Heat exchanger tube failure

Remote contingencies such as heat exchanger tube failure or in case of closure of a CSO valve. 

Electric power loss Accumulation of noncondensibles Failure of automatic controls Loss of heat in series fractionation Volatile material entering system Heat exchanger tube failure... 

In a number of cases, heat exchanger tube failures attributed to flow-induced vibration have resulted In consequential damage to other equipment within a plant. Failures of this nature have proven to be the most destructive, most costly, and have required the longest plant shutdowns for rectification. 

A 1-ft. (30-cm)-long section of steel heat exchanger tubing containing no failure was received. The section was submitted for evaluation of the internal surface, which was lined with a phenolic epoxy resin. 

In production facility design, the most common relieving conditions are (1) blocked discharge, (2) gas blowby, (3) regulator failure, (4) fire. (5) thermal, and (6) heat exchanger tube rupture. Relief valve design How rates are commonly determined as follows. 

The presence of trace quantities of mercury in a process stream can cause the catastrophic failure of brass heat-exchanger tubes, from the formation of a mercury-copper amalgam. Incidents have occurred where the contamination has come from unsuspected sources, such as the failure of mercury-in-steel thermometers. 

Failure of Heat Exchanger Tubes If a heat exchanger shell rating is less than the pressure level of the circulating medium and an internal heat exchanging tube ruptures or leaks it will overpressure the vessel. 

The FMEA method can be illustrated using the second example to do with the shell and tube heat exchanger. Possible failure modes for the exchanger include the following ... 

Refractory lining failure Acid piping and cooler leakages Corrosion of demister pads/failure of candle demisters Heat exchanger tube leakages Loss of catalyst activity... 

Heat Exchanger Valve Failures or Heat Exchanger Tube Leaks... 

In March 1975, a leak occurred as a result of failure in a welded pulled-tee connection between one of the forty parallel cooling tubes and the header in one of these heat exchangers the failure was attributed to a cold tear which developed during manufacture and a repair was effected by fitting a replacement tee. Similar leaks occurred in 1981 and 1982. Strain gauges and thermocouple were fitted to one of the loops and these revealed considerable temperature anomalies in a number of the tubes. 

This type of failure is generally encountered in pump shafts, heat exchanger tubes, rotors, steam turbine blades, aircraft wheels, boiler and steel equipment. Some major examples where corrosion fatigue is encoimtered are given below ... 

Corrective maintenance. Corrective maintenance refers to action taken only after a system or component failure has occurred. It is thus a retroactive strategy. The task of the maintenance team in this scenario is usually to effect repairs as soon as possible. Costs associated with corrective maintenance include repair costs (replacement components, labor, and consumables), lost production, and lost sales. To minimize the effects of lost production and speed up repairs, actions such as increasing the size of maintenance teams, using backup systems, and implementation of emergency procedures can be considered. Unfortunately, such measures are relatively costly and/or effective only in the short term. For example, if heat-exchanger tubes have... 

Blocked outlet 2) inadvertent valve open 3) control valve failure (full open or close) 4) loss cooling stream 5) instrument aii failure 6) power failure 7) abnomiaJ heat input 8) equipment failure 9) heat exchanger tube ruphue ID) thermal expansion 11) fire 12) chemical reaction 13) steam out, 14) operator error, etc. 

Failure of a heat exchanger tube in PWRs (e.g. rupture of a steam generator tube) ... 

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