Handling duties

Table 1.2 Problems of specifying bulk solids condition for handling duties...

Firstly, the specification for the material was not properly defined. The Institution of Mechanical Engineers publication Guide to the specification of bulk materials for storage and handling applications sets out the basic handling parameters of bulk material for handling duties and highlights features of performance that should be considered. 

For fired heaters, the limitations could be heat flux or TWT. The former is applied to heaters with pressure drop larger than 20 psi, which is the most common. The latter is for low-pressure drop heaters. When the heater duty must be increased to handle duty much larger than design, the existing heater may be insufficient in meeting the limits. Installing a new heater could be very expensive. The most effective way to avoid this is to increase feed preheating via process heat recovery. 

It is therefore necessary to understand the limitations of this class of equipment perhaps even more than the many and varied advantages that can be exploited. These mainly depend on the intrinsic nature of the bulk material that is to be handled, therefore the first task of an engineer faced with the selection of equipment for a solids handling duty is to recognise those features that may give rise to unsatisfactory operation. 

Specifications for the principal LPG products are summarized in Table 4. Detailed specifications and test methods for LPG are pubHshed by the Gas Processor s Association (GPA) (3) and ASTM (4). The ASTM specification for special-duty propane and GPA specification for propane HD-5 apply to propane that is intended primarily for engine fuel. Because most domestic U.S. LPG is handled through copper tubing, which could fail if corroded, all products must pass the copper strip corrosion test. A test value of No. 1 represents a LPG noncorrosive to the copper. 

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. 

The thermal duty here is the opposite of solidification operations. The indirect heat-transfer equipment suitable for one operation is not suitable for the other because of the material-handling rather than the thermal aspects. Whether the temperature of transformation is a definite or a ranging one is of little importance in the selection of equipment for fusion. The burden is much agitated, but the beds are deep. 

For steel mill auxiliary drives or for material handling equipment, the duty factor normally chosen for slip-ring motors is either 40%c or 60%. 

Sewage duties, industrial slurries and ash handling De-watering of dirty water when building roads, dams, harbours, tunnels, etc. 

Part II of EPA 90 deals with waste disposal, handling and management. The provisions impose duties on the producers of waste to ensure the safe disposal. There are strong licensing powers for local authorities, with continuing responsibilities for licensees to monitor and maintain sites after closure. 

The disposal of waste oils is largely governed in the UK by the EPA 90. Waste oils are a Special Waste covered by Special Waste Regulations. Establishments handling more than 500 litres per annum have a duty to maintain records. There are also requirements for record keeping where waste oils contain toxic impurities and so become Special Waste . 

Pision Type used for low pressure light duty or intermittent service. Less expensive than the plunger design, but cannot handle gritty liquids. 

The chemical and petrochemical industries specify continuous duty service. This means that the motor can operate indefinitely when handling the specified horsepower (rated) load at the proper voltage. To specify less than continuous duty is uneconomical and not good design practice. 

Plants producing and handling halogens and halogen compounds Tantalum finds extensive use in the production and handling of hydrochloric and hydrobromic acid, chlorine and bromine and many of their derivatives. Absorbers, coolers and heaters which show considerable advantages in terms of heat-flux capabilities and corrosion resistance have been used on hydrochloric acid duties for over 40 years and condensers have been used in bromine plants for at least the same period. Typical applications of tantalum in the bromine and chlorine industries are listed in Table 5.27 . 

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