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5551: Compressed Natural Gas / Retail Motor-Fuel Dispenser

This 4-day seminar will teach students how to conduct an official examination by properly applying all applicable NIST Handbook 44 requirements and in accordance with the minimum procedures outlined in the NIST Examination Procedure Outlines (EPOs) for CNG RMFDs. The sessions will include formal lecture, class discussion, group exercises, audio-visual presentations, and some hands-on practice in both the classroom and field.

Learning Objectives:

Upon completion of the course, you should be able to:

  • IDENTIFY and DESCRIBE the major types of metering systems used for commercial measurement and delivery of CNG;
  • DESCRIBE the design and operation of typical CNG RMFD metering systems and their major components, especially those involved in measuring, indicating, recording, and delivering product;
  • DESCRIBE basic safety procedures and equipment, including emergency procedures, employed in examining CNG RMFD systems;
  • IDENTIFY appropriate test equipment and field test standards used for testing these metering systems in the field and describe procedures for setup, operation, and maintenance of this equipment;
  • DETERMINE whether or not a particular reference scale is suitable for use as a standard in testing a CNG RMFD gravimetrically;
  • DESCRIBE procedures for inspecting CNG RMFD systems to determine whether they conform with specifications and other requirements set forth in NIST Handbook 44 and in accordance with NIST Examination Procedure Outlines for Weighing and Measuring Devices;
  • DESCRIBE procedures for testing these metering systems in the field and be able to determine the amount of product dispensed into a test tank by using a suitable reference scale to weigh it;
  • DETERMINE the amount of error in the RMFD being tested for each test draft of CNG dispensed; the direction of the error; and whether or not the errors conform to performance requirements set forth in the latest edition of NIST Handbook 44, “Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices;” and
  • DESCRIBE post-examination tasks that must be performed upon completion of an official field examination, including documentation and recordkeeping.

Materials & Supplies:

Notebooks and class materials will be provided.


Participants must have completed the NIST Handbook-44 Self Study course found at Legal Devices - Training Materials.

Minimum Requirement(s):

To obtain a course certificate for this class, students must be in attendance for the entire class; participate in all group activities that are planned; and achieve a score of 70 percent or higher on a final exam, which will be administered on the last day of the class. Students who do not fulfill these requirements will not receive a certificate of completion.


State weights and measures officials. Industry by invitation only.


There is no registration fee for this training. However, participants are responsible for making their own transportation and lodging arrangements and for all associated costs. Participants are also responsible for arranging daily transportation to and from their lodgings and the seminar.


Richard Harshman and Juana Williams
Office of Weights and Measures,
Phone: (301) 975 - Ext. 8107 / 3989
Email: richard.harshman [at] (richard[dot]harshman[at]nist[dot]gov) / juana.williams [at] (juana[dot]williams[at]nist[dot]gov) 

Technology Requirement(s):

Participants MUST bring a four function calculator with at minimum capability to calculate standard deviations and a square root function. Participants may also bring laptops; however, laptops are not required for the class.


NIST Office of Weights and Measures / California Division of Measurement Standards

Created March 21, 2018, Updated April 3, 2018