OQ Measurement – Jennings, LA
Performing pressure integrity tests on the welds applied to fabricated flanges.
Pressure the test tree up to the max operating pressure and hold for 4 hours with no leakage.
Small piping, like the one show in Figure 1.1, are often difficult to pressure up and hold steady due to their small diameter and sensitivity environmental changes. Friction from the pump, direct sunlight, and/or cloud cover can cause a rapid spike or dip in pressure as the line is so easily affected by temperature change.
Using digital chart recorders that are ten times more accurate than most paper chart recorders can be unsettling to an inspector due to the ability to see fine resolution in pressure changes on a rectangular x-y axis chart. In other words, on a mechanical paper chart, you may not see these small changes in pressure based on the chart graduations or the actual ink pen used in the test may not be adjusted correctly therefore causing bleed on the chart.
While we cannot control the pipe’s sensitivity to environmental factors, we can make life a little easier. First, we can adjust the resolution on the gauge for those tests where a hundredth of a PSI is not required. Second, we can set the scaling on the software to plot a graph the represents the big picture, instead of displaying the fine dips or rises in pressure. Our encrypted software allows the customer to collect as many data points as they desire, while also allowing them to graph only their required test data set. For example, a customer may only be required to take and report a reading every 15 minutes. For peace of mind, he decides to take a sample every 30 seconds for 4 hours. This creates a huge amount of data on the graph with very dialed in scaling to any fluctuations between points, raising the potential of concern. Thus, while creating his graph, he can choose to plot only every 10th sample taken (or every 5 minutes). What this does is smooth out the pressure line on the graph based on a standard 8.5 x 11 sheet of paper without omitting any data from the actual test. All pressure readings with date and time stamp are printed with the report should the inspector want verify any point along the graph. The gauge itself also has real time clock so data can’t be manipulated once the test begins.
WHAT DOES THIS ACTUALLY SOLVE?
A headache. Inspectors are RELENTLESS in their scrutiny of pressure fluctuations (as they should be). But there is a lack of education in the field surrounding mechanical vs digital charting. We allow the customers to collect the data required for validating their tests, while also allowing them to better present the report to inspectors to avoid unnecessary concern.