1、Manual of PetroleumMeasurement StandardsChapter 3Tank GaugingSection 3Standard Practice for Level Measurement of Liquid Hydrocarbons in Stationary Pressurized Storage Tanks by Automatic Tank GaugingFIRST EDITION, JUNE 1996REAFFIRMED, OCTOBER 2011Manual of PetroleumMeasurement StandardsChapter 3Tank
2、GaugingSection 3Standard Practice for Level Measurement of Liquid Hydrocarbons in Stationary Pressurized Storage Tanks by Automatic Tank GaugingMeasurement CoordinationFIRST EDITION, JUNE 1996REAFFIRMED, OCTOBER 2011SPECIAL NOTESAPI publications necessarily address problems of a general nature. With
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13、d beutilized. The formulation and publication of API standards is not intended in any way toinhibit anyone from using any other practices.Any manufacturer marking equipment or materials in conformance with the markingrequirements of an API standard is solely responsible for complying with all the ap
14、plicablerequirements of that standard. API does not represent, warrant, or guarantee that such prod-ucts do in fact conform to the applicable API standard.All rights reserved. No part of this work may be reproduced, stored in a retrieval system, or transmitted by any means, electronic, mechanical, p
15、hotocopying, recording, or otherwise, without prior written permission from the publisher. Contact the Publisher, API Publishing Services, 1220 L Street, N.W., Washington, D.C. 20005.Copyright 1996 American Petroleum InstituteiiiFOREWORD This publication covers standard practice for level measuremen
16、t of liquid hydrocarbonson stationary pressurized storage tanks by automatic tank gauging, and supersedes all appli-cable sections of API Standard 2545, Method of Gaging Petroleum and Petroleum Products(October 1965).API publications may be used by anyone desiring to do so. Every effort has been mad
17、eby the Institute to assure the accuracy and reliability of the data contained in them; however,the Institute makes no representation, warranty, or guarantee in connection with this publi-cation and hereby expressly disclaims any liability or responsibility for loss or damageresulting from its use o
18、r for the violation of any federal, state, or municipal regulation withwhich this publication may conflict.Suggested revisions are invited and should be submitted to the director of the Explo-ration and Production Department, Measurement Coordination, American Petroleum Insti-tute, 1220 L Street, N.
19、W., Washington, D.C. 20005.vCONTENTSSECTION 3STANDARD PRACTICE FOR LEVEL MEASUREMENT OF LIQUID HYDROCARBONS IN STATIONARY PRESSURIZED STORAGE TANKS BY AUTOMATIC TANK GAUGING1 SCOPE 12 REFERENCES 12.1 Standards . 12.2 Safety Precautions . 13 ACCURACY REQUIREMENT 23.1 Inherent Error of ATGs . 23.2 Cal
20、ibration Prior to Installation. 23.3 Error Caused by Installation and Operating Conditions . 23.4 Use of ATGs in Custody Transfer Service 33.5 Accuracy of ATGs in Custody Transfer Service . 34 INSTALLATION OF ATGs. 34.1 General 34.2 Mounting Location 34.3 Manufacturers Requirements . 34.4 Installati
21、on of ATGs 34.5 Still Pipe Design 55 INITIAL ADJUSTMENT AND FIELD VERIFICATION OF ATGs. 75.1 Preparation 75.2 Initial Adjustment 75.3 Initial Field Verification 85.4 Record Keeping. 86 OPERATION OF ATGs. 87 MAINTENANCE OF ATGs 98 SUBSEQUENT VERIFICATION OF ATGs. 98.1 General 98.2 Frequency of Subseq
22、uent Verification 98.3 Procedure for Subsequent Verification 98.4 Tolerance for Subsequent Verification of ATGs in Custody Transfer. 98.5 Comparison of the ATG Readings From Currentand Previous Verifications 98.6 Adjustment in Subsequent Verification. 99 DATA COMMUNICATION AND RECEIVING 9Figures1Ins
23、tallation of Intrusive ATG in a Pressurized Storage Sphere With Still Pipe. 42Installation of Intrusive ATG in a Pressurized Storage Sphere Using Guide Wires 53Installation of Nonintrusive ATG in a Pressurized Storage Sphere With Still Pipe. 6(This page left intentionally blank)1 ScopeThis standard
24、provides guidance on the installation, cali-bration, and verification of automatic tank gauges (ATGs)used in custody transfer for measuring the level of liquidhydrocarbons having a Reid vapor pressure of 15 psi (103kilopascals) or greater, stored in stationary, pressurizedstorage tanks. The standard
25、 also provides guidance on therequirements for data collection, transmission, and receiving.This standard is not applicable to the following:a. Conversion of tank level to liquid volume.b. Measurement of free water or sediment lying under theliquid hydrocarbon.c. Measurement of temperature, density,
26、 or sediment andwater (S for example, the error ofthe ATGs when tested under defined referenced conditionsas specified by the manufacturers.3.2 CALIBRATION PRIOR TO INSTALLATION The reading of the ATG in custody transfer service shouldbe calibrated prior to installation (in the factory or testinglab
27、oratory under controlled conditions) to agree with a certi-fied reference (for example, a certified gauge tape) within116 inch or 1 millimeter over the entire range of the ATG.The certified reference should be traceable to the NationalInstitute of Standards and Technology standards and shouldbe prov
28、ided with a calibration correction table. The uncer-tainty of the certified reference should not exceed 132 inch or0.5 millimeter with the calibration correction applied. Note: ATGs used for internal inventory control or operational purposes(such as tank filling and emptying, and level control) shou
29、ld be calibratedto ensure safe operation as determined by the tank owner. 3.3 ERROR CAUSED BY INSTALLATION ANDOPERATING CONDITIONS The error caused by installation and operating conditionson the ATGs used in custody transfer service should notexceed 18 inch or 3 millimeters, provided the operatingco
30、nditions are within the limits specified by the ATG manu-facturer.Note 1: The accuracy of measurements using ullage ATGs is affected byvertical movement of the upper reference point used to calibrate the ATG orvertical movement of the ATG top mounting point during tank transfers.Accuracy may also be
31、 affected by tank tilt, hydrostatic pressure, and vaporpressure.Note 2: The accuracy of measurements by innage ATGs may be affected byvertical movement of the ATG bottom mounting point during tank transfersor by variation of pressure.Note 3: Volume measurements using tanks are limited by the followi
32、nginstalled accuracy limitations, regardless of the ATGs used. These limita-tions may have a significant effect on the overall accuracy of manual levelgauging and all types of automatic tank gauges, as well as on the accuracyof the quantity of the content in the tank.a. Tank capacity table accuracy
33、(including the effect of tank tilt and hydro-static pressure).b. Changes of tank geometry due to temperature.SECTION 3STANDARD PRACTICE FOR LEVEL MEASUREMENT OF LIQUID HYDROCARBONS IN STATIONARY PRESSURIZED STORAGE TANKS 3c. Random and systematic errors in level, liquid, vapor density, pressure,and
34、temperature measurement.d. Operational procedures used in the transfer.e. Difference between opening and closing levels (minimum parcel size).Note 4: Special consideration should be given to volume and mass measure-ments in pressurized tanks with respect to the amount of product present inthe vapor
35、space of the tank. API MPMS Chapter 12 and GPA Standard 8195state the procedure and computation method to derive a compensatedvolume and mass assessment. (The section in API MPMS Chapter 12covering calculation of vapor to liquid equivalent was in preparation at thetime this standard was written.)3.4
36、 USE OF ATGS IN CUSTODY TRANSFERSERVICE The total accuracy of level measurement by ATGs, asinstalled, is affected by the inherent error of the ATG, theeffect of installation, and the effect of changes in operatingconditions. Depending on the total (overall) accuracy of theATG as installed (installed
37、 accuracy), ATGs may be used incustody transfer service. The use of ATG in custody transferusually requires mutual contractual agreement between thebuyer and the seller.Note: It is difficult to verify the level accuracy of ATGs in pressurizedstorage tanks by manual level gauging. If the level measur
38、ement by an ATGcannot be verified, the ATG should not be used for custody transfer levelmeasurement.3.5 ACCURACY OF ATGS IN CUSTODYTRANSFER SERVICE3.5.1 The ATG should meet the pre-installation calibra-tion tolerance of 116 inch or 1 millimeter (refer to 3.2). 3.5.2 Including the effects of the inst
39、allation and changesin operating conditions of 18 inch or 3 millimeters, (refer to3.3), the ATG should meet the field verification tolerance asdefined in Sections 5 and 8.3.5.3 The remote readout, if used, should meet therequirements of this standard not to exceed 116 inch or 1millimeter (refer to S
40、ection 9). 4 Installation of ATGs4.1 GENERALATGs that use technology other than those described inthis standard can be used in custody transfer if they providethe required accuracy for the intended application. Installa-tion methods comparable to those described in this standardthat allow the ATG to
41、 be verified with the tank in serviceshould be available .The following sections outline recommendations andprecautions for the installation of ATGs.4.2 MOUNTING LOCATION4.2.1 The mounting location of an ATG may affect theinstalled accuracy. For custody transfer accuracy, the ATGmounting location sh
42、ould have minimal movement withrespect to the tank reference, due to changes in liquid heador vapor pressure. 4.2.2 The ATG should preferably be mounted as close aspractical to the vertical centerline axis of the tank.4.2.3 The level-sensing element should be protectedagainst excessive turbulence ca
43、used by the product inlet oroutlet. If this cannot be achieved, an installation with a stillpipe should be considered.4.3 MANUFACTURERS REQUIREMENTSThe ATG and level transmitter should be installed andwired in accordance with the manufacturers instructions.4.4 INSTALLATION OF ATGS4.4.1 Installation
44、of Intrusive Ullage ATGsMounted on Still Pipes4.4.1.1 For installations shown in the example in Figure1, the ATG should be mounted on a properly suspendedstill pipe. The still pipe protects the ATG level-sensingelement from liquid turbulence and may provide the fixa-tion point for the datum plate.4.
45、4.1.2 For ease of maintenance and verification, theATG should be installed such that it can be isolated fromthe tank (through an isolation valve, for example).Adequate means (such as a calibration chamber equippedwith an inspection hatch) should be provided for access tothe level-sensing element.4.4
46、.2 Installation of Intrusive Ullage ATGsUsing Guide Wires4.4.2.1 For installations shown in the example in Figure2, the ATG should be mounted on a properly installednozzle. The level-sensing element should be protectedagainst excessive turbulence caused by the product inlet oroutlet. Note: Use of th
47、e spring-tensioned guide wire is intended to protect theATG level-sensing element from liquid turbulence.4.4.2.2 For ease of maintenance and verification, theATG should be installed such that the level-sensingelement can be isolated from the tank (through an isolationvalve, for example). Adequate me
48、ans (such as a calibrationchamber equipped with an inspection hatch) should beprovided for access to the level-sensing element.4.4.3 Installation of Nonintrusive Ullage ATGsMounted on Still Pipes4.4.3.1 For installations shown in the example in Figure3, the ATG should be installed on a properly supp
49、orted stillpipe. The still pipe should be designed to ensure that suffi-cient signal strength be obtained and interference be mini-4CHAPTER 3TANK GAUGINGmized under boiling conditions, which can occur duringemptying a high-pressure tank.4.4.3.2 A datum plate, which may serve as a deflectorplate (shown in Figure 3), should be installed close to thetank bottom to avoid any disturbance echo. The plate shouldbe constructed in such a way that accurate manual measure-ment of the distance (L), when practical, can be obtained. 4.4.3.3 The construction of the ATG may not req
