Continuous rating

An example of a modem, tangentially fired, supercritical, lignite-fuel furnace is shown in Figure 5. This unit, at maximum continuous ratings, supplies 2450 metric tons pet hour superheat steam at 26.6 MPa (3850 psi) and 544°C, and 2160 t/h reheat steam at 5.32 MPa (772 psi) and 541°C. These ate the values at the superheater and reheater oudet, respectively. Supercritical fluid-pressure installations ate, however, only rarely needed. Most power plants operate at subcritical pressures in the range of 12.4—19.3 MPa (1800—2800 psi). 

The Minitran system, by 3M Health Care, is a monolithic transdermal system that deUvers nitroglycerin at a continuous rate of 0.03 mg/(cm h) (81). The dmg flux through the skin is higher than the previous two systems thus the Minitran system is a smaller size for equivalent dosing. For example, the 0.1 mg/h dose is achieved with a 3.3 cm system rather than the 5 cm systems of Transderm-Nitro or Nitro-dur. Because the skin is rate-controlling in a monolithic system and the Minitran flux is higher than the similar monolithic Nitro-dur system flux, it appears that 3M Health Care has included an additive to increase the skin flux to 0.03 mg/(cm h). Whereas this information is not apparent in Reference 81, patent information supports the hypothesis (96). 

Since the transformer will be in the circuit for only 15 to 20 seconds, the approximate short-time rating of the transformer can be considered to be 10-15% of its continuous rating. The manufacturer of the auto transformer would be a better judge to suggest the most appropriate rating of the transformer, based on the tapping and starting period of the motor. 

An autotransformer of nearly 100 kVA continuously-rated should be sufficient for this application. 

For continuously rated machines, readings should be taken at intervals of one hour or less. For non-continuously rated machines, readings should be taken at intervals consistent with the time rating of the machine. The temperature rise test should continue until there is a variation of 1°C or less between the two consecutive measurements of temperature. 

Site of Continuous rating Maximum siz.e of three-phase capacitors in kVAr at different svitching currents /, ... 

These are meant to limit the inrush currents occurring during a switching operation of a capacitor. They are connected in series with the capacitors and may be short-time rated for the values of the inrush currents and continuously rated for normal line currents. They are almost the same as the series reactors with fixed reactance. 

But when the neutral is grounded through an arc-suppression coil (reactor) the current through the grounded neutral may be of a limited amplitude, say, up to its continuous rating (Section 20.5) and it may exist for longer. 

Small (Fractional) Machine. AfsmaW machine is either (1) a machine built in a two-digit frame number series in accordance with 11.01.1 (or equivalent for machines without feet) or (2) a machine built in a frame smaller than that frame of a medium machine (see 1.04), which has a continuous rating at 1700-1800 rpm of 1 horsepower for motors or 0.75 kilowatt for generators or (3) a motor rated less than Vs horsepower and less than 800 rpm. 

Direct-Current Medium Machine. A direct-current medium machine is a machine (1) built in a three- or fourdigit frame number series in accordance with 11.01.2 (or equivalent for machines without feet) and (2) having a continuous rating up to and including 1.25 horsepower per rpm for motors 1.0 kilowatt per rpm for generators. 

Direct-Current Large Machine. A direct-current large machine is a machine having a continuous rating greater than 1.25 horsepower per rpm for motors or 1.0 kilowatt per rpm for generators. 

Continuous Rating. The continuous rating defines the load that can be carried for an indefinitely long period of time. 

Table 3-7 gives the typical breakdown torque for Design B and C motors with continuous ratings [8]. Breakdown torques for Design A motors are in excess of the values given for Design B motors. 

Locked-Rotor Torque of Design A and B Motors with Continuous Ratings [8]... 

The 40°C continuous-rated open motors develop the rated horsepower from 150% of minimum speed to the maximum speed. From minimum speed to 159% of minimum speed, the rated horsepower will be developed continuously without exceeding safe temperature limits. 

The majority of shell boilers operate in the pressure range 7 to 10 bar, the flue gas outlet temperature will be in the range of 190 to 250°C. Therefore, it may be appreciated from this that the boiler needs to operate at 50-100 per cent of its maximum continuous rating for most of the working day to produce an economic return. 

A breach of these emission levels is an offence under Section 2(2) of this Act. Best practicable means may be used as a fence against this action, and the Regulations prescribe to which classes of appliance they apply. Schedule 1 furnaces are rated by heat output and are boilers or indirect heating appliances where the material heated is a gas or a liquid. The maximum continuous rating concerned are from 825,000 to 475 million BTUs. 

Two methods are used to remove the dust cake, both of which require interruption of the airflow. The difference in dust-cake removal conveniently divides filters into intermittent and continuous rating. In the intermittent type the pressure increases (with time) up to a pre-arranged level. The airflow is then stopped and the fabric is mechanically shaken. In the continuously rated filter the pressure drop rises to a low set point, after which it remains constant across the filter as a whole. The cleaning is done by isolating a part of the filter from the air stream and that section is cleaned. 

Continuously rated filters have whole sections of the filter shut off from the airflow and then those sections are shaken or cleaned. Shaking is carried out in sequence, usually by electric motor. Where the filter is cleaned it is done by a jet of compressed air being blown in reverse to the airflow through the fabric. This system does not require whole sections to be shut down, as the reverse blow is carried out when the filter is on-stream. The time of blow is very small and is measured in parts of a second rather than in minutes, as in the case of shaking filters. The application of these filters is in continuous processes and where the dust burdens are high (in excess of 100 g/m ). 

Heavy dust burdens Continuously rated filters ... 

In addition, manufacturers boiler operational manuals provide hardcopy data ratings for heat transfer coefficients, local heat flux, fuel utilization, furnace heat release rates, maximum continuous rating... 

Typically, electric boiler designs are limited to under 600 kWh (2,000 lb/hr) output. However, in some countries where electricity is of particularly low cost (say, where where supplied by hydroelectric generation) electric boiler designs of up to 12,000 to 24,000 kWh (40,000-80,000 lb/hr) or more are commonly used in large-process industry. The maximum continuous rated (MCR) output is about 175,000 lb/hr. 

NOTE Deaerator storage capacity is normally sized at 10 to 11 minutes FW demand at boiler full steaming rate (FSR) or maximum continuous rating (MCR). 

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