Revision Date: 08 November 2024
Author: M. Daniels
Pressure Calibration and leaks are not a good combination. To get the best measurement results the leak(s) must be eliminated or minimized to a rate at which they are insignificant to the accuracy of the measurement. Every place where a pressure fitting is made or a seal exists are potential leak locations. The usual suspects are the fittings between the calibrator and the Device Under Test because these are the ones which get changed out / removed / retaped / torqued -- makes them suspectible to leakage. Check these locations first.
If leaks are not found there then it's possible the leak could be coming from inside of the calibrator. In this situation then first remove the Device Under Test and disconnect any tubing connected to the calibrator's TEST port. Then plug the port. Inside of a calibrator such as a 6270A there are seals, pressure fittings, and valves. All of these are potential leak locations. A contaminated control valve seat is a common source for a leak. Most leaks are able to be fixed in the field and do not require the calibrator to come back to the factory. The challenge is to narrow down where the leak is coming from. This article provides guidance on how to do this.
Step1: determine if the leak is coming out from the VENT, REF, or EXHAUST port.
- Plug the test port.
- Find fittings which have a small inside diameter and insert into the three ports. (the idea of a small ID is that it will concentrate gas flow and make it easier to see with liquid soap leak detector.)
- Pressurize the 6270A, "Snoop" for leaks at all of the fittings. If there is an internal valve leak then it will show at one of those fittings.
By knowing which fitting the leak is flowing it helps our Technical Support team narrow down the possible sources.
If no leaks are identified on the external ports, then it means the leak is internal to the chassis. Typically this is the face seal where the PCM meets the manifold block. It could potentially also be where the PMMs face seal on the manifold block. Remove each PMM and inspect he face seal orings to make sure they are still there and that they are not damaged. Repeat this check for the Pressure Control Module.
If unable to locate the leak then call the Fluke Calibration technical support team at +1.877.355.4804 and follow the menu options to reach our pressure team.