Operational spares

In a service environment if there is any equipment upon which the capability of your service depends, this equipment should be maintained. Maintenance may often be subcontracted to specialists but nevertheless needs to be under your control. If you are able to maintain process capability by bringing in spare equipment or using other available equipment, your maintenance procedures can be simple. You merely need to ensure you have an operational spare at all times. Where this is not possible you can still rely on the call-out service if you can be assured that the anticipated downtime will not reduce your capability below that which you have been contracted to maintain. 

Using Spare Braytons at Reduced Capacity and Temperature Leads to Unacceptable Reduction in System Efficiency and the Needs for Larger Reactor and HRS. Operating Spares at Reduced Temperature and Speed Only Improves Situation Marginally. 

Operate two counter-rotating turbines on and two non-operating spare counter-rotating turbines. Each turbine is capable of producing half of the required electrical output. This is the base case used in the JPL/NGST derived PB1 study. 

Operate two co-rotating turbines for most of the mission life with one non-operating spare. The spare will rotate in the opposite direction and be initiated with failure of one Brayton or when the spacecraft reaches science orbit to provide momentum compensation. 

Operate one turbine capable of full electrical power and with one or more non-operating spares. The second unit would be powered up in the event of a failure of the primary unit through the use of an electrical power storage device (battery, flywheel, etc.). 

No spare components ( operational spares ) or spare components list. 

Operational spares (vacuum technology) Spare parts to replace parts which, if they fail or need to be replaced for any reason, will prevent use of the equipment. Examples Spare 0-rings spare roughing pump. 

Spare parts (vacuum technology) See Operational spares (preferred). 

The failure mode of an equipment item describes the reason for the failure, and is often determined by analysing what causes historic failures in the particular item. This is another good reason for keeping records of the performance of equipment. For example, if it is recognised that a pump typically fails due to worn bearings after 8,000 hours in operation, a maintenance strategy may be adopted which replaces the bearings after 7,000 hours if that pump is a critical item. If a spare pump is available as a back-up, then the policy may be to allow the pump to run to failure, but keep a stock of spare parts to allow a quick repair. 

Thus, a computer attached to a mass spectrometer must operate on two levels. When mass spectral information is arriving, this must be acquired in real time. When the computer has spare time, it controls the operation of the instrument. Both operations are carried out at such a high speed that the dual level of computer tasks is not obvious. 

MaintainabiUty is a characteristic of design, installation, and operation, usually expressed as the probabiUty that a system can be restored to specified operable conditions within a specified interval of time when maintenance is performed in accordance with prescribed procedures. The ease of fault detection, isolation, and repair are all influenced by system design and are principal factors contributing to maintainabiUty. Also contributing is the supply of spare parts, the supporting repair organization, and preventative maintenance practices. MaintainabiUty must be designed into the equipment. Some factors to consider foUow. 

The Russian icebreaker Eenin, launched ia 1959, had three 90 MWt PWRs, one of which was a spare. It operated for many years ia the Arctic Ocean. 

Membrane Processes Membrane processes are also used diafiltration is convenient for the removal of small contaminating species such as salts and smaller proteins, and can be combined with subsequent steps to concentrate the protein. Provided that proper membrane materials have been selected to avoid protein-membrane interactions, diafiltration using ultrafiltration membranes is typically straightforward, high-yielding and capital-sparing. These operations can often tolerate the concentration or the desired protein to its solu-bihty limit, maximizing process efficiency. 

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. 

For pumps, it is common to have steam driven primary units with electi-ical spares having inherent fast startup capability. Mixed utilities often allow continuation of operations, after a fashion, when one utility fails. 

Instrument and Plant Air Systems. A typical setup for a large plant could include three to four 50% instrument air compressors and two 100% plant air compressors, with steam drives for normally operated units and electrical drives for spares. Common practice would provide an interconnection to allow makeup from plant air into instrument air, but not vice versa, and two sets (two 100% driers per set—one on-stream and one regenerating) of 1007c instrument air driers. Two main receivers on instrument air near the compressors with several minutes holdup time and satellite receivers at process trains would be likely and proper for feasibility cost estimating. 

Backup systems which depend upon the action of automatic cut-in devices (e.g., a turbine-driven standby spare for a motor-driven cooling water pump, with PLCI control) would not be considered an acceptable means of preventing a utility failure for normal pressure relief design purposes, even though their installation is fully justified by improved continuity and reliability of plant operations. 

Normally an overcapacity line to an elevated flare is provided to handle the excess flow when the flaring rate exceeds the capacity of the multijet flare. The overcapacity flare is usually not equipped with steam injection, and smoke formation is accepted during infrequent operations. The overcapacity line and flare is designed to handle the entire maximum flow so that it can spare the multijet flare when the latter is shut down for maintenance. 

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