The Company, L.L.C. Oklahoma City, Oklahoma Tel: (405) 672-6660 Fax: (405) 672-6661
wellmarkco.com
© The WellMark Company • Litho USA • All registered trademarks are the property of their respective owners. • IOM-6900 090923
2
6900
Series
By attaching a Displacer to the free end of the Sensing Rod, vertical
movement is achieved. The rising and lowering of the fluid gives the
static lift force - either up or down - which is transferred along the rod
to an Actuator Pad (seat) extending out past the anchored end (See
Figure 2). As the Actuator Pad moves to the Nozzle, supply pressure
is diverted to output, opening a diaphragm-operated motor valve. As
fluid is drained away through the motor valve and fluid level declines,
the Actuator Pad moves up and away from the Nozzle and supply
pressure is exhausted from the valve, thereby allowing it to close.
This cycle then repeats as necessary.
Supply
Supply
To Valve
To Valve
WEIGHT
BOUYANT FORCE
Figure 2
Modes:
In , this control will continually throttle the valve to
maintain the fluid level at a desired set point.
In , a Shuttle Pilot is attached to the throttling
head, converting the throttling output pressure to pilot signal
pressure, tripping the shuttle pilot to either full supply pressure,
opening the valve quickly, or to zero supply pressure, allowing the
valve to close.
throttling mode
snap-acting mode
Installation
Prior to installation of the 6900 Cantilever Level
Control system must be isolated from pressure.
Failure to do so may result in personal injury,
environmental spill concerns and/or damage to
equipment.
WARNING!
If supply gas is flammable or noxious, this product
must be located in a well ventilated, non-hazardous
area or sealed and vented to a non-hazardous area.
Insure that threaded connections on both the Series 6900 Cantilever
Level Control and the vessel are clean, free of debris and
undamaged prior to installing. Visually inspect the unit, observing
that the Nozzle Seat and rod-end are centered in the Sensing Rod
connector. If not, the unit has been distorted and should be returned
to center before placing the control in service (See “Centering
Sensing Rod” in the following section).Maintenance
Install the control into appropriately-sized mating female threaded
connections or flanges. For threaded connections utilize a suitable
thread sealant to assure leak-tight makeup and to avoid thread
galling. For flanged connections, utilize proper gaskets or seal rings
as required for the specific flange configuration. After installation in
the vessel, check for mechanical clearance of Displacer, assuring
free movement by flicking the actuator pad and observing that
Displacer travel is unobstructed.
Connect instrument supply line to supply port marked “ ” on side of
the unit. Connect control valve signal line to “ ” port on the
opposite side. Use a suitable thread sealant to assure leak-tight
make up and to avoid thread galling. Do not over-tighten.
Remove the clear Cover Plate and visually check to determine that
the Sensing Rod/Nozzle Seat is properly centered in the Cantilever
Tube. If not, the Cantilever Rod assembly has become misaligned
and must be adjusted before placing the control in service (See
“Centering Sensing Rod” in the following section).
Assure that the vessel liquid levels are below the Displacer, and that
proper system shut-off valves are open or closed as required.
Energize the control by opening the supply gas to the pilot head (20-
30 psi recommended). Supply gas should flow freely from the Nozzle
orifice.
Square the Nozzle Seat and Nozzle orifice. Manually hold the
Nozzle Seat against the Nozzle. Observe the Outlet Pressure
Gauge (left-hand gauge). The outlet pressure should equal the inlet
pressure within 1 psi. If not, inspect the supply system piping for
leaks or malfunctions. Release the Nozzle Seat, again allowing free
flow of supply pressure from the orifice. Outlet Pressure Gauge
should again read zero. Reinstall the clear Cover Plate.
IN
OUT
NOTE: 20-30 psi is recommended for proper operation. Supply
gas should be clean (filtered) and dry to assure longer
maintenance-free operation.
Maintenance
Start-Up
Nozzle
Seat
Nozzle
Seat
