ainter Gates
6-1. Design Analysis
The design of a submergible tainter gate is similar to that
of a spillway tainter gate. Guidance in EM 1110-2-2702
should be followed. Navigation locks are wider and have
lower forebay heads than spillway gates. Because of the
greater lock widths, the gates main horizontal structural
members will be trusses or plate girders.
Secondary
stresses in truss joints should be considered. Because of
lock clearance requirements, trunnion anchorages are
placed in lock wall recesses. Anchor bolts require special
considerations in design.
Eccentricity of hub alignment
during construction introduces some additional stresses
during gate operation.
A typical navigation lock plate
girder, submergible tainter gate is shown in Plates B-45
and B-46.
6-2. Seal and Gate Deicing
Devices for preventing the formation of ice, or to thaw
ice adhering to the gates and seals, will be necessary for
the lock to function during subfreezing weather.
Lock
operation in winter will be facilitated by the use of
deicing (and trash clearing in all seasons) systems
described.
a. Heaters.
Two types of electric heating systems
can be used for gate seals; one is by direct heating the
seal by an electrical resistance element inserted below the
seal face and the other by circulating electrically heated
heat-transfer oil.
(1) Direct electrical heating.
Replaceable heating
elements can be installed in recesses in back of the seal
surfaces to be kept thawed, the recesses being insulated so
as to direct heat toward the surface to be heated. Because
of the length of the sill seal and its inaccessibility, it is
impractical to use this method across the bottom of the
gate.
(2) Heating by circulating fluid. The usual method of
seal heating is done by a design circulating heat-transfer
oil through pipes built into the seal plates next to the
surface to be thawed.
Immersion-type electrical heating
units, thermostatically controlled, heat the oil which is
forced through the pipes by circulating pumps. The heat-
ing stations are located in the hoist machinery spaces at
opposite ends of the gate.
b. Air deicing and trash clearing systems. Air noz-
zles at about 10-ft spacing and 4-ft
3
free air per minute
per nozzle terminate both upstream and downstream of
the gate face.
The air discharging from these nozzles
carries the warmer water to the surface (when water tem-
perature is below 39 deg F) and melts any ice buildup at
the surface.
This air system is most useful in clearing
floating debris from the path of a rising gate at all times
of the year. The air to the upstream nozzle sets is con-
trolled by two sets of reducing valves to prevent one set
from hogging to the lower outlet pressure.
The
upstream and downstream air control valves are separately
operated from the gate control stand to be used at the
discretion of the lock operating personnel.
6-3. Operating Machinery
a. General description.
The machinery used to
operate lock-type tainter gates usually consists of two
equal hoist units of contra-facsimile design arranged to lift
each end of the gate. The hoist units are kept in synchro-
nism by power selsyn motors. Each hoist unit consists of
a rope drum, open gear set, speed reducer, magnetic
brake, hoist motor, and power selsyn.
The drum is
mounted on a cantilevered shaft of a size to prevent
excessive error in the mesh of the final drive pinion and
gear due to shaft deflection. A general arrangement of an
electric-motor-driven hoist for the lock-type tainter gate is
shown in Plate B-60.
b. Design considerations and criteria.
The design
capacity of the hoist should be based on the maximum
load at normal speed which is found to be at the nearly
closed or raised position.
The hoisting speed should be
selected so as to raise the gate from full open to closed in
2 to 3 min, varying so as to allow the selection of a
motor of standard horsepower and speed. General criteria
applicable to the design and selection of various hoist
components are presented in paragraph 1-11.
Shock,
impact, and wear factors are considered negligible and
may be disregarded. Wire rope for these types of hoists
should be stainless steel, lang lay, style G, flattened
strand. Drum diameter should not be less than 30 times
the rope diameter.
c. Determination of machinery loads. The maximum
dynamic load on the hoist normally occurs near the end of
the raising cycle. The maximum holding rope load occurs
when the gate is fully raised and the lock water level is
below the upper sill. No consideration should be given to
rope loads created by the flow of water over a partially
opened gate.
The rope loads from these conditions are
6-1 EM 1110-2-2703
30 Jun 94
indeterminate and control features are provided to prevent
their occurrence. The total load on the rope drum is the
sum of the following:
(1) Deadweight of the gate as applied to a moment
arm (W × CG) divided by the perpendicular distance of
the rope to the gate trunnion center line.
(2) Side seal friction (total seal force × 0.05).
(3) Weight of the ropes can be neglected.
(4) Trunnion
friction
less
than
200 lb
can
be
neglected.
(5) The static load of the water head on the unbal-
anced area on the bottom seal when the lock level is
down.
(6) Ice buildup and silt formation should be consid-
ered when severe freezing or silt-loaded water are factors.
The air deicing and seal heating systems usually minimize
these factors.
d. Operating machinery control.
(1) General. The electrical equipment for the opera-
tion of a power selsyn drive for the hoists for a tainter
gate consists of two squirrel-cage induction-type motors,
two wound rotor induction motors (synchronizing drive),
two electrically operated brakes, two limit switches, and a
control system that will provide operating features appli-
cable to the particular installation. Equipment meeting the
requirements of Guide Specification CW-14615 is consid-
ered to be the best suited for the service.
(2) Motors.
The squirrel-cage induction motors
should have high-torque high-slip (between 8 and 10 per-
cent) speed torque characteristics with drip-proof frames
as this equipment is usually located indoors.
The drive
motor should be continuous rated and sized to drive the
gate machinery without overload during any portion of the
operating cycle.
No arbitrary limit should be placed on
motor speed other than that which is practical and eco-
nomical. The wound rotor motor for synchronizing shall
be of the same horsepower rating as the drive motor, as it
may be necessary, under some circumstances to provide
the full torque of a drive motor. For the protection of the
motor windings, means shall be taken to provide winding
heaters or encapsulation.
Motors should be specified in
accordance with the applicable provisions of Guide Speci-
fication CW-14615.
(3) Brakes.
The brakes should be of the shoe or
split-band type, spring-set with direct current magnet-
operated release, suitable for floor mounting and should
be provided with NEMA 12 moisture-resisting, enclosing
case. The brake mechanism should be of corrosion-resis-
tant construction using nonferrous parts for bearings, pins,
etc. The necessary direct current for operating the brake
should be obtained from a rectifier mounted within the
controller enclosing case. The torque rating of the brake
should be of a value corresponding to approximately
150 percent of full load motor torque when referred to the
shaft on which the brake wheel is mounted.
A space
heater should be provided within the brake enclosure as
required in Guide Specification CW-14615.
(4) Control.
The control equipment consists of a
combination of magnetic controllers, limit switches, con-
trol stations, and remote gate position indication as shown
in Plate B-74. The main control station (remote from the
equipment) is located at the upstream control stand along
with the other controls for the navigation lock.
A local
control station along with a local-remote transfer switch is
located in one of the machinery rooms, and is provided
for operation of the equipment during maintenance. The
control equipment may be located where convenient but
usually in one central location in a control center.
The
rotors of the two wound rotor motors are connected so
that when the stators are energized from a common tie
through a controller the rotors will rotate in a common
direction, either raise or lower.
When final adjustments
are being made and the gate leveled, the rotors are syn-
chronized with the couplings disconnected.
The stators
are energized first single-phase and then three-phase to
pull the rotors into synchronism. Then the couplings are
connected while the gate is in level condition supported
on the ropes.
During normal operation the drive motor,
wound rotor motors, and brakes are all energized simulta-
neously and run until stopped by a limit switch in either
the open or closed position or by the movement of a
control switch to the stop position.
During the stopping
sequence,
both
the
drive
motors
and
brakes
are
de-energized but the wound rotor motors remain energized
for a short time (5 sec) while the brakes are setting. This
prevents skewing of the gate should the brakes set
unevenly because of wear or misadjustment.
A synchro
system is used to show gate position at the control stand.
A system of interlocks is used in the control circuit to
prevent opening the gate at a time which might cause
damage to the equipment or create hazardous conditions.
Among these is a differential level circuit which will
allow opening the gate only when the water surfaces on
6-2