Effective: May, 2009 (Replaces July, 2004)
Supplement 9160
KING-GAGE ® Marine Systems
Tank Level and Draft Indicating Systems for the Marine and Offshore Industries
Tank Level Indicator
Model 7750
■ Easily Monitor Tank Level or Ship Draft
■ Simple All Pneumatic Operation
■ Rugged Marine Grade Construction
KING-GAGE Model 7750 Tank Level Indicator is a
precision well type manometer gauge. It is designed for
use with a downpipe level sensor to measure hydrostatic
pressure due to liquid depth. This simple yet effective
system indicates level in service tanks (fuel oil, ballast) or
liquid cargo tanks. These systems are also used for ship’s
draft readings.
The KING-GAGE 7750 Indicator is an extremely durable
unit well suited to the rigors of marine service. Acting
as a frictionless force balance, its operating principle
is inherently accurate and dependable. All pneumatic
operation makes it compatible for use in explosion
hazard zones. This gauge design is used in thousands of
vessels, both freshwater marine and ocean going fleets.
User reads a graphic column display against a custom
marked scale in one or two units of measurement
(feet/inches, tons, barrels, etc.). The length of the
indicator display can be selected based on range and
desired resolution (minimum readable change in depth
or capacity). Case construction is carbon steel with
durable black polyurethane textured finish. It may be
mounted remotely from the tank on a bulkhead or
grouped with other indicators on a panel assembly.
Model 7750
Principles of Operation The resulting downstream pressure (within the pipe) is
directly proportional to liquid depth. As depth increases,
The KING-GAGE system uses hydrostatic pressure the corresponding pressure increases as well. Conversely,
measurement to determine liquid level. This pressure is as depth decreases, downstream pressure is equally
created by the actual depth of liquid above the measure- reduced as excess air flows out the immersed end of the
ment point. Individual indicator scales are calibrated to pipe. Tubing conveys this pressure to the indicator as the
the pressure range (depth), density (specific gravity) of basis for the tank level reading.
the liquid and the volumetric capacity of the tank or
compartment. For draft measurement, the only factors
Indicator Scales
needed are pressure and density.
Each system scale is individually calibrated and custom
The KING-GAGE Model 7750 works as a frictionless marked in any specified unit of measurement (depth,
hydrostatic force balance. Within the glass display tube, total weight or volume). An optional 2nd scale unit can
a liquid fill rises in direct proportion to the magnitude of be included to combine different measurements such
pressure applied. The indicating liquid used determines as depth and volume. Scales are manufactured for the
the actual pressure range of this instrument (refer to individual tank geometry and specific gravity of tank
Determining Scale Range). contents. Due to the factory calibrated scale, the KING-
GAGE Tank Level Indicator can be used for almost any
Bubbler (Downpipe) System - uses compressed air to kind and shape of tank.
purge an open ended pipe extending down into the
tank. A KING-GAGE Purge Control regulates a continu-
ous flow of air into the downpipe. Pressure is created as Determining Scale Range
liquid is purged from the downpipe, increasing until it
reaches an equilibrium point (air pressure = hydrostatic Overall length of the scale can vary depending upon
pressure). Excess air escapes through the bottom of the the range and degree of readability necessary for the
downpipe (and bubbles up through the tank contents) application. This “readability” refers to the minimum
to maintain equilibrium. readable change in liquid depth that can be observed at
the indicator.
Three factors determine scale length:
Pressure Signal • Maximum tank depth
• Specific gravity (density) of tank contents
Purge • Type of indicating liquid (scale factor)
Control
®
KING-GAGE
LIQUID LEVEL INDICATING SYSTEM
®
A simple calculation using these factors will yield the
Tank Top minimum scale length required:
Fitting
1700
and
1600
D (depth) x G (sp.gr.) x L (liquid
110
GALLONS
GALLONS
Compressed
1500
Downpipe
1400
100
1300
1200
90
Air scale factor) = Scale Length
1100
The resulting value represents the scale length in inches.
1000
80
900
Refer to the scale sizes available for the indicator and
800
70
EACH MARK = 10 GALLONS
700
EACH MARK = 1 GALLON
select one that will accommodate the calculated length.
600
60
500
50
400
40
300
Liquid Color Specific Liquid Scale
200
20
100
K-123-1
K-123-1
Gravity Factor
4
Mercury ...........Silver............13.546........... 0.074
No. 294 . ............Red..............2.940............ 0.337
Typical Downpipe Purge System
No. 175 . .......... Purple............1.750............ 0.566
Page 2
Tank Level and Draft Applications
The KING-GAGE indicators can be mounted directly to
a panel, bulkhead or other rigid structural member. De-
pending upon the application, install these indicators in
the engine room, control center or ship’s bridge.
Applications Include:
• Ship’s draft measurement
• Ballast water tanks
• Fuel oil tanks
• Day tanks
• Bunker oil tanks
• Drill water tanks Optional Gauge Panel Assemblies
• Liquid cargo tanks
Multiple tank gauges can be special ordered mounted
on a rigid steel panel to simplify installation.
Typical Ballast Tank Draft Indicating
Indicating System System
Purge Control supplies Length of pipe
air to downpipe. Pneumatic penetrates hull a
Pneumatic pressure Signal point below minimum
signal is transmitted water line. Purge
through small bore control provides a
tubing to the KING- continuous air flow to
GAGE indicator. This the draft pipe. Tubing
pressure is directly Indicator (1/4-in. OD) conveys
proportional to the pressure resulting
depth. The indicator from depth back
Pneumatic
displays the pressure to the gauge that
Signal
reading against a scale displays draft reading.
corresponding to
actual tank level. Wing Tank
Downpipe
Day Tank
Double
Bottom Tank
Model 7750 Tank Level Indicating Systems
Page 3
KING-GAGE ® Marine Systems
KING-GAGE Marine Signal
Indicator Check Valve Connection
1/4 in.
(included)
Single tank display surface mounts to
bulkhead or other structural surface. Optional
multiple gage panel assembly available on
special order.
Operating Principle
Well-type manometer acts as a frictionless
hydrostatic force-balance. A liquid fill is KING-GAGE
®
raised in direct proportion to the ® LIQUID LEVEL INDICATING SYSTEM
magnitude of pressure applied. (Varies
based on type of indicating liquid
employed.)
Resolution 1700
Infinite based on type of indicating liquid
1600
employed. 110
TONS
TONS
GALLONS
GALLONS
1500
Input Connection(s) LONG
LONG
1/4" NPT tapped connection for typical 1400
tube fittings. 100
1300
Materials of Construction
Formed channel indicator housing; 1200
90
carbon steel with durable black
polyurethane textured finish. Heavy plate 1100
glass window; acrylic plastic window 1000
available as special order. 80
900
Wetted Parts
316 stainless steel liquid well and tubing. 800
70
Indicating Tube 700
High strength, fully annealed glass
(Pyrex ®) 600
60
500
50
Range Overall
400
Dimensions (inches)
40
300
Range Overall Dim. (H x W x D)
LONG TONS
LONG TONS
EACH MARK = 10 GALLONS
200
20 .......... 29" x 4-3/8" x 2-7/8"
EACH MARK = 1 GALLONS
20
35 .......... 45" x 4-3/8" x 2-7/8" 100
43 .......... 53" x 4-3/8" x 2-7/8"
4
51 .......... 61" x 4-3/8" x 2-7/8"
66 .......... 77" x 4-3/8" x 2-7/8"
Front View Right Side View
®
KING
E N G I N E E R I N G ® KING-GAGE and the KE emblem are registered
Since 1937 C O R P O R A T I O N trademarks of King Engineering Corporation,
3201 South State, Ann Arbor, Michigan 48108 U.S.A. Ann Arbor, Michigan U.S.A.
PO Box 1228, Ann Arbor, Michigan 48106-1228
Phone: 734-662-5691 • FAX: 734-662-6652 All specifications are subject to change without notice.
www.king-gage.com © 2009 King Engineering Corporation, all rights reserved.
