Structures Design Guidelines | Jan 2008
8 - Movable Bridges |

## 8.7 Electrical [LRFD-MHBD 8]

### 8.7.1 Electrical Service [LRFD-MHBD 8.3]

A. Wherever possible, design bridge electrical service for 277/480 V, three-phase, "wye."

B. Size feeders to limit voltage drop to not more than 5% from point of service to farthest load.

C. Do not apply a diversity factor when calculating loads.

### 8.7.2 Alternating Current Motors [LRFD-MHBD 8.5] (01/06)

Size and select motors per AASHTO requirements. On hydraulic systems provide 25% spare motor capacity. Specify motors that comply with the following requirements:

A. Design Criteria for Start-Ups: 12 per hour, 2 per ten-minute period.

B. Power Output, Locked Rotor Torque, Breakdown or Pullout Torque: NEMA Design B Characteristics.

C. Testing Procedure: ANSI/IEEE 112, Test Method B. Load test motors to determine freedom from electrical or mechanical defects and compliance with performance data.

D. Motor Frames: NEMA Standard T-frames of steel or cast iron (no aluminum frames allowed) with end brackets of cast iron with steel inserts. Motors 10 Hp and larger must be TEFC.

E. Thermistor System (Motor Sizes 25 Hp and Larger): Three PTC thermistors embedded in motor windings and epoxy encapsulated solid-state control relay for wiring into motor starter.

F. Bearings: Grease-lubricated, anti-friction ball bearings with housings equipped with plugged provision for relubrication, rated for minimum AFBMA 9, L-10 life of 20,000 hours. Calculate bearing load with NEMA minimum V-belt pulley with belt centerline at end of NEMA standard shaft extension. Stamp bearing sizes on nameplate.

G. Nominal Efficiency: Meet or exceed values in ANSI Schedules at full load and rated voltage when tested in accordance with ANSI/IEEE 112.

H. Nominal Power Factor: Meet or exceed values in ANSI Schedules at full load and rated voltage when tested in accordance with ANSI/IEEE 112.

I. Insulation System: NEMA Class F or better.

J. Service Factor: 1.0.

### 8.7.3 Engine Generators [LRFD-MHBD 8.3.9] (07/06) July 2006 - Rev to require 24 hour fuel supply at 100% load . Jan 2005 - Revised to provide direction for rehab and new construction and provide for 2 generators on new construction.

A. Design per the requirements of the latest edition of NFPA 110. Specify only diesel-fueled generators. Specify day tank with a minimum 10-gallon capacity. Do not use the day tank capacity as part of the main tank capacity. Submit calculations justifying recommended fuel tank size.

B. New Bridges:

1. Provide two generators: Main Generator to power leaf drives and House Generator to power “house” loads.

Commentary: Bridges are requiring bigger generators to operate because of the increase in main drive power requirements. It is not cost effective to run these generators continuously to power miscellaneous loads and generator manufacturers do not recommend running diesel generators at low loads for extended periods.

2. Size Main Generator so that one side of the channel (one side of the bridge) can be opened at a time. Main Generator to run during openings only.

3. Size House Generator to power house loads like traffic lights, navigation lights, tender house air conditioner, and house lights. House Generator to run continuously during power outage and is to be inhibited from transferring to the 480 volt bus when the Main Generator is running.

4. Provide fuel tank sized to hold enough fuel to run the Main Generator, at 100% load, for 12 hours and the House Generator, at 75% load, for 72 hours (minimum 50 gallons).

C. Rehabilitations:

1. Size generator so that one side of the channel (one side of the bridge) can be opened at a time concurrent with traffic lights, navigation lights, tender house air conditioners, and house lights.

2. Provide fuel tank sized to hold enough fuel to run the generator, at 100% load, for 24 hours (minimum 50 gallons)

### 8.7.4 Automatic Transfer Switch [LRFD-MHBD 8.3.8]

A. Design switch in conformance with the requirements of the latest edition of NFPA 110.

B. Specify Automatic Transfer Switch with engine generator. Specify an Automatic Transfer Switch that is fully rated to protect all types of loads, inductive and resistive, from loss of continuity of power, without de-rating, either open or enclosed.

C. Specify withstand, closing, and interrupting ratings sufficient for voltage of the system and the available short circuit at the point of application on the drawings. Provide short circuit calculations to justify ATS proposed.

### 8.7.5 Electrical Control [LRFD-MHBD 8.4] (07/06) July 2006 - Added B discouraging touch screen controls.

A. Design an integrated control system. Develop a control interface that matches the operating needs and skill levels of the bridge tenders and maintenance personnel that will be using the system. Design a system configuration, select control devices, and program the Programmable Logic Controller (PLC) to produce the desired interface that will comply with the Operation Sequence furnished by the SDO.

B. The use of touch-screen controls is discouraged. If touch-screen controls are specified provide full backup controls on control console.

C. Design the bridge control system to be powered through an uninterruptible power supply.

D. EMERGENCY-STOP (E-STOP) stops all machinery in the quickest possible time but in no less than 3 seconds main drives only. In an emergency, hit this button to stop machinery and prevent damage or injury. Specify a button that is reset by twisting clockwise (or counterclockwise) to release to normal up position.

E. At a minimum, provide alarms for the following events:

1.) All bridge control failures.

2.) All generator/Automatic Transfer Switch failures.

3.) All traffic signal failures.

4.) All navigation light failures.

5.) All traffic gate failures.

6.) All span-lock failures.

7.) All brake failures (if applicable).

8.) All leaf limit switch failures.

9.) All drive failures; including motor high temperature (motors larger than 25 Hp) and all hydraulic system failures.

10.) Near and far-leaf total openings (not an alarm but part of the monitoring function).

11.) All uses of bypass functions, type and time (not an alarm but part of the monitoring function).

F. See Volume 7-Design Aids for pdf's showing movable bridge alarms, controls sequence flowcharts and limit switches.

### 8.7.6 Motor Controls [LRFD-MHBD 8.6] (07/06) July 2006 - Added B seal-in functions at starters.

A. Specify full-size NEMA rated starters. Do not use IEC starters unless space constraints require their use, and then, only by obtaining prior approval from the SDO.

B. Provide seal-in functions at starters only using auxiliary starter contacts, do not use separate relays or PLC outputs.

C. Do not include panelboards and transformers in the Motor Control Center (MCC) unless space constraints require it, and then, only by obtaining prior approval from the SDO.

### 8.7.7 Programmable Logic Controllers [LRFD-MHBD 8.4.2.3]

Refer to the Technical Special Provisions issued by the SDO.

### 8.7.8 Limit and Seating Switches [LRFD-MHBD 8.4.4] (01/06) Jan 2006 - Per AFR Deleted limit switch labels. Required end of travel limit switches to be wired directly to MCC.

A. Design each movable leaf with FULL-CLOSED, NEAR-CLOSED, NEAR-OPEN, FULL-OPEN, and FULL-SEATED limit switches. Specify NEMA 4, corrosion resistant metallic housings which have a high degree of electrical noise immunity and a wide operating range. Specify that NEAR-OPEN and NEAR-CLOSED limit switches be mounted, initially, approximately eight degrees from FULL-OPEN and FULL-CLOSED, respectively. Final adjustment of NEAR-OPEN and NEAR-CLOSED will depend upon bridge configuration, drive machinery, and bridge operation.

Commentary: The FULL-CLOSED switch controls the drive stop and the FULL-SEATED switch is the safety interlock to allow driving the locks.

B. Do not connect limit switches in series between different drives. Connect each limit switch to a relay coil (use interpose relays to connect to a PLC input.) Provide position encoder (potentiometer or other type) to drive leaf position indicators on control console. The position encoder will also provide a signal to the PLC to use as a reference to determine leaf limit switch failure. Connect limit switches in the following configurations:

Traffic Gates: End-Of-Travel configuration.

Span Locks: End-Of-Travel configuration.

Leaf(s): End-Of-Travel configuration.

Safety Interlocks: Indicating configuration.

Commentary:

“End-Of-Travel” is a NOHC (Normally Open Held Closed) limit switch that opens to stop motion and “Indicating” is a NO (Normally Open) limit switch that closes to indicate position has been reached.

C. Do not use electronic limit switches. Plunger type switches are optional.

D. Connect End-Of-Travel limit switches directly to the HAND-OFF-AUTO switches on the MCC so that manual operation of equipment from the MCC is possible independent of the condition of the control system.

### 8.7.9 Safety Interlocking [LRFD-MHBD 8.4.1] (01/06) Jan 2006 per AFR Added paragraph E.

A. Traffic Lights: Traffic gates LOWER is not enabled until traffic lights RED. Provide bypass capability labeled TRAFFIC LIGHT BYPASS to allow traffic gates LOWER without traffic lights RED.

B. Traffic Gates:

1.) Bridge Opening: Span locks PULL is not enabled until all traffic gates are fully down (or TRAFFIC GATE BYPASS has been engaged).

2.) Bridge Closing: Traffic lights GREEN is not enabled until all traffic gates are fully raised (or TRAFFIC GATE BYPASS has been engaged).

3.) Provide bypass capability labeled TRAFFIC GATE BYPASS to allow span lock PULL without all traffic gates LOWERED or traffic lights GREEN without all traffic gates RAISED.

C. Span Locks:

1.) Bridge Opening: Leaf RAISE is not enabled until all span locks are fully pulled (or SPAN LOCK BYPASS has been engaged).

2.) Bridge Closing: Traffic gate RAISE is not enabled until all span locks are fully driven (or SPAN LOCK BYPASS has been engaged).

3.) Provide bypass capability and label SPAN LOCK BYPASS to allow leaf RAISE without all span locks pulled or traffic gate RAISE without all span locks DRIVEN.

D. Leaf:

1.) Span locks DRIVE is not enabled until leaf (s) is(are) FULLY SEATED (as indicated by the FULLY SEATED switch).

2.) Provide bypass capability and label LEAF BYPASS to allow span lock DRIVE without leaf (s) FULLY SEATED.

E. Manually lowering a traffic gate arm will start RED flashing lights on the gate arm and will turn corresponding traffic lights RED independent of the condition of the control system.

## 8.7.10 Instruments [LRFD-MHBD 8.4.5]

Provide wattmeter for each drive (pump) motor and provide leaf position indication for each leaf.

### 8.7.11 Control Console [LRFD-MHBD 8.4.6]

A. Specify a Control Console that contains the necessary switches and indicators to perform semi-automatic and manual operations as required by the standard FDOT Basic Sequence Diagram.

B. All wiring entering or leaving the Control Console must be broken across approved terminals.

C. No components other than push buttons, selector switches, indicating lights, terminal blocks, etc., must be allowed in the Control Console.

### 8.7.12 Conductors [LRFD-MHBD 8.9](01/08) Jan 2008 Added section. Renumbered balance of chapter.

A. Single conductor insulated wire. Specify THHW/THWN rated 600 VAC 75 degrees C insulation. Specify SE, or RHW insulated wire for incoming services.

B. Do not use aluminum or solid copper conductors.

C. Do not specify wire smaller than No. 12 AWG for power and lighting circuits and smaller than No. 14 AWG for control wiring between cabinets, except that control wiring within a manufactured cabinet may be No. 16 AWG. Minimum field wire size is No. 12 AWG for control conductors between cabinets and field devices and No. 10 AWG for motor loads. No. 14 AWG pigtails, no longer than 12 inches, are allowed for connection of field devices that cannot accommodate a No. 12 AWG wire. Use No. 10 AWG for 20 A, 120 VAC, branch circuit home runs longer than 75 feet, and for 20 A, 277 VAC, branch circuit home runs longer than 200 feet.

D. Do not include power and control conductors in the same conduit.

E. If more than three current carrying conductors are included in a conduit, derate the conductors per Table 310.15(B)(2)(a) of the NEC. For derating purposes, consider all conductors, other than neutrals and ground wires, as current carrying.

### 8.7.13 Electrical Connections between Fixed and Moving Parts [LRFD-MHBD 8.9.5]

Specify extra flexible wire or cable.

### 8.7.14 Electrical Connections across the Navigable Channel [LRFD-MHBD 8.9.7](01/08) Jan 2008 - Revised A. Power Cable requirements. Revised D. to allow Schedule 120 PVC if exposed, or Schedule 80 PVC if encased in concrete.

A. Specify a submarine cable assembly consisting of the following three separate cables:

1.) Power Cable: Specify wire size and number as required for main drive motors but not more than nine conductors per cable. Specify minimum #10 AWG for gate motors, barrier motors, etc., but not more than twelve per cable. The maximum number of conductors per cable allowed is 21 (9 motor cables and 12 #10 cables).

2.) Signal and Control Cable: Jacketed and armored with fifty #12 AWG copper and five pairs of twisted shielded #14 AWG copper conductors.

3.) Bonding Cable: A single #4/0 AWG copper conductor.

B. Determine the total number of conductors required of each size and the number of runs of each type of cable that is required for the project. Use only multiples of the cables listed above. Allow for at least 25% spare conductors for each size.

C. Specify quick-disconnect type terminals for terminating conductors. Specify terminals that isolate wires from a circuit by a removable bridge or other similar means. Specify NEMA 4X enclosures for all terminals.

D. Design all above the water line, vertical runs of cable with supports at every five feet if surface mounted. Specify and detail a protective sleeve (Schedule 120 PVC if exposed or Schedule 80 if encased in concrete) around the cable from a point 5 feet below the mean low tide to a point 5 feet above mean high tide. Specify a watertight seal at both ends of the sleeve.

### 8.7.15 Conduits [LRFD-MHBD 8.10](01/08) Jan 2008 - Added new section, renumbered balance of chapter.

A. Do not specify aluminum, IMC, or EMT conduits. Specify conduit types as follows:

1) One inch minimum size Schedule 80 PVC for underground installations and in slab above grade (embedded).

2) One inch minimum rigid galvanized steel (PVC coated) for outdoor locations, above grade, exposed (leafs) and exposed in dry locations (in pier, control house).

3) 3/4 inch minimum size Schedule 80 PVC for wet and damp locations (fender).

4) Schedule 80 HDPE conduit for submarine cable installation only.

5) 3/4 inch minimum size liquid-tight flexible metal conduit for the connection of motors, limit switches, and other devices that must be periodically adjusted in position. Limit liquid-tight flexible metal conduit to 2 feet in length and specify a bonding jumper.

B. Specify conduit supports at no more than 5 foot spacing.

C. Show no more than the equivalent of three 90-degree bends between boxes.

### 8.7.16 Service Lights [LRFD-MHBD 8.11]

Provide minimum of 20 foot-candles in all areas of the machinery platform. (See SDG 8.9.11
)

### 8.7.17 Navigation Lights [LRFD-MHBD 1.4.4.6.2](01/08) 2008 Jan - Added B. "LED Fixtures."

A. Design a complete navigation light and aids system in accordance with all local and federal requirements and Standard Drawing No. 1211. Comply with the latest edition of the Code of Federal Regulations (CFR) 33, Part 118, and Coast Guard Requirements. (See SDG 8.9.14
)

B. Specify the use of LED fixtures.

### 8.7.18 Grounding and Lightning Protection [LRFD-MHBD and 8.13]

A. Provide the following systems:

1.) Lightning Protection System: Design per the requirements of NFPA 780 Lightning Protection Code. Protect the bridge with Class II materials.

2.) Surge Suppression System: Design Transient Voltage Surge Suppressor (TVSS) system to protect all power, control, signaling, and communication circuits and all submarine conductors that enter or leave the control house. It is imperative to maintain proper segregation of protected and non-protected wiring within the Bridge Tender House.

3.) Grounding and Bonding System: All equipment installed on the bridge/project must be bonded together by means of a copper bonding conductor which runs the entire length of the project (Traffic Light to Traffic Light). All metal bridge components (i.e., handrail, roadway light poles, traffic gate housings, leafs, etc.) will be connected to the copper-bonding conductor. The copper-bonding conductor must remain continuous across the channel by means of the submarine bonding cable.

B. Require earth grounds at regular intervals with no less than two driven grounds at each pier and one driven ground at each overhead traffic light structure and traffic gate. Test all driven grounds to a maximum of 5 ohms to ground.

C. All main connections to the copper-bonding conductor must be cadwelded.

D. In areas where the copper-bonding conductor is accessible to non-authorized personnel, it must be enclosed in Schedule 80 PVC conduit with stainless steel supports every 5 feet.

### 8.7.19 Movable Bridge Traffic Signals and Safety Gates [LRFD-MHBD 1.4.4]

Refer to Design Standard 17890 for Traffic Control Devices for Movable Span Bridge Signals.

### 8.7.20 Communications Systems

Design and specify a Public Address System, an Intercom System, and a Marine Radio System for each movable bridge. The three systems must work independent of each other and meet the following criteria:

A. Public Address System: One-way handset communication from the operators console to multiple zones (marine channel, roadway, machinery platforms, and other rooms). Specify an all call feature so that the operator may call all zones at once. Specify and detail loudspeakers mounted on the pier wall facing in both directions of the channel, one loudspeaker mounted at each overhead traffic signal, facing the oncoming gate, and loudspeakers at opposite ends of the machinery platform.

B. Intercom System: Two-way communication system that will work similar to an office telephone system with station-to-station calling from any station on the system and all call to all stations on the system from the main intercom panel. Each station must have a hands free capability. A call initiated from one station to another must open a channel and give a tone at the receiving end. The receiving party must have the capability of answering the call by speaking into the open speaker channel, or by picking up the local receiver and speaking into it. All intercom equipment must be capable of operation in a high noise, salt air environment. A handset must be mounted adjacent to the control console, in each room on the bridge and on each machinery platform.

C. Marine Radio System: Hand held, portable, operable on or off the charger, tuned to the proper channels, and a 120-volt charger located adjacent to the operator's console.

### 8.7.21 Functional Checkout

A. Develop and specify an outline for performing system checkout of all mechanical/electrical components to insure contract compliance and proper operation. Specify in-depth testing to be performed by the Contractor.

B. Functional testing for the electrical control system consists of two parts. Perform the first part before delivery and the second part after installation on the bridge. Both tests must be comprehensive. Perform the off-site functional testing to verify that all equipment is functioning as intended.

C. All repairs or adjustments must be made before installation on Department property. All major electrical controls must be assembled and tested in one place, at one time. The test must include as a minimum: control console, PLC, relay back-up system, Motor Control Center, and all other equipment required, in the opinion of the Electrical Engineer of Record, to complete the testing to the satisfaction of the SDO.

D. If not satisfactory, repeat the testing at no cost to the Department. All equipment must be assembled and inter-connected (as they would be on the bridge) to simulate bridge operation. No inputs or outputs must be forced. Indication lights must be provided to show operation and hand operated toggle switches may be used to simulate field limit switches.

E. After the off-site testing is completed to the satisfaction of the SDO, the equipment may be delivered and installed. The entire bridge control system must be re-tested before the bridge is put into service. The field functional testing must include, but is not necessarily limited to, the off-site testing procedure.

F. Test all brakes, prior to the first operation of a bridge leaf with the motors, for correct torque settings. Test all brake controls and interlocks with motor controls for correct operation. Do not operate the leaf, even for “testing” purposes, with brakes manually released or with interlocks bypassed.

### 8.7.22 Functional Checkout Tests

As a minimum, perform the following tests of Control Functions for both manual and semi-automatic operations:

Commentary: The Electrical Engineer of Record is encouraged to include tests for other equipment not included in the minimum tests listed below.

A. Demonstrate the correct operation of the bridge sequence as described in the Technical Special Provisions and in the drawings.

B. Demonstrate EMERGENCY STOP of each span (leaf) at, or during, each phase of opening and closing the bridge (phases include ramping up or down, full-speed, and creep-speed).

C. Demonstrate EMERGENCY STOP does prevent energization of all rotating machinery in any mode of operation.

D. Demonstrate that the leafs do not come to a sudden stop on a power failure.

E. Interlocks:

1.) Simulate the operations of each limit switch to demonstrate correct operation and interlocking of systems.

2.) Demonstrate BYPASS operation for each failure for each required bypass.

3.) Simulate each failure for which there is an alarm message to demonstrate correct message displays.

4.) Testing of interlocks must be sufficient to demonstrate that unsafe or out of sequence operations are prevented.

5.) Observe Position Indicator readings with bridge closed and full open to assure correct readings.

F. Navigation Lights:

1.) Demonstrate that all fixtures are working.

2.) Demonstrate proper change of channel lights from red to green.

3.) Demonstrate Battery Backup by simulating a power outage.

G.) Traffic Gates:

1.) Demonstrate proper operation of each gate arm.

2.) Demonstrate opening or closing times. Time should not exceed 15 seconds in either direction.

3.) Demonstrate that gate arms are perpendicular to the roadway when RAISED and parallel to the roadway when LOWERED.

4.) Demonstrate that Traffic Lights turn RED when a gate arm is manually lowered.

H. Span Locks:

1.) Operate each span lock through one complete cycle and record, with chart recorder, motor power (watts) throughout the operation, record lockbar to guide and lockbar to receiver, clearances.

2.) Demonstrate pulling and driving times. Time should not exceed 10 seconds in either direction.

3.) Operate each lock with hand crank or manual pump for one complete cycle.

I. Emergency Power:

1.) The complete installation must be initially started and checked-out for operational compliance by a factory-trained representative of the manufacturer of the generator set and the Automatic Transfer Switch. The supplier of the generator set must provide the engine lubrication oil and antifreeze recommended by the manufacturer for operation under the environmental conditions specified.

2.) Upon completion of initial start-up and system checkout, the supplier of the generator set must notify the Engineer in advance and perform a field test to demonstrate load-carrying capability, stability, voltage, and frequency.

3.) Specify a dielectric absorption test on generator winding with respect to ground. A polarization index must be determined and recorded. Submit copies of test results to the Engineer.

4.) Phase rotation test must be made to determine compatibility with load requirements.

5.) Engine shutdown features such as low oil pressure, over-temperature, over-speed, over-crank, and any other feature as applicable must be function-tested.

6.) In the presence of the Engineer, perform resistive load bank tests at one hundred percent (100%) nameplate rating. Loading must be 25%-rated for 30 minutes, 50%-rated for 30 minutes, 75%-rated for 30 minutes, and 100%-rated for 2 hours. Maintain records throughout this period and record water temperature, oil pressure, ambient air temperature, voltage, current, frequency, kilowatts, and power factor. The above data must be recorded at 15-minute intervals throughout the test.

J. Automatic Transfer Switch: Perform automatic transfer by simulating loss of normal power and return to normal power. Monitor and verify correct operation and timing of: normal voltage sensing relays, engine start sequence, time delay upon transfer, alternate voltage sensing relays, automatic transfer operation, interlocks and limit switch function, timing delay and retransfer upon normal power restoration, and engine shut-down feature.

K. Programmable Logic Controller (PLC) Program:

1.) Demonstrate the completed program's capability prior to installation or connection of the system to the bridge. Arrange and schedule the demonstration with the Engineer and the Electrical Engineer of Record.

2.) A detailed field test procedure must be written and provided to the Electrical Engineer of Record for approval. Provide for testing as listed below:

a.) Exercise all remote limit switches to simulate faults including locks, gates, traffic lights, etc. Readouts must appear on the alphanumeric display.

b.) When the local testing of all individual remote components is completed, check all individual manual override selections for proper operation at the console. When all override selections have been satisfactorily checked-out, switch the system into semi-automatic (PLC) mode and exercise for a full raise and lower cycle. Verify that operation is as diagrammed on the plan sheet for the sequence of events.

c.) Initiate a PLC sequence of operation interweaving the by-pass functions with the semi-automatic functions for all remote equipment.

d.) Remove the power from the input utility lines. The Automatic Transfer Switch (ATS) should activate the engine-generator to supply power. Raise and lower the bridge again. The bascule leafs should operate in sequence; i.e., two adjacent bascule leafs at a time. Upon completion of the test, re-apply utility power to ATS. The load should switch over to utility for normal operation.

e.) Certify that all safety features are included in the program, and that the program will not accept commands that are contrary to the basic sequence diagram. Submit failure mode testing as part of the written field test procedure.