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technical article
Difference between diaphragm pressure gauge and general pressure gauge
2012-2-15 11:11:58

与一般压力表相比,隔膜压力表有什么优点? What are the advantages of diaphragm pressure gauges compared to ordinary pressure gauges?
The difference between a diaphragm pressure gauge and a general pressure gauge is that when the pressure is measured with a general pressure gauge, the measured working medium directly enters the spring tube. When measuring with a diaphragm pressure gauge, the measured working medium cannot enter the spring tube. Such benefits are (1) The most commonly used pipes for manufacturing spring pipes are brass pipes, tin bronze pipes, lcrl8N stainless steel pipes, and SUS316 stainless copper pipes. As other materials that are resistant to various corrosion such as pure titanium, pure tantalum, Hastelloy, Monel gold, etc., due to limited use, procurement is not easy, but the strip used to make the diaphragm is much easier to purchase. . (2) When measuring the pressure of high-viscosity, easy-to-crystal, and easy-to-solidify media, due to the isolation of the diaphragm, the normal requirements of the instrument can be guaranteed.

主要技术指标: 1: 温度特性:由于隔膜压力表系统由填充了密封液作为传递压力的介质,则由于密封液的温度体膨胀系数,使压力仪表随受压部温度升高而示值也升高,其温度影响量与密封液体膨胀系数,隔膜刚度以及受压部温度有关,尤其对于低量程的压力仪表,则影响更明显。 The main technical indicators of the diaphragm pressure gauge : 1: Temperature characteristics: Because the diaphragm pressure gauge system is filled with a sealing liquid as a medium for transmitting pressure, the pressure meter is shown as the temperature of the pressure part rises due to the temperature body expansion coefficient of the sealing liquid. The value also increases, and its temperature influence is related to the expansion coefficient of the sealing liquid, the stiffness of the diaphragm and the temperature of the pressure part, especially for low-range pressure instruments, the effect is more obvious. Generally, the temperature error of the pressure receiving part is not more than 0.1% / ℃. Therefore, the total temperature effect of the diaphragm pressure instrument is generally the sum of the temperature effect of the universal instrument and the temperature of the pressure part of the diaphragm device. 2: Accuracy grade: 1.5; 2.5 grade 3: Measuring range (Mpa) [3] Threaded connection: ~ 0.1 ~ 0 to 0 ~ 60 Flange connection: ~ 0.1 ~ 0 to 0 ~ 25 Clamp Hygienic type: ~ 0.1 ~ 0 to 0 ~ 2.5 4: Separator material: 0Crl7Nil2Mo2 (316); Monel alloy (Cu30Ni70); Hastelloy (H276C); Tantalum (Ta) and fluoroplastic (F4). 5: Internal working fluid filling: (1) Silicone oil (2) Filling according to customer requirements 6: Working conditions (1) Temperature Ambient temperature-20 ~ + [4] 55 ℃ Measured medium temperature-20 ~ + 55 ℃ Working pressure static load: 3/4 (3) to the upper limit of measurement Alternating load: 2/3 (4) to the upper limit of measurement Short-term pressure: To the upper limit of measurement 7: Connection size ( 1) Threaded connection: M20 * 1.5 (G3 / 8 ″ G1 / 2 ″) (2) Flange connection A; Standard of Ministry of Machinery Industry JB81-5 “Flat Welded Steel Flange” B: Standard of Ministry of Chemical Industry “Acid Resistance Flat Welding Steel flange》 C: Customized according to user requirements 8: Instrument outer diameter φ60mm φ75mm φ100mm φ150mm 9: Instrument execution standard JB / T8624-1997

安装:一些用户或安装公司,在安装、使用和维护隔膜压力表过程中,松动了表头、连接器与隔离器间的连接螺纹;或在将仪表拆下送检时,直接从工位上卸下表头,将法兰隔离器保留在工位上,造成仪表失效。 Diaphragm pressure gauge installation: Some users or installation companies loosened the connection threads between the meter head, the connector and the isolator during the installation, use and maintenance of the diaphragm pressure gauge ; or when removing the meter for inspection, directly from Remove the meter head from the station and leave the flange isolator on the station, which will cause the instrument to fail. Specific performances are: the pointer does not return to zero, the diaphragm is concavely deformed, the pointer does not indicate pressure, or the indication error is large. Why do these failures occur after loosening the connection thread between the meter head and the isolator? We know that in the production process of the diaphragm pressure gauge, the pressure-containing space of the gauge measurement system and the upper cavity of the separator diaphragm are evacuated and filled with sealing liquid, and the two are assembled and combined to form a sealing liquid filled hermetic space. The volume of the sealing fluid in this space does not change, so that the pressure sensed by the isolation diaphragm is transmitted to the measuring element. When the threads between the meter head, the connector and the isolator are loosened, the sealing fluid space loses hermeticity, and when the diaphragm is deformed under pressure, the sealing fluid will leak through the loose thread gap under pressure, causing a seal The loss of liquid and the reduction of the volume of the confined space cause the meter measuring element to fail to properly sense the pressure transmitted by the sealing liquid. In severe cases, the isolation diaphragm will be permanently deformed due to the large pressure difference between the two sides, causing the instrument to fail completely.

Diaphragm pressure gauge products produced by our company, the head, connector and the connection thread of the isolator are coated with eye-catching red paint seals, and textual warning instructions are provided on the nameplate and product manual of the isolator. These are to avoid instrument failure caused by loosening the connecting thread between the meter head, the connector and the isolator during the installation or use of the diaphragm pressure gauge. At the same time, the resulting instrument failure should not fall into the category of free product quality issues.