MDE-4334C Atlas Start-up and Service Manual · April 2008
Page 7-17
Measuring Pressure and Vacuum
Hydraulic/Mechanical Components
6
Refer to the following table for a representation of model STP performance. STPs with more
or fewer stages vary from the information in the following table.
Note: More stages usually means higher pressure capability. Variable speed STPs can be set
to different pressures. Do not rely on this chart for the exact values
Operating Pressure
STP Horsepower
Gasoline
Diesel
1/3 HP
26 psi
76 kg-cm
2
30 psi
88 kg-cm
2
3/4 HP
30 psi
88 kg-cm
2
34 psi
99 kg-cm
2
1-1/2 HP
30 psi
91 kg-cm
2
35 psi
102 kg-cm
2
2 HP
41 psi
120 kg-cm
2
46 psi
134 kg-cm
2
3 HP
31 psi
91 kg-cm
2
35 psi
102 kg-cm
2
5 HP
38 psi
111 kg-cm
2
43 psi
126 kg-cm
2
.
For Self-contained Pumps
Refer to
(locations B and C).
To measure STP pressure for pumps, proceed as follows:
• Install the pressure gauge to the discharge side at a test port on the special filter cap
(location B).
• Install the pressure gauge downstream at the nozzle or other locations, as required
(location C).
Measuring Pressure Drop for Pumps and Dispensers
Use the Pressure Drop test to check the specific groups of parts (meters, shear valves, filters,
and others). An exceptionally high pressure drop for a specific flow rate indicates that a part is
clogged or defective.
To measure the pressure drop for pumps and dispensers, proceed as follows:
1
Shut off power to the unit. Multiple disconnects may be required.
2
Ensure that the pump/dispenser handle is in the Off position. For pumps, shut off power to the
motor and pump using Lock-out/Tag-out procedures. While measuring a dispenser, close and
test the shear valve. Place the nozzle in an approved container. Lift the pump handle and
squeeze the nozzle slowly to bleed of the pressure.
3
Wear eye protection and then install pressure gauges. See
on
for
locations.
• For pumps, install pressure gauges at the pumping unit discharge test port (location A) and
the discharge special T-fitting (location C).
• For dispensers, install the pressure gauge at the shear valve test port (location A) or filter
cap port (location B) and at the discharge special T-fitting (location C).
4
Restore power to the unit. Open the shear valve on dispensers. Lift the pump handle to the On
position. Activate the nozzle and pump fuel at full flow into an approved container.
5
Measure the flow rate and read and record the psi reading on both gauges. Return the pump
handle to the Off position.