A Hi Rocky Relationship Is it Not? Water & Electricity!

A Hi Rocky Relationship Is it Not? Water & Electricity! 

Mixing water and electricity doesn’t usually end well, but marine engineering group Knud E Hansen A/S sees this rocky relationship as a challenge.

According to the Handy Shipping Guide, the company has designed a new ferry capable of making an entire voyage on electric power. 

Many shipbuilders are following suit, looking for ways to create more eco-friendly, sustainable seafaring options, but all-electric propulsion systems come with their own unique issues especially in terms of maintenance; how do engineers and operators make sure their boats stay afloat?

Slow & Steady:

The new ferry comes in at 35 meters in length with a beam of 11 meters, capable of carrying 170 passengers and 12 cars from Nolsoy island to Torshavn and back again on single battery charge. 

It can also withstand waves of up to three meters high and was designed with energy conservation in mind, featuring both batteries and a heat recovery system. 

It won’t win any speed records, since it’s nowhere near the 100 km/hr or better ships designed to run on liquid natural gas (LNG), but the ability to run entirely on battery power and survive a potentially rough sea crossing is no mean feat. 

Simply put, the Knud E Hansen A/S ferry speaks to function more than form—and eschews traditional fuel-based thrust for clean and reliable electricity. 

Emerging Issues:

According to a Hitachi white paper, on board electrical propulsion systems come with a number of advantages including reduced noise and the integration of both power and thrust systems, but they aren’t without issues: Electric systems come with a higher initial cost, increased energy conversion loss and large overall “footprint” owing to more total component parts. 

Water infiltration can cause serious issues, anything from short circuits to total system failure.For example, Cruise Critic reports that last year a Carnival Cruise ship was forced to cut out a port of call after an electrical transformer malfunction, which limited the ship’s overall speed. In the case of a complete electrical drive system, such a short could be disastrous.

The New Maintenance:

What does this mean for shipping companies and marine organizations? That in an era of clean power, new maintenance tools are needed. 

Marine Insight argues that on board engineers must now be able to tackle challenges such as electrical motor overhauling and shore power supply connection, in addition to having complete knowledge of an engine’s automation system. 

Scale deposits also pose an issue, potentially inhibiting electrical connections and leaving a ship dead in the water; regular and precise descaling is required to keep engines in top shape.

The rise of Eco-friendly ship propulsion systems means less waste and better ROI for companies, but also comes with unique maintenance challenges—even the best electric system generates no profit in dry dock. 

Dealing with Scale Deposits in Maritime Environments:

Within ocean water, dissolved solids lead to lime scale deposits in offshore equipment systems.

Build-up of lime scale (calcium carbonate) deposits present problems, particularly in water cooled engine jackets as well as heat ex changers for production of hot water service for crew and passengers. In ship waste water piping, scale deposits will block off lines and scale up tanks as well causing adverse effects on pump seals and valves.

Boilers, steam turbines and ballast systems are also vulnerable to scale build-up of and subsequent problems of overheat, shut down or blockages.

Lime Scale deposits in these equipment systems can be effectively remedied by the use of inhibited acid descaling. 

Descalers quickly dissolve calcium, lime, rust, lithium carbonate and other types of deposits from passages in water cooled or heated equipment as described.

Hi Sustainable Development in Industrial Ventilation

Sustainable Development in Industrial Ventilation

The best route to sustainable development in industrial ventilation, dust extraction and waste extraction is through the design of the system. Moving air requires energy. Heating air requires energy. In both cases the potential to save energy over a prolonged period through good design exceeds that from other current efficiency developments. Key points of design include:

• The air volume
• Fan efficiency and motor control
• Heat recovery and air make-up
• Training and maintenance

Air volume:

The broad spectrum of industrial ventilation and process extraction requirements means that a simple solution to sustainable development is not possible as, for the most part, each system is a bespoke design for the specific application. However, optimizing the air volume in each design is without doubt one of the best. Why?

• Air volume is directly proportional to power
• 10% less air means 10% less energy

How is this achieved? Often through the design of the hood, the position relative to the emission source and how much that source is enclosed.

The hood designs in the diagram above represent concepts as there will often be limitations on how far this design philosophy can be followed. However, it is clear to see that the position of the hood relative to the emission source and changing to an enclosure hood design, where practicable, could reduce the required extraction air volume significantly.

Fan efficiency:

The range of fans used across the application of ventilation and process extraction systems being typically considered could have efficiency from 50% to 80%. The fan efficiency compares the input energy to the work done and has a significant impact on energy consumption, for example,

• 40,000 hours operation broadly equates to 5-years @ 24/7 or 10-years @ 16 hours 5 days per week.

Based on 25kW aerodynamic energy requirement and an energy cost of 10p/kWh

• A 50% efficiency fan would consume 50kW/h, at a cost of £200,000.00
• A 75% efficiency fan would consume 33.3kW/h, at a cost of £133,200.00

If this is compared to the stated difference in efficiency between IE3, IE2 and IE1 motors of around 1.5-2%, at these motor ratings, then notwithstanding the possibly increased capital cost of selecting a higher efficiency fan, the energy savings through the 40,000 hour life cycle are vastly more significant than the initial costs. For more information on these motor standards, look up "Premium efficiency" on Wikipedia.

Motor control:

A related aspect to consider is the motor control where further energy saving possibilities exists although often not through the widely promoted speed or frequency inverter control.

In the first instance it is necessary to appreciate the laws of physics which apply to fans once installed in a system, assuming there are no changes to the ducting design.

• A 10% increase in the fan speed increases the volumetric airflow by 10%; however it requires a 33% increase in electrical power.
• Conversely, a 10% reduction in the fan speed reduces the airflow by 10% and reduces the electrical power by 27%. Just 5% speed reduction reduces the power by 14% so the savings through speed optimization can be significant.

However, a fan only absorbs the power required to do the work so, reducing the speed by 10% through a change in the drive belts may provide the saving at a modest investment. And as the power and motor size increase the savings become disproportionately greater.

% fan speed	80%	90%	100%	110%
% motor load kW	51%	73%	100%	133%

Table of motor power change with fan speed change

Example

• 37kW motor installed
• 32kW absorbed by the fan
• Energy cost per annum, 24/7 operation, is £27,955 @ 10p/kWh.
• Energy cost per annum, 16/5 operation, is £13,312
• 10% speed reduction means absorbed power becomes 24kW
• Assuming new drive belts and labour costs £500 (renewed annually anyway)
• Then first year net saving at 24/7 operation is circa £7,000, then £7,500
• And first year saving at 16/5 operation is circa £3,000, then £3,500.

Of course this is only applicable to a fan with a drive belt system fitted. An inverter controller will do the same, although the installation would cost more and an older motor may not be suitable for frequency variation control.

It should be noted there are certain advantages in using an inverter over the simple drive belt option including:

• Applicable to all fans; direct drive or belt drive
• Further speed change adjustments are easily made
• Little loss in motor efficiency at reduced speeds, whereas reduced power at unchanged motor speeds may reduce the motor efficiency
• Fan speed reduction is limited to reducing the rated motor power by 50%, when other factors may come into play
• Applications with frequent start/stop cycles

In designing an extraction system, it is prudent and not untypical to err on the side of caution and allow for a modest increase in airflow and hence fan speed on completion of the installation, which would have an impact on the power required, and to select a motor one size above the bare minimum required. However, once installed and commissioned at the correct speed, the load on the motor may be some way below the motor duty, although only drawing the proportionate electrical current. Often a case is made for inverters based on the installed power rather than absorbed power of the fan motor. It is fairly simple for an electrical engineer to measure the running current of the motor compared to the motor rated full load current (FLC) to provide an indication of the energy being used.

Air input:

Exhausted air must be replenished either uncontrolled through egress into the building or controlled through an air make-up supply. Whenever the external temperature is below the required internal level, heat energy will also be required. Whether or not the air entering is controlled or not is often dependant on the building size and relative amount of extracted air. As an example, 70kW of heat energy would be required for a 20OC temperature rise in 10,000m3/h and with a 5p/kWh heat energy, could cost around £10,000 per annum on a 24/7 operation.

More sustainable approaches to air make-up include controlled introduction which reduces draughts and may, in some instances, lessen the heat load required. Re-using exhausted and filtered air will have an operational cost however often shows a payback within two to three years. Although less efficient than returning filtered air, heat exchangers may also enable the re-use of exhausted heat energy when filtering in impracticable. Sources of "free" heat should also be considered, compressors and hot process areas being valuable sources on occasion.

Once into operation the levels of training and maintenance can have an impact on wasted energy, environmental emissions or waste materials requiring landfill disposal.

The main objective under these headings is achieving optimum performance. By definition energy, emissions and waste are then controlled. It is a difficult position to reach and maintain. As ventilation and process extraction, (dust or waste), provide secondary or support roles to the principle production process all too often they get a lesser level of training and maintenance. Performance may decline gradually over time and often goes unnoticed with some examples including:

• Incorrect low compressed air pressure or cleaning control settings resulting in lower filter cleaning efficiency. This increases pressure drop and hence the absorbed motor power, and may reduce extraction efficiency.
• Incorrect high compressed air pressure resulting in "puffing"- dust passing through the filter bags due to over-cleaning which increases the carry-over emissions and reduces the life of the filter bags through fatigue during the cleaning process.
• Incorrect fan belt drive adjustment leading to a loss of fan speed which could lead to lost production through a build-up in the ducting or lower efficiency in the extraction and a reduction in the control measure. Complying with COSHH/LEV guidelines may help to identify this, however with 14 month intervals there is a risk of long term deficiency.
• Operators using equipment in an unintended manner is all too frequent and often goes unrecognised. When this situation occurs, performance as a control measure, emissions to atmosphere and an increase in energy consumption may easily result.

In conclusion, sustainable developments in industrial ventilation and process extraction applications are not only achievable but may be quite significant because they are based on good system understanding, design and use. Interestingly many recent developments in energy efficiency are over shadowed by the improvements which may be possible through design, equipment selection and an on-going user training and maintenance programme. It is clear that any low cost installation advantage may be far from the lowest overall cost and soon offset as running and service costs are included over a modest period of time. Also, when using and maintaining the system as intended, the safety and protection provided will be optimised.

Hi Energy Tips – Process Heating & Dust Collector Explosion Protection

Process heating applications involving flammable solvent removal use large amounts  of energy to maintain safe lower flammable limits (LFL) in the exhaust air. National  Fire Protection Association (NFPA) guidelines require the removal of significant amounts of exhaust air to maintain a safe, low-vapor solvent concentration. If LFL monitoring equipment is used to ensure proper vapor concentrations, these guidelines allow for less exhaust air removal. LFL monitoring equipment can improve the efficiency of the solvent removal process and significantly lower process  energy requirements.

Free access to all NFPA Codes & Standards

Flammable solvents used in industrial production processes are typically evaporated in industrial ovens. Higher oven temperatures evaporate solvent vapors more quickly, allowing for faster production. Because the vapors are flammable, the exhaust air is discharged (along with the heat) to prevent the accumulation of the vapors in the oven.  As the oven temperatures increase, plants have to maintain higher ventilation ratios to  reduce the solvent vapor concentration levels and maintain the respective LFL.

For example, the NFPA ventilation safety ratio for batch-loaded ovens operating  below 250ºF is 10:1 and xylol has an LFL of 1%. Therefore, exhaust ventilation  needs to be added to the vapor until the solvent concentration reaches 0.1%, meaning  that the plant has to exhaust 10 times the amount of air required by the process to  meet the NFPA requirement. If the process operates above 250ºF, the required safety  ratio rises to 14:1, the LFL goes down to 0.07%, and the plant has to exhaust 14 times the amount of air required to keep the process from becoming flammable.

The non-uniform rate of solvent vaporization is one of the reasons why LFLs are so stringent. Solvent vaporization is inherently non-uniform mainly because of wall losses and load characteristics; this causes periodically high solvent concentrations in  the oven during the vaporization process. As a result, safe ventilation ratios are calculated using the theoretical peak needs of ventilation based on the highest vapor concentrations that can accumulate during the vaporization process.

LFL Monitoring Equipment

LFL monitoring equipment can reduce energy used in solvent removal by adjusting  the ventilation ratio according to the fluctuations in vapor concentration. The equipment continuously tracks the solvent extraction rate in real time and controls the rate of ventilation air based on real needs, thereby maintaining a safe ratio throughout the process. LFL monitoring equipment can employ several technologies including catalytic systems, infrared sensors, ionization systems and combustion sensors. LFL monitoring equipment has self-check functions and uses a calibrated test gas for periodic self-calibration. Because the vaporization process depends on the intake and exhaust air, linking the LFL controller to an adjustable speed drive on the exhaust system fan can improve process efficiency even further (damper adjustments can also be used).

Suggested Actions

Evaluate energy costs, process load and production requirements to determine the economic feasibility of LFL monitoring equipment.

Examine process energy requirements to confirm the flammable solvent load. If this 

load has changed over time, ventilation rates may need to be adjusted.

Using a booster oven can reduce the evaporation requirements in the main oven, thus reducing its exhaust requirements

Consider a professional outside evaluation to determine the technical and economic feasibility of additional improvements including reducing wall losses, installing heat ex-changers and fume incinerators, and recuperating exhaust air to capture the heat value of exhaust air.

Check all relevant NFPA and other applicable codes, regulations, and standards before adding equipment or making adjustments and consider consulting with an expert.

Example

The NFPA safety ventilation ratios are significantly lower when LFL monitoring equipment is used than when such equipment is absent. This lowers the energy requirements for the process because less air needs to be exhausted to keep the process from becoming flammable. For a continuous strip coating process requiring 46 gallons of xylol with a maximum oven temperature of 800ºF and ambient air temperature of 70ºF, the safety ventilation ratio is 4:1 without LFL monitoring equipment. This results in an exhaust requirement of 8,330 standard cubic feet per minute and energy consumption of 6.7 million British thermal units (MMBtu) per hour. At a cost of $8/MMBtu assuming a two-shift operation, this process costs approximately $214,000 annually. Installing LFL monitoring equipment would reduce the ratio to 2:1, halving the exhaust and energy requirements. Annual energy savings would total $107,000. With an installed cost of $12,500 for an LFL controller, the simple payback is very attractive at less than 1.5 months.

Understanding Dust Collector Explosion Protection

Many production operations generate combustible dusts that are highly flammable and explosive under the certain conditions. A combustible dust is defined as any finely divided solid material, 420 microns or less in diameter, that presents a fire or explosion hazard when dispersed and ignited in air or other gaseous oxidizer. Plastic, agricultural, food, pharmaceutical, carbonaceous and metal are some of the dusts that can be explosive.

Combustion occurs when dust and air mix together in the proper quantities in the presence of an ignition source. When combustion takes place in a confined space, an explosion occurs accompanied by an increase in pressure inside the confined space. If the confined space is strong enough, the explosion will be contained.

The National Fire Protection Association (NFPA) has issued a number of publications related to the prevention of industrial dust explosions. These standards and guides should be reviewed in detail if your dust control system handles combustible dust. Some of these standards have been made part of state safety codes and should be incorporated in your dust control system specifications and design. 

View The National Fire Protection Association Standards NFPA 654 Click Here

The purpose of NFPA 654, is the prevention of fire and dust explosions in the chemical, dye, pharmaceutical and plastics industries and to prescribe reasonable requirements for safety to life and property from fire and explosion and to minimize the resulting damage should a fire or explosion occur. Some highlights from this standard are:

1. A continuous industrial exhaust system shall be installed for processes where combustible dust is liberated in normal operations.
   
   
2. The industrial exhaust system shall incorporate a dust collector. Industrial exhaust system components including the duct-work and dust collector must be so constructed such that dust does not leak out of the system components when the system is shut down.
   
   
3. The dust control system shall comply with the requirements of NFPA 91, Standard for Exhaust Systems for Air Conveying of Materials.
   
   
4. Dust collectors for industrial dust control shall be located outside of buildings. Dust collectors may be located inside of buildings if they are located near an outside wall, are vented to the outside through straight reinforced ducts not exceeding 10 feet in length, and have explosion vents designed according to information in NFPA 68, Venting of Deflagrations. Some think that installing an explosion vent on a dust collector prevents an explosion. This is not the case. The vent relieves the pressure of an explosion. Dust collectors can be installed safely inside buildings only under one of the following conditions:
   
   
   
   
   
   
   
   * The dust collector is protected by an explosion suppression system meeting the requirements of NFPA 69, Explosion Prevention Systems.
   
   
   * The dust collector has an explosion relief vent meeting the requirements of NFPA 68, Venting of Deflagrations, and the vent is properly ducted in accordance with NFPA 68 through a nearby outside wall.

   Choosing Methods of Dust Control, Dust Collection, and Dust Explosion Protection

   

   
   

   It is not normally practical to build a dust collector strong enough to fully withstand the maximum pressure of a dust explosion. Other methods of protection are usually taken. Suppression or venting or a combination of both can be used to minimize the safety hazard and property damage caused by a dust explosion in the dust collector.

   
   

   
   

   The most important factor in determining the best method of dust explosion protection is a proper analysis of the dust. Samples of the dust should be tested by a qualified lab to determine dust explosion severity and the minimum ignition concentration for explosion. Tests following ASTM E1226, Standard Test Method for Pressure and Rate of Pressure Rise for Combustible Dusts, will provide details about your dust's explosive characteristics. It is important to note that the sample tested must be a sample of collected dust and not a sample of your powdered product. The explosion characteristics of the two are usually different with the collected dust being more explosive because of smaller particle size.

   
   

   

   
   

   You should also realize that changes in powdered product composition, particle size or moisture content, and, as a result, the collected dust may affect dust explosion severity and the minimum concentration for explosion. Don't use someone else's test data. Analyze your own test information to set correct specifications. Test the collected dust, not the product powder, periodically after installation to confirm that safe conditions continue to exist. If conditions have changed, the explosion suppression system and/or explosion venting may need to be upgraded.

   Dust Explosion Suppression

   NFPA 69, Explosion Prevention Systems, 1992 Edition, defines dust explosion suppression as the technique of detecting and arresting combustion in a confined space while the combustion is in its incipient stage, thus preventing the development of pressures that could result in an explosion. Explosion suppression systems will be successful in cases where the suppressant can be effectively distributed.

   
   

   VIEW NFPA 69: STANDARD ON EXPLOSION PREVENTION SYSTEMS cLICK HERE

   
   

   

   
   

   The design of every dust explosion suppression system must be thoroughly analyzed with respect to the equipment to be protected, dust characteristics, type and location of detectors, suppressant chemistry and the installation and operation of the dust explosion control system and the related process. Although some explosion suppression systems are more expensive to install and to maintain as compared to explosion venting, suppression systems may be the only choice when venting cannot be properly installed.

   There are three dust explosion suppression system manufacturers in the United States who can advise you on applying dust explosion suppression systems to your dust collector as part of your industrial dust control system. Your specification must provide enough details so that the suppression system manufacturer can select the proper system configuration.

   
   

   

   Dust Explosion Venting

   NFPA 68, Venting of Deflagrations, applies to equipment or enclosures needing to withstand more than 1.5 psig pressure. Most dust collectors need additional reinforcement for that capability. The maximum pressure that will be reached during an explosion will always be greater than the pressure at which the vent device releases. NFPA 68 calls for a pressure differential of at least 50 lbs./ft2 or 0.35 psi between the vent release pressure and the resistive pressure of the dust collector (enclosure). This NFPA guide lists the following basic principles that are common to the venting of deflagrations. You should become familiar with these principles so that you can correctly specify the conditions the dust collector and explosion vent must satisfy.

   
   

   View NFPA 68: STANDARD ON EXPLOSION PROTECTION BY DEFLAGRATION Click Here

   

   
   

   
   

   1. The vent design must be sufficient to prevent deflagration pressure inside the dust collector from exceeding two-thirds of the ultimate strength of the weakest part of the dust collector, which must not fail. This criterion does anticipate that the dust collector may deform. So do expect some downtime with the dust control system after an explosion.
   2. Dust vent explosion operation must not be affected by snow, ice, sticky materials or similar interference's.
   3. Dust explosion vent closures must have a low mass per unit area to reduce opening time. NFPA recommends a maximum total mass divided by the area of the vent opening of 2.5 lbs./ft2.
   4. Dust explosion vent closures should not become projectiles as a result of their operation. The closure should be properly restrained without affecting its function.
   5. Vent closures must not be affected by the process conditions which it protects nor by conditions on the non-process side.
   6. Explosion vent closures must release at over pressures close to their design release pressures. Magnetic or spring-loaded closures will satisfy this criterion when properly designed.
   7. Explosion vent closures must reliably withstand fluctuating pressure differentials that are below the design release pressure.
   8. Dust explosion vent closures must be inspected and properly maintained in order to ensure dependable operation. In some cases, this may mean replacing the vent closure at suitable time intervals.
   9. The supporting structure for the dust collector must be strong enough to withstand any reaction forces developed as a result of operation of the dust explosion vent.
   10. Industrial exhaust system duct-work connected to the dust collector may also require explosion venting.

   
   

   
   

   Dust Explosion Vent Ducts

   Dust collectors that are vented for dust explosions should be installed in an outdoor location with vents directed safely away from persons and property. When there is no alternative to locating a dust collector inside a building, vent ducts should be installed to safely direct the vented flames, gases and debris from the dust collector to the outside of the building.

   
   

   

   
   

   You must be aware of the fact that adding a vent duct to a dust collector will change the conditions that the dust collector will be exposed to during an explosion. The use of explosion vent ducts will significantly increase the pressure in the dust collector during venting. The vent duct must have a cross-section at least as great as that of the vent itself. A vent duct with a cross-section larger than that of the vent will result in a smaller increase in the maximum pressure produced during venting. NFPA 68 includes a graph showing the increase in over pressure (within the dust collector) due to the use of vent ducts as a function of straight duct length.

   
   

   Dust explosion vent ducts should be kept under 3 meters in length and as straight as possible. Any changes in vent duct direction increases the over pressure developed during venting. In all cases, the vent duct must be made as strong as the dust collector. The vent duct configuration must be submitted to the dust collector manufacturer with the dust collector specification for proper design.

   Dust Control Explosion Prevention System Inspection and Maintenance

   Inspection and maintenance of suppression and venting systems should be done in accordance with the manufacturer's recommendations and NFPA standards.

   
   

   For dust explosion suppression systems, NFPA 69 states that suppression systems shall be thoroughly inspected and tested at 3-month intervals by personnel trained by the system's manufacturer. In the event of suppression system operation, all components shall be inspected, replacement parts installed if necessary, and the system tested prior to restoration to full operating condition. See NFPA 69 for more details.

   
   

   

   
   

   For dust explosion vents, NFPA 68 calls for visual verification that the vent closure is in place and able to function as intended. This is done by ensuring that the vent closure is properly installed, that it has not operated or been tampered with, and that there is no condition that might hinder its operation. Maintenance includes preventive and remedial actions taken to ensure proper operation of the vent closure. See NFPA 68 for more details.

   
   

   

   
   

   
   

   An important activity often neglected is the periodic sampling of the collected dust for an explosibility determination. If the process has changed so that the particle size or shape of the collected dust has changed, dust explosibility may be affected. If the chemistry of the processed product has changed, dust explosibility may again be affected. If the collected dust shows an increase in explosibility above the level for which the installed explosion suppression or venting system was designed, immediate action must be taken to correct the deviation from the design condition.
   
   

   Product Highlight

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Exactly what you need for dust, fume & mist collection, Donaldson Torit's broad range of collectors and filters gives the customers interviewed in this video exactly what they need for dust, fume and mist collection. 

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