泄漏标准和标准条件
我们的两点校准工艺采用了具有泄漏标准的压力衰减测试。我们使用泄漏标准（内部制造），我们知道在给定压力下的流量 - 如果我们在泄漏标准的一侧增加了一定的压力，它将可靠地使空气渗入到大气压力以一定的速度。有了这些信息，我们可以在所谓的“标准条件”下限定泄漏标准的泄漏率：20°C的环境温度和气压压力等于海平面。当我们知道泄漏标准的可追溯泄漏率时，我们可以使用该泄漏标准来校准压力衰减测试。在压力衰减测试中，使用压力传感器来测量测试部分中的压降。然后，由于泄漏标准，基于已知的压降下降，将压降与流速相关。CTS的泄漏标准可符合NIST标准。首先，无泄漏的主部件进行标准压力衰减测试作为对照，测量正常压力衰减。Then, after a mandatory period of relax time (the test part is relaxing, not us—we’re always hard at work!), the same test is repeated, with one key difference: the leak standard valve on the test instrument manifold remains open, allowing the pressure in the test part to bleed out through the leak standard. This results in a larger pressure drop in the second test, as we are intentionally letting some of the pressure out. We now know two pressure drop values: the control value (the expected pressure drop for every like part tested in the future), and the larger second value (with additional pressure loss from the leak standard). The difference in pressure drop values between the first test and the second is equal to the flow rate of the leak standard. If the two pressure loss values associated with the zero leak and the leak rate value of the leak standard were plotted on an X-Y graph—the horizontal X-axis representing flow rate and the vertical Y-axis showing the pressure drop—the line between the two points would be the calibration slope for the part being tested. Using this calibration slope, we can calculate the flow or leak rate using the pressure loss of any other similar tested parts. Wherever the newly-tested part’s pressure loss falls on the calibration slope, the corresponding value on the X-axis is the part’s flow rate. This simple two-point calibration correlates pressure loss to flow rate. Once you know the measured pressure loss values, you can calculate the flow rate values.
两点校准图的示例显示了压力损失与流速的相关性。
单点校准缺陷
单点校准不足以进行复杂的泄漏测试。如果任何过程的各个方面从测试变为测试，即使是测试线长度或测试零件温度的看似简单和无害的东西 - 结果将不那么精确。另外，压降值无法追溯到通过泄漏标准的校准流量的方式。使用流量泄漏规格可提供主要优势。每当测试零件的体积变化时，通过两个测试循环进行快速重新校准（如上所述）以及任何未来测试都会具有可追溯的泄漏值。负泄漏率
如果生产零件的压力损失小于第一个校准周期中观察到的压力损失（控制测试），则压力损失将与低于零的流量或负泄漏速率相关。有两个可能导致负泄漏率的原因。首先，测试零件的体积可能比主零件更大。与具有相同尺寸孔/泄漏的较小体积部分相比，具有较大体积的零件将经历较小的压力损失。第二，更可能的情况是，在校准过程中，正在测试的生产部分比主部分要温暖。当测量测试零件的压力损失时，结果至少会受到空气分子压缩的部分影响以及它们之间的摩擦增加。这种摩擦会产生热量，从而在填充周期结束时产生压力尖峰。为了解决这个问题，应在填充后测试的零件“稳定时间”，以便在测试周期开始之前的压力可以稳定。由于其他原因，校准过程中的主部分和生产零件也可能处于不同的温度。主部件可以将其保存在特定位置（在架子上，柜子等），在环境温度下平衡。 A production part may have just gone through any number of production processes—machining, gluing, ultrasonic welding, cleaning—that can raise its temperature. Additionally, ambient conditions within a plant may change during the day. Certain temperature conditions during the calibration cycle that is cooler than temperature conditions during production testing may also cause negative leak rate measurements. How much these conditions affect your testing repeatability is dependent upon your reject rate criteria. If these conditions occur, contact CTS for in-depth discussions with our Application Specialists on how our instrumentation can be utilized correctly for your leak testing needs.有关泄漏测试工具和负泄漏率的两点校准的更多信息，联系辛辛那提测试betway必威首页系统今天。我们是泄漏测试专家！
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