圓缺孔板的開孔是圓的一部分（圓缺部分），這個圓的直徑是管道直徑的98%，開孔的圓弧部分的圓心應(yīng)地定位，使之與管道同心，這樣可保證開孔不會被管道及兩端的墊片或由于管道偏心而發(fā)生遮蓋。圓缺孔板適用于濕煤氣等臟污介質(zhì)的測量，可以避免臟物在孔板前后淤積，被廣泛應(yīng)用在各種煤氣和臟污流體的測量上。
測量原理：
圓缺孔板是在標(biāo)準(zhǔn)孔板的基礎(chǔ)上研發(fā)的節(jié)流式流量傳感器。由于它采用環(huán)形通道式結(jié)構(gòu)，使各種臟腑介質(zhì)通過孔板與管道之間環(huán)縫間輕松通過。因此圓缺孔板廣泛應(yīng)用于臟污介質(zhì)的流量測量。
—分別為質(zhì)量流量（㎏/s）和體積流量（m3/s）；
—流出系數(shù) ；
—可膨脹性系數(shù)；
—節(jié)流件開孔直徑，m；
—直徑比，
—管道內(nèi)徑，m；
—被測流體密度，㎏/m；
—差壓，pa；
特點：
1.含有固體微粒的液體或含有液滴的氣體易于從節(jié)流件的環(huán)隙通過，不會發(fā)生積累。
2.適合臟污流體、腐蝕性流體的測量。
3.無需長直管段，可在惡劣的管道條件下工作
4.適用于飽和蒸汽、壓縮空氣、煤氣、燃爐廢氣、冷卻水、冷凝液和各種腐蝕性化工溶液以及各種流體介質(zhì)的測量。
5.壓力損失小，功耗低，所需直管段短。
6.在惡劣條件下流出系數(shù)穩(wěn)定，精度高，可靠性好。
技術(shù)參數(shù)
1.公稱通徑： 50 mm～3600 mm
2.工作溫度： -200℃～+530℃
3.公稱壓力：- 0.1 mpa～42 mpa
4.雷諾數(shù)（red）范圍： 普通型 4×103～1×107
5.度：±0.5%、 ±1.0% 、±2.0%
6.參照標(biāo)準(zhǔn)：gb/t2624-2006、jjg640-94及流量測量節(jié)流裝置設(shè)計手冊
7.連接方式：法蘭連接、 焊接連接
安裝要求:
1. 圓缺孔板只適用于安裝在水平或傾斜管道上，不能在垂直管道上使用，被測流體中含有固體顆粒時，缺口應(yīng)處于下方，如果液體中有氣體析出，則缺口應(yīng)置于上
2. 取壓管道焊接前，應(yīng)先將管道上的取壓孔鉆好，其直徑與取壓法蘭上的取壓孔徑相同，取壓法蘭上的取壓孔與管道上的取壓孔對準(zhǔn)。
3. 節(jié)流裝置與管道連接時，焊接處端面與管道軸線的不垂直度不得大于1°，焊接后內(nèi)部焊縫應(yīng)加工處理，使其光滑，無焊巴和焊渣。
英文版本：
circular part opening shiyuan lack hole plate （round part）, the diameter of this circle is the pipe diameter of 98%, opening of the arc part of the center should be accurate positioning, and make the pipeline concentric, thus opening will not be pipe and both ends of the gasket or due to pipe eccentric and cover. measurement of round orifice plate is suitable for wet gas dirty medium, can prevent dirt in the hole plate before and after deposition, is widely used in the measurement of various gas and dirt on the fluid.
the measuring principle:
round orifice plate throttle type flow sensor is developed on the basis of the standard orifice plate. due to the adoption of the annular channel structure, various viscera medium make circular seam between easily through the through hole plate and pipe. hence the circular flow measuring orifice plate is widely used in dirty medium.
- were mass flow （kg /s） and flow volume （m3/s）;
- outflow coefficient;
- expandable coefficient;
- throttle hole diameter, m;
diameter ratio,
and the inner diameter of the pipe, m;
- measured fluid density, kg /m;
pressure difference, pa;
characteristic.
1 containing solid particles of liquid or gas containing liquid droplets easily through the annular throttling element, no accumulation.
measurement of 2 for the dirty liquid, corrosive fluids.
3 no long straight section, can work in harsh channel conditions
4 for saturated steam, compressed air, gas, furnace gas, cooling water, condensate and all kinds of corrosive chemical solution and measuring various fluid medium.
5 small pressure loss, low power consumption, required less straight pipe.
6 in the harsh conditions of outflow coefficient and stability, high accuracy, good reliability.
technical parameters
1 nominal diameter: 50 mm ~ 3600 mm
2 operating temperature: -200 ℃ ~ +530 ℃
nominal pressure: 3 - 0.1 mpa ~ 42 mpa
4 reynolds number （red） range: ordinary type 4 × 103 ~ 1 × 107
accuracy: 5 ± 0.5%, ± 1%, ± 2%
6 reference standards: gb/t2624-2006, jjg640-94 and design flow measurement throttling device manual
the 7 connection: flange connection, welding connection
installation requirements:
the 1 round orifice plate is only suitable for horizontal or inclined pipe, can not be used in vertical pipe, the measured fluid containing solid particles in the gap, should be on the bottom, if there is gas evolution in the liquid, then the gap should be placed on
2 the pressure pipe before welding, should be first pressure hole drilled from the pipe, the diameter and pressure aperture take the same on the flange, the pressure holes aligned pressure hole and pipe flange.
the 3 throttling device and pipeline connection, welding end face and the pipe axis is not perpendicular shall not be greater than 1 degrees, after welding the weld shall be processed inside, make it smooth, without welding, and welding slag.