ASTM E2931-13
可燃粉尘云极限氧(氧化剂)浓度的标准试验方法

Standard Test Method for Limiting Oxygen (Oxidant) Concentration of Combustible Dust Clouds

被代替

标准号

ASTM E2931-13

发布

2013年

发布单位

美国材料与试验协会

替代标准

ASTM E2931-13(2019)

当前最新

ASTM E2931-13(2019)

 

 

引用标准

ASTM D3173 ASTM D3175 ASTM E1226 ASTM E1515 ASTM E177 ASTM E2079 ASTM E691

适用范围

5.1 This test method provides a procedure for performing laboratory tests to evaluate relative deflagration parameters of dusts.

5.2 Knowledge of the limiting oxygen (oxidant) concentration is needed for safe operation of some chemical processes. This information may be needed in order to start up, shut down or operate a process while avoiding the creation of flammable dust-gas atmospheres therein, or to pneumatically transport materials safely. NFPA 69 provides guidance for the practical use of LOC data, including the appropriate safety margin to use.

5.3 Since the LOC as measured by this method may vary with the energy of the ignitor and the propagation criteria, the LOC should be considered a relative rather than absolute measurement.

5.4 If too weak an ignition source is used, the measured LOC would be higher than the “true” value and would not be sufficiently conservative. This is an ignitability limit rather than a flammability limit, and the test could be described as “underdriven.” Ideally, the ignition energy is increased until the measured LOC is independent of ignition energy (that is, the “true” value). However, at some point the ignition energy may become too strong for the size of the test chamber, and the system becomes “overdriven.” When the ignitor flame becomes too large relative to the chamber volume, a test could appear to result in an explosion, while it is actually just dust burning in the ignitor flame with no real propagation beyond the ignitor (1-3).⁵ This LOC value would be overly conservative.

5.5 The recommended ignition source for measuring the LOC of dusts in 20-L chambers is a 2500-J pyrotechnic ignitor.⁶ This ignitor contains 0.6 g of a powder mixture of 40 % zirconium, 30 % barium nitrate, and 30 % barium peroxide. Measuring the LOC at several ignition energies will provide information on the possible overdriving of the system to evaluate the effect of possible overdriving in a 20-L chamber, comparison tests may also be made in a larger chamber such as a 1-m³ chamber (1-3).

5.6 The values obtained by this testing technique are specific to the sample tested (particularly the particle size distribution) and the method used and are not to be considered intrinsic material constants.

Note 1—Much of the previously published LOC data (4). were obtained using a spark ignition source in a 1.2-L Hartmann chamber and may not be sufficiently conservative. The European method of LOC determination EN 14034–4事故案例｜多尘作业现场的安全风险如何评估与防范？

下面是发生粉尘爆炸的必要因素：01有一定的粉尘浓度粉尘爆炸所采用的化学计量浓度单位与气体爆炸不同，气体爆炸采用体积百分数表示。而粉尘浓度采用单位体积所含粉尘粒子的质量来表示。单位是g/m³或mg/L，如浓度太低，粉尘粒子间距过大，火焰难以传播。02有一定的氧含量氧气是粉尘得以燃烧的基础。氧含量过低不会发生爆炸。空气中氧的含量高时，点燃粉尘的温度可以降低；氧的含量低时，点燃粉尘云相对困难。...

粉尘浓度和颗粒对爆炸的影响

　　⑴粉尘浓度可燃粉尘爆炸也存在粉尘浓度的上下限。该值受点火能量、氧浓度、粉体粒度、粉体品种、水分等多种因素的影响。采用简化公式，可估算出爆炸极限，一般而言粉尘爆炸下限浓度为20～60g/m3，上限介于2～6kg/m3。上限受到多种因素的影响，其值不如下限易确定，通常也不易达到上限的浓度。所以，下限值更重要、更有用。　　⑵粉体粒度可燃物粉体颗粒大于400um时，所形成的粉尘云不再具有可爆性。...

事故案例｜可燃气体突发闪爆致3死3伤，生产危险怎么防？

01闪点测试明确可燃性液体闪点能够更好地保障生产作业安全。闪点是在规定的试验条件下，点火源能够引发可燃液体表面蒸气发生闪火时的最低温度。02爆炸特性测试任何一种不稳定化学品的爆炸都需要外界供给一定的能量才能发生。爆炸的发生可以是可燃气体 / 可燃液体蒸气和助燃气体的混合物（气相燃爆）、可燃粉末与空气的混合物（粉尘爆炸）或爆炸性化学品自身遇到加热、明火、电火花等引起。...

粉尘爆炸的特点

可燃粉体的分类方法和标准在不同的国家有所不同。  美国将可燃粉体划为Ⅱ级危险品，同时又将其中的金属粉、含碳粉尘、谷物粉尘列入不同的组。美国制定的分类方法是按被测粉体在标准试验装置内发生粉尘爆炸时所得升压速度来进行分类，并划分为三个等级。我国目前尚未见到关于可燃粉尘分类的现成标准。...