Conveying system types

A variety of specialized idlers are available. Examples are plastic disk catenary idlers for handling wet corrosive materials two roU idlers, where the roUs are oriented in a vee for lighter duty conveying system and suspended idler supports for severe service. In this last type, three to five idler roUs are linked end-to-end and suspended from conveyor frame stringers to form a catemary that cradles the belt. 

FIG. 21-12 Types of air-conveying systems, a) Pressure, (h) Vacuum, (c) Pressure-vacuum, (d) Pressure vacuum unloading and transfer. (Whitlock, Inc.) (e) Fluidizing system. (Fuller Co.) (/) Blowtank. 

Hopper Trucks These trucks are used to transport by highway a wide variety of materials. Vehicle types range from the open-dumping kind to the closed type. Most common is the type that unloads by pressure differential into its own pneumatic-conveying system, which is temporarily connected to a storage silo. On this type of truck, the unloading of 18,100 kg (40,000 lb) of produces takes about 1 h, sometimes less. 

Conveying systems normally use air as the transport medium to convey granular, crushed, or pulverized materials. Modelling the flow of pneumatic conveying and calculating its pressure loss is a problematic task. The greatest problem arises from the fact that different mass flow ratios, solid flow rate divided by the gas flow rate, imply different flow types in pneumatic conveying. Each of these flow types, which can be classified in many different ways, requires its own specific model in order to provide a concrete calculation method. 

Another basic question is what type of facility would be most applicable —i.e., is a fixed or a mobile irradiator most applicable If a fixed facility is applicable, should it be an in-plant unit or a central facility to be used by several processors Seasonal availability of a product, near one location, is critical to the economics of radiation processing since typical capital costs for a moderate food irradiation plant may run anywhere between a quarter and two million dollars or more. Where there are relatively short harvest seasons, it would be economically advantageous to plan for irradiation of several products. This, however, requires a more flexible or versatile conveying system past the radiation source and generally less efficient use of the radiation. Thus, while a slight increase in capital cost may be required, the unit cost for processing would be less. 

Once the value-added service has been designed, fees established, and the method(s) for compensation selected, the pharmacist must learn how to submit claims. When providers submit claims to Medicare, Medicaid, or any other third-party payers, the claim typically is submitted on the CMS Form 1500. One exception to this is the hospital outpatient clinic, which uses CMS Form 1450. On CMS Form 1500, information regarding the submitting entity, referring physician, type of services offered, and related health condition is included. To convey this type of information, CPT codes and ICD-9-CM codes are used. These coding systems provide detailed information regarding the types of services provided and the specific health condition in a numerical format. Example CMS 1500 and 1450 forms are available on the CMS Web site (www.CMS.hhs.gov). 

Polymerization plants are now planned with throughputs of up to 70 t/h for polypropylene (PP) and over 100 t/h for different types of polyethylene (PE), and many licensors would like to process and pelletize these volumes to specification with just one processing plant. In addition to intake, melting, and homogenization of the raw materials, there is a need for discharge parts, conveying systems, and post-treatment units of an appropriate size. 

Various properties and characteristics of materials used in the plastics industry that can be conveyed pneumatically affect the sizing and design of the conveying system. As an example the specific gravity is an aid in determining how much airflow is needed to lift a particle in an air stream. Particle size is also a consideration in pneumatic conveying systems. The material has to be tested to determine the amount of fines and dust that may be contained in the material. This will help determine the type of... 

Pneumatic conveying is frequently a cost effective option, using a Rootes-type blower and a rotary blowing seal. Alternative proprietary units are available. Pipelines should normally have a nominal bore of at least 50 mm and bends should have a radius of at least 1 m. The reception hopper should be fitted with an air-pressure relief valve. Powder pumps are also used successfully. They tend to use less air than pneumatic conveying systems. 

It should be pointed out that the two-fluid approach, as was described and demonstrated in the previous sections, was widely used and validated for various types of pneumatic conveying systems and pneumatic flash dryers. Nevertheless, it is only one of various approaches that can be adopted. Section 17.1 presents a summary of the various studies that were conducted on pneumatic flash dryers and the various mathematical models that have been adopted by them. 

Head rope configurations for rope guided conveyance systems are arranged to limit the torque applied to the conveyance. Koepe winding systems, with multiple head ropes use opposite handed pairs of ropes to balance the torque. Despite these efforts, a small amoimt of residual unbalanced torque may be apphed to the conveyance due to small differences in the rope loads and the rope torque characteristics. The residual unbalanced torque is given by M = TUF)CdTj where - C is the torque factor applicable to the head rope construction (available from rope manufacturer s data) d is the head rope diameter is the tension in one head rope TUF is a torsional unbalance factor. For both drum winders and Koepe winders the applicable tension in the head rope is a function of the conveyance mass, the ratio of head rope mass to conveyance mass and the position in the shaft. However the functional dependence differs between the two winder types. can be expressed as... 

The product from the compaction process is the flake. The thickness of the potash flake varies from plant to plant but on average is about 20 mm. After compaction the flake is cured in the conveying system. For potash the normal design of the plant provides about 3 minutes of curing time. The flake is broken into smaller pieces immediately below the roller. Pin-type breakers and coarse tooth roll crushers are used to break the flakes. 

Automatic conveyor and shuttle systems— Devices comprised of various types of conveying systems linked together with various shuttle mechanisms for the prime purpose of conveying materials or parts to prepositioned and predetermined locations automatically. 

Many different methods are used to transfer the unloaded salt to the process. Most coarse salt handles well, and most of the conunon types of conveyor are used where appropriate. This section reviews some of the characteristics of the different salts and describes the types of conveying equipment found most often in chlor-alkali plants. First, we consider some of the properties that are important to the design and operation of conveying systems. 

Two basic types of pneumatic conveying systems have been adopted for railcar unloading service the vacuum system and the combination negative-positive pressure system. Each possesses certain advantages which make it useful for different types of applications. Figure 7.15 shows schematically a straight vacuum type of loader that utilizes a silo-mounted vacuum chamber. In this type system, the vacuum pump... 

As with any type of pneumatic conveying system, the transfer rate depends upon material characteristics and distance. Railcar unloading has the added complication of always being a high-lift situation, anywhere from 40 to 70 ft vertical. A 25-hp unit with a 4-in conveying line moving polyethylene pellets approximately 100 ft horizontal and 60 ft vertical will maintain an approximate throughput of 10,000 Ib/h. 

All conveying systems require controls to monitor the status of level switches and other sensors and to control the sequence of operation of pumps, valves, filters, and other system elements (see Fig. 7.32). Basic types of loading system controls include ... 

The above classification groups the different types of conveying systems in virtue of their operating principle. For example, regardless of whether a bulk material is being moved horizontally, inclined, or vertically, chain conveying can perform the duty based on the same principle of fixing an element (a paddle or a bucket) to a system of chains exfernally powered. 

Dense-phase conveying, also termed "nonsuspension" conveying, is normally used to discharge particulate solids or to move materials over short distances. There are several types of equipment such as plug-phase conveyors, fluidized systems, blow tanks, and, more innovative, long-distance systems. Dilute-phase, or dispersed-phase conveyors, are more versatile in use and can be considered the typical pneumatic conveying systems as described in the literature. The most accepted classification of dilute-phase conveyors comprises pressure, vacuum, combined, and closed-loop systems. 

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