Valve failure

Overfill drum due Calibrate weighing devices and maintain equip-to operator error ment in good working order or valve failure,. metering pumps can lead to opera- tor exposure, slip- fill operation with weighing device pery floors, spread of flammable liquids. CCPS G-3 CCPS G-15 CCPS G-22 CCPS G-29... 

Valve Failure Positions In the event of instrument air or electrical power failure, valves either Fail Closed (FC), Fail Open (FO), or Fail in the last position (FL). The position of failure must be carefully selected so as to bring the system to, or leave the system in a safe operating state. 

If refrigerant temperature Is high and 3. Compressor valve failure. 

When a fire occurs, it is assumed that all fluid flow to and from the fire risk area has been stopped. Therefore, flow loads such as control valve failure or incoming feed streams are not additive to the fire load. Credit is not generally given to flow out through normal channels, since they could also be blocked during the fire emergency. 

Failure of Individual Control Valve - The following individual control valve failures should be included in the analysis of control systems for determination of pressure rehef requirements ... 

When analyzing such individual control valve failures, one should consider the action of other control valves in the system. In the first two cases above, credit may be taken, where applicable for the reduction in pressure of a high-pressure source due to net inventory depletion during the period that the downstream equipment pressure is rising to relieving pressure. However, the pressure relieving facilities must be sized to handle the calculated peak flow conditions. 

Valve cin vil loo tai [iiloni-il valve failure Operation No Ny pressure to HF cylinder - no HF flow Lo vaporizer, B-l wing Local pressure indication on N2 line None tv ... 

Table 5.1-3 Motor-Operated Valve Failure Modes...

Turbine trip 1 Turbine trip with turbine bypass valve failure... 

A Statistical Analysis of Nuclear Power Plant (Pump and Valve) Failure Rale Variability me Preliminary Results Nuclear All IPRDS data base records for the pumps and valves selected for analysis The set of valves and pumps selected for analysis from the IPRDS data base 104. 

Investigation of Valve Failure Problems in LWR Power Plants Nuclear 195 LERs valve failures causing trips from 12/72 to 12/78. plus all valve failures for 10 stations from 2/66 to 1/79 Valve-related events reported in LERs. as noted above 105. 

Investigation of Valve Failure Problems in LWR Power Plants... 

NUMBER AND TYPE OF RECORDS 195 LERs valve failures causing trips from... 

The study performed by Burns and Roe (BSR) shows that valve failures constitute the component category most responsible for the shutdown of PWR and BWR plants. This Investigation, contracted with SNL for DOE, identified the principal types and causes of valve failures that led to plant trips for the period from 12/72 to 12/78. The primary sources of data for the report were searches of the data base, the monthly Gray Books, Nuclear Power Experience publications, as well as discussions with utilities, valve manufacturers, and suppliers. 

This study is a good reference for the construction of fault/event trees of systems that are affected by valve performance. The valve failure modes are identified, the associated mechanisms are described in detail, and preventive measures are offered. 

Component Name AIR-OPERATED VALVE Failure Mode SPURIOUS OPERATION... 

Typical pipe and valve failures and tlie reasons for tlieir occurrence are discussed by Kletz. The paragraphs tliat follow give some examples. 

Safety Valve Required to Prelect Reducing Station Discharge Pressure in Cose of Valve Failure. SV-I is Set at Slightly Above Downstream Pressure of Reducing Station,and Protects All Equipment Operating at this Pressure on Steam Header. 

Possible causes—blockage, valve failure (mechanical or power), failure of steam supply (fracture of main, boiler shut-down). 

The charcoal beds must be thermally isolated from each other. The air inlets must be positioned far enough apart so as to minimize feedback of clean air back into the system. To prevent the accumulation of radon in the house in the event of a valve failure, all valves should be provided with backups. The volume of air cleaned per unit mass of carbon increases exponentially with decreasing temperature (Kapitanov et al., 1967). Thus greatly increased adsorption capacity can be obtained by cooling the carbon below ambient temperature. Although this process will require additional energy input, it may be worthwhile to consider some form of cooling. 

It was considered necessary, however, to expose the cyckxie to wider and various conditions to confirm that H could handle higher levels of inlet contamination. Its response to process upsets, when t valve failure could result in a slug of oil being carried out in the produced water stream was also tested. 

The full system input flow continues to feed the vessel while the outlet is partially or totally blocked due to personnel error, valve failure, actuator failure,... 

This is clearly a double jeopardy failure two unrelated events occurring at exactly the same time. One has nothing to do with the other. Therefore, you need to calculate the relief capacity for one scenario at a time. For the loss of power to a pump scenario, the relief load would be based on the amount of vapour generated at the normal rate of steam. For the steam control valve failure scenario, the relief capacity would be based on the amount of vapour generated by the heat provided by a wide-open steam valve even accounting for the amount of vapour condensed in this failure, the condenser would still be in operation. So the SRV should be sized for the worst condition. 

An actuator fault can be generated by a malfunction of the cooling system, such as electric-power failures, pomp failures, valves failures, and leaking pipes. Without loss of generality, actuator faults may be modeled as an unknown additive term affecting the state equation in (6.5), due to unexpected variations of the input u with respect to its nominal value, i.e., the value computed by the reactor control system. 

Each pair of chambers is connected to the protein sample and one of 48 crystallization solution reservoirs. The chip has 480 integrated valves that are actuated through three separately addressable control lines. As a precaution, 48 safety valves are included at the solution inlets to avoid the unwanted loss of protein sample in the unlikely event of an interface valve failure. The remaining two lines simultaneously control all interface and containment valves. By virtue of this parallel architecture and the robustness of the BIM scheme, solutions of varying viscosity, surface tension, pH and ionic strength may be simultaneously metered and mixed at three different mixing ratios using only two hydraulic control lines. 

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