Gasboy Atlas Start-up - Manual (Page 138)

Page 6-18 MDE-4334D Atlas™ Start-up and Service Manual · July 2013
Hydraulic/Mechanical Components Measuring Pressure and Vacuum
3
Measuring Pressure and Vacuum Test Chart
Pressure at shear valve or filter cap with no flow Maximum pressure capability of the STP
Pressure at shear valve with full flow Actual capability of STP and in-ground piping to supply
pressure at maximum flow rate
Pressure at shear valve or filter cap minus pressure at
hose at full flow Pressure drop across dispenser meter and valve at
maximum flow rate
Pressure at shear valve or filter cap minus pressure at
hose at no flow Maximum pressure available to force fuel through
meter and valve
Pressure at hose at full flow Pressure drop across nozzle and hose at full flow
Compare the observed flow rate to the chart and actual inlet pressure for the dispenser model
being checked. If the flow rate is low relative to the pressure, it is likely that a dispenser or
hanging hardware problem exists. If the readings are similar to the specification, it is likely
that the dispenser is working properly and it is a system problem.
Use this table to evaluate the probable cause of dispenser low flow rate.
Reaching Required Flow Rate
Suggested methods for achieving the required flow rate are:
• Correct and replace the faulty components
• Use a larger STP or manifolded STP
• Use larger inlet piping to the pump or dispenser
• Use less restrictive hoses and nozzles
• Reduce the maximum lift of product from the tank
• For a pump, reduce the maximum lift of product from the tank and minimize feed line
lengths
Low Flow Rate Symptom Probable Causes
Observed pressure drop across the meter and valve is
more than a few psi higher than indicated in the charts Flow restriction or defective pump/dispenser component,
assuming that the filter is new
Observed and expected pressure drop across the 
pump/dispenser components is close to specification
Hanging hardware or dispenser pressure supply (STP)
problem upstream or issue with pumping unit/installation
for pumps
Observed pressure at the hose and nozzle during full
flow is too high Undersized or defective hanging hardware
Pressure at the dispenser inlet or pumping unit is too low
at full flow Undersized or defective STP/piping to dispenser or
pumping unit hardware or installation problem