净水器各级滤壳用什么尼龙 —— 水里那点事，比油箱复杂
净水器不是"装水的塑料壳"。从 PP 棉到反渗透膜，从前置到末端直饮，
过滤精度从 1 微米到 0.0001 微米，承压从 0.3 MPa 到 1.6 MPa，
水温从冰水到 60℃ 热水，每一段工况都不同。
滤壳选料踩过的坑：一个品牌的反渗透机，前 3 年没问题，第 4 年开始漏水。拆下来一看——壳体已经沿熔接线开裂。
原因是早期用了 PA66-GF30，热水长期接触下吸水后胀，嵌件又没预热。
一、净水器六段水路，材料各不相同
按精度从粗到细，净水器通常分成六级：
| 段 | 功能 | 滤芯壳材料 | 主要工况 |
|---|
| 第 1 段 | PP 棉粗滤 | PP / PA6 | 5 微米，水压 0.3 MPa |
| 第 2 段 | 活性炭吸附 | ABS / PP | 接触吸附剂 |
| 第 3 段 | 1 微米精滤 | PP / PA6 | 1 微米 |
| 第 4 段 | 反渗透膜壳 | PP / 改 PA | 1.0-1.6 MPa |
| 第 5 段 | 后置活性炭 | ABS / PP | 出水口感调整 |
| 第 6 段 | 即热管路 | PA12 / PPS | 60℃ 热水瞬时 |
水处理壳体不是"塑料壳"——承压、热水、反复拆卸、酸碱洗涤剂浸泡，四件事同时作用。
现场还原
去年十月，慈溪一家整机厂的试产线上，第三级滤壳在保压测试时爆了。测试员按规程打到0.8兆帕保压三十分钟，滤壳进水口螺纹根部裂开一道缝，水顺着治具流了半台子。
厂长在电话里的原话是，料单上写的和实物对不上，供应商说是通用级，我们按增强级付的钱。第二天我们带了三个批次的样件过去，同一套模具，三种料，装上治具一轮一轮打，裂缝全部出现在同一个位置。问题不在模具，在料。
螺纹根部有应力集中，通用级料的韧性撑不住反复的水锤冲击，最后换成玻纤增强的PA66，同一套治具连续打了两百次，再没裂过。
这件事之后，那家厂的来料检验里多了一条，滤壳料进场要验增强含量，烧一张样片看玻纤残留，两分钟的事，能省后面一整批的返工。
二、滤壳选料的三个硬要求
第一：长期承压下蠕变小。 反渗透膜壳长期在 0.6-0.8 MPa 工作，玻璃化温度不够的料会缓慢变形，三五年后螺纹咬不住。
PA66-GF30 在这里已经踩坑，原因就是吸水后胀 + 高温下玻璃化区下移。
第二：耐热水水解。 即热管线常接触 50-60℃ 水，PA66、PA6 在这种温度长期工作会水解——分子链断裂、强度下降。这类件必须用长碳链尼龙（PA12 / PA612）或 PPS。
第三：耐反复拆装。 滤芯每 3-6 个月要换一次，壳体上螺纹、密封槽、卡扣，长期吸湿后胀，拧紧的力矩会把塑料拉爆。
这一条对任何家用净水器都成立——选料必须按"饱和吸湿态"的尺寸算公差。
三、不同段的料怎么配
前置段（粗滤 + 精滤）：接触冷水、压力低，PP 和 PA6 都行。选 PA6 是为了螺纹强度，PP 太软，拧几次就花。
RO 膜壳：1 MPa 的长期蠕变考验。PA66-GF30 是经典方案，但要加防胀体系（玻纤 + 矿物复合）；更保险的方案是 PP-GF30，蠕变比 PA66 还小，但螺纹强度弱。
后置炭壳：主要是吸附剂摩擦 + 偶尔热水冲洗，ABS 或 PP 都行。
即热管线：50-60℃ 热水，长期水解。必须 PA12 或 PPS。PA12 比 PPS 便宜，是这一段的主流。
四、家用 vs 商用选料不同
家用净水器一般流速 2 L/min，压力 0.3 MPa，间歇使用。商用净水器（咖啡机、医院、实验室）24 小时连续工作，水温高，流量大。
家用段，PA6、PP 都过关；商用段，所有件都要重新算蠕变，特别即热管线必须升级到 PPS 或 PA12。
这一条一定要分清楚——把家用料的物性表直接套到商用场景，是商用净水器漏水的最常见原因。
五、连接件的陷阱
净水器漏水 80% 出在连接处：螺纹、快速接头、卡箍、密封圈。塑料与塑料的连接比金属难做，因为：
1. 塑料螺纹的拧紧力矩小：力矩太大直接崩，太小又密封不住
2. 塑料与密封圈的热膨胀差：水温一变就漏
3. 塑料与金属嵌件的连接：水温循环时最容易开裂
对策：螺纹深度放大到 8-10 牙、密封槽吸湿留 0.1-0.15 mm 余量、嵌件预热到 80-120℃ 再注塑。改结构比换料有效得多。
六、装在户外会怎样？
有些净水器装在阳台、户外、阳光直晒的位置。普通 ABS、PP 用半年就黄变、变脆。这一类必须用耐候配方——紫外线吸收剂 + 受阻胺光稳定剂（HALS）+ 抗氧化剂三件套。
不加耐候剂的普通 ABS，半年强度下降 30% 以上；加足三件套后，五年内保持 80% 以上强度。这是单价差异 10-15% 的取舍，但寿命差 3-5 倍。
工程实测：四条强制测试
测试一：长期承压蠕变。 0.8 MPa 持续 1000 小时，PA66-GF30 沿玻纤取向方向蠕变 1.5% 以上，PP-GF30 蠕变 0.5-0.8%，PA12-GF30 蠕变 0.3% 以内。RO 膜壳选料必须看这条数据。
测试二：热水水解加速。 60℃ 水浸泡 1000 小时，PA66-GF30 拉伸强度下降 35%，PA6-GF30 下降 40%，PA12 几乎不变。家用即热管线必须用 PA12 / PPS。
测试三：反复拆装疲劳。 螺纹拧紧松开 200 次循环，PA6 在吸湿后径向胀大 0.3 mm，拧紧力矩从 1.2 N·m 跌到 0.6 N·m——密封失效。
测试四：户外氙灯老化 1000 小时。 加耐候三件套的 ABS 拉伸保持率 82%；不加的 ABS 仅 47%，变脆肉眼可见。
边界声明
| 工况 | 推荐材料 |
|---|
| 家用冷水 + 0.3 MPa | PA6 / PP |
| 家用即热管线 | PA12 |
| 商用 24h 连续 | PPS / PA12 |
| RO 膜壳 | PA66-GF30 + 防胀 / PP-GF30 |
| 户外安装 | 加耐候三件套的 ABS / ASA |
| 滤芯频繁拆 | PA6-GF30 + 吸湿公差补偿 |
深一层：几个数字的来历
先说水锤那个数。泵启停瞬间的压力波能冲到静压的两到三倍，家用机的静压标称0.4到0.6兆帕，水锤瞬间就是1.2兆帕往上，试产线按0.8兆帕保压其实已经留了余量，出问题的从来不是余量不够，是料在交变压力下的疲劳强度不行。
静态强度报告看不出来这个，必须做交变测试。
再说壁厚和爆破的关系。3毫米壁厚的增强滤壳，爆破压力普遍能到4兆帕以上，但爆破压力和疲劳寿命是两回事，一个是静态强度，一个是交变载荷下裂纹怎么扩展。只看爆破报告选料，会把安全余量高估一大截，这是我们见过的最普遍的误判。
热水段的账要单独算。温度每升高10摄氏度，PA66的寿命大致减半，厨房水温常年40到50度，滤壳的实际寿命比常温数据缩水一大截。反渗透机后置滤壳常年接触温水，这就是为什么同一颗滤壳装在不同段位上表现差很多。
涉水卫生许可和食品接触国标是两套体系，一张管水的口感和安全，一张管材料迁移。经销商问起来经常混着问，报给客户时要把两张证的编号分开写清楚，混着写会被渠道商的审核退回来。
密封槽的公差要压在正负0.05毫米以内。塑料会蠕变，装上三个月后槽宽被撑大一点点，预紧就丢了。渗漏投诉里一半以上不是料坏了，是槽的设计没把蠕变算进去，这笔账在图纸阶段就该算完。
商用机的循环次数是另一本账。商用机每天几十次启停，一年下来上万次压力循环，家用机按每天五次算一年也就一千八百次。所以商用机滤壳的验证不是把家用测试多做几遍，是换一套交变疲劳的判定标准。
螺纹和卡扣的取舍也有讲究。螺纹可靠但要涂密封胶，卡扣装拆快但公差链长。商用机走螺纹加O圈，家用机为了换芯体验走卡扣，两条路线的料差别不大，模具精度要求差一个档。
工程备忘
净水器壳体量产前必须做长期承压蠕变 + 热水水解两项强制测试，任何一项不过立即换料号方案。
这是商用净水器漏水事故的 80% 来源，家用段可以放宽但必须做吸湿后尺寸验证。
追问三连
问一：能不能全换PP省成本？PP便宜三成，但刚性差，大口径滤壳装满水之后上盖会肉眼可见地鼓起来，卡扣还会随着冷热循环松掉。家用小滤芯可以用，商用大滤壳不建议，鼓壳的投诉比贵三成的料贵得多。
问二：玻纤外露会不会有卫生问题？熔接线位置玻纤外露确实影响观感，也有经销商拿这个做文章。实际迁移量在国标限值以内，担心观感可以做高光面，或者把熔接线挪到非水路一侧，模具上动一刀就解决。
问三：颜色怎么定？白色壳体装几个月会透出滤料的颜色，深色客户又嫌压抑，多数厂最后落在浅灰和米白之间。色母要选耐水解的型号，普通色母在温水里三个月就开始泛花，泛花的壳体被当成质量问题退货，比色母差价冤枉得多。
反向案例与收尾判断
今年春天有个客户拿着去年改过料的方案来复检，热水段的滤壳也换成了增强PA66，结果用了一年出现粉化脆裂。拆开看，问题出在水质，当地水源偏碱，氯离子含量高，高温碱水对PA66的水解是加速的，同样的料在隔壁城市用了两年还好好的。
后来热水段换了耐水解等级更高的牌号，复测三千小时没再出问题。这个案例说明同一张料单不能全国通用，水质是滤壳选料的隐藏变量，签样之前把客户所在地的水质报告要过来，比多打十轮测试都有用。
补记：工艺与制度层面的四件事
滤壳这类件的注塑工艺，残余应力是隐形变量。进水口螺纹根部之所以反复出问题，一半是料，一半是保压曲线太激进，浇口附近的内应力没释放。改料之后这家厂把保压时间延长了两秒，再补了一道80度的退火，同位置的强度又上了一个台阶。
料的钱花了，工艺的便宜也要占全，两件事一起做才算把问题关掉。
来料抽检的制度值得多说一句。这家厂现在的做法是每个批次烧片看玻纤，每月做一次破坏性的爆破抽检，数据记在台账上按季度看趋势。趋势比单点数据有用，料厂换批次、换产线，趋势线上都会先冒头，比等整机出问题早两个月。
制度的价值不在拦住多少坏料，在于让料厂知道你在看，供应端的态度会自己端正。
更换周期是渠道最关心的问题。家用滤壳的推荐更换周期写在说明书上，多数用户不换，滤壳本身扛得住，扛不住的是里面的滤料。但商用渠道会按周期真换，换的时候拆装力度、密封圈的复用次数，都会变成投诉。
给商用渠道的滤壳，卡扣要按拆装五十次验证，这是家用机上不用做的项目，料单上要单独标出来。
签样流程里最后提醒一点，样板签的是常温常湿的样板，仓库里放半年的货是另一回事。滤壳料在仓库存放超过六个月，颜色和韧性都会有可见的漂移，先进先出写在标签上，仓库执行，采购对账。
这些事没有一件是高深的，全做到的厂，售后记录就是比别人干净一整档。
结语
三年五年之后还那样，是改性尼龙这件活最朴素的验收标准。
净水器每一段水路工况都不一样的活，可以一起聊。
What type of nylon is used for each filter housing in a water purifier — the stuff in water is more complicated than in a fuel tank
A water purifier is not a 'plastic shell for holding water.' From PP cotton to reverse osmosis membranes, from the pre-filter to the end-point direct drinking,
Filtration precision ranges from 1 micron to 0.0001 micron, and pressure resistance ranges from 0.3 MPa to 1.6 MPa.
The water temperature ranges from ice water to 60°C hot water, and each stage operates under different conditions.
Pitfalls in choosing filter housings: A brand of reverse osmosis machine worked fine for the first three years, but started leaking in the fourth year. Upon taking it apart — the housing had already cracked along the weld line.
The reason is that PA66-GF30 was used early on, which swells after absorbing water when in long-term contact with hot water, and the insert was not preheated.
1. The water purifier has six stages of water flow, with different materials for each.
According to precision from coarse to fine, water purifiers are usually divided into six levels:
| Section | Function | Filter cartridge housing material | Main operating conditions |
|---|
| Paragraph 1 | PP Cotton Coarse Filter | PP / PA6 | 5 microns, water pressure 0.3 MPa |
| Paragraph 2 | Activated carbon adsorption | ABS / PP | Contact adsorbent |
| Paragraph 3 | 1 Micron Precision Filtration | PP / PA6 | 1 micrometer |
| Paragraph 4 | Reverse osmosis membrane housing | PP / Change PA | 1.0-1.6 MPa |
| Paragraph 5 | Post-positioned activated carbon | ABS / PP | Outlet taste adjustment |
| Paragraph 6 | Instant heating pipeline | PA12 / PPS | 60℃ Hot Water Instant |
A water treatment housing is not a 'plastic shell'—pressure, hot water, repeated disassembly, and soaking in acidic or alkaline detergents, all four things act at the same time.
On-site restoration
Last October, on the trial production line of a complete machine factory in Cixi, the tertiary filter housing burst during the pressure-holding test. The tester followed the procedure to pressurize to 0.8 MPa and hold for thirty minutes, but a crack appeared at the root of the threads at the water inlet of the filter housing, and water flowed along the fixture, wetting half of the workstation.
The plant manager said on the phone that the materials listed on the order form did not match the actual items. The supplier said it was a general grade, but we paid for the enhanced grade. The next day, we brought three batches of samples over. Using the same set of molds with three types of material, we mounted them on the fixture and ran them cycle by cycle, and the cracks all appeared in the same spot. The problem was not with the mold, but with the material.
There is stress concentration at the root of the thread. The toughness of general-grade material cannot withstand repeated water hammer impacts. Eventually, it was changed to glass fiber reinforced PA66, and the same set of fixtures was used continuously for two hundred shots without cracking again.
After this incident, the incoming material inspection at that factory added an extra step: the filter housing material must be checked for reinforcement content upon arrival, and a sample piece is burned to check for fiberglass residue. It takes two minutes and can save reworking an entire batch later.
2. Three Strict Requirements for Selecting Filter Housing Materials
First: Long-term pressure leads to little creep. The reverse osmosis membrane housing operates at 0.6-0.8 MPa for a long time, and materials with insufficient glass transition temperature will slowly deform, so that after three to five years, the threads cannot hold.
PA66-GF30 has already encountered problems here, the reason being it absorbs water and swells, causing the glass transition zone to shift downward under high temperatures.
Second: Hydrolysis resistant to hot water. That is, hot water pipelines are often in contact with water at 50-60°C, and PA66 and PA6 will undergo hydrolysis when working at this temperature for a long time—molecular chains break and strength decreases. Such parts must use long-chain nylon (PA12/PA612) or PPS.
Third: Resistant to repeated disassembly and assembly. The filter element needs to be replaced every 3-6 months, and the threads, sealing grooves, and clips on the housing will swell after long-term moisture absorption, and the tightening torque can cause the plastic to crack.
This principle applies to any household water purifier—the material selection must consider tolerances based on the 'saturated hygroscopic state' size.
3. How to mix materials from different batches
Pre-stage (coarse filtration and fine filtration): Contact with cold water, low pressure, both PP and PA6 are acceptable. PA6 is chosen for thread strength, as PP is too soft and will get damaged after a few screwings.
RO membrane housing: Long-term creep test at 1 MPa. PA66-GF30 is the classic solution, but an anti-swelling system needs to be added (glass fiber + mineral composite); a safer option is PP-GF30, which has even lower creep than PA66, but the thread strength is weak.
Rear carbon shell: Mainly the friction of the adsorbent. Occasionally rinse with hot water, either ABS or PP is fine.
Instant hot water line: 50-60℃ hot water, long-term hydrolysis. Must use PA12 or PPS. PA12 is cheaper than PPS and is the mainstream choice for this section.
4. Different Material Selection for Home vs Commercial Use
Household water purifiers generally have a flow rate of 2 L/min, a pressure of 0.3 MPa, and are used intermittently. Commercial water purifiers (coffee machines, hospitals, laboratories) operate continuously for 24 hours, with high water temperature and large flow rate.
For household use, PA6 and PP pass; for commercial use, all parts need to be recalculated for creep, and especially the instant heating pipeline must be upgraded to PPS or PA12.
This point must be clearly understood — directly applying the material properties table for household use to commercial scenarios is the most common reason for leaks in commercial water purifiers.
5. The Pitfalls of Connectors
80% of water purifier leaks occur at the connections: threads, quick connectors, clamps, and sealing rings. Connections between plastic and plastic are harder to make than those of metal because:
1. The tightening torque of plastic threads is low: if the torque is too high, they will break directly; if too low, they won't seal properly.
2. The thermal expansion difference between plastic and the sealing ring: it leaks as soon as the water temperature changes
3. Connection between plastic and metal inserts: most prone to cracking during water temperature cycling
Countermeasures: Increase the thread depth to 8-10 turns, leave a 0.1-0.15 mm allowance in the moisture-absorbing sealing groove, and preheat the insert to 80-120°C before injection molding. Changing the structure is much more effective than changing the material.
6. What happens if it is installed outdoors?
Some water purifiers are installed on balconies, outdoors, or in places exposed to direct sunlight. Ordinary ABS and PP turn yellow and become brittle after half a year. These must use weather-resistant formulas — a trio of ultraviolet absorbers, hindered amine light stabilizers (HALS), and antioxidants.
Ordinary ABS without weather-resistant additives loses more than 30% of its strength in half a year; with a full set of three additives, it maintains over 80% of its strength for five years. This is a trade-off with a unit price difference of 10-15%, but a lifespan difference of 3-5 times.
Engineering field measurement: four mandatory tests
Test 1: Long-term stress creep. At 0.8 MPa for 1000 hours, PA66-GF30 creeps more than 1.5% along the glass fiber orientation, PP-GF30 creeps 0.5-0.8%, and PA12-GF30 creeps within 0.3%. This data must be considered when selecting RO membrane housings.
Test 2: Accelerated hydrolysis in hot water. Soaking in 60°C water for 1000 hours, the tensile strength of PA66-GF30 decreased by 35%, PA6-GF30 decreased by 40%, and PA12 remained almost unchanged. Household instant heating pipes must use PA12 / PPS.
Test 3: Repeated assembly and disassembly fatigue. The threads were tightened and loosened for 200 cycles, PA6 expanded radially by 0.3 mm after moisture absorption, and the tightening torque dropped from 1.2 N·m to 0.6 N·m—seal failure.
Test 4: Outdoor xenon lamp aging for 1000 hours. ABS with weather-resistant three-piece set has a tensile retention rate of 82%; ABS without it is only 47%, becoming brittle visibly.
Boundary Declaration
| Operating condition | Recommended materials |
|---|
| Household cold water 0.3 MPa | PA6 / PP |
| Household Instant Heating Pipeline | PA12 |
| Commercial 24h continuous | PPS / PA12 |
| RO membrane housing | PA66-GF30 Anti-bloating / PP-GF30 |
| Outdoor installation | Weather-resistant three-piece ABS / ASA |
| Frequent filter replacement | PA6-GF30 Moisture Absorption Tolerance Compensation |
A deeper look: The origin of a few numbers
Let's talk about the water hammer number first. The pressure wave at the instant of pump start and stop can surge to two to three times the static pressure. For household machines, the nominal static pressure is 0.4 to 0.6 MPa, so the water hammer instantaneous pressure can go up to 1.2 MPa or higher. The trial production line maintains 0.8 MPa to hold pressure, which actually leaves a margin. The problem is never that the margin is insufficient; it's that the material's fatigue strength under alternating pressure is inadequate.
You can't see this from the static strength report; cyclic testing must be done.
Let's also talk about the relationship between wall thickness and burst pressure. An enhanced filter shell with a 3mm wall thickness generally can withstand burst pressures above 4 MPa, but burst pressure and fatigue life are two different things: one is static strength, the other is how cracks propagate under cyclic loading. Choosing materials based solely on burst reports will greatly overestimate the safety margin, which is the most common misjudgment we've seen.
The accounts for the hot water section need to be calculated separately. For every 10 degrees Celsius increase in temperature, the lifespan of PA66 roughly halves. The kitchen water temperature is consistently between 40 to 50 degrees, so the actual lifespan of the filter housing is much shorter than the data at normal temperature. The post-filter housing of the reverse osmosis machine is in contact with warm water all year round, which is why the same filter housing performs very differently when installed in different stages.
Water-related hygiene permits and food contact national standards are two separate systems: one controls the taste and safety of water, the other controls material migration. Distributors often mix them up when asking questions. When reporting to clients, the numbers of the two certificates must be written separately and clearly; mixing them up will result in the channel distributor's review being returned.
The tolerance of the sealing groove should be kept within plus or minus 0.05 millimeters. Plastics will creep, and after three months of assembly, the groove width will expand slightly, causing the preload to be lost. More than half of the leakage complaints are not due to material failure, but because the groove design did not account for creep. This calculation should have been completed at the drawing stage.
The number of cycles for a commercial machine is a completely different matter. A commercial machine starts and stops dozens of times a day, resulting in tens of thousands of pressure cycles a year, while a household machine, assuming five starts and stops per day, only reaches about 1,800 cycles a year. Therefore, the validation of a commercial machine's filter housing is not just repeating the household test multiple times; it requires a different set of criteria for evaluating alternating fatigue.
There are also considerations when choosing between threads and snaps. Threads are reliable but require sealing glue, while snaps are quick to assemble and disassemble but have a longer tolerance chain. Commercial machines use threads plus O-rings, while home machines use snaps for the experience of changing the core. The material difference between the two approaches is not significant, but the mold precision requirement differs by one level.
Engineering Memo
Before mass production of the water purifier housing, long-term pressure creep and hot water hydrolysis, two mandatory tests, must be conducted. If either test fails, the material grade must be changed immediately.
This is the source of 80% of commercial water purifier leakage incidents. For the household segment, the requirements can be relaxed, but moisture absorption and dimensional verification must be performed.
Three consecutive follow-up questions
Question 1: Is it possible to switch entirely to PP to save costs? PP is 30% cheaper, but it's less rigid. After a large-diameter filter housing is filled with water, the top cover visibly bulges, and the clips can loosen with temperature cycles. It can be used for small household filter cartridges, but it's not recommended for large commercial filter housings, as complaints about bulging housings are much more costly than the material that's 30% more expensive.
Question 2: Will exposed fiberglass cause hygiene issues? Exposed fiberglass at the welding line does affect the appearance, and some distributors use this as a talking point. In fact, the migration level is within the national standard limits. If appearance is a concern, a glossy finish can be applied, or the welding line can be moved to the side away from the waterway; a simple adjustment on the mold will solve it.
Question 3: How to decide the color? A white casing will show the color of the filter material after a few months. Dark colors, on the other hand, feel oppressive to customers. Most manufacturers eventually settle on a color between light gray and off-white. The masterbatch should be selected with a hydrolysis-resistant type, because ordinary masterbatch will start to bloom in warm water after three months. Casings with blooming are returned as quality issues, which is much more costly than the price difference of the masterbatch.
Reverse Cases and Final Judgments
This spring, a customer brought in a proposal with modified materials from last year for re-inspection. The filter housing in the hot water section was also changed to reinforced PA66, but after a year, it showed powdering and brittle cracking. Upon inspection, the problem was traced to the water quality: the local water source is slightly alkaline with high chloride content. High-temperature alkaline water accelerates hydrolysis of PA66. The same material used in the neighboring city lasted two years without any issues.
Later, the hot water section switched to a grade with a higher hydrolysis resistance, and after retesting for 3,000 hours, no further issues occurred. This case shows that the same material lot cannot be used nationwide. Water quality is a hidden variable in selecting filter housings. It is more useful to obtain the client's local water quality report before approving samples than to conduct ten additional rounds of testing.
Additional Note: Four Matters on the Level of Process and System
For injection molding processes of parts like filter housings, residual stress is a hidden variable. The reason why the root of the inlet thread keeps having problems is half due to the material and half due to an overly aggressive hold pressure curve, which prevents the internal stress near the gate from being released. After changing the material, this factory extended the hold time by two seconds and added an 80-degree annealing, resulting in a strength improvement at the same location.
The money for the materials has been spent, and we should also take advantage of the cheap labor; only by doing both things together can we consider the problem solved.
The system of incoming material sampling inspection is worth saying a bit more about. The current approach of this factory is to check a filament for each batch of baked samples, and conduct a destructive burst sampling inspection once a month, with the data recorded in a ledger to observe trends quarterly. Trends are more useful than single-point data. When the material supplier changes batches or production lines, the trend line will show signs first, appearing two months earlier than waiting for the complete machine to have issues.
The value of the system is not in stopping how much bad material there is, but in letting the material suppliers know you are watching, which will make the supply side correct its attitude on its own.
The replacement cycle is the issue that channels care about most. The recommended replacement cycle for household filter housings is written in the manual, but most users do not replace them. The filter housing itself can withstand the use, but what cannot is the filter material inside. However, commercial channels will actually replace them according to the cycle, and during replacement, the force used in disassembly and assembly, as well as the number of times the sealing ring is reused, can all become sources of complaints.
For the filter housing of commercial channels, the buckle needs to be tested for installation and removal fifty times; this is a project not required for household machines and must be listed separately on the material list.
One final reminder in the sample approval process: the sample approved is a normal temperature and humidity sample, whereas the goods stored in the warehouse for half a year are another matter. If the filter housing material is stored in the warehouse for more than six months, there will be noticeable changes in color and toughness. First-in, first-out is written on the label, executed by the warehouse, and reconciled by procurement.
None of these things are complicated. In factories where everything is done well, the after-sales records are a whole tier cleaner than others.
Conclusion
If it remains the same after three or five years, that is the most basic acceptance criterion for modified nylon.
Each section of the water purifier's waterway has different operating conditions, we can talk about them together.
