Bypass pipe connection

A bypass pipe connection may be used to isolate the mixing tank from the rest of the dyeing vessel in this way low liquor ratios can also be established. The fluid flow loop through the pipes, however, can be controlled by means of pneumatic valves that direct the fluid from inside to outside, or vice versa, of yam packages. This may be done with the aid of a four-way valve located at the base of the kier. A ventilator valve may be used to direct the liquid in the top of the kier to the mixing tank, and once the kier is full this valve is shut off. Valves may be controlled manually via a control box or via connections to the interface, which in the example in Table 7.2 are BlTs 0-5 of PORT B. All pneumatically operated ball valves on the machine may be fitted with doubleacting actuators. The actuators may be controlled by solenoid/spring spool valves (e.g. 5/2). The term 5/2 denotes a valve with five ports and two positions. 

The piping around any facility, other than the straight pipe connecting the equipment, is made up primarily of a series of control stations. Flow from one vessel goes through a control station and into a piece of pipe that goe.s to another vessel. In addition to considering the use of block valves, check valves, etc., all control stations should be designed so that the control valve can be removed and any bypass valve is located above or on a level with the main control valve. If the bypass is below the con tiol valve, it provides a dead space for water accumulation and corrosion. 

In the Flixborough disaster, one of six reactors in series, through which hot cyclohexane was passed, was removed from service (see Figure 2.1). Each reactor was connected by a short pipe with a bellows at each end to allow for expansion. The fifth reactor was replaced by a temporary bypass pipe with two bends in it to allow for differences in height between reactors 4 and 6. Because the bypass was not properly supported and had a bellows at either end, it moved when there were pressure variations. This movement eventually caused the bellows to fail, releasing 50 tons of cyclohexane which exploded, killing 28 men. 

The feed pipes connecting the reactors were 28 inches in diameter. Because only 20-inch pipe stock was available at the plant, the connections to reactor 4 and reactor 6 were made using flexible bellows-type piping, as shown in Figure 1-10. It is hypothesized that the bypass pipe section ruptured because of inadequate support and overflexing of the pipe section as a result of internal reactor pressures. Upon rupture of the bypass, an estimated 30 tons of cyclohexane volatilized and formed a large vapor cloud. The cloud was ignited by an unknown source an estimated 45 seconds after the release. 

The accident happened when the plant had to replace one of six reactors and rushed to refit the plant to bypass the disabled reactor. Scaffolding was jerry-rigged to support a 20-in. pipe connecting reactor four with reactor six, which violated industry and the manufacturer s recommendations. The reactor that failed showed stress crack corrosion. The only drawings for the repair were in chalk on the machine shop floor. Both ends of the 20-in. 

FIGURE 10 Three ways of coupling an auxiliary heater with the solar space heating system (1) In the storage tank, (2) in the distribution circuit flow pipe (series connection), and (3) In a storage bypass (parallel connection). 

The secondary circuit comprises the steam generators, turbine, condenser, condensate pumps, deaerator, feedwater pump, feedwater heaters, bypass line, connecting pipes and control valves. 

The turbine bypass pipe woik and valves connected to the main steam lines must have sufficient capacity to dump to the main condenser the steam arising during any Design Basis initiating event, for cooling down the steam generators and the reactor coolant system when the main condenser is available. 

Most state laws and safe practice require a safety relief valve ahead of the first stop valve in every positive displacement compressed air system. It is set to release at 1.25 times the normal discharge pressure of the compressor or at the maximum working pressure of the system, whichever is lower. The relief valve piping system sometimes includes a manual vent valve and/or a bypass valve to the suction to facilitate startup and shutdown operations. Quick line sizing equations are (1) line connection, (i/1.75 (2) bypass, ii/4.5 (3) vent, dl63 and (4) relief valve port, cU9. 

The heating mediums of steam or a hot process stream always connect to the tube side of horizontal reboilers. The inlet piping should have a control valve — with block valves and a bypass globe valve, if required. This should be arranged near the reboiler s tube side inlet. 

Fig. 14.3 Centrifugal compressor installation. Note that the designer has chosen to locate the connecting piperack on a level above the compressor this provides the facility to anchor the piping loads caused by thermal expansion, and also maximizes access to the compressor (while minimizing the elevation). Note also the bypass control valve for surge protection...

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