WellMark 6900 Series Installation, Operation & Maintenance Instructions

Note: This document is to be used in conjunction
with WellMark Catalog Document, Section No.
3.5, "Series 6900 Cantilever Liquid Level Control".
WARNING!
Over-pressure of this control or installation of the
control in applications which may see pressure
levels beyond those for which the control is
designed may result in leakage and/or catastrophic
failure. This failure could result in leaking gas, or
produced liquid, damage to surrounding equipment
and/or environment, personal injury or death.
S u i t a b l e p r e s s u r e - r e l i e v i n g d e v i c e s , a s
recommended by appropriate codes or standards,
should be installed in your system to assure that
maximum rated pressures are not exceeded.

Specifications

Connections
Process
3", 4", 5", 6" Flanges, Yale and Hammer Union
Pilot
Output
Throttle (Proportional)
Snap-Acting
General
Maximum Working Pressure (CWP)
Pilot Operating Pressure Normal: 20
Overpressure Protection: Gauges are the limiting factor.
Temp. Limits
(Higher temperatures available - Consult factory)
Materials
Displacer
Sight Glass
Seals
The Company, L.L.C.
© The WellMark Company • Litho USA • All registered trademarks are the property of their respective owners. • IOM-6900 090923
Installation, Operation & Maintenance Instructions
for Series 6900 Cantilever Liquid Level Control
2" MNPT Std.
Configurations also available
1/4" FNPT
3-15 psig
0 to Full Supply (Pilot rated to 75
1500 psi
psi minimum -30 psi
-40°F to + 00°F 2
PVC (165°F max.)
Delrin (200°F max.)
Phenolic Screw-on (275°F max.)
Phenolic Slip-on (400°F max.)
Polycarbonate (Pyrex® available)
Buna-N standard (others available)
Oklahoma City, Oklahoma

Application

The Series 6900 Cantilever Level Control is designed for use in liquid
level and interface liquid control applications. They are commonly
used in oil and gas processing, manufacturing plants, hazardous
waste disposal, food processing, water treatment, petrochemical
facilities or wherever fluid levels need to be controlled. The unit is
available in either Snap-Acting or Throttling configuration, controlling
pneumatic pressure for various control devices. The standard
displacer is 2" x 10" Delrin and is mounted in a horizontal
configuration. Displacers of other materials and dimensions, as well
as Vertical Displacers are optionally available.

Principle of Operation

This liquid level control operates based on two physical laws:
w
"A solid, heavier than a fluid [such as a displacer] will descend to
the bottom of the fluid, and the solid will, when weighed in the fluid,
be lighter than its true weight by the weight of the fluid displaced."
Archimedes' Principle
w
A Cantilever beam (sensing rod) projecting outward, anchored at
one end, will flex in proportion ot the weight applied, or removed, at
the free end.
Therefore, following Archimedes Principle, a body (displacer or float)
immersed in a fluid experiences a bouyant, or lift force equal to the
weight of the displaced fluid. This static lift force acts vertically
through the center of gravity of the displaced volume (Figure 1).
psi)
Weight
Max.
(Deflection exaggerated for clarification)
Applying the above fundamentals to this liquid level control, we can
sense and regulate levels of most gas-to-fluid interface applications
as well as many fluid- to-fluid interfaces.
Tel: (405) 672-6660
Series
Weight
H
1
Fluid level
rises
Bouyant
Force
Figure 1
Fax: (405) 672-6661 wellmarkco.com
6900
-
H
1
H
2
1