System_and_Interface_Description.pdf

USNS ZEUS (T-ARC 7) Cable Handling Equipment System and Interface Description

20 August 2014

Table of Contents

1. Purpose 3

2. Overview 3

2.1 The Vessel 3

2.2 Cable Handling Equipment 7

3. CHE Systems Description 9

3.1 Dynamometer/Fairleader 9

3.2 Self-Fleeting Cable Drum Engine 12

3.3 Cable Speed/Distance Sensor (Roto’s) 16

3.4 Draw-Off and Holdback Tension Machine 18

3.4.1 Aft DOHBs 22

3.4.2 Forward DOHBs 22

3.5 Control Console 25

3.5.1 Control Functions 28

3.5.2 Gauges and Readouts 32

3.5.3 Indicator Lights and Displays 34

3.5.4 Miscellaneous Items 35

1. Purpose

The purpose of this Systems Description is to provide an overview of the Cable Handling Equipment (CHE) used aboard the USNS ZEUS for deploying and recovering cable. A functional description of the major pieces of equipment used in cable laying and repair operations is provided as well as the relevant nomenclature.

2. Overview

2.1. The Vessel

The USNS ZEUS, like its peers in the T-ARC class, was specifically designed as a cable laying vessel. She was launched in 1982 and is still in service. The vessel is under the operational control of the US Navy, but is operated by the Military Sealift Command (MSC). The vessel’s general characteristics are given in Table 1. Photographs of the USNS ZEUS are given in Figures 1, 2, and 3.

Table 1: USNS ZEUS (T-ARC 7) General Characteristics

Length Overall: 502’6” Length at Waterline: 454’0” Beam: 73’0” Depth to main deck: 54’6” Draft at full load: 24’0” Displacement at full load: 14,157 LT Propulsion HP: 10,200 HP Max speed: 15 kn Accommodations: 108 persons

Figure 1: USNS ZEUS While Pierside

Figure 2: Bow and Bridge of USNS ZEUS While Pierside

Figure 3: Stern Area of USNS ZEUS While Pierside

The vessel has a diesel electric propulsion system in which multiple diesel generators provide electric power to a propulsion bus. For propulsion, the AC power provided by the diesel generators is converted to DC power via a large bank of Silicon Controlled Rectifiers (SCRs), which then power and control two 5000 HP DC propulsion motors. Each of the two DC motors turns a shaft with a 12.5’ diameter fixed-pitch propeller. The vessel has two screws and one centerline rudder.

The vessel must be capable of stationkeeping and accurate low-speed maneuverability for various aspects of its cable laying and repair missions. Therefore, it is equipped with two 1200 HP tunnel thrusters forward and two 1200 HP tunnel thrusters aft, and has a dynamic positioning (DP) certification of DP-2.

USNS ZEUS has two large cable tanks and three smaller cable tanks for storing mission cable and systems for transport to deployment sites. The area on main deck in which cable runs from the tops of the cable tanks to the overboarding sheaves on the bow and stern is known as the “cable highway.” The cable highway contains numerous pieces of equipment including but not limited to:

Cable Handling Equipment (described in more detail below) which is used to deploy and recover cable. The Cable Handling Equipment (CHE) consists of many pieces of equipment that work together, including a Dynamometer/Fairleader, Cable Drum Engine (CDE), Draw-Off and Holdback (DOHB) tension machine, and Control Console.

Cable haulers which are used to load cable onto the vessel and move cable and rope from tank to tank when necessary. The cable haulers aboard the ZEUS apply force to the cable by squeezing the cable between an upper and lower set of tracked loops that are electrically powered.

Cable troughing that provides support and protection for the cable as it travels along the cable highway.

Racks for storing repeaters and other deployed gear.

Overhead bridge crane system (5T) and other handling devices for moving repeaters and other gear throughout the cable highway. There is also a 5T bow gantry and hoist on the foredeck.

Portable equipment such as loading quadrants, troughing sections, portable bellmouth sections, rigging, etc. are normally stored but are assembled and used during certain types of operations like cable loading, cable transfer, etc.

Spaces and equipment for cable splicing and maintenance and repair of repeaters and other systems.

The vessel has three bow sheaves and three stern sheaves. The aft center stern sheave is used for the plow tow wire. The other sheaves are used for product cable and rope.

The vessel has systems for deploying and recovering buoys that are used during cable repair operations. There are two buoy skids forward and two aft. The vessel also has cranes that are used to assist with loading, launch and recovery of various systems.

Inside the ship are the Mission Control area and the Test Room. The Test Room contains all the systems necessary to test the product cable system electrically and optically continuously from initial loading through ultimate deployment. At-sea cable operations are managed by highly skilled personnel within the Mission Control room. Personnel in Mission Control use advanced cable lay software and feedback and displays from numerous systems to monitor, supervise, and direct needed actions to safely and effectively complete the mission.

Some systems, such as a plow system for burying cable during lay, or a Remotely Operated Vehicle (ROV) for burying cable after being laid and for other tasks, are needed only for certain types of operations. These systems are mobilize aboard the USNS ZEUS only for missions requiring them. The vessel reserves space on deck for these systems and maintains the necessary interfaces to facilitate quick and efficient mobilization and de-mobilization on the vessel. The large A-frame crane on the stern of the vessel is used for plow launch and recovery, and remains permanently on the vessel.

2.2. Cable Handling Equipment (CHE)

The machinery that provides the motive force on the product cable needed for deployment and recovery of cable is collectively called the Cable Handling Equipment (CHE). The USNS ZEUS has four sets of CHE: two sets are forward and two sets are aft. The four sets of CHE are controlled and operated independently. Each of the forward and aft sets of CHE has a port set of equipment and a starboard set of equipment. Therefore, the four sets of CHE are forward/port, forward/starboard, aft/port, and aft/starboard. The four sets of CHE are functionally the same, but there are a few differences in implementation which will be specifically noted in the following sections.

Two Control Consoles control the four sets of CHE. The forward Control Console controls the forward two sets of CHE, and the aft Control Console controls the aft two sets of CHE. The Control Consoles are divided into port and starboard sections. The forward and aft Control Consoles are almost identical, but there are small differences that will be noted in the sections that follow.

Figure 4 provides a block diagram of the CHE system. Each of the four sets of CHE consists of a:

Dynamometer/Fairleader Self-fleeting Cable Drum Engine (CDE) Draw-Off and Holdback tension machine (DOHB) Control Console

D yn am o m et e r (N o te a rr o w in d ic at e s th at D yn o c an b e m ve d a th w ar th sh ip s)

P la n V ie

Fo rw ar

A ft

Fa ir le ad er N te ro w in d ic at es t h at le ad er c an ve d a th w ar ts h ya n am o m et er N w in d ic at es t h at D yn ca n b e m o ve w ar ts h

C ab le D ru

O H B N o te t h at a ft D O H B u se s ti re p ai rs A rr ic at es t h at D O H B c an ve d a th w ar ts h le P

H B N o te t h at f o rw

H B u se s tr ac ks A rr ic at es t h at D O H B c an ve d a th w ar ts h le D ru

A ft C o n tr o l

C o n so le

Fo rw ar d C o n tr o l

C o n so le ad er N w in d ic at es t le ad er c an ve a th w ar ts h ip s)

C

Fi gu re C ab le H an d lin g Eq u ip m en t B lo ck D ia gr am

The path that the product cable takes during a deployment is as follows. The cable comes up from its storage location in a cable tank and travels through a bellmouth at the top of the tank.

The bellmouth consists of faired surfaces that prevent the cable from encountering any bends that are sharper than the specified minimum bend radius of the cable. The cable then enters troughing that guides it and protects it along its path to the CHE. The cable then enters the Draw-Off and Holdback tension machine which maintains a certain amount of tension on the inboard side of the cable drum engine. On the outboard end of the DOHB is the cable speed sensor, called a “Roto”. The Roto measures linear cable speed and distance payed out or in. The cable then goes around the cable drum engine for nominally three wraps. The cable enters the cable drum engine at the top of the drum and also exits at the top of the drum. The cable then goes through the Dynamometer/Fairleader. The Fairleader aligns the cable athwartships and the Dynamometer measures the tension in the cable. The cable then proceeds to the overboarding sheave where it turns downward to enter the sea.

Each element of the CHE is described in more detail in Section 3 below.

3. CHE System Description

In this section, each of the key pieces of cable handling equipment shown in Figure 4 is discussed in more detail. Although the sets of CHE are controlled independently, they are used in conjunction for certain types of operations such as for cable repair.

3.1. Dynamometer/Fairleader

The Dynamometer/Fairleader performs two separate and distinct functions. The Fairleader function is to guide the cable and to impart side force on the cable to help create wrap separation on the cable drum. The Dynamometer function measures tension in the cable. The Fairleader and Dynamometer are separate pieces of equipment but are contained within a common frame, as seen in Figure 5. The Fairleader and the Dynamometer traverse athwartships independently and are independently controlled.

The Fairleader portion of the Dynamometer/Fairleader is used in conjunction with the self-fleeting feature of the cable drum engine (and to a lesser extent, the traversing feature of the DOHB) to induce separation between wraps of cable on the CDE. Wrap separation is particularly critical during the passage of bodies (such as a repeaters) in the product cable system. Wrap separation prevents damage to the cable and various bodies in the cable system during deployment or recovery. If successive wraps do not have sufficient space between them, the repeater body and/or the cable may be damaged by large reaction forces as they interfere with each other on the drum surface. Wrap separation is primarily achieved by the self-fleeting feature of the cable drum engine, as described in a later section. Additional wrap separation can be induced by the traversing feature of the Fairleader (on the outboard side of the cable drum engine) and the traversing feature of the DOHB (on the inboard side of the cable drum engine).

The Fairleader traverses athwartships (to port or starboard) to induce side force on the cable by pushing the cable guide against the side of the cable. Fairleader movement is actuated by an air motor that turns a jack screw that moves the fairleader athwartships. The air motor is controlled by a stick-type lever air control valve on the Control Console. In the event of a failure in the air motor system, the jack screw can be mechanically turned manually to move the Fairleader to the needed position. Figure 6 provides a closeup of the Dynamometer/Fairleader and shows the tubes along which the Fairleader and the Dynamometer traverse athwartships independently. The jack screws are visible between each set of tubes.

The “Dynamometer” portion of the Dynamometer/Fairleader measures the tension in the product cable. The Dynamometer/Fairleader incorporates a Dynamometer Table (or “dyno-table”) which is a flat plate with rounded edges over which the product cable passes. The surface of the dyno-table is slightly elevated above the surrounding surfaces which results in a small vertical deflection of the cable as it passes over the dyno-table. Figure 7 gives a view of the aft, port Dynamometer/Fairleader from directly aft looking forward. The surface of the “Dyno-Table” can be seen and the cable drum engine is visible in the background.

The downward force imparted to the dyno-table by the product cable is measured by a load cell between the dyno-table and the frame. The downward force imparted is proportional to the tension in the product cable. The load cell is accurately and regularly calibrated. The analog output of the load cell goes to an amplifier card and is then digitized, sent to a Programmable Logic Controller (PLC), and converted to units of force using calibration factors programmed into the PLC. The tension output is then sent to various network sites on the Control Net network, including displays at the CHE Control Console and Mission Control.

Fig 5: Aft, Port Dynamometer/Fairleader (photo taken from port side, looking to starboard obliquely). The Aft, Starboard Dynamometer/Fairleader is visible at upper right.

Fig 6: Close-up of Aft, Port Dynamometer/Fairleader (photo taken from aft, port side, looking forward obliquely).

Figure 7: Close-up of the Aft, Port Dynamometer/Fairleader (aft end looking forward).

Note the dyno-table between the cable guides.

3.2. Self-Fleeting Cable Drum Engine (CDE)

The function of the CDE is to provide longitudinal force on the product cable, and to control the linear speed of the product cable. A photograph of the upper portion of the 15 ft diameter CDE is given in Figure 8.

The CDE functions like a winch on a sailboat or a mooring capstan on a ship. The high tension side of the line is wrapped three to four times around a rotating drum. Friction between the line and the drum results in a reduction in line tension with each successive wrap. The “tail tension” on the inboard side of the drum is significantly lower than the outboard tension.

Fig 8: Aft, Port Cable Drum Engine (photo taken from port side looking forward/starboard obliquely). Note Fairleader at right and DOHB at upper left.

The product cable is routed around the cable drum for three to four wraps to reduce the very high outboard tension to a more manageable tension on the inboard side of the drum. The CDE works in conjunction with the DOHB in that the DOHB provides the “tailing” force on the inboard side of the CDE. The four CDEs are rated for a maximum line pull of 100,000 lbs while rotating.

The two forward CDEs are rated for a static (i.e., while in a “locked”, non-rotating condition) holding force of 120,000 lbs. The two aft CDEs are rated for a static holding force of 150,000 lbs due to the fact that the aft CDEs have a second caliper brake installed.

Figure 9 provides a functional block diagram of major components of the cable drum engine and associated systems. Alternating Current (AC) electrical power from the ship’s service generators is nominally 660 VAC. The raw ship’s service power is fed to a 750 kVA isolation transformer that converts the 660 VAC to 600 VAC and 460 VAC, and provides isolation from power fluctuations due to transients caused by other equipment connected to the electrical bus being turned on and off. The AC electrical power is then converted to DC electrical power by Silicon Controlled Rectifiers (SCRs) in the drum motor drive panels. Motor controllers regulate the DC

AC AC DC

power applied to the GE 250 HP electric motor that turns the cable drum via a mechanical gearbox. The drum braking system consists of a motor brake on the DC drive motor and a caliper brake on the gearbox. The two forward CDEs have one caliper brake, but the two aft CDEs have two caliper brakes.

Figure 9: Cable Drum Engine Functional Block Diagram

In case of motor system failure, a means exists to run the port CDE using the starboard drum motor and vice versa. External, normally-stored shafts and other equipment must be rigged to connect the two gear trains. Also, operators must be aware that the cable drum controls are reversed. In other words, if the starboard drum motor fails, for example, and the port cable drum motor is rigged to drive the starboard drum, the port cable drum gauges and controls must be used to drive the starboard drum (with the exception of the caliper brake).

The Instrumentation Drive Assembly (IDA) performs two functions. The most important function is to provide lubrication to the bull gear and other components. After so many revolutions of the CDE, the IDA activates an oil pump that delivers oil to the gears. The second

Cable Drum

Ship’s Power

SCR

Drive/Motor

Controller

Gear Box

250 HP DC

Electric Motor

Jack Shaft

Instrumentation Drive

Assembly Caliper Brake

Caliper Brake

(second caliper brake is installed on two aft Cable

Drum Engines only)

Self‐Fleeting

“Modules”

Blower

Motor

Brake

Isolation

Transformer

Drum tire function is to provide a tachometer readout of the drum rotational speed. This was originally envisioned as a backup means of determining cable speed, but is currently not used by the system or displayed. The tachometer output is currently only accessible on a maintenance screen at the operator’s console. Drum speed is measured via the output of the motor servo.

All four CDEs are self-fleeting, which means that space between wraps is automatically maintained during drum rotation. As stated above, wrap separation is necessary to allow the passage of bodies in the cable system, such as repeaters, over the drum without damage to the cable or the repeaters. The desired wrap separation is established during the set-up of the drum for each cable operation, during which the cable (or rope) is wrapped nominally three times around the drum. On these CDEs, wrap separation is maintained during operations by “fleeting modules” that consist of tracks that move in continuous loops across the drum surface perpendicular to the circumferential path of the product cable. The modules are directly geared to the drum so that the speed of the fleeting modules is kept directly proportional to the drum rotational speed. The force caused by friction between the product cable and the surface of the fleeting modules results in the cable laying on the drum surface in a helix pattern. Therefore, the position at which the cable enters and exits the top of the drum surface is offset considerably.

Fleeting can be maximized by adjusting the athwartships positions of the Fairleader portion of the Dynamometer/Fairleader (and adjusting the athwartships position of the DOHB) to obtain greater wrap separation.

The rotational speed of the drum is controlled by a stick-type lever control on the front of the Control Console. The lever rotates a potentiometer that sends an electrical signal to the motor drive controller, which then uses the drive circuitry to command the 250 HP electric drive motor.

The cable drum engine rotational speed is controlled only in an open-loop speed mode, in that the drum rotational speed is commanded only by the stick moved by the operator. There is no automatic closed loop control of any kind. The human operator provides the feedback circuit by visually observing the linear cable speed, and then manually adjusting the drum rotational speed using the stick control to achieve the required speed.

Typically, the cable engineer will call down to the CHE operator at the Control Console using the internal communications system and request a certain cable speed. The operator will then move the cable drum control lever and watch the cable speed display (based on input from the Roto). After allowing some time for the system to settle back into a steady state, the operator will then “bump” the control lever to make fine adjustments to the drum speed until the requested linear cable speed is achieved as closely as possible.

Sometimes the cable speed is close to but not exactly the requested cable speed. There are a couple of reasons for this. The Makai software indicates the required cable speed to three decimal places, but the cable speed is only displayed at the Control Console and remote displays to two decimal places. So, the cable engineers “round” the linear cable speed calculated by Makai to create the commanded linear cable speed for the equipment operator. Also, the resolution to which the operator can adjust the drum rotational speed is limited by the manual, open loop, stick-type speed control and operator proficiency and experience. Whenever the actual linear cable speed differs from the requested linear cable speed for a significant period of time, the cable engineers must make corrections to the lay at some point in order to remain in concert with the lay plan.

On the top, inboard side of the cable drum engine is mounted a pair of “drum tires”. The drum tires pinch the cable between the tires and the surface of the cable drum. The drum tires are activated pneumatically from the Control Console.

3.3. Cable Speed/Distance Sensor (Roto)

The sensor for determining the linear speed of the product cable is mounted on the outboard end of the DOHB, but is discussed separately here because it such an important element of the CHE.

The cable speed sensor is most commonly referred to as the “Roto” because it uses a rotating roller to determine linear speed through a calibration process. The cable speed sensor will be called the “Roto” for the remainder of this document. In addition to measuring speed, the Roto output is also used to compute the cable distance that has travelled through the Roto. Having accurate measurements of cable speed and cable distance is very important to the cable engineers that direct, monitor, and make corrections to the cable lay in real time.

At the outboard end of each DOHB, the pair of stainless steel Roto rollers, with vertical axes of rotation, is mounted on arms that bring the rollers together to squeeze the cable and move them apart to release the cable. The rollers are opened and closed pneumatically via an air-over-air control on the operator’s console. In the closed position, the rollers make contact with the product cable with sufficient force to prevent any slip from occurring between the surface of the product cable and the surface of the roller. The inboard roller has a shaft encoder on its shaft that optically determines the rotational speed of the roller.

Figure 10 gives a photograph of the Roto rollers and Figure 11 provides a functional block diagram of the Roto system. The shaft encoder output goes to an Encoder Counter that then feeds the data into a PLC. Inside the PLC, the conversion of rotational speed to linear speed of the cable is performed. The Rotos are calibrated periodically using accurately known test cable distances and calibration factors are updated. The output of the PLC is provided to user sites via serial RS-232 interfaces. User sites include the data logger, Makai software, displays at the operator’s console, bridge, forward deck station, aft deck station, and Mission Control, etc.

Figure 10: Aft, Port Roto-Rollers Mounted on Outboard End of DOHB (photo taken from port side looking forward obliquely). Roto shown in closed position. Note cable drum at lower right and DOHB tires at top.

Shaft Encoder

Encoder Counter

PLC

Outboard ROTO Drum

Inboard ROTO Drum

Control Console Display

Other Displays

Serial Interface Box

Makai

RS‐232

RS‐232

WINFROG

Figure 11 : Roto Functional Block Diagram

Although the current Rotos have been reliable in terms of basic functionality, there has been a history of problems that often frustrate the cable engineers that rely on its output. The Rotos are often “off” in their measurement of cable distance by unacceptable amounts of several percent.

The cable engineers know this because the cable distance between repeaters is very accurately known and can be measured optically. When this known distance differs from the Roto-based distance measurement, Roto error is apparent. However, there is not currently a way to “re-calibrate” a Roto on the fly. Re-calibrating a Roto requires accessing the PLC software and changing parameters there, an action that is currently only done pier side by skilled technicians during vessel maintenance periods. The cable engineers have to live with the distance measurement error and make corrections to the lay manually. A cable distance error of less than 0.5% is desired, but this is rarely achieved.

3.4. Draw-Off and Holdback (DOHB) Tension Machine

As stated previously, the function of the DOHB is to provide the “tailing tension” on the inboard, low tension side of the cable drum engine. DOHBs are sometimes referred to as “tension machines” and the names are often used interchangeably or together, as in the title of this section. This document will use the term DOHB. Ironically, the Control Console uses the term “Tension Machine” to label the DOHB controls.

Figure 12 shows a side view of the Aft, Port DOHB and Figure 13 gives an end view from forward of the DOHB looking aft.

Figure 12: Aft, Port DOHB (photo taken from port side looking to starboard). Note cable drum engine at far right, Roto rollers on aft end (right) of the DOHB, 2-tire pairs in closed position, tank-side dragboards on the forward (left) side of the DOHB, and cable troughing at far left.

Figure 13: End View of Aft, Port DOHB (photo taken from forward looking aft). Note the tank-side dragboards, gear box, and drive shafts of the DOHB. A portion of the Aft Control Console is visible at far left.

The DOHBs are mounted on a traversing system such that the entire DOHB can be adjusted to port or starboard to ensure proper alignment of the DOHB with the cable path. The traversing system is an air over hydraulic system and is controlled by a rotating, return-to-center, switch-type valve actuator on the Control Console. Athwartships translation is a maximum of 9”.

A load cell is mounted under the DOHBs. This load cell measures the longitudinal (i.e., fore-and-aft) force that the DOHB imparts on the product cable. This force is the “tailing tension” in the cable between the DOHB and the cable drum and is displayed on the Control Console. The tension measurement is used by DOHB control circuitry as the feedback parameter that allows operation of the DOHB in an automatic constant tension mode when selected.

The DOHBs can be operated in three modes.

Speed Mode: in this mode, the speed of the DOHB is determined by the setting of the speed control on the Control Console. No closed-loop feedback is used to keep the speed constant. All speed changes must be made manually by the operator. The speed control lever on the console has a locking feature via a thumbwheel.

Constant Tension Mode: in this mode, the DOHB automatically maintains a constant tension on the cable. The tension measurement made by the DOHB load cell is used as the feedback parameter in the closed-loop control system. Once the operator selects the constant tension mode, the control system automatically adjusts the torque of the motors to maintain the cable tension at a constant value. The constant tension control algorithm is currently set up to automatically provide a constant maximum cable tension of 1000 lb when the DOHB is in high gear and 4000 lb when in low gear. The constant tension value may be adjusted by the operator via the keypad on the Control Console.

Calibration Mode: in this mode, only the Roto that is mounted on the outboard end of the DOHB is powered and operating. All other segments of the DOHB are not powered or functioning. The calibration mode is used when loading cable and when calibrating the Rotos with measured test cables. When loading cable, force is applied to the cable by cable haulers rather than with the cable handling equipment. Cable length and cable speed are still needed during loading and calibration operations, so a mode is provided to allow the Roto to operate independently of the rest of the DOHB. The Calibration Mode is selected via the keypad/monitor at the center of the console by entering the Operational Setup page.

The DOHBs may be operated in a high gear or a low gear. In high gear, the DOHB runs at a maximum speed of 700 fpm and generates a maximum tension of 1000 lb. In low gear, the DOHB runs at a maximum speed of 200 fpm and generates a maximum tension of 4000 lb.

The DOHBs have cable guides on the outboard and inboard ends of the DOHB to keep the cable properly aligned with the machine. These cable guides are sometimes called “Dragboards” and are labelled as such on the Control Console. The outboard dragboards on the DOHB are actually the Roto rollers. Hence, the Roto rollers actually perform two functions at the same time:

They act as a cable guide to align the cable with the DOHB tires (aft DOHBs) or the DOHB tracks (forward DOHBs).

They measure linear cable speed and cable distance. The Roto rollers pinch the cable when closed with sufficient force that no slip occurs between the Roto rollers and the cable, forcing the rollers to rotate and provide a measurement of cable speed and cable count. (Note: On rare occasions, the Roto rollers may be used to perform a third function - to apply side force to the cable to maximize wrap separation on the cable drum engine. This is accomplished by traversing the entire DOHB athwartships. This is usually done only for short periods of time while a body, like a repeater, is passing over the cable drum engine, but is most often unnecessary).

The inboard cable guide/dragboard consists of opposing curved metal plates, through which the cable passes.

The open/close position of the Roto rollers and the inboard dragboards is activated pneumatically via a stick-type lever air control valve on the Control Console.

Although the forward and aft DOHBs are functionally the same, they differ in some aspects of their engineering implementation. The differences between the forward DOHBs and aft DOHBs are discussed below.

3.4.1. Aft DOHBs

The aft DOHBs use 2-tire pairs to squeeze the cable and impart longitudinal force on the cable by the friction between the tire surfaces and the cable. A side view and an end view of the aft, port DOHB can be seen in Figures 12 and 13. The aft DOHBs are powered by two DC electric motors that drive the two tire pairs via a gear box on the inboard side of the DOHB. The forward motor powers the forward upper and forward lower tires, and the aft motor powers the aft upper and aft lower tires. Because a single motor drives opposing tires that are both contacting the cable, the tires must be of exactly the same diameter to avoid slippage. The two 20 HP Reliance DC motors are powered and controlled by Silicon Controlled Rectifiers (SCRs) (Reliance Electric Distributed System Power Modules with Automax Distributed Control System motor controllers located on the 2nd deck). The DC motor’s shaft goes into the DOHB gear box, and drive shafts connect the gear box to the tire axles (see Figure 13).

The two upper tires are mounted on an upper frame assembly which can be raised and lowered.

The upper frame is raised to separate the tire pairs to load cable, for example. The upper frame is lowered to squeeze the cable between the upper and lower tire pairs. The upper frame is raised and lowered pneumatically by two air cylinders mounted to the forward and aft ends of the upper frame. The upper frame cylinders are controlled via a stick-type lever air control valve on the Control Console.

To change from high to low gear and vice versa on the aft DOHBs, three actions must be taken.

The first action is to stop the DOHB. The second action is to manually throw a lockable, 2-position lever on the gear box of the DOHB, and the third action is to turn the 2-position gear selector switch on the Control Console.

3.4.2. Forward DOHBs

The forward DOHBs use tracks instead of tires to squeeze the cable and impart longitudinal force on the cable. Figures 14 and 15 show the forward, port DOHB. The tracks are turned hydraulically via hydraulic motors supplied by a dedicated Hydraulic Power Unit (HPU). The upper track is mounted on an upper frame that can be raised and lowered. The upper frame is raised to separate the track pair to load cable, for example. The upper frame is lowered to squeeze the cable between the upper and lower tracks. The upper frame is raised and lowered pneumatically using a single air cylinder. The upper frame can be raised to a maximum of

12.75”. The upper frame cylinder is controlled via a stick-type lever air control valve on the Control Console. Figure 16 shows the Forward, Starboard DOHB with the upper frame raised.

Figure 14: Forward, Port DOHB (photo taken from a port, forward position looking aft obliquely).

Figure 15: Forward, Port DOHB (photo taken from port looking to starboard).

Figure 16: Forward, Starboard DOHB with Upper Frame Raised (photo taken from starboard looking to port).

Within each track assembly are air springs whose pressure is adjusted by the operator from the Control Console. Each track has five air springs. Two of the air springs act in a longitudinal direction and three act in a vertical direction. The two air springs that act in the longitudinal direction are used to tighten the track on its guides. One of these longitudinal air springs is mounted in the forward section of the track and one is mounted in the aft section of the track.

The force they produce oppose one another and serve to tighten the track on its guides longitudinally.

The three air springs that act in a vertical direction are used to increase or decrease the amount of “track squeeze” on the product cable. When pressure is applied, these air springs causes a roller bar, over which the track elements must move, to displace vertically. When the upper frame is in the lowered position such that the tracks are touching (and therefore pinching the product cable), increasing the pressure in these three air springs results in increased track squeeze force on the cable.

All five air springs (three vertical and two longitudinal) are plumbed together and see a common air pressure. The air spring pressure is controlled by a stick-type lever air control valve on the Control Console. Nominal operating pressure is about 80 psi when the DOHB is in low gear and about 60 psi when the DOHB is in high gear.

3.5. Control Console

The cable handling equipment is controlled by operators from the Control Consoles. There is one forward Control Console and one aft Control Console. Each console has controls for port and starboard sets of cable handling equipment. The two Control Consoles are practically identical, and the few differences are described in the appropriate sections below. The aft Control Console faces aft and the forward Control Console faces forward so that operators can visually see the cable handling equipment from their position at the console.

Photographs of the Control Console (aft) are provided in Figures 17 and 18. The console itself consists of a large base cabinet with a slightly inclined top surface. The top surface has controls, gauges, switches, a keypad, displays, etc. mounted on it. Two large displays and some switches are mounted in a T-shaped cabinet that sits on the top, rear of the console surface. This cabinet with its vertically oriented displays is called the “turret”. Figure 19 gives a close-up of the aft Control Console turret.

The pneumatic controls on the Control Console are manufactured by either Rexroth or Wabco.

Figure 17: Aft Control Console (photo taken from a forward position looking aft obliquely).

Figure 18: Aft Control Console Side View (photo taken from port looking to starboard).

Figure 19: Close-up of the Aft Control Consule “Turret”.

3.5.1. Control Console Control Functions

The Control Console has the control functions that are given in the bulletized list below. For each item listed, there is a port and starboard implementation of the item unless otherwise noted. Controls on the port side of the console are the same as the controls on the starboard side and vice versa.

Power On/Off: Rotary, two-position on/off switches for the port and starboard cable handling equipment. Located at far bottom right and far bottom left of the turret.

Emergency Stop: Large, red, non-recessed button for the port and starboard cable handling equipment. Located at far bottom right and far bottom left of the turret. Must be manually reset by pulling up after being pushed for an emergency stop.

Instrumentation Power Start/Stop: Pushbutton switches for power on/off for the port and starboard instrumentation and controls. Located at center bottom right and center bottom left of the turret. Start button is green and stop button is red.

“Counter” Toggle Switch: Stick-type toggle switches for the port and starboard cable count. Located at center bottom right and center bottom left of the turret. Toggle left is for cable payout and toggle right is for cable pickup.

Dynamometer Traverse: Stick-type lever pneumatic control valve. Located at center left and center right of console surface. Lever routes 100 psi ship’s air to a four-way pilot operated directional control valve, that then routes ship’s air to an air motor that turns the jack screw that moves the Dynamometer athwartships. Located at the center right and center left of the console surface.

Fairleader Traverse: Stick-type lever pneumatic control valve. Located at center left and center right of console surface. Lever routes 100 psi ship’s air to a four-way pilot operated directional control valve, that then routes ship’s air to an air motor that turns the jack screw that moves the Fairleader athwartships. Located at the center right and center left of the console surface.

Cable Drum Engine Caliper Brake Set/Release: Stick-type lever, directional, pneumatic control valve. Located at upper left and upper right of console surface. Routes 100 psi ship’s air to a pilot operated blocking valve. If the cable drum is not in neutral, an actuator rod shifts the blocking valve that allows 100 psi ship’s air to be applied to a pilot operated two-way valve. This valve allows hydraulic fluid at 900-950 psi to be applied to the caliper disc brake to release it.

Cable Drum Engine Electric Motor Start/Stop: Rotary two-position switch, located at bottom center left and bottom center right of console surface.

Cable Drum Engine Electric Motor Torque Limit Adjustment: Set via keypad and display located at center left and center right of console surface.

Cable Drum Engine Speed Control: Stick-type throttle lever connected to a potentiometer. Throttle lever is rotated away from operator to pay out cable at increasing speed, and is rotated toward the operator to pick up cable at increasing speed. Located at bottom front of console.

Cable Drum Tire Up/Down: Stick-type pneumatic control lever. On the forward console, this control is located at far upper left and far upper right of console surface. On the aft console, this control is located on the lower left and lower right of the console surface.

Alarm Override: Push button that silences the audible alarm. Located at bottom center left and bottom center right of console surface.

DOHB System Select: Keyed, two position switch that activates DOHB system. Located at bottom center left and bottom center right of console surface.

DOHB Power Unit Transfer Switch (forward Control Console only): Rotary return-to-center switch. Turning this switch to the “ON” position energizes relays that remain energized until the switch is turned to the “OFF” position.

Switch causes starboard DOHB to be run by the port DOHB hydraulic system and controls and vice versa. This switch must only be activated in conjunction with the proper positioning of the manual cross-connect valves.

An electronic interlock prevents transfer from occurring unless the HPU is powered off. Located in lower center of console.

DOHB Power Unit Start/Stop Switch (forward Control Console only): Rotary two-position switch the starts and stops the DOHB Hydraulic Power Unit

(HPU).

DOHB Mode Select Switch: Rotary two-position switch that selects either the Speed Mode or the Tension Mode of DOHB operation. Located at bottom center left and bottom center right of console surface.

DOHB Brake Switch: Rotary two-position switch for Set and Release of the DOHB brake system. Located at bottom center left and bottom center right of console surface.

DOHB Traverse: Rotary, return-to-center switch that when turned one direction moves the DOHB outboard, and when turned in the opposite direction moves the DOHB inboard. Located at bottom center left and bottom center right of console surface.

DOHB Gear Mode: Rotary two-position switch that selects High or Low gear. This switch changes the gain in operational amplifiers in the DOHB control circuitry. On the aft DOHBs, use of this switch must be done in conjunction with changing the position of a gear-control arm on the gear box.

Switch is located at bottom center left and bottom center right of console surface.

DOHB Speed Control: Stick-type lever connected to a potentiometer. Lever is rotated away from the operator for payout and toward the operator for haul

in. Lever position can be locked in position with a thumb wheel. Located at far left center and far right center of console surface.

DOHB “Forward Dragboard” (Labelled as “Drum-Side Dragboard” on the Aft Control Console) Open/Close: Stick-type pneumatic control lever. Lever is rotated away from operator for the open position and toward the operator for the closed position. Lever operates a graduating control valve that routes regulated air to the open/close air cylinder. Located at the lower left and lower right of the console surface. Note that “Forward Dragboards” on the forward DOHBs are actually the Roto rollers. Similarly, “Drum-Side Dragboards” on the aft DOHBs are the Roto rollers.

DOHB Aft Dragboard (Labelled as “Tank-Side Dragboard” on the Aft Control Console) Open/Close: Stick-type pneumatic control lever. Lever is rotated away from operator for the open position and toward the operator for the closed position. Lever operates a graduating control valve that routes regulated air to the open/close air cylinder. Located at the lower left and lower right of the console surface.

DOHB Track Squeeze (forward, tracked DOHBs only): Stick-type pneumatic control lever that controls the pressure in the air springs in the forward DOHB track assemblies. Lever is rotated away from operator to apply squeeze to the cable via the air springs, and is rotated toward the operator to release squeeze pressure. Lever remains in position when released. Lever operates a three-way pressure regulating valve that controls both pressure and air flow to the track squeeze air springs. Maximum pressure is limited to 80 psi by a pressure regulator. Pressure is lowered by the operator during the passage of a body to allow the upper and lower tracks to be forced apart by the body as it passes through the DOHB. This control is located at the lower left and lower right of the console surface

DOHB Upper Frame Squeeze (forward, tracked DOHBs only): Stick-type pneumatic control lever that separates and closes the upper track from the lower track of the forward DOHBs. Lever is rotated away from operator to apply upper frame squeeze (i.e., closing the tracks by lowering the upper track assembly such that the cable is pinched between the upper and lower tracks).

Lever is rotated toward the operator to release upper frame squeeze (i.e., separate the tracks by raising the upper track assembly). Lever remains in position when released. Lever operates a four-way pressure regulating valve that controls both pressure and air flow to the upper frame squeeze cylinder.

Upper frame can be raised to a maximum distance of 12.75”. This control is located at the lower left and lower right of the console surface.

DOHB Squeeze Pressure (Aft, tire-pair DOHBs only): Stick-type pneumatic control lever. Lever is rotated away from operator to close the tire pairs and apply squeeze to the cable, and is rotated toward the operator to release squeeze pressure and open the tire pairs. Located at the lower left and lower right of the console surface.

Keypad and Monitor Display: Keypad and display are used to select and change various parameters and is located in the center of the console surface.

The following pages can be selected:

o Operational Setup o Dyno Table Setup o Temperature Monitoring and Setup o System Data Log o Maintenance o Select Screen Color o Alarm Summary o Cable Drum Drive Amps Alarm o Cable Drum Lube Cycle o Toggle Scale o Help o Shutdown

Key pad buttons are:

Speed Vernier Amp Meter Torque Limit Tension Set Alarm Set Units Count Zero Marker Tag Split Screen Alarm Acknowledge Home Enter Scrolling keys for up, down, right, left

3.5.2. Control Console Gauges and Readouts

The Control Console has the gauges and readouts given in the bulletized list below.

For each item listed, there is a port and starboard implementation of the item unless otherwise noted. Each item is present on both the forward and aft Control Consoles unless otherwise noted. Gauges on the port side of the console are the same as the gauges on the starboard side and vice versa.

Cable Drum Engine Caliper Brake Pressure: Analog gauge. Reading is

0.0 psi when the caliper brake is set and about 950 psi when the caliper brake is released (brake is set until hydraulic pressure is applied to release it). Located at upper left and upper right of console surface.

Cable Drum Engine Caliper Brake Charge Pressure: Analog gauge.

Reading should be about 950 psi. Located at upper left and upper right of console surface.

DOHB System Pressure (forward console only): Analog gauge. Reading is taken at the output of the hydraulic pump and should be about 3000 psi.

Located at upper left and upper right of console surface.

DOHB Replenishment Pressure (forward console only): Analog gauge.

Reading should be about 225 – 300 psi. Located at upper left and upper right of console surface.

Cable Drum Hour Meter (aft console only): Digital readout. On the aft Control Console, the cable drum hour meters are located at upper left and upper right of console surface. The forward control console does not have cable drum hour meters.

Cable Drum Tire Pressure: Analog gauge. This gauge shows the pressure applied to the air cylinder that pushes the drum tire onto the cable on the cable drum surface. Pressure is controlled in the 0-60 psi range, but is nominally set for about 10 psi. The gauge is collocated with the Cable Drum Tire Up/Down pneumatic control lever. On the forward console, this gauge is located at far upper left and far upper right of console surface. On the aft console, this control is located on the lower left and lower right of the console surface.

DOHB Hour Meter (Aft Control Console only): Digital readout. On the aft Control Console, the hour meter is located at the upper left and upper right of the console surface. The forward console does not have DOHB hour meters.

Ship’s Air Pressure: Analog gauge. Reading should be approximately 125 psi. Located at upper left and upper right of the console surface.

Regulated Air Pressure: Analog gauge. Reading should be approximately 105 psi. Located at upper left and upper right of the console surface.

DOHB Forward Dragboard Pressure (Labelled as “Drum-Side Drag Board” on the Aft Control Console): Analog gauge. Pressure can be in the 0-60 psi range, and adjusted to 15-20 psi for the passage of bodies.

This is the pinch pressure of the Roto rollers on the cable.

DOHB Aft Dragboard Pressure (Labelled as “Tank-Side Drag Board” on the Aft Control Console): Analog gauge. Pressure controlled to be in the 0-90 psi range, and adjusted to 15-20 psi for the passage of bodies.

DOHB Max Squeeze Pressure (Aft Control Console only): Analog gauge. This is the pressure in the air cylinders that open and close the tire pairs of the aft DOHBs.

DOHB Track Squeeze Pressure (Forward Control Console only): Analog gauge. Should read about 60 psi in high gear and 80 psi in low gear.

This is pressure being applied to the air springs in the forward DOHB track assemblies.

DOHB Upper Frame Squeeze Pressure (Forward Control Console only):

Analog gauge. Upper Frame Squeeze is nominally 80 psi. This is the pressure applied to the air cylinders that raise and lower the upper tracks of the forward DOHBs.

Fathometer Counter (Forward Control Console only): Digital readout with reset button and dimmer switch. Mounted on the upper outboard sides of the forward console turret.

3.5.3. Control Console Indicator Lights and Displays:

Console Power Available: Green indicator light located at bottom/center of the turret. Illuminated green when the circuit breaker for the console is closed (normal condition). There is only one Console Power Available light on the console.

Monitor Display and Keypad: Display and keypad are used to monitor, select, and change various parameters. See description in section 3.5.1 under the heading “Keypad and Monitor Display”. Cable drum speed (vs.

linear cable speed) is displayed here. Cable drum speed is based on motor servo output (not on Roto output). Located in the center of the console surface

Critical Information Display: Two monitors (One for port and one for starboard) mounted vertically in the front face of the console turret. The displays provide important information to the operators and others involved in cable lay operations. The data displayed includes:

Cable Tension (from the Dynamometer): numerical display Cable Tension Graph: graphical display Cable Speed (from the Roto): numerical display Cable Count (from the Roto): numerical display DOHB Tension (from the DOHB load cell): numerical display Run/Standby Indicator: text with green background window for

Run and yellow background window for Standby Payout/Pickup Indicator: text with blue background window Cable Count Markers: text with white background window Alarms, as follows:

o Holdback Tension alarm o Cable Tension alarm o Fault alarm o HPU Motor Overload alarm (forward Control Console only) o Temperature alarm:

The Critical Information Display is also presented on monitors in Mission Control, the port and starboard aft deck stations, and the port and starboard forward deck stations.

3.5.4. Miscellaneous Items

Siren: Serves as…