Figures 19 shows the result of equation (5) (case x = Removed Suspension Shields, case y = Removed Tunnel Shield) evaluated at each pressure tap
location (shown in Figure 20) over the base of the vehicle.
Estimated errors are in measured pressure associated with the different pressure tap
Placing an outdoor pressure tap
on the roof, however, helps confirm that the entire building is either pressurized or depressurized so that the air flow is either all into or out of the building for each test period, and that stack effect is not introducing unmeasured airflows due a change in interior pressures.
When the impeller was pumping upward the fluid velocities near the pressure tap
increased thus reducing the pressure readings as the impeller speed was increased.
The cost of Strip Tube is $10/m, so it is much cheaper than the conventional pressure tap
These meters have no downstream and shorter upstream straight pipe requirements for standard accuracy, have lower head-loss, and are less susceptible to blockages and plugging as the annular chamber was replaced with a single pressure tap
Figure 2 shows a single chamber orifice meter with a downstream pressure tap
and an extra DP transmitter.
As mentioned, the conventional pressure tap
approach provides good information.
Were both the downstream and upstream pressure tap
distances varied to determine the effect or were they maintained at the SPC 120 recommended length of 11 diameters?
The problems of centering the plate, alignment of the inlet and outlet piping, and pressure tap
to plate dimensions have also been solved using standard fittings and patented plate holder designs.
Note that the side pressure measurements were routed to the top of the pressure tap
sleeve, as described in Figure 5.
The flow measurement also showed a 20% under-prediction of flow, indicating possible sensitivity to the pressure tap