Principles of naval engineering - Historic Naval Ships Association

Chapter 7-PRINCIPLES OF MEASUREMENTHEATING OilVESSELCORK38.214Figure 7-39.— Details of viscosimeter tube.measuring equipment received from Type IIStandards Laboratories. There are only twoType I Standards Laboratories: the Eastern SL,in Washington D.C., and the Western SL, in SanDiego, California.Navy Standards Laboratories designated asType II furnish the second highest level of calibrationservices to assigned geographical areaswithin the Naval Establishment. The Tj^De IIStandards Laboratories obtain standards calibrationservices from the cognizant Type IStandard Laboratory and calibrate standardsand associated measuring equipment receivedfrom lower level laboratories. There are halfa dozen Type II Navy Standards Laboratories,located in various shore activities throughoutthe United States.Navy Calibration Laboratories furnish thethird highest level of calibration services in theNavy Calibration Program. The Navy CalibrationLaboratories obtain calibration servicesfrom the Type n Standards Laboratories andthey calibrate test equipment received fromships and from shore activities. There are twobasic types of Navy Calibration Laboratories.Fleet Calibration Laboratories, which are locatedon repair ships and tenders (MIRCS) receiveand calibrate fleet equipment only. ShoreCalibration Laboratories, which are located invarious shore activities of the Navy, receive andcalibrate shore equipment and also handle theoverflow from Fleet Calibration Laboratories.As indicated in figure 7-40 equipment to becalibrated may go directly to a Navy CalibrationLaboratory or it may go to a shop or repairfacility for "qualification." Qualification is notthe same as calibration, and the two termsshould be clearly distinguished.Calibration is the process by which CalibrationLaboratories and Standards Laboratoriescompare a standard or a measuring instrumentwith a standard of higher accuracy in order toensure that the item being compared is accuratewithin specified limits throughout its entirerange. The calibration process involves the useof approved instrument calibration procedures;it may also include any adjustments or incidentalrepairs necessary to bring the standard or instrumentbeing calibrated within specifiedlimits. Calibration of standards is consideredmandatory.Qualification is the process by which anactivity other than officially designated StandardsLaboratories or Calibration Laboratoriescompares a test or measuring instrument withone of higher accuracy in order to determinethe need for calibration. Qualification may beperformed by ships or stations that have beenfurnished with approved measurement standardsand procedures. However, the instruments usedto qualify the test or measuring equipmentshould be calibrated periodically by a NavyStandards Laboratory or a Navy CalibrationLaboratory in order for the qualification to bevalid.Several additional terms used in connectionwith the Navy Calibration Program are definedin the following paragraphs. It is important tounderstand the precise meaning of these termsand to use them correctly.Calibration Procedure is the term used fora document that outlines the steps and operationsto be followed by standards and calibrationlaboratory personnel in the performance ofinstrument calibration.Calibration cycle is the length of time betweencalibration services during which eachtest equipment is expected to maintain reliablemeasurement capability. The Metrology153