American Petroleum Institute

Recommended Practice for Metering Viscous Hydrocarbons - First Edition
 N RP 2533

Annotation

INTRODUCTION

This recommended practice has been prepared as a guide to assist in the design, installation, operation, and proving of meters and meter accessories for the measurement of viscous hydrocarbons. The basic intent is to educate, inform, and warn prospective users—stressing the difference between this field of metering and the metering of less viscous hydrocarbons, and giving them ing the benefit of the experience in this field of measurement to date. In general, the procedures outlined in API Standard 1101 (USAS Zl I.l70),* API Standard 2531 (USAS ZI1.l71),' and a forthcoming publication, API Standard 2534,' will apply. Viscous hydrocarbons have characteristics which can affect the various phases of meter installation, operation, and proving; therefore, certain designs and procedures not provided in API Standard 1101 and API Standard 2534 are recognized and should be taken into consideration. This recommended practice should supplement all applicable API metering standards.

A viscous hydrocarbon, for the purpose of this publication, will be any liquid hydrocarbon that requires special treatment in handling or storage, such as heating, or that requires special meter or special pump construction. It is possible that a fluid not requiring these precautions might have some of the characteristics or might present some of the measurement problems characteristic of viscous liquids. This publication also would apply to those liquidS. Exa!l1ples of liquids generally considered as viscous fluids in handling or metering are No. 5 and No. 6 bunker fuels; asphalts, both penetration grades and cutbacks; most lubricating oils; and lubricating oil and grease components; as well as some crude oils.

Positive displacement meters have different performance characteristics on viscous fluids than do the various inferential or turbine meters. Meter performance in the positive displacement meter is affected by meter slippage (see API Standard 1101, Par. 4004 and 4005). There is considerably less slippage through the meter as the viscosity of the liquid increases. There is some change in slippage with change in viscosity. Where a high degree of accuracy is required, proving is suggested with any viscosity change to reestablish the meter accuracy.