Hydraulic Power and Control
Hydraulic Power is perhaps the best choice of equipment power on a ship. Hydraulic power is clean, quiet, safe, easily routed through the vessel and reliably controlled. Hydraulic power supplies the steering system, trim stabilizers, bow and stern thrusters, warping capstans and anchor windlass, passerelle, accommodation stairway, shell-doors, hatches, davits and cranes. Is there any doubt that hydraulic power is the first choice of equipment designers and shipyard engineers when selecting the type of power equipment used in their builds?
Nautical Structures has been utilizing hydraulic power in the design of our equipment for over twenty years. Over this period of time we have learned what works well, and what doesn't. We have focused the design philosophy of all of our equipment towards hydraulic control; eliminating much of the need for unreliable electronic controls by innovating specialized control manifolds, sequencing and supply-management valving to control our equipment. Nautical Structures has developed both simple and complex central hydraulic power units for many well-known shipyards, providing our engineering experience in the interface of multiple hydraulic components.
Hydraulic Power Units
Nautical Structures supplies hydraulic power units in sizes from 1-Hp to 60-Hp (.74-kW to 45-kW). Nautical Structures' Hydraulic Power Units (HPU) are supplied with a properly sized steel reservoir tank, ensuring appropriate fluid volume is available in the system for the intended application. Fluid quality is the key to a reliable hydraulic system. Most failures in a hydraulic system can be traced back to fluid contamination in the system. For this reason Nautical Structures takes a multifaceted approach to fluid / system cleanliness. The hydraulic power unit is assembled with a proper suction strainer (boulder-stopper) in the reservoir. A second high-pressure filter housing with a 3-micron filter element is plumbed into the pressure (supply) side of the system. A low-pressure filter housing with a 10-micron filter element is plumbed into the return side of the system to filter the fluid as it returns back to the tank. Nautical Structures processes all of the hydraulic fluid used in our hydraulic systems through a filter cart prior to being used in a hydraulic system. Fluid samples are taken and analyzed to ensure that each batch of fluid processed meets the stringent requirements of ISO fluid quality.
The Hydraulic Power Unit is configured with the specified motor-pump assembly required to power the equipment to established performance standards. Most power units are configured with a TEFC motor in horsepower ratings from one to sixty. A variety of pump-types may be used, depending upon the application / types of components being powered. Fixed-displacement gear pumps are common, and typically used in simple one-component applications, or used in an Emergency Hydraulic Power Unit (EHPU) configurations. Variable-displacement piston pumps (with or without load-sensing) are used in power units where higher demands are anticipated. A load-sensing variable displacement pump is the most energy efficient type; the pump may be set to utilize the full electric power supply available to power the unit. Most power units are configured with the pump/motor assembly mounted on top-of or adjacent-to the reservoir tank. Alternatively the pump may be mounted inside of the reservoir tank, potentially reducing noise and allowing for a more compact configuration. Noise and vibration control is a critical design element of any well-engineered hydraulic system. Mounted improperly vibration and noise may be transmitted through the vessel along the hydraulic lines. For this reason Nautical Structures offers appropriate mounting frames and vibration isolators to reduce noise and vibration in the system.
Emergency Hydraulic Power Supplies
Alternative sources of hydraulic power are now requirements of MCA-LY2 and SOLAS equipment configurations. Per LSA Code 6.1.1.3, “A launching appliance shall not depend on any means other than gravity or stored mechanical power which is independent of the ship’s power supplies to launch the survival craft or rescue boat it serves in the fully loaded and equipped condition and also in the light condition”. This requirement may be resolved with a dedicated diesel-powered generator supplying electrical power through the ship’s emergency electrical power buss (Requires Flag State approval), or with a battery-powered Emergency Hydraulic Power Unit supplied with a dedicated bank of batteries. Nautical Structures has been in the vanguard of EHPU development for use in the Luxury Yacht Industry. Currently we have multiple configurations of 24V DC power units in a variety of horsepower ratings available to power the life saving equipment. In applications where we supply a stand-alone EHPU we have developed a very specialized switching-manifold to automatically switch between the primary source of hydraulic power and the emergency source of hydraulic power. It does this with hydraulic porting that senses the source of power and automatically sends return fluid to the current power-source. This has eliminated potential valve-configuration mistakes by the crew when switching manually between sources, a common problem in most other emergency switching configurations. A high-fluid level sensor ensures that should the system be switched during normal operation of the crane, the small reservoir tank in the emergency system can not be overflowed. In a typical EHPU configuration Nautical Structures will supply the power unit(s), mounting frame, switch panel, AGM-type batteries and a battery conditioner. Alternatively the 24V DC EHPU may share the same reservoir as the AC-powered primary power unit. This configuration simplifies the plumbing of the system and combines all of the components into a common unit.
Manifolds and Valving
Supplying hydraulic power is only one element of hydraulic power control. Because of the versatility of hydraulic energy, pressure and flow may be varied to accomplish a wide variety of tasks. Nautical Structures has designed and engineered a variety of manifolds to control hydraulic equipment. These components assembled with a 24V DC power unit will power and control a hydraulic transom-lift. A very specialized manifold assembled with a power unit brings all of the many functions and control elements of a high-end passerelle into a single assembly, enhancing the reliability and serviceability of the system. Our manifolds and controls are capable of directing power and control to most ship-board hydraulic equipment; the basic elements of a ship's central hydraulic system.
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| Load Sensing Hydraulic System |
Load sensing is a term used to describe a type of variable pump control used in open circuits. It is so called because the load-induced pressure downstream of an orifice is sensed and pump flow is adjusted to maintain a constant pressure drop (and therefore flow) across the orifice. Click here to learn more about our Load Sensing Hydraulic System.
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