25 um filter, to remove the cloudy material in the liquid may need 1 to 5 um filter, and 0.2 um filter may be required to remove micro bactria.
Absolute precise / nominated precises This has been an annoying issue. For example, to remove the seeable particulars may need 25 um filter, to remove the cloudy material in the liquid may need 1 to 5 um filter, and 0.2 um filter may be required to remove micro bactria.absolute precise / nominated precises.
Absolute precise refer to 100% remove the indicated sized particulars. It is impossible and not feasible for every filter , since 100% is an infinite value. The absolute filter such as films in the market is actually close to the absolute filter. The issue for the nominated precise is that there is no common recognized and executable standard. For instance, company A may defines as 85-95%, company B may defines as 50-70%. In another word, the 25 um filter of company A may equals to 5 um filter of company B. Experience filter supplier can help to determine the most suitable filter, and most effective way is “try use”
3. Filter supplier can calculate the size of the filter based upon the flow speed that bag can bear, and estimation of primary pressure drop and viscosity at filtration temperature. The estimated life time can be made if the content of foreign material in the fluid is known.
4. Design of filtration system 
This may involve various aspects, such as the selection of pressure source, pressure range, whether two sets of filters should be parallel to assist continuous operation. The coarse filtration and fine filtration matching, whether check valve or other facilities shall be equipped in the system. All of above shall be communicated with the filter supplier to get most appropriate design.
5. Way of filter bag use  
Close filtration in filter: filter bag is used with the filter, liquid is squeezed pass through the filter bag via system fluid pressure and filtration is achieved. Such application has the advantage of rapid fluid speed and high capacity, long life cycle of the filter bag. And mostly suitable for high flow closed loop filtration application.
Difference between surface filtration and deep filtration：
1. Sieve (nylon single filament, non ferrous steel single filament) The foreign material in the filtration process trapped on the material surface. The advantage is the filtration net can be reused after using and low consumption cost. The disadvantage is of surface filtration, which easy to cause surface block. Such type of sieve is suitable for coarse filtration application, the sieve mesh is 25-1200μm
2．Acicular blanket can effectively remove solids and soft particulars. The acicular 100% pure fiber has the multi dimensional structure and purred filtering layers, especially the internal layer has the pure fiber high strength net to prevent the filter bag from damage and abrasion due to the pressure increase.
The major property of the filter blanket is as follow:
Polyester -The conventional filtration fiber, ideal for anti-chemical contamination, working temperature below 70-190
Polypropylene –Used for liquid filtration in chemical industry, have good anti-acid and anti-caustic, working temperature lower 100-110
Wool-good anti-solvency , but applicable for anti-acid, anti-caustic filtration
Nylon—satisfactory anti-chemical (except acid), working temperature lower than 170-190
Fluorin—have good anti-heating and anti-chemical property, working temperature lower than 250-270.