FRCSW Home to Navy’s Premier Calibration Lab
The Navy Primary Standards Laboratory (NPSL), located in Buildings 469 and 379 aboard Fleet Readiness Center Southwest (FRCSW), is the Navy’s highest echelon for metrology calibration (the science of measurements) and provides technical assistance and training to shore metrology and calibration program personnel.
The NPSL calibration program is compliant to the National Institute of Standards and Technology (NIST), an agency of the U.S. Department of Commerce. NIST establishes measurement standards for a variety of devices from atomic clocks to semiconductors.
In late 2016, the NPSL moved its laminar (liquid and gas) and air flow calibration facility from Building 66 to Building 379.
The shop is staffed by two metrology engineers and one metrology engineering technician, who handles most of the liquid flow calibration.
The 2,000 square-foot laboratory is equipped with a closed-circuit wind tunnel used to calibrate anemometers, or air velocity meters, found onboard ships for wind speed checks during aircraft operations.
Gas flow calibration tests meters that measure aircraft cabin pressure, breathing apparatus in oxygen masks, or how much air is going through an oxygen tank, and nitrogen from fuel pumps.
Though the shop has the ability to calibrate using nitrogen, Joe Allen, senior metrology engineer, said that air is commonly used in the testing of gas flow meters. Testing flow rates may be as low as one cubic centimeter per minute, to 400 cubic feet per minute.
“We use sonic nozzles to calibrate the gas flow. The fastest you can put air through them is at the speed of sound. Once it reaches that, it stays there. We can calculate the density of the air and tell what the volume or mass flow rate is going through it at the different pressure,” Allen said.
Liquid flow calibration is used to test turbine flow meters found throughout the Navy. In the fleet, they are typically used to transfer jet fuel and water from supply ships to aircraft carriers. Many are high capacity flow meters, with a two-inch diameter.
Allen said that it is possible for one meter to require multiple calibrations with jet fuel, hydraulics, or engine oil.
“If we calibrated with jet fuel and then hydraulic oil, for example, we would clean it first. If there is some residual fluid, we put it on a test stand with mineral oil in it. It’s okay if it mixes with the mineral oil because we care about the viscosity of the fluid, so we’ll adjust our calibrations to the viscosity,” he said.
“Before, we had the very specific fluids the Navy used at certain benches. The newer benches can cover a broad range of flow runs and viscosities, giving us greater flexibility,” he noted.
Some of the calibration benches use a mixture of propylene glycol and water. Propylene is thinned with water and heated or cooled to reach a specific viscosity.
“We’re starting a study to see if we can get the propylene mixture to mimic jet fuel. The problem is there’s some question as to how thin you can get the propylene. Jet fuel is very thin, like diesel. The more watery the mixture, the less it lubricates and the less it lubricates, it can affect the flow rate.”
Allen added that in the past few years, the Navy is adapting to technological advances that have enabled certain meters to be interchangeable from fluids to gas.
About 70 percent of the shop’s equipment was upgraded within the past five years, increasing its capability and automated functions such as generating reports immediately after calibration.
“We are a lot more open to our customers with custom needs and viscosity measurements,” Allen said. “The Marines had a liquid flow meter that had a computer. It had a very wide range of viscosity and we were able to model the lower range with a certain fluid and model the upper range with a different fluid. We married those together and got into the computer and put in a new model for a liquid flow measurement over the customized range they wanted.”
If time permits and parts are on-hand, the laboratory services the instruments it calibrates; otherwise, they are returned to the customer for repair or replacement.
Annually, the shop calibrates about 400 gas meters, 150 liquid flow meters and 80 air velocity meters.
FRCSW is the parent command to two other calibration labs: one in Okinawa and the other in Iwakuni, Japan.