GPA STD 8186-2017 Measurement of Liquid Hydrocarbons By Truck Scales.pdf

1、 Measurement of Liquid Hydrocarbons By Truck Scales Adopted as a Standard, 1986 Revised 2017 GPA Midstream Association Sixty Sixty American Plaza, Suite 700 Tulsa, Oklahoma 74135 GPA Midstream Standard 8186-17 i DISCLAIMER GPA Midstream Association publications necessarily address problems of a gene

2、ral nature and may be used by anyone desiring to do so. Every effort has been made by GPA Midstream to assure accuracy and reliability of the information contained in this publication. Each person who uses or refers to this publication will need to make their own decisions based on consideration of

3、their own internal best practices, recommendations, and engineering judgment. GPA Midstream and its members do not guarantee the accuracy, completeness, efficacy, timeliness, or correct sequencing of such information, including without limitation, the reference material and information of the variou

4、s other industry associations that may be provided herein. Use of the information provided in this publication is voluntary, and reliance on it should only be undertaken after an independent review of its accuracy, completeness, efficacy, timeliness, and consideration of the applicability of any loc

5、al, state, and federal laws and regulations. It is not the intent of GPA Midstream to assume the duties of employers, manufacturers, or suppliers to warn and properly train employees, or others exposed, concerning health and safety risks or precautions. Reference herein to any specific commercial pr

6、oduct, process, or service by trade name, trademark, service mark, manufacturer, or otherwise does not constitute or imply endorsement, recommendation, or favoring by GPA Midstream. GPA Midstream makes no representation, warranty, or guarantee in connection with this publication and hereby expressly

7、 disclaims any liability or responsibility for loss or damage resulting from its use or for the violation of any federal, state or municipal regulation with which this publication may conflict, or for any infringement of letters of patent regarding apparatus, equipment, or method so covered. “Copyri

8、ght2017 by GPA Midstream Association. All rights reserved. No part of this Report may be reproduced without the written consent of GPA Midstream Association.” ii FOREWORD GPA Midstream Standard 8186 provides the gas processing industry a method for measuring liquid hydrocarbons on trucks using scale

9、s. References to safety and operation contained herein are only for guidance and not intended to supersede official agency or individual company requirements. Additional guidance on safety and operation can be found in other publications. This standard was developed by the cooperative efforts of man

10、y individuals from industry under the sponsorship of GPA Midstreams Measurement and Quantity Determination Committee. Throughout this publication the latest appropriate GPA Midstream Standards and other industry standards are referenced. 1 Measurement of Liquid Hydrocarbons By Truck Scales 1. SCOPE

11、This standard presents guidance for weighing systems, equipment specifications, testing, calibration and calculations pertaining to the static measurement of liquid hydrocarbons at gas processing plants, refineries, tank farms, marine and pipeline terminals by the use of truck scales. 2. DEFINITIONS

12、 2.1 Accuracy The ability to indicate values closely approximating the true value of the measured variable. 2.2 Automatic-Indicating Scale A scale on which the weights of applied loads of various magnitudes are automatically indicated throughout all or a portion of the weighing range of the scale. 2

13、.3 Balance Indicator A combination of elements, one or both of which will oscillate with respect to the other, for indicating the balance condition of a non-automatic-indicating scale. The combination may consist of two indicating edges, lines, or points, or a single edge, line, or point and a gradu

14、ated scale. 2.4 Beam Scale A scale on which the weights of loads of various magnitudes are indicated solely by means of one or more weighbeam bars either alone or in combination with counterpoise weights. 2.5 Calibration The testing and adjustment of a system or system components to conform with tra

15、ceable reference standards to provide accurate values over the prescribed operating range. 2.6 Certification A document confirming that required tests have been performed to meet applicable regulations and/or custody transfer requirements. 2.7 Gross Weight Total weight of the vehicle loaded. 2.8 Liq

16、uid Hydrocarbons For the purpose of this standard, the intent is to measure liquid hydrocarbons such as liquefied petroleum gas (LPG), ethane-propane (EP) mixes and natural gas liquids (NGL) contained in trucks. The methods included herein may or may not be applicable to other fluids. 2.9 Load Cell

17、The basic weighing element of a load-cell scale. The load cell, whether electric, hydraulic, or pneumatic, produces a signal proportional to the load applied. A load cell may also be utilized on a mechanical lever type scale to convert mechanical force to an electronic signal. 2.10 Load-Receiving El

18、ement The platform or deck of a scale which is designed to receive the load to be weighed. Also referred to as the weighbridge. 2 2.11 Net Weight The weight of the fluid loaded into the truck; the difference between the gross weight and tare weight. 2.12 Nominal Capacity The nominal capacity of a sc

19、ale is the lesser of (a) the largest weight indication that can be obtained by the use of all of the reading or recording elements, or (b) the capacity marked on the scale by the manufacturer. 2.13 Overload A load weight greater than that permitted by regulation or rating of equipment. 2.14 Parallax

20、 The effect whereby the position or direction of an object appears to differ when viewed from different lines of sight. 2.15 Repeatability A measure of the agreement between the results of successive measurements of the same variable carried out by the same method, with the same instrument, at the s

21、ame location, and within a short period of time. 2.16 Scale Division The value of the smallest subdivision expressed in units of mass for analog indication or the difference between two consecutively indicated or printed values for digital indication or printing. 2.17 Section Test A test intended to

22、 disclose the weighing performance of each scale section individually. 2.18 Shift Test A test intended to disclose the weighing performance of a scale under off-center loading. 2.19 Tare Weight The weight of the vehicle without a load. 2.20 Truck Scale A scale adapted to weighing highway motor truck

23、s, loaded or unloaded. 2.21 Verification The process of confirming or substantiating the accuracy of input variables to a system at normal operating conditions, using reference equipment traceable to certified standards. 2.22 Weighbeam On a mechanical scale, this is an element comprising one or more

24、 bars, equipped with movable poises or means for applying counterpoise weights or both. 2.23 Zero Balance Shift Test A test for a change or shift of zero indication. 2.24 Zero-Setting Mechanism (Mechanical) Means provided to attain a zero balance indication with no load on the load-receiving element

25、. Types of zero-setting mechanisms are: 2.24.1 Automatic Zero-Setting Mechanism Automatic means provided to set the zero-balance indication without the intervention of an operator. 2.24.2 Manual Zero-Setting Mechanism Nonautomatic means provided to attain a zero balance indication by the direct oper

26、ation of a control. 2.24.3 Semiautomatic Zero-Setting Mechanism Automatic means provided to attain a direct zero balance indication requiring a single initiation by an operator. 3 3. APPARATUS The following items identify the components and equipment along with their corresponding performance requir

27、ement. 3.1 Accuracy The scale system shall be capable of maintaining an accuracy as defined in Table 3 of National Institute of Standards and Technology (NIST) Handbook 44, Section 2.20. 3.2 Repeatability The scale system shall repeat within three scale divisions. The value of the scale division sha

28、ll not be greater than two hundredths of one percent (0.02%) of the nominal capacity of the scale with the largest allowed scale division limited to 20 pounds for truck scales. For systems that generate outputs electronically utilizing conversions from analog to digital, the A/D converters used shal

29、l be of at least 16-bit resolution in order to achieve the 0.02% scale resolution. 3.3 Scale 3.3.1 The scale shall be suitable for the service in which it is used with respect to elements of its design, including but not limited to weighing capacity, computing capability; the character, number, size

30、 and location of indicating or recording elements; and the magnitude of its scale division. 3.3.2 The equipment shall be suitable for the environment in which it is used including but not limited to the effects of wind, weather, earthquakes, electromagnetic interference (EMI), and radio frequency in

31、terference (RFI). 3.3.3 Adjustable components, such as potentiometers, shall be held securely in adjustment, and shall not be adjustable from outside of the device, except for level or no-load adjustments. A device shall be designed with provision(s) for applying a security seal that must be broken,

32、 or for using other approved means of providing security (e.g., data change audit trail available at the time of inspection), before any change that affects the metrological integrity of the device can be made to any electronic mechanism. Provisions for determining the method of sealing which is dep

33、endent on the device, are detailed in Table S.1.11 of Section 2.20 of NIST Handbook 44. 3.3.4 A semi-automatic zero-load or no-load reference value setting mechanism shall be operable only when the indication is stable within plus or minus one (1) scale division, and should not be operated during a

34、weighing operation. However, when operating in adverse weather environments such as during snow or ice events, it is impractical to remove all ice and snow from the weight platform during the weighing operations and therefore the scale mechanism may need to be re-zeroed between events. 3.3.5 Marking

35、s such as the nominal capacity and the maximum state weight limits shall be marked in accordance with Section 2.20 of NIST Handbook 44 and/or local regulatory requirements. 4 3.3.6 For mechanical scales, a manual zero-load or no-load reference setting mechanism shall be operable or accessible only b

36、y a tool outside of or entirely separate from this mechanism or enclosed in a cabinet. 4. CAPTURING AND REPORTING OF DATA 4.1 There are many different methods for capturing the output from a scale. These methods include direct output to a printer, digital communications and dial indicators. Each met

37、hod is discussed in this section. 4.2 Indicators 4.2.1 The indicator shall be installed in such a manner that the operator can read the indicator while maintaining visual contact with the scale platform. 4.2.2 The weighing system shall be equipped with a zero-setting mechanism by which the zero-load

38、 balance or no-load reference value indication may be adjusted. 4.2.3 All systems shall be equipped with effective means necessary to bring the indications quickly to a stable readable equilibrium. Effective means shall also be provided to permit the recording of weigh values only when the indicatio

39、n is stable within plus or minus one (1) scale division, or less. 4.2.4 The value of the scale division shall be conspicuously marked adjacent to the weight display on any scale, marked such that the value of the scale division is immediately apparent. 4.2.5 On multi-range devices capable of indicat

40、ing in two or more units, each range and unit shall be marked. 4.3 Mechanical Indicators 4.3.1 The index of an indicator shall be symmetrical with respect to the graduations with which it is associated and at least throughout that portion of its length that is associated with the graduations. The in

41、dex of an indicator shall reach to the finest graduations with which it is used, unless the indicator and the graduations are in the same plane, in which case the distance between the end of the indicator and the ends of the graduations, measured along the line of the graduations, shall be not more

42、than four-hundredths (0.04) of an inch. The width of the index of an indicator in relation to the series of graduations with which it is used shall be not greater than the width of the widest graduation or the width of the minimum clear interval between weight graduations. 4.3.2 When the index of an

43、 indicator extends along the entire length of a graduation, that portion of the index that may be brought into coincidence with the graduation shall be of the same width throughout the length of the index. The clearance between the index of an indicator and the graduations shall in no case be more t

44、han six-hundredths (0.06) inch. Parallax effects shall be reduced to the practical minimum. The zone of uncertainty on digital indicating scales 5 shall be no greater than three-tenths (0.3) the value of the minimum operating increment. 4.3.3 Provision shall be made on scales equipped with indicatin

45、g or recording elements to either indicate or record a zero balance condition, and on an automatic-indicating scale or balance indicator to indicate or record an out-of-balance condition on both sides of zero. A zero or center-of-zero indication shall represent a balance condition that is within plu

46、s or minus one-fourth (0.25) the value of the minimum scale division that can be indicated or recorded. 4.4 Electronic Indicators A digital indicating element and recording element shall not display or record any values when the gross platform load is in excess of one-hundred five percent (105%) of

47、the nominal capacity of the system. A digital indicating or recording element shall not display or record any usable values until the operating temperature (warm-up time) necessary for accurate weighing and a stable zero balance condition has been attained. 4.5 Quantity Transaction Record (QTR) The

48、following defines the minimum information required for measurement purposes. Operational and regulatory requirements may necessitate additional information. - Tare weight - Tare weight date and time - Gross weight - Gross weight date and time - Density1- Product - Unique transaction ID Note 1: When

49、product is valued on a volumetric basis, a density will need to be used to convert the mass to volume. This density needs to be at the appropriate conditions for conversion. See Section 9 for further details. 5. INSTALLATION 5.1 The foundation and supports of a scale installed in a fixed location shall be installed to provide strength, rigidity and permanence of all components according to the scale manufacturers recommendations. Clearance shall be provided around all live parts to the extent that no contact results when the load