Standby

Find a way to overcome the constraint while still maintaining the areas. This is often possible by using indirect heat transfer between the two areas. The simplest option is via the existing utility system. For example, rather than have a direct match between two streams, one can perhaps generate steam to be fed into the steam mains and the other use steam from the same mains. The utility system then acts as a buffer between the two areas. Another possibility might be to use a heat transfer medium such as a hot oil which circulates between the two streams being matched. To maintain operational independence, a standby heater and cooler supplied by utilities is needed in the hot oil circuit such that if either area is not operational, utilities could substitute heat recovery for short periods. 

Minimize the number of shutdowns by designing for high availability. Install more reliable equipment or standby equipment. 

Actual contracts often involve a combination of the above. For instance, an operator may agree to pay footage rates to a certain depth, day rates below that depth, and standby rates for days when the rig is on site, but not drilling. 

In case of a major disaster, one platform in a region will be equipped to act as a control centre from which rescue operations are co-ordinated. Evacuation routes will be provided, and where large complexes are clustered together, a standby vessel will be available in the region to supply emergency services such as fire fighting and rescue. 

The way out of this dilemma is easily stated, although not easily acted upon. It is not adequate to consider any one of these approaches for the explanation of something as complicated as these reactions. Polarity effects and resonance are both operative, and, if these still fall short of explaining all observations, there is another old standby to fall back on steric effects. 

The Ube plant consists of four complete trains of Texaco quench-type gasifiers. During normal operation, three gasifiers are on line and one is on standby. Each gasifier consumes 500 t/day of coal to generate syngas for 350 t/day of ammonia. Up to the middle of 1990 the Ube plant gasified 2.2 million t of coal and petroleum coke. 

Most sulfonation plants monitor and control operations by computer. Sulfur-buming catalytic SO -generating equipment may require a 1—2 h stabilization period on startup. The unit can be kept in a standby position by maintaining heat to the unit when it is off-line. Liquid SO -based sulfonation plants do not require such a stabilization period and hence are more flexible to operate than sulfur-buming sulfonation plants. 

Includes capacity at operating plants as well as plants on standby basis. ""Ref. 21. 

High energy density batteries with long shelf life, developed originally for military use, are based on lithium and thionyl chloride. These batteries are used ia backup or standby power sources for computer, missile, and telephone systems (191,192). 

The case is the largest portion of the container. The case is divided into compartments which hold the cell elements. The cores normally have a mud-rest area used to collect shed soHds from the battery plates and supply support to the element. Typical materials of constmction for the battery container are polypropylene, polycarbonate, SAN, ABS, and to a much lesser extent, hard mbber. The material used in fabrication depends on the battery s appHcation. Typical material selections include a polypropylene—ethylene copolymer for SLI batteries polystyrene for stationary batteries polycarbonate for large, single ceU standby power batteries and ABS for certain sealed lead—acid batteries. 

Brazil has two small producers of chlorobenzenes. One producer has a capacity of 4.8 thousand metric tons. The other producer s faciUty has a rated capacity of 28 thousand metric tons, which produces mono and ortho for local consumption, and the para may be used in Brazil and possibly exported. A third plant with a 400 metric ton capacity is beheved to be on standby. 

In addition to using an arrester element with greater flow capacity, it is common to use two arresters in parallel where frequent cleaning is required, with one arrester in standby. A three-way valve can be used to allow uninterrupted operation during changeover. Where elements have an intrinsically high pressure drop, suA as sintered metal elements used in acetylene sei vice, multiple parallel elements can be used. 

LPG is widely used for domestic service, supplied either in tanks or by pipehnes. It is also used to augment natural-gas deliveries on peak days and by some industries as a standby fuel. 

Pipe-hne and marine installations are frequently arranged so that the engine drives all its auxiharies from the crankshaft by means of chains and V belts. But process-plant practice is to have all the auxiliaries independently driven, using standby pumps to minimize engine downtime. 

The lubrication system, for reliabihty reasons, usually has an operating and a standby pump and dual switchable filters. If there is a cooling-water scahng problem, coolers may also be switchable. 

NFPA 110 Standard for Emergency and Standby Power Systems, 1999 edition. National Fire Protection Association, Quincy, MA. 

It is common practice to provide a standby emergency source of supply at all important installations such as large factories, railways, airports and other essential services. This is usually achieved with the use of a captive diesel generator (DG) set (Figure 16.1). Here we briefly discuss these machines, their characteristics and selection for a required application. We also consider schemes that are commonly used to start a DG set and run it individually or in parallel with an existing source of supply, which may be another DG set or an infinite bus. 

The total sequence of auto-synehronizing a standby generating unit with an existing system can thus be summarized as follows ... 

ANSI/IEEE 446/1995 Recommended practice for emergency and standby power systems for industrial and commercial applications. (IEEE Orange Book) ... 

Captive (emergency) power generation covers the application of a diesel generating set, its starting, protection, synchronizing and load sharing. This forms an important part of power distribution at any installation to provide a standby source of supply,... 

Continuity and reliahility of this energy source was required if it were used as base load, which required standby equipment, spares, and appropriate operator attention. 

Lube oil pressure is generally eontrolled by a self-eontained pressureregulating valve that automatieally maintains a eonstant lube oil pressure aeross the bearings. The valve is normally adjustable, but is usually preset at the faetory. The valve flow eapaeity must be suffieient to bypass exeessive flow if both main and standby pumps are operating simultaneously. 

A differential pressure controller acts in split range on the inlet control valve and the bypass valves. The differential pressure governor is retained as the standby and backup system. 

Forced Circulation System—Using foreed eireulation in a waste heat reeovery system allows the use of smaller tube sizes with inherent inereased heat transfer eoeffieients. Flow stability eonsiderations must be addressed. The reeireulating pump is a eritieal eomponent from a reliability standpoint and standby (redundant) pumps must be eonsidered. In any event, great eare must go into preparing speeifieations for this pump. 

Small standby power turbines less than 2-MW. The smaller size of these turbines in many cases have centrifugal compressors driven by radial inflow turbines, the larger units in this range are usually axial... 

Accomplish a filter cooler changeover without causing startup of the standby pump. 

Omit the bypass PCV circuit it centrifugal pumps are used. tS. Switch <0 start standby pump. 

Power plants in both peaking and standby modes aehieved 30,000 hours between major overhauls. It was during these operations that the deposit problem on the turbine nozzles beeame apparent. Also, deposits developed on the fuel nozzles, a situation that eould eause deviation in the fuel spray angle and related eombustion problems. Therefore, both turbine and fuel nozzles needed frequent eleaning. 

The oil system should be equipped with a main oil pump, a standby and, for eritieal maehines, an emergeney pump. Eaeh pump must have its own driver, and eheek valves must be installed on eaeh pump diseharge to prevent reverse flow through idle pumps. The pump eapaeity of the main and standby pumps should be 10-15% greater than maximum system usage. The pumps should be provided with different prime movers. 

Low oil pressure switehes are provided on the pumps and diseharge header ahead of the eoolers and filters, sometimes after the eooler and filters, and always at the end of the line where the redueed oil pressure feeds the various users. A signal from any of these should start the motor-driven pump and all alarms should be aetivated in the eontrol room. The emergeney oil pump ean be driven with an AC motor but from a power souree that is different to the standby pump. When de power is available, DC eleetrie motors ean also be used. Proeess gas or air-driven turbines and quiek-start steam turbines are often used to drive the emergeney pumps. 

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