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Operation
Since the ME990S-2F-16 and ME990S-2DFM Series Internal
Valves are most often used on bobtail trucks, the following
procedure applies to that type of application. Follow
these steps:
1.
ME990S series internal valves on bobtails and
transports should never be open when the truck is in
motion. If the control system is not interlocked to
prevent this, the operator is responsible to ensure
that the valves are closed.
2.
Always open the internal valve before opening any
other valves in the line or starting the pump.
3.
Move the lever to the half-open (rapid equalizing)
position (Figure 3, View 2) to equalize pressure. When
the main poppet clicks open, move the operating
lever fully open.
4.
Open other line valves slowly to avoid sudden surges
which could slug the excess flow valve shut.
5.
If the excess flow valve does close, stop the pump and
close the nearest downstream valve. Move the
internal valve's operating lever back to the rapid
equalizing position (outlined in step 3) and wait for
the valve to click open. Then move the operating
lever fully open and slowly open the downstream
valve.
6.
All valves should be completely open when pumping.
(Throttling type valves could prevent the excess flow
valve from closing when required.
7.
The operator must always be aware of where the
remote closure controls are located and know how to
operate the controls if an emergency requires valve
closure. When pumping is finished, make a habit of
closing the internal valve from the remote closure
point, thus checking to see that the control actually is
capable of closing the valve and operating correctly.
8.
The valve should be open when backfilling through
the valve to fill the tank.
Form #995 ME990S-2F-16 & ME990S-2DFM IOM
ME990S-2F-16 and ME990S-2DFM
Troubleshooting
Internal Valve Will Not Open: This could be due to leakage
downstream, engaging the pump too soon or from
excessive wear in the internal valve. If excessive volume is
In the downstream system, a longer time is required to
equalize the pressures (tank and downstream) before the
pump can be engaged. To determine if the valve pilot seat
is opening, install a gauge downstream of the valve,
operate the valve actuator; if pressure does not build up to
the tank pressure, the valve pilot seat is not open. This test
should be done with the pump off. If the pilot is not
opening, it may be plugged with dirt or some internal part
may be broken. If by operating the lever manually it can be
rotated past the fully open position, there is something
wrong internally and the valve must be disassembled.
Premature Valve Closure: This can be caused from
engaging the pump too soon, by an underrated excess
flow valve spring, or by an improperly connected internal
valve operating lever which does not fully open the valve.
The trouble could also be from a valve that has its inlet
port obstructed or from sudden line surges. In order to
check the valve opening travel, operate the lever manually
to the full travel, wait until valve opens (usually about 15
seconds), then engage the pump. If the excess flow closes,
the points mentioned above should be investigated.
Internal Valve Will Not Close: The stub shaft could be
binding or the stem could be bent in the valve. Before
disassembling the valve, check the actuator mechanism to
see that it operates freely by disconnecting it from the
valve lever and cycling it several times. Also, operate the
valve lever manually. If it sticks in the open position, the
packing and bushings should be replaced. This should free
the operating mechanism if the valve has not been
damaged internally. Refer to the "Maintenance" section.
Rev E 2/3/21
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