What is the difference between foreign standards and domestic standards for gas turbine flowmeters
2021-05-18
As an important branch of measuring gas flow meters, gas turbine flowmeters have recently received more and more attention from users in industrial production, what kind of standards are followed by gas turbine flowmeters in production and manufacturing, and what kind of differences exist between international standards and domestic standards. As a professional gas turbine flowmeter manufacturer, Aister Instrument gives you an overview of this situation:
The international gas turbine flowmeter mainly has the following standards:
1. ISO9951:1993 "Measurementofgasflowinclosedconduits - turbinemeter" and its revision in 1994.
2. International Organization of Legal Metrology (OIML) OIMLR137-1:2006 "Gas Flow Meter".
3. The American gas association AGANo7 Measurementoffuelgasbyturbinemeters (1981 edition).
4. Eu Standard PrEN (Draft Standard) 12261 "Turbinegasmeters" and its 2005 revision.
5. Japanese industrial standard JISZ8765-1980 "タ-ヒシ" flowmeter "じよろ method of flow determination", etc.
Domestic standards and specifications for gas turbine flowmeters mainly include the national standard GB/T18940-2003 "Gas flow measurement turbine flowmeter in closed pipelines" and JJG198-1994 "velocity flowmeter" verification regulations.
1. Comparison
At present, for domestic gas turbine flow meter manufacturers, as long as they obtain the "Manufacturing measuring instrument production License" and "Measuring instrument type Approval Certificate", they can produce and sell gas turbine flow meters in the domestic market. Unfortunately, for this equipment used in the explosion-proof zone 1 or even zone 0, there is no mandatory explosion-proof requirements; Similarly, in the face of a few or even tens of pa pressure in the pipeline, there is no mandatory pressure requirements to regulate.
In contrast, the development and utilization of natural gas has been at the forefront of the European Union, from October 30, 2006, the gas turbine flow meter in the European Union has been mandatory, and the product must pass the CE certification before it can be sold on the market. In accordance with the CE certification requirements, the gas turbine flowmeter must comply with the MID (measuring instrument instruction), PED (pressure equipment instruction), ATEX (explosion-proof instruction) and other three instructions to obtain the CE certificate. We have made a detailed comparison of the current international and domestic gas turbine flowmeter standards.
a. EN12261, as the current gas turbine flowmeter standard adopted by all member states of the European Union, from October 30, 2006, together with OIMLR137, has become the mandatory directive MID guidance testing standard. From the comparison of the existing standards, EN12261 is a comprehensive and targeted standard specification for gas turbine flowmeters, which not only provides a specific and comprehensive specification for gas turbine flowmeters from the aspects of measurement performance, design and material requirements, output, marking, documentation, etc., but also puts forward a more detailed detection method for each requirement.
b. OIMLR137 is the International legal metrology organization launched on August 14, 2006, OIMLR6:1989 "General Specification for gas volume Flowmeters", OIMLR31:1995 "membrane gas flowmeters", OIMLR32: 1989 "Rotary piston gas flowmeter and turbine gas flowmeter" and other three alternative files. This recommendation was drafted by the NMI (National Metrology Institute of the Netherlands) and entered into force on 14 August 2006. At present, it is also the guiding testing standard of the EU MID directive, which not only has requirements for turbine flowmeters, but also has requirements for the overall performance and installation of other types of flowmeters and their secondary electronic instruments. From the perspective of gas turbine flowmeter alone, its requirements are relatively close to EN12261, and more comprehensive requirements are made for the basic performance of the product, the detection method and its product identification, and the operation manual.
c. AGANo7 is not a standard, is an American Gas Association technical report on gas turbine flow meters, is about the measurement of axial turbine flow meters operating specifications. It summarizes the theory and practice of gas turbine flowmeters used in gas after the 1960s. AGANo7 includes application scope, structural installation, operation, meter characteristics, calibration, volume flow and mass flow measurement, field inspection, calculation tables, etc. From the information we have consulted, AGANo7 in the United States should have the same status as GB/T18940-2003 in China, and it has also been recognized by many domestic turbine flowmeter manufacturers.
d. ISO9951:1993 is the international standard for gas turbine flowmeters, which marks that gas turbine flowmeters have become internationally recognized universal flowmeters. The standard specifies the structure of the instrument, pressure test, flow meter characteristics, on-site calibration of the reading device, pressure loss, pipeline regulations, etc., which makes the product technical parameters of the countries consistent. Especially in order to meet the needs of field installation, it is required that the flow meter can be installed without a long straight pipe section under serious flow interference, which puts forward high requirements for the metering quality of the flow meter.
e. GB/T18940-2003 is the national standard of the People's Republic of China, which is equivalent to ISO9951:1993, and the content and requirements are basically consistent with ISO9951:1993. However, in the course of work, it was found that there were some problems in the translation of ISO9951:1993, such as some unprofessional terms and some unclear requirements.
f. JISZ8775-1980 is the Japanese turbine flow meter standard, because there is no Chinese/English version of the standard, the relevant domestic turbine flow meter manufacturers and their natural gas companies are rarely involved in the standard, here, the author does not discuss the standard.
2. Detailed comparison of metering performance of gas turbine flowmeter
Here is mainly from the basic error (including weighted average error), repeatability, linearity, durability, installation position, short-term overload, temperature range, installation conditions, large allowable pressure loss and other aspects of EN12261, OIMLR137, AGANo7, ISO9951: The requirements of 1993, GB/T18940-2003 and other standards are compared.
3, the influence of international standards on our country
Natural gas metering is an important part of energy metering, and gas turbine flowmeter is a common instrument used in natural gas metering. At present, most countries in the world have updated their standard regulations. Among them, OIMLR137 is a new international recommendation approved in October 2006, EN12261 also launched an updated version in 2005, and AGANo7 further revised the standard in 2006. We, as a large producer and consumer of energy, are still using the imprecisely translated equivalent of international standards from the mid-1990s. This is undoubtedly inconsistent with our energy conservation and emission reduction situation, let alone the implementation of the scientific outlook on development.
We must deeply understand the status quo of the lagging development of natural gas metering meters in our country, narrow the gap with developed countries, and start from two aspects as soon as possible: First, rewrite the standard of natural gas metering meters that meet our national conditions, rather than the simple translation of international standards. Through the implementation of the new standard, the production industry of China's metering instruments is further standardized. The second is to build a set of independent intellectual property rights, internationally recognized, full range, traceable standard devices, so that manufacturers of metering instruments can have evidence to rely on, rather than acting separately.
From the current development of the international natural gas metering industry, we must pay attention to and develop natural gas metering meters from the following aspects:
a. Measurement performance under field installation conditions
First of all, as a measuring instrument used for trade handover, if the accuracy is poor, it will undoubtedly lose its significance as a measuring instrument. Secondly, it must be accurate under field installation conditions. After all, the field conditions are far more complex than the laboratory, and the accuracy level of laboratory calibration can at best be regarded as a reference value for field accuracy. Therefore, it is necessary to improve the adaptability of the meter to the field environment, so that it has the ability of self-rectification, self-cleaning, self-mixing and self-protection.
b. Combined with China's national conditions, it is necessary to extend the calibration period of the measuring instrument to ensure that the on-site instrument can meet the measurement accuracy requirements for a longer period of time.
c. The pressure loss should be small, saving the cost of pumping upstream gas, which is of great significance for energy saving.
d. In order to further improve the accuracy and fairness of measurement, mass and energy measurement of natural gas is carried out.
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