Cement companies appreciate MacGregor self-loading/unloading systems
Flexible design and a range of solutions allow Cargotec to maintain its position as a supplier of customized, energy-efficient, environmentally friendly cement handling systems.
When designing MacGregor cement handling systems, Cargotec can take advantage of a full range of mechanical and pneumatic conveyors, combined in the best manner to deliver
the specified functions and the required cargo handling rate. At the end of January this year, Cargotec received an order
from Shin Yang Shipping for MacGregor cement self-loading and unloading systems to be installed on two 7,000dwt barges being built by the Shin Yang Shipyard in Miri, Malaysia. Delivery is scheduled for September 2011 and the barges will trade on two
Malaysian routes linking Kuching with Sibu and Miri. The cargo owner is a cement manufacturer based in Sarawak, CMS Cement Sdn Bhd.
Pankaj Thakker, sales manager for Cargotec Marine Selfunloaders says the pneumatic systems will have rated capacities of 300tph (tonnes per hour) for loading and 250tph for unloading. “Shin Yang Shipping chose this system from Cargotec because it is a simple, well-proven concept and the company recognizes that Cargotec has a solid track record in this field. In addition to simplicity and reliability, the system is very environmentally friendly, featuring dust-free operation and low power consumption.”
 
MODULAR CONCEPT ENSURES FLEXIBILITY
Thakker says the modular concept employed in Cargotec’s MacGregor cement handling systems offers shipowners unrivalled levels of flexibility, allowing vessels to perform at high capacity rates in virtually any existing port facility, as well as those planned for the future.
“Operational circumstances change and such changes may be planned or forced by factors such as market fluctuations. Our systems are carefully designed to be able to accommodate future alterations, add-ons and upgrades without the need to undertake major modifications to the original solution. The ship owner therefore benefits from substantial cost and time savings if it does become necessary to modify a system. For example, an existing cement carrier can generally be modified to cope with a change of receiving system from that for which it was originally intended.”
In addition to providing quality hardware, MacGregor can also take the strain out of cargo operations by way of sophisticated electrical control systems to conduct the loading and unloading operations.
“Cement loading rates can be as high as 1,600tph and this puts heavy demands on a ship’s ballast system. Cargotec can
supply MacGregor fully automatic, regulated distribution systems ensuring the correct loading sequence to keep the ship in a level and stable condition at all stages of the loading process.
“Cargotec’s intelligent MacGregor control systems can deliver automatic operation supervised by just one operator, even when handling different grades of cement at high capacities. Systems can also be equipped with remote diagnostics, which MacGregor engineers can access via modem.”
 
APPLICABLE TO NEW BUILDS AND CONVERSIONS
Cargotec’s cement handling solutions are equally applicable to new buildings and conversion projects. General bulk carriers are very suitable for retrofitting cement handling equipment and any size of second hand bulk carrier can quickly and easily be converted into a self-loading and unloading cement carrier at a much lower overall cost than a new ship.
Thakker says this is a very popular option and, since 1995, it has represented about 30% of MacGregor cement handling systems installations. Single hull oil tankers also present conversion opportunities. “Shipowners must take into account a range of factors when
choosing between newbuilding and conversion. These include the price that second-hand ships can command along with the availability of shipyards and lead times for machinery supply. It takes a minimum of 18 months from contract date until a new build enters service, while a conversion requires only about three months off hire. This is achieved by careful planning and the prefabrication of steel structures before the vessel enters the shipyard.
“The nature of the intended trade is important and has direct influence on the financial commitment, bearing in mind that a new build self-loading and unloading cement carrier will cost about twice as much as purchasing and converting an existing bulk carrier. A new build benefits from lower operational costs
and limited maintenance requirements and is generally the better option for a long-term shipping contract that allows a longer write-off time. A conversion project may be more appropriate for a shorter contract period, offering lower initial cost allowing a shorter write-off time. Cargotec can provide valuable advice based on experience and market knowledge to help ship owners make the right choice for their specific requirements.”
 
LONG-TERM COMMITMENT
As with all sectors of Cargotec’s commercial activities, the company puts great emphasis on the importance of effective long-term product support, maintenance and service. “The MacGregor Onboard Care agreement is designed to meet a company’s strategic and tactical needs. It aims to reduce costs and improve the return on investment,” Thakker says.
 
 
Carlsen cement systems ensure cost-effectiveness and reliability
Carlsen Bulk Handling Systems BV is part of the Carlsen Group of Companies.
Carlsen is a pioneer and a leading expert in the field of maritime and port side dry bulk handling equipment. Its extensive portfolio includes a wide range of equipment and systems to handle cement.
The company designs and engineers its own key components, adding other proven technology from leading manufactures, to form completely integrated dry bulk handling systems.
With more than 44 years of design and engineering experience in equipping dry bulk ships, barges, supply vessels, harbour loading and unloading equipment, drilling rigs and floating terminals, Carlsen can supply numerous excellent references from new building and conversion projects from around the world.
The Carlsen dry bulk handling and management systems delivers cost effective, reliable and proven solutions that are economical, simple to operate and maintain.
Whether the customer plans to build a new ship, a drilling rig or convert an existing ship, equip a supply vessel or simply needs spare parts, Carlsen is up to the challenge.
Carlsen has over the last 44 years been a reputed supplier in the cement distribution and cement handling field. During these years the company has become more and more specialized in the seaborne transportation between factories and cement terminals, which also involved Carlsen in the supply of loading equipment and cement terminals. Carlsen offers equipment and expertise for the complete chain for cement distribution by sea,
supporting its customers proposing suitable arrangements to meet their requirements.
 
BULK CEMENT CARRIERS
Carlsen equipment is suitable both for new buildings and conversions from standard bulk ships to cement carriers.
Carlsen offers pneumatic systems as well as mechanical systems.
1) The Carlsen DR Pump System
Carlsen’s most well-known and the basic system for self- unloading cement carriers is the Carlsen DR (Double Reloader) Pump System. This system is not particularly new. The principle remains the same as when originally introduced 44 years ago, only that basically all components and the control system have been substantially upgraded and more and more refined over the years in order to get higher unloading rates and less maintenance without investing more money.
2) The Carlsen Screw Conveyor System
In this type of self unloading systems, instead of sucking the cement from the low points in the holds, vertical screw conveyors are used to bring the cement up above deck level. These are then in principle replacing the suction pipes of the DR pump system and standing centric in the holds.
3) The FK Pump System
The oldest cement pump system on the market is the FK Pump System. This type of system is a pure pneumatic self unloader system, where one as standard uses air slide channels of a box type for installation on top of the sloping tank tops in the holds, for feeding of the cement directly to their respective cement pumps.
4) The Carlsen CSP System
Naturally, Carlsen also has a pneumatic system of ‘suction-only’ type. This is called the CSP (Continuous Suction Pump) System. The cement is sucked from the fluidized holds into a special filter vessel (the CSP- tank), from where the cement is discharged mechanically via a special screw conveyor at its bottom instead of pneumatically as in case of the DR-Pump System described before.
This system is useful when there is no requirement to pump the cement onwards to silos and all cement is unloaded by gravity directly on the quay, for example into trucks or onto a belt conveyor.
5) The Carlsen 3-tank System
The concept of this system is such that instead of having regular DR-tanks, where each tank has its own filter, a separate suction tank with the filter inside will be installed on top of two or more standard blow tanks in the central unloading machinery room onboard the ship.
 
BULK CEMENT BARGE CARRIERS
The Carlsen suction unloading system has been very successful when barges are used for transportation, especially where several barges are used between factory and terminals. The barge itself has very limited equipment on board, and the unloading machinery is installed on the shore side.
 
CEMENT TERMINALS
Carlsen designs and delivers complete equipment and systems for smaller terminals, including truck loading and bagging equipment. These are usually in combination with a Carlsen suction unloading system for bulk cement barge carriers.
 
CEMENT LOADERS
Carlsen delivers cement loaders to be installed at the factory side. It offers both simple types, with low to medium loading capacity, as well as heavy-duty loaders with high loading capacity.
 
AN ONGOING CEMENT CARRIER PROJECT
Carlsen has worked with design and preparation for the supply of the complete cement handling equipment for Construction Number 371 of Juliana Shipyard a now under construction. This
is a middle size modern cement carrier. The initial yard was ‘Factorias Juliana’ in Spain, but the vessel was finished at ‘Astilleros de Santander SA’. The vessel is planned to be handed over to the owner May 2011.
The dry bulk handling system for this newbuilding of a 10,600dwt cement carrier is a combined pneumatic and mechanical self-loading and self-unloading system. The loading capacity is 1,000tph (tonnes per hour), achieved by a combined screw conveyor and airslide type of system. The unloading capacity is 600tph by a pneumatic and a mechanical system.
The cement carrier is a 10,600dwt vessel with eight holds. The vessel will be equipped with a mechanical hold unloading system combined with a pneumatic discharge system for blowing the cement to the shore-based storage facility. The loading system consists of central feeding airslides with one horizontal screw conveyer going forward and one going aft. From these, one airslide goes to the centre of each hold. Inside each hold, a further two open type airslides are installed for further distribution inside the hold.
The mechanical hold unloading system consists of an inclined fluidization bed in each of the holds, plus four vertical screw conveyors and blowers. From the vertical screw conveyor outlets, the cement flows into horizontal screw conveyors installed on top of the deck to two buffer hoppers in the centre of the vessel. From these hoppers the cement drops by gravity into two FK pumps. By means of compressed air, the cement is conveyed via shore pipes to the storage silos
The operation of the complete loading and unloading system is fully automatic and operated from the control panel.
 
OTHER ONGOING INSTALLATIONS
During the recent years and right now Carlsen has also delivered a substantial number of various types of bulk handling systems for the offshore industry for both supply vessels and drilling rigs. The construction of these supply vessels and drilling rigs are spread to different ship-owners and shipyards all over the world
 
ADAPTING TO DIFFERENT SHIP SIZES, CONVEYING DISTANCES TO SILOS AND UNLOADING RATES
All the available systems blow cement (or similar powders) to silos using air compressors, with an optimized flow calculation as its base. The above basic system differences will remain.
A longer distance requires larger size compressors to obtain
the same unloading rate and vice versa. At the same time the pipe diameters have to be dimensioned
accordingly to achieve the lowest possible power consumption. The pipe diameters can be stepped up on the way from ship
to the receiving silo in order to optimize the flow characteristics for the cement transport and thereby minimize the power consumption further. The principle changes are the same for all systems though and consequently the effect on the power requirements and the total equipment prices too.
Based on its long history and involvement in many important projects, Carlsen is well equipped to assist in projects of different kinds.
 
Keeping silos safe with Hycontrol systems that follow MPA guidelines
The Mineral Products Association (MPA) has worked with the British Pre-Cast Concrete Foundation (BPCF) and the Health & Safety Executive (HSE/HSL) in the UK to develop guidelines to ‘prevent over-pressurization of storage silos during the delivery of (non-explosive) powder in the cement, concrete and quarrying industries’.
As stated in the report generated by the above-mentioned organizations, the cement/quarrying industry handles many millions of tonnes of powder every year, and it is common practice for these to be transported in tankers. Loads are discharged by fluidizing the powders and blowing them into a silo. The air used to carry the powder is vented from the top of the silo through filters. If the air entering the silo is not vented adequately, there could be over-pressurization and consequent rupture of the silo, so pressure-relief devices should be fitted.
 
TANKERS
Tankers can be pressurized to deliver powders. They have a blowing system which provides air to transport powder into the silo. Tankers currently operate at up to 200kPa and a modern tanker typically has a volume in excess of 40m3 when operating at 44 tonnes.
 
Air discharge
A compressor (blower) mounted on the tanker lorry (or on the tank with an auxiliary engine) provides a supply of air which:
* pressurizes the tanker vessel;
* fluidizes the powder around the distributor plate; and
* transports fluidized powder from the tanker, along the connecting pipework to the silo.
 
Interconnecting hoses and feed lines
The feed line which takes the powder from ground level to the top of the silo is a 100mm rigid pipe. The tanker is usually connected to the feed pipe via a flexible hose using a cone-type coupling. The hose is typically rated to a pressure of ~500kPa, and the couplings to >800kPa, provided the coupling is sound and a good connection is made.
 
RECEIVING SILOS
These can be of varying styles, sizes and shapes; some are divided into compartments. A silo’s height, and the length of interconnecting pipework, affect the speed at which powder is delivered from a tanker. On entering the silo from the feed line, the velocity of air/material decreases rapidly, allowing the powder to fall from suspension. The powder is deposited in the silo whilst the air is vented from the silo, through filters, to the atmosphere.
 
Filter systems
Not all powder transported into the silo settles rapidly, so the air leaving the silo needs to be filtered to protect the environment. This is done through filter bag systems or filter cartridge systems.
Filter cleaning systems are essential for reliable operation and to maintain filter efficiency. This is achieved usually by either reverse jet cleaning or mechanical shaking.
 
Warning systems
To determine level of fill and internal pressure, silos should be fitted with warning sensors activating audible and visual alarms. Typical sensors are:
* high-pressure sensors — usually a pressure sensor, located at the top of the silo. This monitors pressure and if safe levels are exceeded, activates alarms or fill-pipe shut-off valves; and
* high powder level — either a mechanical device, which detects the presence of powder by interference with a moving sensor, or an electric device which detects the presence of powder. The location of the sensor determines the degree of warning given by the alarm; the lower the sensor, the earlier the warning.
The high-level warning system is designed to prevent the silo from being over-filled by providing the tanker and silo operators with a warning when the level in the silo approaches the maximum fill level.
 
Pressure relief valve (PRV)
Although silos have a degree of inherent strength, they are not designed as pressure vessels and therefore they must be protected against a build-up of pressure. Pressure relief valves are mechanical valves or vents which open at a pre-set pressure to allow excess air to vent from the silo. Frequently used designs are:
* dead weight valve — the weight of the lid of the vent usually keeps the pressure relief device closed. When the pressure in the silo exceeds the designed lift-pressure, the force on the underside of the vent overcomes the weight of the lid, which lifts and vents the excess air to atmosphere. Once the pressure subsides, the lid reseats, resetting the valve; and
* spring-loaded valve — the resistance to opening comes from a spring acting on the valve, rather than the weight of the valve cover. The valve opens if the pressure exceeds the design pressure, and resets once the pressure has fallen.
 
HYCONTROL OFFERS SILO-PROTECTION SYSTEMS
One company that is heavily involved in the provision of safety systems to protect silos is UK level control specialist Hycontrol. Hycontrol has developed an integrated silo protection system designed to prevent the problems caused by the overfilling or
over-pressurization of storage silos used to store bulk products — including cement. The SiloSafe concept provides a comprehensive system where the operational integrity of the primary sensing elements can be fully checked at ground level prior to each filling. For more details on the SiloSafe systems, please see ‘Keeping a lid on potentially explosive problems when storing cement,’ on p59 of the November 2010 issue of Dry Cargo International.
Hycontrol has been pleased to note that the recent guidelines from the MPA highlight the basic points that it has been promoting for the last three years. This document recommends that the high level probe, pressure sensor and the PRV need to be checked and tested regularly. Hycontrol is the only company who can carry out all of these functionality checks with a simple push of one button.
The high level probe function is tested, the pressure sensor is pressure tested over its full range and the PRV is lifted at the same time. The PRV also has an additional lift facility for seal inspection while on the silo roof which no other pressure relief valve company can supply. To check or test any other manufacturers PRV it is necessary to dismantle or remove it from the silo roof which is very impractical and costly.
However, although Hycontrol is pleased that its systems have been recognized, it has taken the silo protection principle one step further by providing a maintenance indicator for an early warning that things are not operating correctly. The new Hycontrol system will test full functionality of the above items and also log every time a test is carried out (required for maintenance purposes) and will also log high-pressure near miss events as standard. This facility will provide the total number of high pressure events recorded since the system is switched on and will time and date stamp the last event. This information can then be checked as part of a maintenance regime to see if high- pressure events are a regular occurrence. If they are then this would indicate that the silo is regularly experiencing a dangerous condition which could be due to several reasons.
Firstly it could indicate that the filters are becoming old, blocked, need replacing or are in need of maintenance as the air cannot escape quickly enough to prevent a pressure increase. Secondly it may indicate that the filters are not the correct size for the silo and would need upgrading. Thirdly it could indicate that the tanker driver is discharging in an uncontrolled manner and this will need to be addressed to stop future potential silo damage.
No other silo protection system can provide such information and test all components within the safety system to provide absolute silo safety.
Over-pressurization accidents are happening all over the UK with a number of examples detailed in the latest guidelines (see below for a few extracts). Hycontrol silo protection systems will stop this problem and remove this safety issue from site.
 
UK SILO INCIDENTS AND OUTCOMES
Incident: a road tanker was blowing cement under pressure into a 25-tonne silo at a concrete batching plant. The bag filter unit on top of the silo became blocked because of overfilling. Air pressure in the silo built up and the relief device failed to operate. The bolts holding the filter unit in place pulled through the metal retaining flange causing the filter unit, which weighed a quarter of a tonne, to be blown upwards. It cleared the handrails around the top of the silo and fell to the ground below.
Outcome: the movement of the PRV was greatly restricted. The company was prosecuted as a result of this incident.
Incident: one compartment of a two-compartment cement silo split along a weld. The silo roof was so heavily encrusted with cement that the access doors to the filter compartment had become obstructed.
Outcome: the filters were blocked and clearly had not been cleaned for some considerable time. The silo was not fitted with a PRV.
Incident: due to a misunderstanding between a cement tanker driver and a plant operator, cement was delivered into a silo which had been filled the previous day. The high level alarm on the full silo had been muted when it activated during the delivery on the previous day. In normal circumstances, once the cement level fell below the level of the detector, the high level alarm automatically reset. However, because the cement still covered the detector, this had not happened. During the second delivery, a loud explosion occurred and the filter unit was ejected from the silo roof.
Outcome: the air filter was not operating correctly due, first, to a considerable build-up of cement within the filter body and, secondly, to it being incorrectly reassembled after maintenance. Over a period of time, cement powder had built up in the PRV and hardened, causing it to seize up. Incident: a 24-tonne cement tanker operating at 200kPa discharged 10 tonnes of cement into a 15-tonne silo. Just as the high level alarm went off, the last of the cement was discharged from the tanker. Whilst the driver was in the process of closing the cement delivery valve, the retaining clip between the filter body and the location upstand failed. As a result, the filter body was blown off the top of the silo, landing on the ground below. Outcome: although the pressure relief device activated, it seems likely that it was not sufficiently large and was overwhelmed by the volume of air involved.
Incident: a silo was overfilled and the filter housing blew off.
Outcome: high level alarms and sensors had not been switched on.
 
Mole•Master redesigns silo and bin cleaning system
Mole•Master Services Corporation is a major provider of do-it-yourself silo and bin cleaning equipment, which is used in a variety of industries, including cement handling. The company’s flagship system has been completely redesigned and now offers both a new hydraulic cutting head option (JR360H) and the previously available pneumatic cutting head (JR360P).
The redesign and new options, recently introduced at the International Poultry Exhibition (IPE) in Atlanta, were all done to enhance ease of operation and improve worker safety.
“The hydraulic cutting head option is brand new and offers a clear advantage in many circumstances,” said Dave Laing, general manager for Mole•Master Services Corporation. “While our original JuniorTM used hydraulics for certain operations, the cutting head was operated pneumatically.
“Now, for the first time, we are able to offer our customers a choice of a pneumatic cutting head or our all-new hydraulic cutting head,” he said. “The JR360H system simply requires access to electricity, whereas the JR360P system requires an air compressor or plant air, which may pose an inconvenience.”
Laing also noted that the hydraulic cutting head provides the operator with greater torque and, due to the availability of a new, higher RPM motor, equivalent operating speed.
Customers who still prefer Mole•Master’s pneumatic cutting head for their silo and bin cleaning system will need access to an air source. However, they still will benefit from enhancements to the overall design and the confidence of knowing that there is zero chance for contamination of their material since hydraulic fluid is not powering the cutting head.
“With the expanded JuniorTM    360o lineup, lost storage capacity is still restored quickly, safely and economically without the risk of product contamination,” Laing said. “As always, the unit provides 100% coverage of the vessel’s interior walls from its original set-up position.”
The enhanced JuniorTM 360o silo and bin cleaning system features:
* a hydraulically assisted sectional boom, providing the flexibility to adapt to different size vessels;
* pneumatically or hydraulically actuated cutting head, featuring interchangeable blades, flails, or chain cutters engineered to safely remove a wide variety of materials; and
* a new chain cutter, or whip mounts, which swivel into the hydraulic cutting head to keep the overall diameter of the cutting head to 5”.
Another great feature, the all-new, hydraulic cutting head, is significantly smaller in diameter (5”) than any head on the market, enabling it to fit into extremely small flow channels or ratholes without losing any power or cleaning capacity. A smaller diameter lessens time to enlarge the flow channel.
Furthermore, a hydraulic cylinder and fixed length cable now raise and lower the boom, providing superior control while eliminating costly gear reducers and associated parts.
With the new hydraulic options, the silo and bin cleaning system remains easy to transport and to assemble, making it a great choice for do-it-yourself cleanout projects. Plus, the JuniorTM’s 360o flexibility and range eliminate the need for workers to enter bins or silos during cleanout, dramatically increasing worker safety in the process.
Ohio-based Mole•Master is a major manufacturer and provider of silo and bin cleaning equipment and services.
 

Euromec claims its rightful place in the cement market
Euromec Srl is at the forefront of the production of electrohydraulic equipment for the handling of all different types of buik handling commodities.
The company has 60 years of experience, which has enabled it to specialize in the handling of all types of bulk materials.
It is certified worldwide, including ATEX, NEC500, NEMA rules for dangerous environment, and GOST.
Because of its high level of specialization, it is able to meet all customer requirements. Its extensive customer list therefore includes major companies such as Italcementi, Buzzi Unicem, LaFarge, Cementir and many others.
Furthermore, Euromec builds all its equipment — using the expertise gained over its 60 years of experience — of the best available materials, including high-quality sheet metals. All automated systems can work 24 hours a day. Euromec’s grabs can be used in extremely hot environments, such as those where clinker is produced, keeping machine downtime to a minimum. Maintenance time is also minimized.
Euromec is careful to pay attention to the requirements of its customers, and carries out in-depth technical studies. Combined with its considerable expertise in the materials handling market, its products are very widely used and can be found in most large
ports and plants all over the world. Euromec is a firm believer in the importance of reliability and after-sales service.
Simplicity is a watchword in Euromec’s planning process, so that production costs can be kept low and the final quality of the products is as good as it can be. Maintenance is kept to a minimum, ensuring that customers receive an economical product which is reliable, low-maintenance and has a long working life.
The company’s 60 years of experience are evident in the quality of its products, and Euromec is always happy for potential customers to visit its facilities.
 
Arthur Loibl supplies equipment for limestone and gypsum handling at UK plant
In the coal-fired power station Rugeley/Staffordshire in England the two existing coal-fired boilers 6 and 7 of 500MW each were equipped with a flue gas cleaning plant.
The Anlagenbau und Fördertechnik Arthur Loibl GmbH supplied and installed the materials handling equipment for limestone receiving and the REA gypsum transport.
The required limestone with a grain size of 20mm is delivered by wagons and discharged onto a hopper in an enclosed unloading station.
For dust suppression and dust removal in the unloading area a dedusting plant with a dedusting air volume of approximately 60,000Nm3/h is applied, with feeding of the cleaned dust to the adjacent materials handling equipment by means of screw conveyor.
Compressed air supply is provided by means of the delivered screw compressors.
The reinforced concrete hopper is covered with an open grid of 110mm spacing and lined with wear rubber plates 27+3mm to minimize wear.
Underneath the hopper in the basement area discharging is made via 2 unbalanced vibratory conveyors having a width of 1,500mm, which in turn are feeding a vibratory cross conveyor.
The total discharge capacity is 600tph (tonnes per hour) = approximately 480m3/h maximum.
For removal of metallic parts, an electric overbelt magnet is installed above the discharge of the vibratory cross conveyor onto the adjacent troughing belt conveyor which discharges the ferrous parts into a container.
For mass flow measuring the following conveyor belt with a belt width of 1,000mm and a conveying capacity of 600tph is equipped with a belt weigher.
On the discharge side, a hammer sampling station is integrated into the hood for quality inspection of the delivered limestone.
Limestone discharge is made onto a sidewall belt conveyor with a belt width of 1,400mm and a centre distance of approximately 34,000mm for the following transfer to a customer-supplied pipe conveyor.
Underneath the horizontal sections of the sidewall belt conveyor belt scrapers are used, which collect the spillage and return it into the conveyed flow.
After the customer-supplied pipe conveyor, the feeding of the two limestone silos is made via a reversible troughing belt conveyor with a belt width of 1,000mm, centre distance of approximately 19,000mm and a conveying capacity of 600tph.
The REA gypsum coming from the dewatering station is transported with a reversible conveyor BW 650mm for the main and auxiliary route and by means of an enclosed and curve- negotiable Sicon® conveyor S100/650 x 80,000mm with a conveying capacity of 25.0tph to the gypsum silo.
The Sicon® conveyor begins on a platform + 11.50m outside the dewatering building and ascending at about 17° and 12°, with concave and convex curve, as well as two horizontal deflections it runs around a limestone silo. For this purpose the conveyor belt frame is designed as self-supporting structure and fastened to the limestone silo.
On the REA gypsum silo at + 33.0 m the REA gypsum is discharged into the gypsum silo which was not part of LOIBL’s scope of supply.
From the gypsum silo the REA gypsum moves through a customer-supplied pipe conveyor to the REA gypsum loading silo V 150 m3 for which the engineering was provided by the Arthur Loibl GmbH.
Discharge from the silo standing on weighing cells is made with a capacity of 280tph by means of a discharge arm supplied.
The discharge arm Ø 5,500mm is frequency- controlled and driven by two motors P = 22.0kW.
The discharged REA gypsum drops on the adjacent moving belt conveyor, belt width 1,000mm, centre distance 16,000mm, to be discharged onto a telescopic loader. The loader in pipe segment design with dust cap fills up containers placed on wagons. The loading process can be controlled on site by means of an operating panel.
In August 2009 the equipment was preliminarily handed over to the customer and since that time has operated trouble-free to the complete satisfaction of the customer.
 

Protecting the environment by keeping dust emissions to a minimum
Controlling dust emissions is an ongoing challenge when handling dry bulk materials as the presence of dust pollution is an environmental threat and constitutes a severe hazard to health. Intensified focus on this matter combined with strengthened legislation demands better technological solutions and high performance equipment.
Cimbria Moduflex has a long history of supplying dust-free loading chutes to the cement industry throughout the world, not the least to improve the general environment and working conditions but also to assist cement producers in reducing the running cost in their outloading stations. The company’s success is based on the ability to differentiate on a market characterized by increased demands for flexible and environmentally compatible equipment. A wide high-quality product programme consisting of standard parts makes it possible to customize loading chutes so it matches specific customer applications. This ability combined with short and reliable time of delivery makes Cimbria Moduflex a preferred supplier of loading solutions. In addition to this, the company has also managed to distinguish themselves by being acknowledged problem solvers with the ability to create innovative solutions where particular customer requirements are taken into account.
 
MODUFLEX ‘PLUG AND PLAY’ SOLUTION
Recently, Cimbria Bulk Equipment was contacted by Aalborg Portland A/S, a company that is renowned worldwide in the white cement industry and is a member of the Italian-based cement company Cementir Holding SpA. The company needed a solution for its new outloading station in Korsør, Denmark. The station is unmanned and Aalborg Portland therefore needed autonomous outloading equipment that is easy to operate for the truck drivers.
The solution was the installation of a ‘plug and play’ system from Cimbria Moduflex consisting of a Moduflex F300 loading chute. The F300 model is constructed with an integrated fully self- contained filter system that is equipped with its own fan with regulating valve and pressure tank ensuring that the filter is continuously kept clean. The filter module is retractable, and thus providing a very compact construction. As a result the loading chute only requires a low built-in height.
Using standard parts, the chute is customized in order to fit customer requirements.
The chute is equipped with two NPG modules which have a working range of up to 130°C, good wearing qualities and a high degree of chemical resistance. In order to ensure a complete dust-proof outloading situation, the chute is supplied with a FlexSeal, an inflatable seal mounted on the chute outlet for tanker truck loading which ensures an active sealing between chute outlet and tanker truck inlet. Furthermore, the chute is supplied with FlexClose in order to avoid dust emission when the chute is being retracted.
According to Portland, the company is very
satisfied with the installation and the loading operation is running smoothly.
 
SUPPLYING RECENTLY DEVELOPED MODEL
In co-operation with VDE-Engineering, Cimbria Moduflex’s Belgian partner, Cimbria Bulk Equipment has delivered a Moduflex loading chute for the Holcim site in Obourg, Belgium.
The loading station is situated along the quay site and the company needed equipment for open and closed outloading of cement into various types of ships and barges from the same installation taking specific requirement as flexibility, dust elimination and installation height into account. The solution was a Moduflex loading chute of the type N300 with interchangeable outlets. The reason for choosing this specific model was that it contains an integrated filter and has a low built- in height. For years, Cimbria Bulk Equipment has supplied loading chutes with integral filter, where the filter module is part of the inlet construction. This is a well-proven solution when it comes to functionality; nevertheless, it requires a certain built-in height for installation. The supplied N300 model is a recently developed model with a side-mounted filter which makes the built-in height virtually the same as a non-filter loading chute. At the same time, the model also contains an integral filter and therefore the costly installation of the duct work into a central filter bag installation is avoided. The filter is mounted on a rectangular flange built out on a transition piece from the inlet part of the chute and it is externally supplied with 5–6 bar pressurized air. The control of the filter is carried out by the PLC in the control box of the loading chute. The side-mounted filter is characterized by being very service friendly as it provides easy access to replacement of the filter cartridges from the ‘clean side’. At the same time, it has been possible to increase the filter surface area which in some cases is needed to handle particular products.
For increased outloading flexibility the loading chute is equipped with interchangeable outlets for loading into both tanker ships and open barges from the same installation. For easy change-over the chute outlets are equipped with a special snap lock system. The loading chute is fitted on an articulating boom to enable loading in as many hatches as possible, without the need for moving the ship/barge. However, the articulating boom was not long enough for the loading chute to reach the river side cargo hatches of the barge, so to compensate for this, the Moduflex chute is supplied with a special designed chute outlet for off-centre outloading. For stabilizing the loading chute during the outloading process, the outlet is fitted with adjustable supporting legs.
Due to the abrasive character of the product, the chute inlet is supplied with an inlet liner in Hardox 400. The chute is equipped with 27 PVC chute modules which give the chute an extended length of more than 9000mm. The modular construction ensures an easy and quick replacement in case of modification or repairs. The replacement can be carried out
with limited downtime as it can be done out without dismantling the loading chute.
The chute is equipped with internal overlapping cones in steel for optimum separation of product and exhaust air.
On previous occasions, Holcim has chosen Cimbria Bulk Equipment as its preferred supplier of loading solutions and the above-mentioned delivery follows a recent order on six Moduflex D300 for outloading cement at the Holcim plant in Spain.
With more than 11,000 units produced, Cimbria Moduflex dust-free loading chutes for bulk materials loading are in operation worldwide. Inherent functional efficiency is enhanced by the modular nature of their design, an innovation that contributes significant savings in overall lifecycle costs. Cimbria Bulk Equipment supplies dust-free chute systems through a network of agents in more than 30 countries around the world. Further information on Cimbria Bulk Equipment and the Cimbria Group of companies can be obtained by accessing the company’s website.


Fly ash storage primer — an expert’s view
Storage of power plant fly ash has been a mainstay for the concrete dome industry, writes Thomas W. Hedrick, P.E.   Many of the pneumatic designs were developed by the mechanical systems suppliers, with more an eye towards selling components than value engineering. This article provides a storage project cost with a value engineered approach. With a limited budget, how can a designer develop an optimum fly ash storage system?
We will quickly review the general arrangements that were previously popular, then critique them, refine them and develop a truly cost-effective storage system.
 
BACKGROUND OF DOME BULK STORAGE
Fly ash concrete has become popular for its important characteristics. Fly ash is pozzolanic and has some cementitious properties.The particle size of fly ash is reported to be 200 times smaller than Portland cement. The small and rounded shape means that it acts as a water-reducer in the concrete (think strength gain) and it physically plugs up the interstices between the other aggregate and cement. The combined effect is that fly ash concrete is very salt resistant, and becomes particularly desirable in all coastal locations where durable concrete is needed.
Retaining power plant fly ash between the power industry peaks and the concrete usage peaks requires mass storage.Thin shelled concrete storage domes, as best described in ACI 334.3R-05 are very well suited for containing a dry product like fly ash.
 
Brunner's Island, PA; typical fly ash storage
1. Domes are relatively short, fat and low to the ground. Structural advantages of this prevail:
   a.    Wind loads are rather insignificant; 200–300mph winds really only involve design of attached items
   b.    Seismic loads are evaluated, but rarely control the structural design
   c.    Soils under domes are rarely enhanced to respond to these loads
      i.    Dome shells, foundations and tunnels easily accommodate high settlements
      ii.    Soft soils can generally just tolerate the dome storage loads
      iii.    Soil enhancements start with low-cost solutions like stone columns
      iv.    Very seldom does a dome structure require driven piling or drilled caissons
      v.    Typically less than 15% of fly ash storage domes need deep foundations
 
Figure 2:Air gravity troughs with branch piping
2. The interior of a thin shelled dome is well suited for a dry product
   a.    The air form is a roofing membrane and keeps out water just like a convention centre roof
   b.    In the ACI 334 construction process, low pressure air stabilizes the air form then the form is made rigid with       polyurethane insulation
      i.    The urethane keeps the interior from sweating like metal roofs on silos
      ii.    The insulation also means very small temperature changes occur on the dome shell
   c.    The shotcrete process of reinforced concrete inherently produces the most dense concrete matrix
      i.    High strength dense concrete envelopes the complete
shell around the dry product
      ii.    Only openings create a pathway for water leakage (we cover this later in our discussion)
 
HISTORICAL FLOOR SYSTEMS
Mechanical systems like the Cambelt auger system were popular in early storage projects. The popularity has now shifted to pneumatic floor systems. Air gravity conveyors are relatively inexpensive and several internal geometries have been popular. The drawback of contouring the floor of a dome is that the structural fill is using available volume. Good dome arrangements balance the mechanical floor area with cylinder height under the hemispherical dome to achieve a more optimum project cost. Let’s look at some issues that pneumatic floor systems present:
1. Floor systems, particularly pneumatic systems tend to ‘float’ inside the dome shell
   a.    Structural fill and differential internal pressures have settlement
      i.    It is difficult to get homogeneous compaction of the structural fill against the shell wall
      ii.    The centre of the dome imparts more pressure on the soils, thus the structural fill system will need to accommodate the deflection, as well the mechanical piping system
   b.    I prefer to use a cross-tunnel under the floor to house the piping runs to these floor systems
      i.    With the tunnel deflecting across the dome, so too will the piping assemblies.
      ii.    Cross-tunnel piping more rigidly follows the natural movement of the floor system.
      iii.    Alternate external piping connections use more pipelength to plumb the floor
      iv.    Air and water leaks around the piping are moremanageable with the tunnel
      v.    Lower project cost is the net effect
2. Dihedral faceted systems (one outlet) or double dihedral faceted floor system (see figure 2 above) have been the most popular pneumatic arrangements.
   a.    The floor systems supplier typically tries to place the air gravity troughs ‘relatively’ close together.
   b.    Each trough must be plumbed to the fluidization blower with piping systems
   c.    The space between the troughs eventually becomes a static mass of fly ash, never to be recovered
   d.    Typically a laboratory test could tell you the static angle of repose, but for this article we will conservatively set this angle at 70°
   e.    The customary spacing of these floor systems has been such that it ranges to 5-10% of the stored volume is staticvolume. (we discuss more later)
   f.    The 5% rule means that a hemisphere (with little or no cylinder height) will have a large number of piping branches to connect to the pneumatic air header.
      i.    Each branch of pipe has an air-over-mechanical valve, electrically controlled by a PLC (programmable logic
controller)
      ii.    Each of these valves has an instrument air connection to activate the valve
      iii.    Each valve has an electrical wiring harness, again to activate the valve
      iv.    Each branch additionally has a hand-operated valve to trim and balance the airflow.
      v.    Each branch is another hole to be water-tight (andair-pressure tight) in the structural shell
g.    To value engineer a pneumatic system, a design shouldrestrict the number of valves.
 
INTRODUCING A CONICAL FLOOR SYSTEM
Conical floors, such as the one in Figure 3 and Figure 4 on p68 take advantage of several things.The cross-tunnel has been coupled with a vault that allows the owner to utilize an FLSmidth type F-K pump to convey the fly ash into a process or load-out.
This lowered centre takes advantage of somewhat reducing the volume of structural fill.There is no reason that the site could not be slightly mounded to assist in high water-table locations.
Figure 3: Conical floor fly ash storage dome, elevation view
This system is a pneumatic fill dome, so the in-fill pipe route is along a ladder access, then across the hemisphere on stairs to a contained area, an apex handrail corral. Inside the corral would be located the piping inlet, instrument gauging for monitoring the level of storage and a dust collector, directly discharge into the dome. Ladder access is appropriate in that very little occasion will be necessary to have maintenance in this apex area.
Basically, just to monitor the bag-house condition.
 
The floor system introduced here is a modified hub-and-spoke system. Basically the hub is fluidized for a portion of the stored volume then the spokes are individually activated to withdraw the design volume.
 
EXAMINE THE STATIC MASS
The hub and spoke system in Figure 4 below is designed to work in two zones. Zone 1, or the hub will fluidize the centre portion of the stored material. Figure 5 is a 3-D model of the the conical material removed by this hub zone.
Figure 5: Just the hub, or zone 1 is fluidized
Zone 2 consists of a second positive displacement blower
with a valve on the zone 2 header for each spoke. One spoke at a time is fluidized to create the empty geometry shown in Figure 6. As discussed earlier, it could be argued that with ‘fresh’ fly ash, the static angle is much more flat, however to be conservative the work for this article assumes that the ash has
compacted over time creates a 70° static angle.
Figure 6: Fully empty condition assuming a 70° static angle
In the 3-D model, the red surface is the ash that rests against the inside face of the dome shell. The pink areas are the fluidized floor sections. The amber area is the sliding static surface. All material above this surface has been reclaimed.The green surface is just the cone shape, created by the turn-box on each spoke. Within the limitations of viewing a 3-D model, this hopefully gives a fairly clear view of the static material. Each storage dome must be oversized by this volume to net the design storage capacity.
Table 1: Storage capacity of various diameter dome systems Table 1 on p69 specifically looks at four sizes of dome storage from 12,000 to 80,000 metric tonnes. Each dome has a total volume that has been reduced by 4–5% from the static analysis of the hub and spoke systems. Each dome is capable of discharging between one third and one half of its volume with just the hub zone. Obviously, if an owner wanted to vary this percent, the diameter of the hub could be altered to yield a precise percent.
Table 2: Pneumatic reclaim system power and properties Table 2 on p69 represents the cost of the pneumatic reclaim system for each of the diameters in Table 1. Customers with high energy prices will be interested in the blower size. If energy is a concern, the mechanical supplier can further zone the floor system; particularly the hub. This was noted in the 150’ diameter column as the hub size increased from 4 metres to 6 metres.
The main benefit of this hub and spoke system is that thereare very few valves to plumb.The pipe routing is simple, straight and short.The electrical and instrument air installation is correspondingly efficient.
 
COST EVALUATION
The cost tabulated on Figure 7 on p71 includes what is generally considered the core storage system. Specifically included are:
Structural items
1. F-K pumping vault
2. Cross-tunnel
3. Ring beam Foundation
4. Shell
5. Structural fill and reinforced concrete floor
6. Bolt-on door for interior access
7. Ladder/stair apex
8. Infill pipe racks
9. Handrail corral around apex area

 
Mechanical items
1. 18,000 acfm dust collector
2. Pneumatic floor system with installation
3. P-D blower support pads, with installation
4. Valves and attachment to plant air header
5. Startup commissioning and balancing
Owners typically like to use local electrical installation and have unique fill and empty requirements. The following items are not included in the core costs tabulated in Figure 7.
1. Air Compressor/ dryer (plant air header)
2. Electrical Installation
3. System PLC
4. Level controls
5. Infill piping, source to dome apex
6. Outflow conveyance (FK pump) and outflow piping
The costs developed in Figure 7 are based on some assumptions. Transit mixed concrete price is $100/yd3 ($131/m3) the corresponding 4000 psi shotcrete (280kg/cm2; all fine aggregate) is $115/yd3 ($150/m3). I use mill length, non- fabricated rebar, delivered at $700/sT ($635/mT). I use structural fill, delivered to the site at $22/yd3 ($29/m3). I am using open shop labour costs.
Again, it bears repeating that dome fly ash storage projects typically do not generally involve deep foundation costs. We work closely with the owner’s geotechnical engineer as the concept is developed to verify the soils suitability, and likely reaction to the storage loads.
Just to keep things on the conservative side, the costs developed in Figure 7 were done with a structural load of 100pcf (1.6 t/m3).This is generally only 5% larger than the process density, but allows for the same structure to be modified (the floor changed to 100% coverage) and used as cement storage. If you convert to cement storage, the capacity of the dome will change by the difference in process density (typically 70pcf) or in this case 128% larger volume. This is a nice option, at the expense of the initial investment.
 
GREENFIELD FLY ASH TERMINAL
Occasionally, the fly ash storage is also linked to a
truck loading (or rail loading) terminal. Recently, I priced the configuration in Figures 8, 9 and 10 to a client. By integrating the loading system inside the dome (this is a patented arrangement), the overall cost is considerably less than an owner constructing a separate loading facility. In this case the 30,000 mT drive- through terminal, with mechanical systems installed (similar to the scoping list in this article) was less than $7 million.
Figure 8: Drive-through 30,000-tonne fly ash terminal; elevation 1 A portion of the stored fly ash naturally feeds into the surge bin. The remainder of stored product is conveyed with the mechanical floor to an air-lift conveyor, then into the surge bin.
An advantage of the air-lift system, with no moving parts, is that air lift vessel can be embedded in a wet site, and still function.The control room, mechanical room and electrical room are all located (think short plumbing and wiring runs) at the centre of the mechanical equipment. Other than an optional rest room, this terminal is ready. I have developed multiple lane versions, rail loading versions and versions that convey to other site facilities. This is a very adaptable arrangement.
 
SUMMARIZING YOUR KNOWLEDGE
We have learned that although popular, dihedral (and double dihedral) floors are more project cost intensive than the conical floor model. This cost is introduced in the more complex mechanical plumbing. Consider the high number of piping connections in Figure 2, contrasted with the simplicity of Table 1. Dihedral floors can involve very large volumes of structural fill that must be offset with larger structural shell size.
The use of a cross-tunnel and vault is a real advantage to plumbing and electrical cost. The structural advantage of penetrating the plumbing through the tunnel rather than the dome shell is secondary, but still is a significant advantage.
Equipment noise suppression and the location of valves in a protected area out of the sunlight is a big advantage to many owners.
Domes are fat and low to the ground inherently resisting seismic and wind loads. Contrasted to silos, with high centre of gravity issues that generally result in piling costs, domes are favourite storage choice.
If the project is a complete greenfield, consider the cost saving of a drive-through arrangement. All systems are tightly integrated in a very small footprint that offers site advantages that are not available with traditional options.
By working with the mechanical floor systems supplier, the energy needed to withdraw the fly ash from storage is minor. These systems are reliable and generally maintenance free. Owners of pneumatic floor storage report decades between interior maintenance, even in high throughput terminals.
Power plant fly ash is a very desirable and sought after product. Use this article as a resource in planning on your specific handling and storage needs.
 
ABOUT THE AUTHOR
Thomas W. Hedrick, P.E. is a registered engineer with two degrees in Civil Engineering from the
University of Missouri- Columbia. He has over 40 years experience in materials handling and engineering management. Tom Hedrick is a patent holder for several US material handling patents and a regular technical writing contributor.
Hedrick often works in the conceptual phase of a project to optimize the integration of various types of storage with the site and preferred mechanical equipment systems.
This project would not have been successful without the technical knowledge of David Bergenstock, Market Manager — Distribution Systems, Pneumatic Transport, FLSmidth Bethlehem, PA. Tough requirements, on time scheduling and in budget results always make a great project.