Gems Sensors - PRODUCT NEWS

Sensors for shipping

With the effects of marine failure and interrupted schedules potentially more costly than ever, the need to streamline services with sensor technology is clear. Mike Powers, Product Marketing Director for Gems Sensors and Controls, discusses how the latest sensor technology can protect and optimise shipboard systems in a variety of marine applications.

A lack of preventative maintenance is one of the primary causes of degradation and failure in marine systems and, in today’s industry, with the high tolerances of modern technology, the need to eliminate the problem is perhaps more critical than ever if engineers are to realise cuts and extend the service life of components. One way to achieve this is through the application of modern sensor technology. While such tools may have been beyond the expertise or awareness of ship owners and engineers in the past, the latest sensor technology can be simple and cost-effective to apply.

The sensors used to measure criteria such as pressure, level and flow are extremely robust, yet provide high levels of accuracy under often extremely demanding environmental and mechanical conditions. In addition, the ever growing need for ship operators to reduce costs means that machine systems need to run for longer, with less maintenance, so long term reliability combined with factors such as low hysteresis and zero drift have become essential.

Traditionally, many of the tasks now managed by sensors have been achieved manually, requiring a substantial amount of time and resources, and where problems that could have been avoided by installing appropriate sensors become severe enough to warrant docking the vessel so that work can be performed, costs can escalate quickly. In addition to these direct expenses incurred by unscheduled maintenance, indirect costs can also arise from the interruption of schedules.

Sensors can defend shipboard systems against any number of problems, including wear, mechanical damage and even changes in the operating environment, such as fluctuations in temperature. For example, the fact that space is always at a premium on marine vessels causes heat dissipation problems where the ambient temperature is extremely low, causing extreme thermal cycling in control systems. However, cooling systems incorporating sensors can ensure that electronic equipment stays within specific operating temperatures to maintain reliability in ever more arduous environments. Regulating systems using sensors also reduces unnecessary wear to other components, which, in turn, leads to less maintenance. Consequently, the performance and service life of components is increased, while the operating and maintenance costs are reduced significantly.

Although advances in engineering have led to the development of more robust components, extending the service life of shipboard systems, these components alone are unable to minimise the need for maintenance sufficiently. Only if these latest technologies are combined with modern sensor technology to provide continuous monitoring and measurement can unnecessary wastage of time and costs can be achieved.

Pressure, level and flow are all essential criteria that have to be measured in a wide range of shipboard systems, from bilges, fuel and water tanks, to alarm, hydraulic and diesel equipment. Measuring pressure level and flow in vital shipboard equipment is an essential process that is increasingly gaining in popularity, although the equipment and techniques used are not always widely understood. This may be because while sensing has become established among the larger operators, such as military and cruise ships, it has not yet penetrated quite so fully to smaller classes. Nevertheless, it’s worth bearing in mind that advances in the manufacture of these devices, and the range of challenges that have been met by the designers and engineers of marine sensors, have resulted in a range of extremely cost-effective off-the-shelf solutions to common problems.

Leading manufacturers have recently initiated a number of significant advances in pressure sensing technologies that ensure robust and reliable measurement of both high and low frequencies, with low hysteresis characteristics and excellent levels of accuracy over a wide temperature range. Additionally, these sensors can be packaged in a compact stainless steel sensor housing sealed against moisture, dust, oils and other contaminants. This is particularly important in the marine sector where operating conditions are subject to a far wider range of variables, as opposed to many other industries where plant or factory operations remain largely static.

The latest developments in pressure sensor construction have yielded excellent results and ensured that these components function accurately over extended periods, overcoming such challenges as contamination and extremes of temperature. Pressure transducers, for example, are currently used to perform a wide variety of tasks throughout the marine sector, offering dependable operation in particularly aggressive conditions. Today’s pressure transducers can withstand everything from high-pressure hydraulic spikes originating from pumps and valves to extremes of temperature, mechanical shock and vibration.

A pressure transducer converts pressure, typically that of fluid or gas, into an electrical signal and delivers a continuous output of electrical signals that correspond to the precise pressure status. Pressure sensors contain a thin sealed sensing element or diaphragm that is in direct contact with the pressure media. Displacement of the diaphragm thus causes the strain gauge to flex, either in compression or under tension, with the electrical output being directly proportional to the pressure or vacuum applied. Output from the sensor is connected to on-board electronics, with the entire unit being contained in a compact and sealed stainless steel housing.

Pressure transducers are typically used to handle liquid interfaces, high temperature environments and high-pressure fluids. In equipment such as propulsion units and gearboxes, the monitoring and management of oil, temperature and clutch pressure with transducers can make a major difference to performance and overall efficiency.

Gems Sensors and Controls manufactures a range of highly versatile and resilient pressure transducers using CVD, including the 2600 Series, a submersible sensor offering stability and accuracy in a variety of enclosure options rated at IP65 and above. For marine applications, the Gems 5000 Series transducer is cased in duplex stainless steel, providing a tough resistance to the corrosive effect of sea water, and has provided a highly efficient solution on board ship in low pressure applications, such as gauging large but shallow tanks.

Level sensing can also deliver a valuable level of defence for shipboard systems provided the design addresses the specific needs of the application. For example, level sensing components for the bilges require robust resistance to contamination in compact form. The best of today’s components have protective housings that maintain reliable operation even if there is solid matter in the bilge water. These components can now be obtained with vulcanised cables, offering level switches with an ingress protection rating of IP67 for use as submersibles. These switches deliver a powerful solution for marine engineers when point level sensing is required in inaccessible areas of tanks. The LS-270-E level sensor from Gems Sensors and Controls provides all of the qualities described above plus a float that pivots with changing liquid levels, displacing a shuttle that magnetically actuates a hermetically sealed switch within the unit.

Exceptional durability is also available in flow switches for marine applications. The large flow paths now designed into flow sensors keep pressure drop low; they also enable detection to be effectively carried out where liquids, including oil, are being handled in high volumes, such as within lubrication, cooling or process applications. To enable switch actuation at the desired flow rate, flow paddles can be trimmed during installation; this allows the paddle of the switch to pivot and move out of the liquid path as flow increases, keeping pressure drop to a minimum regardless of pipe size.

Pressure, level and flow are all essential criteria that have to be measured in a wide range of shipboard systems under often extremely demanding environmental and mechanical conditions. With the effects of marine failure and interrupted schedules potentially more costly than ever, the need to streamline services with sensor technology is clear. By adding this level of protection to shipboard systems, vessel owners and maintenance engineers alike can reduce boost efficiency, which ultimately can help to improve operating margins.

About Gems Sensors & Controls
Founded in 1955, Gems is a preferred supplier to thousands of OEM companies across a broad range of industries throughout the world due to its extensive application knowledge, innovative sensor and miniature solenoid valve designs, and customer centric approach to problem solving to meet customer-specific needs. Gems Sensors and Controls is a leading global manufacturer of: liquid level, flow, and pressure sensors; solid-state relays and barriers; liquid and pneumatic miniature solenoid valves; and pre-assembled fluidic systems with facilities in North America, Europe, and Asia. Gems Sensors & Controls is ISO 9001, ISO 13485, UL, and CE certified.

August 2013

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