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GB/T 17286 Liquid hydrocarbons dynamic measurement proving systems for volumetric meters is divided into four parts: ——Part 1: General principles; ——Part 2: Pipe provers; ——Part 3: Pulse interpolation techniques ——Part 4: Guide for operators of pipe provers This is Part 1 of GB/T 17286. This part is developed in accordance with the rules given in GB/T 1.1- 2009. This part replaces GB/T 17286.1-1998 Liquid hydrocarbons - Dynamic measurement - Proving systems for volumetric meters - Part 1: General principles. The following main technical changes have been made with respect to GB/T 17286.1-1998: ——the Foreword in ISO standard is deleted; ——the standard structure is adjusted, the suspension sections in the original ISO standard are deleted, and some secondary title names are added; —— the explanation of "tank prover systems" is given in 3.1 to unify the format; —— the term "counting mechanism" in 4.6 and the subsequent paragraphs is changed to “tolerance modulator”； ——as for 4.9, the sentence “or if four individual unadjusted proving runs are made without any two successive runs checking within an acceptable repeatability” in the ISO standard is changed to “or if four individual unadjusted proving runs are made without any three successive runs checking within an acceptable repeatability”; —— the titles of Clause 5, 6, 7 and 8 are modified; ——some inaccurate and irregular statements in the standard are modified. This part, by translation, is identical to the international standard ISO 7278 - 1: 1987 Liquid hydrocarbons - Dynamic measurement - Proving systems for volumetric meters - Part 1 : General principles. The Chinese document corresponding to the normative documents given in this part is as follows: ——GB/T 17287-1998 Liquid hydrocarbons - Dynamic measurement - Statistical control of volumetric metering systems (ISO 4124: 1994, IDT) This part is under the jurisdiction of SAC/TC 355 National Technical Committee on Petroleum and Gas of Standardization Administration of China. The previous edition replaced by this part is as follows: ——GB/T 17286.1-1998. Introduction GB/T 17286.1-1998 is drafted according to Part 1 of ISO 7278 Liquid hydrocarbons - Dynamic measurement - Proving systems for volumetric meters, it is of significant guidance in the dynamic measurement of liquid hydrocarbons in China. It is necessary to revise GB/T 17286.1-1988 in order to meet the needs of the continuous development of China's petroleum industry and promote international trade and exchanges. ISO 7278 provides detailed descriptions of pipe provers, tank provers and pulse interpolation techniques. Parts covering other types of proving systems may be added as the need arises. The purpose of proving a meter is to determine its relative error or its meter factor as a function of flow rate and other parameters such as temperature, pressure and viscosity. The purpose of determining the relative error is to find out whether the meter is working within prescribed or specially accepted limits of error, whereas the meter factor is used to correct any error in the indication of a meter by calculation. Liquid hydrocarbons - Dynamic measurement - Proving systems for volumetric meters - Part 1 : General principles 1 Scope This part of GB/T 17286 provides general principles for proving systems for meters used in dynamic measurement of liquid hydrocarbons. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 4124 Liquid hydrocarbons - Dynamic measurement - Statistical control of volumetric metering systems 3 Prover 3.1 Types of prover The following types of proving systems are in use: a) tank prover systems: made of metal (stainless steel, carbon steel, etc.), of the specified structure, with certain volume, and may be used as a means of standardization of transfer b) pipe provers: bidirectional and unidirectional. Pipe provers with precision tubes as described in 6.7 are available for special applications. c) master meters: a meter is used as a means of standardization of transfer. Master meters shall be verified as qualified under the condition close to the actual working condition, and then the working meter shall be verified by volume comparison method. This method may produce additional errors. 3.2 Setting of provers Provers may be used either connected (fixed or mobile) to the metering station or in a central proving station to which the meters or the measures can be taken to be proved unconnected. 3.3 Minimum pulses In order to limit the maximum error to ±0.01% when using a pulse generator for proving, at least 10000 pulses shall be obtained from the meter per proving run. This number of pulses may be reduced by pulse-interpolation techniques which allow either the use of meters with fewer pulses per unit volume or reduction of the prover volume. 4 General considerations 4.1 Proving requirements A meter shall be proved at the expected operating or prescribed or agreed rates of flow, under the pressure and temperature at which it will operate and on the liquid which it will measure. In situations where it is not feasible to prove the meter on the liquid to be metered, the meter shall be proved on a liquid having a density, viscosity and, if possible, temperature as close as possible to those of the liquid to be measured. A meter that is used to measure several different liquids shall be proved on each such liquid. Similar liquids may be used if a simple, known relationship exists between the relative error, flow rate and viscosity, provided that the uncertainty of measurement remains within acceptable limits. Generally, calibration shall take place at a flow rate equivalent to that at which the meter will be used. A meter may be proved in different circumstances as follows: a) Initial proving. This shall be carried out on the permanent location or in a central station where the expected conditions of operation can be reproduced. The initial proving shall make it possible to determine the relationship between the relative error (or meter factor) and different parameters such as viscosity or temperature. b) Occasional or periodical proving. If a simple relationship between the relative error (or meter factor) and influencing parameters can be determined, the meters shall be reproved periodically using a prover either on the site or in a centralised station. Otherwise, the meter shall be reproved on the site whenever significant changes in the influencing parameters, such as viscosity or temperature, occur. Regular provings are also needed to follow effects of mechanical changes. 4.2 Evaporation of liquid Many petroleum liquids of high vapour pressures are measured by meter. If liquid evaporation during normal operation or proving could occur and affect measurement, the proving system shall provide means to avoid evaporation. 4.3 Factors affecting proving results The proving of a meter is like a laboratory test: when properly done, it provides a high degree of repeatability, which is necessary for measurement accuracy. Its piping and the proving systems, which can contribute to measurement uncertainty, as there are in determining physical properties of the measured liquid. Furthermore, the proving system shall be maintained in good operating condition. Thorough inspection of provers and their ancillary equipment shall be made with sufficient frequency to ensure reproducibility of proving results. It is essential that meter performance data be observed, recorded and studied and that calculations be correct (see ISO 4124). The accuracy and repeatability of the proving can be affected by observation errors in determining the opening meter reading or the closing meter reading, the test volume passing through or delivered to the prover and in reading temperature and pressure, and by implicit errors in computation in the process of correcting a measurement to standard conditions. 4.4 Meter proving procedures Meter proving procedures including: a) Standing start-and-stop procedure. It uses registers from which the opening and closing readings are obtained at no-flow conditions. Opening and closing of valves shall be performed rapidly. b) Running start-and-stop procedure. It involves obtaining the opening and closing meter readings of the proof while the meter is in operation. This is accomplished by the use of auxiliary or secondary registers of high discrimination which can be started and stopped while the meter and primary register continue to operate. 4.5 Register Every meter proof shall be made with the same register as is used in regular operation or with additional synchronised auxiliary registers for the running start-and-stop procedure [4.4 b)]. Inclusion of special auxiliary equipment such as the following is permitted: density selector, temperature compensator, and quantity-predetermining register. If employed, the auxiliary equipment shall be set and operative when making the proof runs. Time between proving runs shall be kept to a minimum. 4.6 Objectives to meter proving There are two general objectives to meter proving which usually depend on the type of service. a) To determine the error characteristics of a meter. The relative error of a meter can be determined by adjustment of its meter tolerance regulator according to the proving result. To give a meter factor of 1.0000 so that its indicated volume will be the volume of liquid actually delivered. This is the normal practice for a meter operating on intermittent deliveries, such as a tank truck meter or a loading rack meter at a terminal or bulk plant. b) To determine its meter factor. The relationship between its meter factor and influencing parameters such as viscosity or temperature so that this factor or this relationship can be applied to the indicated volume to compute the gross volume delivered through the meter. This is the normal practice in the case of continuous or long-duration measurement. 4.7 Test run When a meter is being proved, a test run shall be made, to equalise temperatures, displace vapours or gases and wet the interior of the prover. Subsequent proving test runs shall be made in the required range of flow rates and the registration adjusted as necessary. Each calibration point for the same flow shall be repeated at least three times. Further repeats may be necessary, if specified. See ISO 4124. 4.8 Prove flow rate When a meter is being proved to determine the meter factor at one or several flow rates, the procedure shall be essentially as specified in 4.7, except that no changes shall be made to the meter registration adjusting device between runs. Proof runs shall be made and recorded until the specified number of consecutive runs at the same flow rate agree within an acceptable repeatability, at which point the average of these three runs shall be accepted as the established meter correction factor for this flow rate. 4.9 Data Analysis If the registration of a meter, during proving, is not changing in accordance with adjustments made to the register adjusting device, or if four individual unadjusted proving runs are made without any three successive runs checking within an acceptable repeatability, all phases of the proving operation shall be examined for the cause of the discrepancy. If the cause is not found, the meter and its register mechanisms shall be inspected for electronic or mechanical defects, repaired and proved before being returned to service. 4.10 Rounding off for data The practical limit of accuracy in any observed value such as the volume in the reference vessel during a meter proof is 0.01%. For this reason, meter factors shall be rounded to four decimal places, not more and not less, for example 1.001 6. 4.11 Proving results The results of proving can be adversely affected by the use of abbreviated tables, the unstandardized rounding of factors and/or intermediate calculations. The observed and computed data for all proving made in obtaining a meter factor or other expression of meter performance shall be reported on a suitable meter proving report form. 4.12 Proving of meter Most of the procedures specified above have been for the proving of a single meter. If the meter to be proved is part of a battery of meters, it is necessary either to divert the stream from the selected meter to be proved through the prover or remove the meter to a central proving station. 5 Tank prover systems 5.1 As far as possible, the movement of all united supplementary bodies/matters inside the standard gauge shall be avoided, and in no case shall the gauge be adjusted to a given value by this means. The prover shall be recalibrated after any changes to components within the calibrated volume section such as gauge glasses, thermometer well or spray lines. The tank prover shall be designed in order to avoid any variation in its metrological characteristics and also to reduce clingage of liquid to the walls. The prover tank shall be inspected frequently for internal corrosion and for accumulation of sediment, rust, valve lubricant and other foreign material. Gauge scales shall be inspected frequently and the prover recalibrated if there is indication of gauge scale movements. 5.2 Proving with open prover tanks consists of a comparison of the change in volume of liquid indicated on the register and of the known volume in the tank prover. The liquid shall be passed through the meter under actual or simulated operating conditions of temperature, pressure, rate of flow, density and viscosity, into the prover, where its volume shall be determined from the gauge scales. The meter factor is the ratio between the actual volume measured with the prover converted to the conditions of temperature of the liquid during proving and the volume indicated on the meter register. 5.3 After a preliminary filling and draining of the prover tank, the lower level of the test liquid shall be determined. The meter to be proved shall then be stopped and the opening meter reading recorded. The proof run shall then be started by directing the liquid from the meter into the prover, maintaining the flow rate and meter pressure to simulate operating conditions. During the filling of the prover, the temperature of the metered stream near the meter shall be determined and recorded frequently enough to ensure art accurate average temperature of liquid as it passes through the meter. Flow shall be continued into the prover until the liquid reaches a suitable reading level. (Liquid levels in gauge glasses shall be determined by reading the bottom of the meniscus with transparent liquids, or the top of the meniscus with opaque liquids.) Flow shall then be stopped and stablized, the volume delivered to the prover promptly observed on the top gauge glass scale and recorded. Prover tank temperatures shall be taken, recorded and averaged, and the meter factor for the proof run calculated. The meter can be returned to service after proving. 5.4 Meter registration adjustments, if called for, can be made as required and subsequent proof runs can be made by repeating the proof run procedure just described. 5.5 In some types of open prover tanks, a top spray is used during the emptying of the prover to saturate the air drawn into the prover with the vapour of the test liquid to reduce evaporation of the test liquid during a subsequent proof run. Where this is done, the spray shall be turned on prior to each emptying of the prover and closed off prior to zeroing the liquid level. 5.6 There are certain variations inherent in the foregoing general procedure, arising primarily from design differences with respect to the method of establishing the starting liquid or zero level at the beginning of the proof run. 6 On-line pipe prover systems 6.1 In proving with pipe provers, checking of equipment prior to proving shall include inspection of all valves to ensure against internal leakage, and of the attachment of accessories used for proving and energizing electrical circuits. Thermometers and pressure gauges shall be checked periodically. 6.2 The entire liquid stream from the meter or battery of meters to be proved shall be diverted to flow through the pipe prover. In some permanently installed pipe proving systems, flow through the meter and the prover is continuous. Flow shall always be maintained through the meter and prover sections until stable conditions of temperature are reached. Vent connections shall be checked to ensure that the meter and prover sections are completely purged and that no pockets of air or vapour remain in the system. 6.3 A trial proving run is frequently conducted as a final check before starting the recorded meter proving. This is a good practice and is recommended for those provers where it can be readily accomplished. The trial run shall include checking of the electronic or other register. Observation of the readings from the trial run will often indicate equipment maladjustment not otherwise apparent. 6.4 Operations necessary to conduct proving runs will vary with the installations and can range from completely manual to fully automatic. The essential step will consist of operating a valve or combination of valves, which causes the metered stream to move the movable element (piston, sphere, etc.) through the calibrated section of the prover. The proving counter register shall be recorded prior to the start of every run or, if so equipped, it may be reset to zero. The switching operation shall be completed well before the movable element enters the calibrated section of the prover. In automatic systems, a pushbutton normally initiates a complete meter proof cycle and the timing of the operations is a matter of adjustment of the valve and the proper sequencing of the control system. Foreword I Introduction III 1 Scope 2 Normative references 3 Prover 4 General considerations 5 Tank prover systems 6 On-line pipe prover systems 7 Centralized prover systems 8 Master meter systems ICS 75. 180.30 E 98 中 华 人 民 共 和 国 国 家 标 准 GB/T 17286.1-2016/ISO 7278-1：1987 代替GB/T 17286.1-1998 液态烃动态测量 体积计量流量计检定系统 第1部分：一般原则 Liquid hydrocarbons dynamic measurement proving systems for volumetric meters— Part 1：General principles （ISO 7278—1：1987，IDT） 2016-12-30发布 2017-07-01实施 中华人民共和国国家质量监督检验检疫总局 中国国家标准化管理委员会 GB/T 17286.1-2016/ISO 7278-1：1987 前 言 GB/T 17286《液态烃动态测量 体积计量流量计检定系统》分为四个部分： ——第1部分：一般原则； ——第2部分：体积管； ——第3部分：脉冲插入技术； ——第4部分：体积管操作人员指南。 本部分为GB/T 17286的第1部分。 本部分按照GB/T 1.1——2009给出的规则起草。 本部分代替GB/T 17286.1——1998《液态烃动态测量 体积计量流量计检定系统第1部分：一般原则》。本部分与GB/T 17286.1——1998技术内容上的主要变化如下： ——删除了ISO前言； ——调整标准结构，去掉了原ISO标准中的悬置段，增加了部分二级标题名称； ——为统一格式，在3.1中，给出了“标准量器”的解释； ——对4.6及以后出现的“计数机构”一词，统一改为“容差调制器”； ——对4.9中，原文中“......连续进行四次检定后，没有连续两次的数据达到允许的重复性......” 改为"......连续进行四次检定后，没有连续三次的数据达到允许的重复性”； ——对第5、6，7，8章的标题进行了修改； ——对标准中的一些不准确、不规范的语句进行了修改。 本部分使用翻译法等同采用国际标准ISO 7278——1：1987《液态烃动态测量 体积计量流量计检定系统第1部分：一般原则》。 与本部分规范性引用文件有对应关系的我国文件有： ——GB/T 17287——1998 液态烃动态测量 体积计量系统的统计控制（ISO 4124：1994.1DT） 本部分由全国石油天然气标准化技术委员会（SAC/TC 355）提出并归口。 本部分起草单位：中国石油天然气股份有限公司计量测试研究所本部分主要起草人：高军、刘晓光、赵成海、陈洪举、曹阳、孙宝权。 本部分所代替标准的历次版本发布情况为： ——GB/T 17286.1——1998。 GB/T 17286.1-2016/ISO 7278-1：1987 引 言 GB/T 17286.1——1988是依据国际标准1SO 7278&液态烃动态测量体积计量流量计检定系统》第1部分起草的，在我国液态烃动态测量方面发挥了重要的指导作用。为了适应我国石油工业不断发展的需要，促进国际间贸易和交流，有必要对GB/T 17286.1——1988进行修订。ISO 7278对体积管、标准量器和脉冲插入技术作了详细阐述。有关其他类型检定系统的相关标准，将根据需要陆续增补。检定流量计是为了确定流量计的相对误差或流量计系数。流量计系数与被测液体流量、温度、压力和黏度等因素有关。 确定流量计相对误差的目的是要知道流量计是否在规定的或允许的误差范围内工作；而确定流量计系数则是为了用于修正流量计指示值。 GB/T 17286.1-2016/ISO 7278-1：1987 液态烃动态测量 体积计量流量计检定系统 第1部分：一般原则 1 范围 GB/T 17286的本部分确立了体积计量流量计检定系统所要遵循的一般原则，适用于液态烃动态测量。 2 规范性引用文件 下列文件对于本文件的应用是必不可少的。凡是注日期的引用文件，仅注日期的版本适用于本文件。凡是不注日期的引用文件，其最新版本（包括所有的修改单）适用于本文件。 ISO 4124 液态烃动态测量 体积计量系统的统计控制（Liquid hydrocarbons-Dynamic meas-urement-Statistical control of volumetric metering systems） 3 计量标准器 3.1 标准器的类型 标准器的类型主要分为： a）标准量器。按规定的结构，用金属（不锈钠、碳素钢等）制成的，具有确定的容积，可作为容量量值传递的计量器具。 b）体积管。包括双向体积管和单向体积管，以及6.7描述的用于特殊场合的小容积体积管。 c）标准流量计。作为传递标准的流量计称为标准流量计。标准流量计应在接近实际工况条件下检定合格后，以容积比对的方法检定工作流量计。该方法可能会产生附加误差。 3.2 标准器的设置 标准器既可设在计量站（固定式的或活动式的），对流量计进行在线实液检定，也可设在中心检定站，对流量计进行离线检定。 3.3 最少脉冲数 为使计数系统最大误差控制在士0.01%之内，检定时，每检定运行一次，流量计至少应发出10 000个脉冲。若采用脉冲插入技术，脉冲数目可以减少，并允许使用每单位体积发出较少脉冲的流量计或较小容积的计量标准器。 4 一般条件 4.1 检定要求 在实际工况的压力和温度条件下，用被测液体按预期的、或规定的、或双方约定的流量，对流量计进 GB/T 17286.1-2016/ISO 7278-1：1987 行实液检定。不能用实液检定时，应选用与被测液体的密度、黏度和温度尽可能接近的液体检定流量计。测量多种不同液体的流量计时，应使用被测量的每一种液体分别检定流量计。如果某种相近液体在相对误差、流量和黏度之间与被测液体存在一个简单的已知关系，且不确定度在可接受的范围内时，可用这种相近液体代替。在一般情况下，应使用流量计运行时的接近流量检定流量计。 流量计的检定可以分为： a）首次检定。这种检定应该在流量计固定安装的现场或能够再现预期工作条件的中心检定站进行。首次检定应尽可能确定出相对误差或流量计系数与黏度、温度等参数之间的关系。 b）周期检定或后续检定。如果流量计相对误差（或流量计系数）与影响参数间的简单关系已被确定，应在现场或在中心检定站用计量标准器周期检定流量计。另外，当液体黏度或温度等影响参数发生明显变化时，应在现场重新检定流量计。为跟踪研究流量计机械变化的影响，也需要定期检定流量计。 4.2 液体的蒸发 用流量计测量高蒸气压的石油液体时，在流量计正常工作或检定期间，如果液体蒸发，将影响到测量结果，检定系统应具有避免液体蒸发的措施。 4.3 影响检定结果的因素 流量计的检定类似于实验室的测试，正确地操作可以获得较好的重复性，保证测量的准确度。像确定被测液体的物理性质一样，工艺管线和检定系统有很多影响流量计不确定度的因素。为保证检定结果的重复性，应经常对计量器具和辅助设备进行全面检查，保持检定系统良好的工作状态。观测、记录、分析流量计特性的数据和修正计算是必要的（见ISO 4124）。 影响检定流量计的准确度和重复性的因素包括：流量计开始与结束时读数误差，计量标准器测量体积误差，温度和压力的读数误差，以及将测量结果修正到标准参比条件下计算误差等。 4.4 流量计检定方法 流量计检定方法分为： a）静止启停法。在流量计内液体不流动条件下，使用计数器读取开、关流量计时的读数，开关阀门应快速完成。 b）流动启停法。在流量计运行时，动态记录流量计开始和结束读数。读数可使用高分辨力的辅助或二次计数器来完成，当流量计和一次计数器连续运行时，辅助的或二次计数器也可启停。 4.5 计数器 每次检定流量计应使用流量计正常运行时使用的计数器，或使用流动启停法用的辅助同步计数器[见4.4.b）]。也允许使用密度选择器、温度补偿器和定量预置计数器等辅助设备。在检定时，如果应用这些辅助设备，他们应能进行设置和调整。相邻两次检定运行之间的时间间隔应尽量保持最小。 4.6 流量计的检定目的 依据流量计使用方式，检定流量计一般有两个目的： a）确定流量计的误差特性。通过检定结果调整流量计容差调整器，确定流量计的相对误差。若流量计系数为1.0000时，流量计的指示值正好等于实际输送液体的体积量。在间断输送液体时，通常采用这种方法。例如油罐车的流量计，油库装车栈台的流量计等。 b）确定流量计的流量特性。通过检定来确定流量计的流量与影响参数（如黏度或温度）之间的关系，即流量计系数。使用流量计系数可以将通过流量计的指示体积量换算成毛体积量，这种方 GB/T 17286.1-2016/ISO 7278-1：1987 法适用于连续或长期计量。 4.7 预运行 检定流量计前应进行预运行，建立稳定温度场、排出蒸气或气体、润湿标准量器内壁，然后在要求的流量范围内进行正式检定，并根据需要调整容差调整器。 同一流量下的每一检定点至少应重复检定三次，如另有规定，可以重复更多的次数（见ISO 4124）。 4.8 检定流量点 在一个或几个流量下检定以确定流量计系数时，如检定期间没有调整流量计的容差调整器，检定程序可按照4.7规定的方法进行，在同一流量下连续检定并记录数据，直至达到规定的检定次数，重复性应在允许的范围内。用该流量点三次检定的流量计系数平均值，作为流量计在该流量点的流量计系数。 4.9 数据分析 检定期间，流量计的读数如果不随流量计容差调整器的调整而发生变化，或在未经调整情况下连续进行四次检定后，没有连续三次的数据达到允许的重复性，这时应对检定运行有关的各部位进行检查，找出引起偏差的原因。如果未找出原因，还应检查流量计及其容差调整器是否存在电子或机械故障，如有故障应经维修后重新进行检定。 4.10 数据修约 所有测量值准确度的适用范围是0.01%，如流量计检定期间计量标准器的容积准确度为0.01%，则流量计系数应修约到小数点后第四位，不多于也不少于四位，例如1.001 6。 4.11 检定记录 简略的数据计算表、不标准的数据修约或中间计算都可能对检定结果产生不利影响。为得到准确的流量计系数或流量计计量特性，所有检定时的观测数据或计算数据，应填写在规定的流量计检定表格中。 4.12 流量计的检定 以上给出的大多数方法，适用于单台流量计的检定。如果对流量计组中的一台流量计进行检定，可使液体通过被检流量计和计量标准器实现在线检定，或者将流量计拆下送中心检定站进行离线检定。 5 标准量器检定系统 5.1 应尽量避免移动标准量器内液位计等辅助仪表和部件，更不能通过调整液位计的方法达到标称值。标准量器的标准容积部分内任何部分（如玻璃液位计、温度计套管或连接管等）发生变化后，标准量器应重新检定。标准量器在结构设计时应考虑到避免量器计量特性发生变化，并减少液体在罐壁的粘附。应经常检查标准量器内部的腐蚀、沉淀物、锈、阀门润滑剂和其他异物的聚集等。液位计的刻度尺应经常检查，如果液位计刻度尺发生位移，标准量器应重新检定。 5.2 用开口式标准量器检定流量计，是将标准量器的已知容积量与流量计指示的液体体积量相比较。液体应在实际的或相近的运行温度、压力、流量、密度和黏度条件下，经过流量计进入标准量器，由液位计刻度尺确定标准量器内的液体体积。流量计系数是把标准量器测得的实际体积，换算到检定温度条下所得体积与流量计指示体积的比值。 5.3 经过对标准量器充液和排液的预检定，以确定最低检定液位。被检流量计停止运行，开启流量计 GB/T 17286.1-2016/ISO 7278-1：1987 计算器。开始检定，使液体经过流量计进入标准量器，并保持接近运行条件下的流量和压力。在检定过程中，尽可能靠近流量计处测量液体的温度，应多次测量和记录，以确保测得通过流量计液位的准确温度。液体应连续流入标准量器直到液面达到合适的读数位置（玻璃液位计中的液位，对透明液体读弯月形底部的刻度；不透明液体读弯月形顶部的刻度）。液面停止流动且稳定后，观测玻璃液位计的刻度，并记录标准量器的液体体积，观测和记录标准量器的温度并求平均值，同时观测和记录流量计停止时的读数，计算流量计系数。检定完成后，流量计恢复正常运行流程。 5.4 如果需要，按要求调整流量计的容差调整器，并按上述方法重新进行检定。 5.5 某些类型的开口式标准量器使用上部喷嘴排空，为降低一次检定时液体的蒸发，吸入罐内的空气和检定液体的蒸气应达到饱和状态。采用这种做法时，每次将标准量器排空之前应将喷嘴打开，在液面降到零液位之前，再将喷嘴关闭。 5.6 在前述的检定过程中，由于检定运行开始时启动液位或确定零液位的方法不同，检定程序可能存在某些变化。 6 在线体积管检定系统 6.1 用体积管检定流量计，检定前应检查所有的阀门，以防止阀门泄漏，检查有关辅助设备的连接和供电电路。检定用的温度计和压力表应定期检定。 6.2 通常液体通过切换从被检流量计全部流经体积管。在某些固定安装的体积管系统中，液体始终通过流量计和体积管。保持通过流量计和体积管液体流量，达到稳定的温度。应检查排气连接管，保证流量计和体积管中的气体完全被排除，系统中不应留有空气或蒸气的气穴。 6.3 流量计正式检定之前，通常要进行一次预检定，作为对系统的最后检查。这是一种非常好的值得推荐的做法，对在线体积管检定系统来说方便易行。预检定应包括对电子和其他计数器的检查，通常可反映设备外观不易察觉的问题。 6.4 检定操作随装置的工艺状况而变化，可从手动到全部自动。检定的基本步骤包括操作阀或阀组引导被计量液体推动置换器（活塞、球等）通过体积管的标准管段。每次检定运行前，应记录检定计数器的读数，检定计数器如果装备有调零机构可预置零。在置换器进入体积管标准管段之前，应完成阀门开关的操作。在自动操作系统中，按启动按钮就可以完成流量计一次检定循环，并通过对阀门的调节和控制，实现有序的控制过程。 6.5 用单向体积管检定流量计时，一次检定运行由置换器通过标准管段的一个单行程构成。 6.6 用双向体积管检定流量计时，一次检定运行由置换器在标准管段中往返行程，即两次连续运行构成。标准体积是两次行程的容积之和。 6.7 小容积体积管通常由内径光滑的缸体、缸体中运动的置换器、检测开关等组成。这类体积管的性能取决于缸体的加工精度、检测开关的分辨力、温度和压力测量的准确度和稳定性、活塞的密封性、缸体直径与活塞的行程之比值。 6.8 按要求完成每次检定，记录检定数据。记录计数器初始读数或将其置零后，再根据需要进行下次检定。对双向体积管，应记录每个行程的检定数据。为检查系统的重复性应进行多次检定运行。检定完成后应根据记录数据和计算所得流量计系数或相对误差，编制流量计检定报告。 7 中心检定站检定系统 7.1 中心检定站的组成 中心检定站的组成包括： a）管道回路； GB/T 17286.1-2016/ISO 7278-1：1987 b）流量计检定台位； c）体积管或标准量器； d）管道回路静压调节系统； e）具有存储不同黏度液体的储罐； f）测量黏度、温度等参数的仪器仪表。 7.2 一般要求 检定系统的流量、黏度、压力、温度以及流量计检定曲线的影响因素和要求： a）流量和黏度的变化。应对流量计全量程范围进行不同流量和黏度的试验，所得到的流量计系数按数学函数关系绘成平滑的曲线。也可使用其他方法，特别是基于流量计系数与运动黏度对应的流速关系的雷诺数。 b）压力、温度的变化。流量计在工作和检定条件下，如果机械公差、叶片角度等因素的影响可忽略不计，压力和温度变化引起流量计本体尺寸的变化可用数学的方法修正。 c）曲线漂移。流量计计量系统总的可靠性不是指在两次连续检定之间的影响，曲线漂移是计量系统长期受计量液体性质变化的影响。 7.3 站址选择 中心检定站不必设在计量场所，可以设在远离计量现场的地方。但拆卸和运输流量计时应非常小心。 7.4 流量计安装 涡轮流量计的安装应特别小心，以避免偏心。整流装置在运输和检定时都应与流量计连接在一起。 7.5 检定数据库 同一类型流量计得到的大量试验数据，可用来统计预测流量计总的重复性，同时还应考虑到所有参数、操作及运输引起的曲线漂移。足够多的试验统计分析将有助于判定下列参数： a）最佳检定频次； b）需要维修的时间。 8 标准流量计检定系统 8.1 使用标准流量计法检定流量计时，要选择性能优于被检流量计的流量计作为标准流量计。标准流量计可以是并联流量计组中的一台，也可以是活动式流量计或是安装在检定站的流量计。 标准流量计的特性应可靠、稳定，并维持最佳的工作状态。如果使用活动式标准流量计，应采取保护措施以防止运输损伤或不正确的安装。标准流量计应在接近其工作条件下的流量点，且合格的检定系统中经常进行检定。 检定后的标准流量计，应在允许误差、流量范围内使用。 检定标准流量计时的数据应保存完好，以便使用标准流量计检定其他流量计时进行数据修正。如果压力和温度与检定标准流量计时不同，流量计的检定结果应进行修正。应该注意，标准流量计是次级计量标准器，它不能给出同体积管或标准量器一样高的准确度。 8.2 标准流量计应与被检流量计串联连接，并尽量靠近被检流量计，注意避免两台流量计之间的相互影响，两台流量计应在要求的流量下运行。在一次检定过程中，通过流量计液体量，至少应大于流量计最小分度值的10000倍。 GB/T 17286.1—2016/ISO 7278-1：1987 静止启停法就是在液体停止流动时记录两台流量计的启、停读数。开始检定时，开启流量计下游侧的阀门，使液体同时通过两台流量计，保持要求的流量，检定期间应观测、记录压力和温度值。经过足够长的检定时间获得满意结果后，关闭流量计下游侧的阀门，液体停止流动，记录流量计的读数。 用流动启停法时，计数器应同步启停。 8.3 影响检定结果的所有阀门，应有合适的检漏手段，或者能提供防止泄漏的方法。 |
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| GB/T 17286.1-2016, GB 17286.1-2016, GBT 17286.1-2016, GB/T17286.1-2016, GB/T 17286.1, GB/T17286.1, GB17286.1-2016, GB 17286.1, GB17286.1, GBT17286.1-2016, GBT 17286.1, GBT17286.1 |