With implementation of the US Coast Guard Subchapter M regulations just around the corner, owners of uninspected towing vessels are scrambling to understand and prepare for what’s to come, even while the rules are still evolving. Among the proposed changes for towing vessels are standards for propulsion and steering controls that closely resemble the existing standards for fully inspected offshore vessels. One component of the rules would require certain vessels to be equipped with auxiliary steering capabilities that essentially dictate a completely redundant and independent set of steering machinery and controls.
If this component of the new regulations seems unprecedented or unreasonable, consider this – long before the advent of Subchapter M, Louisiana-based Engine Monitor, Inc. was building and installing fully redundant steering systems with significant safety and reliability enhancements for vessels. EMI has worked alongside the U.S. Coast Guard, ABS and other regulatory bodies, setting the standards for safety and reliability for steering, propulsion controls, machinery alarms and related vessel systems.
According to EMI’s Larry Dulcich, “Installing a fully redundant steering system should be an easy decision for the modern boat operator. Most vessels have two or more generators and main engines, providing redundancy in those critical systems. Redundant steering capabilities were not originally prioritized, because using the two main engines to “twin-screw” a vessel was previously considered a sufficient measure. However, stricter safety standards, lower average pilot experience, congested waterways and productivity demands are justifying back-up steering equipment.”
Early Mechanical Systems Adapt to Hydraulic Power
The original “remote” steering capabilities relied on direct mechanical actuation via levers, gears, pulleys and cables. Through considerable effort by the pilot (and constant maintenance by the engineer), the task of steering was accomplished. The major evolution occurred with the advent of hydraulic steering systems, affording very high steering torque with little effort by the pilot. Large control valves divert pressurized fluid to stroke the steering rams back and forth, thereby rotating the rudder stocks. Control valves are actuated by mechanical linkages that are painstakingly routed from the pilothouse to the steering compartment. In this type of system, mechanical linkage is also used to compare the actual rudder angle to the angle of the sticks, reflected by the main steering control linkage.
The operation of a well-designed and properly maintained mechanical/hydraulic steering system can be very smooth, because the valve opening (and thus the flow rate) varies with the amount of effort that the pilot places on the steering sticks. However, there are many downfalls to mechanical systems, including – but not limited to – the need for regular adjustment and tightening of the linkage, regular lubrication, protective guards to prevent crew members or misplaced objects from interfering with the linkage mechanism, duplicate linkage mechanism and control valves and restrictive location of the mechanically operated hydraulic valve.
Replacing Mechanical Linkages
These numerous challenges dictated improvements in electrical solenoid technology, allowing hydraulic valves to be reliably operated with electrical signals. Ken Cognevich, founder and owner of EMI, said recently, “The electrical steering business was a natural fit for EMI. Like the alarm and monitoring systems we made back then (and still make today), steering systems have a direct impact on vessel safety and require a high degree of reliability.” Eventually, EMI began to fit steering sticks and rudder stocks with electrical contacts and potentiometers. Shipyards were instructed in replacing the mechanical linkage assemblies from the pilothouse and rudder stocks with electrical cable runs. EMI designs and builds every component of their marine steering systems, including the interface electronic boards, meters, control panels, steering lever assemblies and hydraulic power units. The early electro-hydraulic systems were fitted with “on/off” solenoid valves; a compromise of performance and cost that worked well for small to medium sized vessels. However, for larger vessels, the bigger steering rams required higher flow rates, and the rapid shifting of the on/off solenoid valves did not always provide for adequate “cushioning” to prevent abrupt starts and stops. As a result, larger vessels continued to favor the smoother operating mechanical/hydraulic systems. Eventually, improvements in hydraulic valve technology gave rise to cost effective, reliable “proportional” solenoid valves with flow metering characteristics that provide smooth starts and stops. This allows installation of proportional electro-hydraulic steering systems on larger inland and offshore vessels, providing smooth and responsive steering, without the hassle of mechanical linkages.
EMI’s SmartSense Technology Reduces Electrical Load
Another significant improvement to marine steering is EMI’s “SmartSense” technology. Larger workboat steering rudders require a significant amount of torque during hard maneuvers in heavy currents or at higher speeds. Depending on rudder size and vessel speed, this torque can dictate a 60 horsepower or larger electric motor. With marine generators often taxed to their limit, simply starting these electric motors can cause an electrical overload. With EMI’s SmartSense technology, the ability to handle those peak torque requirements with significantly less power is accomplished by modulating the rudder travel speed, but only as needed to prevent an overload. Some of the benefits of electro-hydraulic steering systems include lower installation costs, high reliability, improved calibration, more precise rudder movement and the flexibility to add special steering modes and control features. Electro-hydraulic steering systems are available with electronic interfaces for modern autopilot and dynamic positioning systems. Proportional type systems with EMI’s SmartSense technology can significantly reduce electrical load for larger offshore and inland vessels. According to owner Ken Cognevich, “EMI has installed electro-hydraulic steering systems on nearly one thousand vessels, including workboats, yachts and military vessels. We have standard designs, but we can custom tailor a system for virtually any application.”
(As published in the September 2012 edition of Marine News - www.marinelink.com)