1、GPA STDx8IIBb 8b m 382Lib 00003LlLi II m OPA Standard 81 86-86 Measu rem en t of Li q u id Hydrocarbon by Truck Scales Adopted as a Standard, 1986 Gas Processors Association 6526 East 60th St. Tulsa, Oklahoma 74145 9 i a1493-3872 Non-Members: Single copies .$ 4.00 Members: Single copies . 2.50 1 O o
2、r more copies. each . 2.00 I I GPA STD*dLBb 86 382L)b 00003L)b 5 = Measurement of Liquid Hydrocarbon by Truck Scales 1. INTRODUCTION AND SCOPE This standard presents apparatus, procedures and safety practices pertaining to measurement of liquid hydro- carbons at gas processing plants, refineries, ta
3、nk farms, marine and pipeline terminals by the use of truck scales. Although many existing codes, standards, regulations and safety practices employed by the industry have been used in its preparation, it is not intended that this document be considered as a code or standard for loading or unloading
4、 procedures of a liquid hydrocarbons facility design. The GPA takes no position as to whether any method, apparatus, or product mentioned herein is covered by an existing patent, nor as to the validity of any patent alleged to cover any such method, apparatus, or product. Furthermore, nothing contai
5、ned in this standard grants any right, by implication or otherwise, for manufacture, sale or use in connection with any method, apparatus, or product covered by letter patents; nor does it insure anyone against liability for infringement of letter patent. This standard may be used by anyone desiring
6、 to do so, but the GPA shall not be held responsible or liable in any way, either for any loss or damage resulting therefrom or from any violation of any federal, state, or municipal regulations with which it may conflict. In all instances, applicable federal, state, or municipal regulations should
7、be followed. 1.4 Included in this standard are references to material that pertain to design and operation of liquid hydrocarbons installations. Although some states have regulations pertaining to loading and unloading of liquid hydrocarbons into or out of tank trucks, and tank cars at loading facil
8、ities which are a part of a gasoline plant, refinery, tank farm and pipeline terminal, references to individual state regulations have not been included because many states either do not have existing, regulations or the regulations are not codified. 1.1 1.2 1.3 2. DEFINITIONS 2.1 Accuracy-The sligh
9、t deviation from standard limits. The error which is the difference between the scale indication and the true value of that which is being weighed. 2.2 Automatic-Indicating Scale-One on which the weights of applied loads of various magnitudes are automatically indicated throughout all or a portion o
10、f the weighing range of the scale. 2.3 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 nonautomatic-indicating scale. The combination may consist of two indicating edges, lines, or points, or a sing
11、le edge, line, or point and a graduated scale. 2.4 Beam Scale-One 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 Gross Weight-Total weight of the vehicle loaded. 2.6 Liquid
12、HydrocarbonsFor the purpose of this standard, liquid hydrocarbons include but are not limited to liquefied petroleum gas (LP-gas), ethane-propane (EP) mixes and natural gas liquids (NGL). 2.7 Load Cell-The basic weighing element of a load-cell scale. The load cell, whether electric, hydraulic, or pn
13、eumatic, 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. 2.8 Load-Receiving Element-The platform or deck of a scale which is designed to receive the load to be weighed. Also ref
14、erred to as the weighbridge. 2.9 Net Weight-The weight of the load. The tare weight subtracted from the gross weight equals net weight. 2.10 Nominal CapacieThe nominal capacity of a scale is (a) the largest weight indication that can be obtained by the use of all of the reading or recording elements
15、, or (b) the capacity marked on the scale by the manufacturer, whichever is less. 2.11 Overload-A load weight greater than that permitted by regulation or rating of equipment. Repeatability-The ability to duplicate the indication each time the same weight is applied, regardless of direction of appro
16、ach. Scale Diuision-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. 2.14 Section Test-A test intended to disclose the weighing performance of each scale
17、section individually. 2.15 Shift Test-A test intended to disclose the weighing performance of a scale under off-center loading. 2.16 Tare Weight-The weight of the vehicle without a load. Ticket-Printer-A device whichissues a ticket or other form containing printed information, including the identity
18、 and quantity of the material being transferred. Truck Scale-A scale adapted to weighing highway motor trucks, loaded or unloaded. Weighbeam-An element comprising one or more bars, equipped with movable poises or means for applying counter- poise weights or both. 2.20 Zero Balanceshift Test-A test f
19、or a change or shift of zero indication. 2.21 Zero Setting Mechanism-Means provided to attain a zero balance indication with no load on the load receiving element. 2.2111 Automatic Zero Setting Mechanism-Automatic means provided to maintain a zero balance indication without the intervention of an op
20、erator. 2.21.2 Manual Zero Setting Mechanism-Non-automatic means provided to attain a zero balance indication by the direct operation of a control. 2.21.3 Semi-Automatic Zero Setting Mechanism-Semi- automatic means provided to attain a direct zero balance indication requiring a single initiation by
21、an operator. 2.12 2.13 2.17 2.18 2.1 9 3 GPA STD*LBb 8b 3824699 00003Ll7 7 I 3. APPARATUS 3.1 Accuracy-The scale system shaii be capable of main- taining an accuracy of plus or minus one tenth of one percent (f0.1%) of applied load. 3.2 Repeatability-The scale system shall repeat, per Section 2115,
22、within one scale division. The value of the scale division shall not be greater than two hundredths of one percent (.02%) of the nominal capacity of the scale with the largest allowed scale division limited to twenty (20) pounds. 3.3 Scale 3.3.1 The scale shall be suitable for the service in which i
23、t is used with respect to elements of its design, including but not limited to weighing capacity, computing capability; the character, number, size and location of indicating or recording elements; and the value of its smallest unit. 3.3.2 The equipment shall be suitable for the environment in which
24、 it is used including but not limited to the effects of wind, weather, earthquakes, electromagnetic interference (EMI) and radio frequency interference (RFI). At all points at which a live part of the mechanism may come into contact with another part in the course of normal usage, frictional effects
25、 shall be reduced to a minimum by suitable anti-friction means, in addition to the opposing surfaces and points being properly shaped, finished and hardened. 3.3.4 All adjustable components, such as potentiometers, shall be held securely in adjustment, and shall not be adjustable frm outside of the
26、device, except for level or no- load adjustments. All weighing systems shall be vented so that any internal or external pressure will not affect the accuracy or operation of the system. 3.3.6 A manual zero-load or no-load reference setting mechanism shall be operable or accessible only by a tool out
27、side of or entirely separate from this mechanism or enclosed in a cabinet. 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 cannot be operated during a weighing operation. The
28、 nominal capacity and the maximum state weight limits shall be conspicuously marked. 4. SCALE INDICATOR AND/OR PRINTER 3.3.3 3.3.5 3.3.7 3.3.8 4.1 Indicator 4.1.1 The index of an indicator shall be symmetrical with respect to the graduations with which it is associated and at least throughout that p
29、ortion of its length that is associated with the graduations. The index 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 graduat
30、ions, measured along the line of the graduations, shall be not more than four-hundredths (0.04) inch. The width of the index of an indicator in relation to the series of graduations with which it is used shail be not greater than the width of the widest graduation or the width of the minimum clear i
31、nterval between weight graduations. The indicator shall be installed in such a manner that the operator has visual contact with the scales. 4.1.2 4.1.3 When the index of an indicator extends along the entire length of a graduation, that portion of the index that may be brought into coincidence with
32、the graduation shall be of the same width throughout the length of the index. The clearance between the index of an indicator and the grad- uations shall in no case be more than six-hundredths (0.06) inch. Parallax effects shall be reduced to the practical minimum. The zone of uncertainty on digital
33、 indicating scales shall be no greater than three-tenths (0.3) the value of the minimum operating increment. 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 the nominal capacity
34、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 weighjng and a stable zero balance condition has been attained. 4.1.4 The weighing system shall be equipped with manual or semi
35、-automatic means by which the zero-load balance or no load reference value indication may be adjusted. Provision shall be made on scales equipped with indicating or recording elements to either indicate or record a zero balance condition, and on an automatic-indicating scale or balance indicator to
36、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 plus or minus one-fourth (f0.25) the value of the minimum scale division that can be indicated or recorded. All systems shall be equipped with
37、effective means necessary to bring the indications quickiy to a stable readable equilibrium. Effective means shall also be provided to permit the recording of weight values oniy when the indication is stable within plus or minus one (Il) scale division, or less. 4.1.7 The value of the scale division
38、 shall be conspicuously marked adjacent to the weight display on any scale so constructed that the value of the scale division is immediately apparent. 4.1.8 On multi-range devices capable of indicating in two or more units, each range and unit shall be marked. 4.2 Printer-Any printed ticket issued
39、by a device shall have printed on it, as a minimum, gross weight and tare weight, other items to be either printed or hand written are: Date, Time, Net Weight, Product and LD. Number. 4.1.5 4.1.6 Example: BRAND X Oil Company 201 E. Main Street Any Town, TX O0000 Time: 750 a.m. Date: September 8, 198
40、5 LD.: 99999 Product: Propane Weight 80,000 Gross 40,000 Tare 40,000 Net Driver Signature: Company Representative Signature 4 6. RECOMMENDED PROTECTION Surge Protection-When scales are equipped with digital electronics devices shall be incorporated to provide surge protection. As a minimum, the leve
41、l of surge protection shall be such that the equipment and protective devices shall survive, without damage, the IEEE Surge Withstand Capability (SWC) Test, IEEE Standard 472. Short CircuiVLightning Protection-The scale shall be grounded for short circuit protection in accordance with Article 250 of
42、 the National Electrical Code (NEC). Lightning protection shall be in accordance with NFPA Code Number 78. 5.3 RFI and EMI Protection-Adequate radio frequency interference (RFI) and electromotive interference (Em protection shall be provided for the overall system, as per IEEE Std. 518. 6. INSTALLAT
43、ION The foundation and supports of a scale installed in a fixed location shall be such as to provide strength, rigidity and permanence of all components. Clearance shall be provided around all live parts to the extent that no contacts may result when the load-receiving element is empty, and througho
44、ut the weighing range of the scale. Adequate provision shall be made for ready access to ail components of a scale for inspection and maintenance. The length of the scale shall be sufficient to accom- modate any tractor trailer truck in one weighing. On the approach end or ends of the scale there sh
45、all be a straight approach at least the width of the platform, and at least one- half (0.5) the length of the platform but not required to be more than forty (40) feet. Not less than ten (10) feet of any approach adjacent to the platform shall be constructed of concrete or similar durable material t
46、o insure that this portion remains relatively smooth and level, and in the same plane as the platform so as not to cause scale shifting which might render the system less repeatable. However, grating of sufficient strength to withstand all loads equal to the sectional capacity of the scale may be in
47、stalled in this portion. Any slope in the remaining portion of the approach shall insure ease of vehicle access, ease for testing purposes and drainage away from the scale. 6.4 The scale system shall be constructed and installed to function safely in the potentially hazardous presence of hydrocarbon
48、 liquids and/or vapors, The system shall conform to the National Electrical Code (NEC) and the National Fire Protection Association Manual (NFPA) 58 requirements. 7. WEIGHING AND LOADING PROCEDURES The established loading and weighing procedures and safety precautions as defiied in GPA publication 8
49、162 shall be adhered to at this time. When GPA Reference Bulletin 187-87 is published it will supersede 8162. 8. TESTING AND CALIBRATION 8.1 Frequency of Testing and Calibration-Testing and calibration shall be conducted at a minimum of every six (6) months and immediately following any maintenance performed on the scales that may affect accuracy and/or repeatability. 8.2 A Calibration Report shall be included with the scale calibration certificate. This report shall include at minimum the data of the section test, load tests and shift tests; “as found” before calibration and “as left
