WellMark 6900 Series Guide

The Company, L.L.C. Oklahoma City, Oklahoma Tel: [phone] Fax: [phone]
wellmarkco.com
© The WellMark Company • Litho USA • All registered trademarks are the property of their respective owners. • IOM-6900 090923
Specifications
Connections
Output
General
Process 2” MNPT Std.
3”, 4”, 5”, 6” Flanges, Yale and Hammer Union
Configurations also available
Pilot 1/4” FNPT
Throttle (Proportional) 3-15 psig
Snap-Acting 0 to Full Supply (Pilot rated to psi)
Maximum Working Pressure (CWP) 1500 psi
Pilot Operating Pressure Normal: 20 -30 psi
Overpressure Protection: Gauges are the limiting factor.
75
psi minimum Max.
Temp. Limits -40°F to + 00°F
(Higher temperatures available - Consult factory)
Displacer PVC (165°F max.)
Delrin (200°F max.)
Phenolic Screw-on (275°F max.)
Phenolic Slip-on (400°F max.)
Sight Glass Polycarbonate
Seals Buna-N standard (others available)
2
(Pyrex® available)
Materials
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.
Suitable pressure-relieving devices, as
recommended by appropriate codes or standards,
should be installed in your system to assure that
maximum rated pressures are not exceeded.
1
WARNING!
6900
Series
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.
This liquid level control operates based on two physical laws:
-
Archimedes’Principle
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, followingArchimedes 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).
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.
Principleof Operation
w
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.”
Note: This document is to be used in conjunction
with WellMark Catalog Document, Section No.
3.5, “Series 6900 Cantilever Liquid Level Control”.
Installation, Operation & Maintenance Instructions
for Series 6900 Cantilever Liquid Level Control
H1
Weight
H1
H2
Weight
Bouyant
Force
Fluid level
rises
Figure 1
(Deflection exaggerated for clarification)

The Company, L.L.C. Oklahoma City, Oklahoma Tel: [phone] Fax: [phone]
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

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© The WellMark Company • Litho USA • All registered trademarks are the property of their respective owners. • IOM-6900 090923 3
6900
Series
Adjust the Adjusting Screw/Nozzle upward toward the Nozzle Seat,
by loosening Jam Nut and turning Adjustment Screw clockwise
(when looking at the bottom of the unit) until Output Pressure Gauge
starts to indicate a reading (1-3 psi).
Open the vessel inlet and observe the rising liquid level. Once the
liquid reaches the Displacer fine adjustment of the control can be
made within the diameter range of the Displacer by adjusting the
Adjusting Screw up or down to actuate the diaphragm-operated
motor valve. Once the desired adjustments are complete, tighten the
Jam Nut, being very careful not to inadvertently disturb the Adjusting
Screw setting.
- Turn Adjusting Screw counter-
clockwise (moves Nozzle orifice away from actuator pad).
- Turn Adjusting Screw clockwise
(moves Nozzle orifice toward actuator pad).
Normal pilot installation is (rise in liquid level resulting
from an increase of output). For (rise in liquid level
resulting in a decrease of output), simply loosen 3/4-16 Jam Nut
behind Pilot Head, and rotate Pilot Head 180° and re-tighten Jam Nut
(See Figure 3).
To INCREASE Liquid Level
To DECREASE Liquid Level
direct-acting
indirect-acting
Direct-Acting Indirect-Acting
Figure 3
Maintenance
The Series 6900 Cantilever Liquid Level Control requires very little
maintenance. As with any instrumentation, the most important
factors for long life and consistent operation is that supply pressure
be clean and dry.
From time to time the entire pilot head may come loose on the
Cantilever Rod. Check to assure that this connection is sound and
that the jam nut is properly tightened.
The flow of gas in the supply line will draw any foreign material or
particles as the gas moves to and through the control and valve.
Occasionally, this may result in a particle of sand, weld slag, etc.
becoming lodged in an orifice in theAdjusting Screw or Nozzle.
Shut off supply pressure to the control. Loosen the Jam Nut on the
bottom of the unit and unscrew the Adjusting Screw/Nozzle from the
Pilot Housing. Pull the Adjusting Screw/Nozzle completely free of
Clearing a Clogged Orifice
the Pilot Housing.
Remove O-Rings from Adjusting Screw. Clean Adjusting
Screw/Nozzle with solvent. Inspect for debris in orifices on side and
end of Nozzle, removing as necessary with thin gage wire. Care
should be exercised not to deform the orifice openings.
Inspect O-Rings for wear and replace if necessary. Lubricate O-
Rings with a light coating of general-purpose grease and reinstall on
the Nozzle. Take care that no grease clogs the orifices.
Gently re-insert the Adjusting Screw/Nozzle with O-Rings back into
the Pilot Housing, taking care not to damage the O-Rings in the
process. Readjust the Nozzle as directed on Page 2 under “Start
Up”. Once proper adjustment is made re-tighten the Jam Nut.
Occasionally, the Sensing Rod/Nozzle Seat will become misaligned
in the Sensing Rod Housing and must be re-alinged prior to
installation and use. This is a relatively easy procedure.
Once the unit is removed from service, remove the entire Rod
Assembly from the Pilot Head, detaching the Displacer as well.
Remove the Nozzle Seat by loosening the Hex Nut and pulling the
Nozzle Seat off the Sensing Rod. Peer into the end of the Rod
Assembly and note in which direction the Sensing Rod is off center.
Rotate the Rod Assembly such that the Sensing Rod offset is now in
the uppermost or 12-o’clock position (See Figure 4).
Centering Sensing Rod
Grasp the Rod Assembly by this end and lightly tap the opposite end
(the Displacer end) on a bench or block of wood. The Sensing Rod
will begin to move back into the center of the Sensing Rod Housing.
Continue with light taps until the Sensing Rod is properly centered
(Figure 5).
12 o’clock
Figure 4
Lightly tap Correct
Alignment
Figure 5

HEAD ASSEMBLY
THROTTLING 06500-1307
SNAP ACTING 06500-1315
THROTTLING MIZER¨ 06500-6947
SNAP ACTING MIZER¨ 06500-6955
JAM NUT
05010-2359
HAMMER UNION
3" BLIND FLG. 06500-0663
3" SIGHT GLASS 06500-0671
4" STD. THREAD 05012-6705
4" ACME THREAD 05012-3702
5" STD. THREAD 05012-9439
5" ACME THREAD 05012-9496
WELD NECK O-RING
3" 05000-0405
4" 05000-0561
5" STD. 05000-0579
5" ACME 05000-5537
WELD NECK
3" X 5" LG. 05011-2200
3" X 8" LG. 05010-2961
4" X 5" STD. 05011-5468
4" X 8" STD. 05010-1799
4" X 5" ACME 05013-0216
4" X 8" ACME 05012-3694
5" X 8" STD. 05010-4686
5" X 6" ACME 05012-9470
5" X 8" ACME 05013-0232
SENSING ROD ASSEMBLY
SHORT 06500-0630
MEDIUM 06500-0036
DISPLACER
2" X 10" DELRIN¨ 05011-1582
2" X 12" DELRIN¨ 05011-1590
2" X 10" PHENOLIC 06500-2545
2" X 12" PHENOLIC 06500-2537
2 1/2" X 8" DELRIN¨ 05011-0311
2 1/2" X 7" DELRIN¨ 05011-0584
2 3/4" X 10" PVC 30055
2 1/2" X 8" DELRIN¨ 05011-0352
3 1/4" X 2 3/4" PHENOLIC 05010-2342 (3 Req’d.)
(illustrated)
WASHER
(LONG & OFFSET ROD ONLY)
06000-1054
HEX SCREW
(LONG & OFFSET ROD ONLY)
05000-1767
FLANGE
3" BLIND 05011-0337
3" SIGHT GLASS 05011-0667
4" BLIND 05010-5766
4" SIGHT GLASS 06500-2040
5" SIGHT GLASS 06500-2917
5" ACME SIGHT GLASS 06500-5076
REFLECTOR
(SIGHT GLASS MODELS ONLY)
3" 05011-0741
4"& 5" 10052
TRU-ARC RING
(SIGHT GLASS ONLY)
06000-0692
COLLAR
(LONG ROD ONLY)
10059
SNAP ACTING
HEAD
O-RING
05000-0447
NOZZLE SEAT
05010-1781
HEX NUT
05000-1510
LONG 06500-0085
OFFSET 06500-0002
6900
Series
The Company, L.L.C. Oklahoma City, Oklahoma Tel: [phone] Fax: [phone]
wellmarkco.com
© The WellMark Company • Litho USA • All registered trademarks are the property of their respective owners. • IOM-6900 090923
4
30
0
255
20
10
15
WELLMARK
psi
30
0
255
20
10
15
WELLMARK
psi
9
10 11
5
3
2
1
6
4
8
7
9
10 11
5
3
2
1
6
4
8
7
13 15 16 12
21 19 201817 14
30
0
255
20
10
15
WELLMARK
psi
30
0
255
20
10
15
WELLMARK
psi
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
1
2
2
1
1
2
1
1
1
2
2
1
1
1
1
1
1
1
1
1
4
1
05010-3472
06000-0684
06000-0700
05010-1674
05010-1682
05000-0033
05010-2334
05000-0074
05010-3720
05010-3761
05000-0009
05010-3456
05010-3464
05010-3423
05010-3431
05010-3449
05000-2591
05010-3704
05010-3712
05010-3696
06000-1601
05010-3829
PILOT HOUSING, ALUM. ALLOY 383
STREET-L, MALLEABLE
PRESSURE GAUGE
ADJUSTING SCREW, 303 SS
NOZZLE, 303 SS
O-RING, NITRILE
JAM NUT, 18-8 SS
O-RING, NITRILE
COVER PLATE, POLYCARBONATE
COVER SCREW, NYLON
O-RING, NITRILE
BOOSTER BODY, ALUMINUM
COVER, ALUMINUM
LOWER SEAT, ALUMINUM
UPPER SEAT, ALUMINUM
CONNECTOR, ALUMINUM
SCREW, PLATED STEEL
SPRING, ASTM A-313
DIAPHRAGM, FAIRPRENE
GASKET, FAIRPRENE
FILSTER HEAD SCREW, STEEL
DAMPENER, SS
Parts List for Snap-Acting Pilot Head
Item Qty. Part NumberDescription
1
2
3
4
5
6
7
8
9
10
11
1
2
2
1
1
2
1
1
1
2
2
05010-1617
06000-0676
06000-0700
05010-1674
05010-1682
05000-0033
05010-2334
05000-0074
05010-3720
05010-3761
05000-0009
PILOT HOUSING, ALUM. ALLOY 383
STREET-T, MALLEABLE
PRESSURE GAUGE
ADJUSTING SCREW, 303 SS
NOZZLE, 303 SS
O-RING, NITRILE
JAM NUT, 18-8 SS
O-RING, NITRILE
COVER PLATE, POLYCARBONATE
COVER SCREW, NYLON
O-RING, NITRILE
Parts List for Throttling Pilot Head
Item Qty. Part NumberDescription
FLANGE
2"-150RF 05013-0869
2"-300RF 05012-9454
3"-150RF 05011-5922
3"-300RF 05011-5948
3"-600RF 05011-5955
4"-150RF 05010-6889
4"-300RF 05010-6897
4"-600RF 05010-6905
2” MNPT PLUG
05010-5709