Drain diameter

Tank dimensions - tank diameter of D = 3 m and drain diameter of d 30 cm... 

Dg = Skirt Diameter Dy = Vessei Diameter Hg= Skirt Height Hy = Vessei Height Dg = Vapor Exit Diameter Dq= Liquid Drain Diameter Dg = False Bottom Diameter... 

For deep deposits, the consolidation times may be long—months or even years. Drains can be used effectively to shorten the times, and are used universally with deep deposits. Sand drains can be put in place using the same method as for sand piles. A hollow steel shell is driven, cleaned out if necessary, and filled from the surface with a narrowly graded sand. Contrary to a sand pile, the sand fill is not compacted as the shell is withdrawn. The capacity of a sand drain to carry water depends primarily upon the drain diameter. Drains may become clogged over a period of time,... 

Appendix D, section D.3.2 presents the calculation of the consolidation period as a function of the coefficient of consohdation of the compressible strata, the drain spacing and the drain diameter. To a certain extent the consolidation rate can be controlled by adjusting the drain spacing. 

In the Sulser-MWB process the naphthalene fractions produced by the crystallisation process are stored in tanks and fed alternately into the crystalliser. The crystalliser contains around 1100 cooling tubes of 25-mm diameter, through which the naphthalene fraction passes downward in turbulent flow and pardy crystallises out on the tube walls. The residual melt is recycled and pumped into a storage tank at the end of the crystallisation process. The crystals that have been deposited on the tube walls are then pardy melted for further purification. Following the removal of the drained Hquid, the purified naphthalene is melted. Four to six crystallisation stages are required to obtain refined naphthalene with a crystallisation point of 80°C, depending on the quaHty of the feedstock. The yield is typically between 88 and 94%, depending on the concentration of the feedstock fraction. 

High density polyethylene is widely used for pipes and drains, especially in large-diameter cormgated forms. The cormgations provide stronger walls at less thickness, which reduces the materials cost of the pipe. 

Vl = liquid velocity in the drain pipe Pl = liquid density Pg = g3.s density D = pipe inside diameter h = liquid height... 

Where inerting is not used, one guideline restricts operations to metal or enameled metal tanks having a volume no greater than 5 m, a diameter no greater than 3 m and all conductive parts grounded. The liquid should contain a maximum of 1 wt% insoluble solids, have a maximum feed rate of 60 L/min and the delivery pressure should not exceed 50 bar. The vessel should be continuously drained to prevent liquid accumulation [127]. 

Eliminate all vents, drains and small diameter connections. 

Closed drain headers are normally provided for safe drainage of equipment containing severely toxic, corrosive, pollutant or high cost chemicals (e.g., phenol, sulfuric acid, monoethanolamine, sulfur dioxide, catacarb) where there is an appreciable inventory in a number of processing vessels in a plant. The header should be at least 50 mm in diameter, and should be tied into the major vessels and equipment with 25 mm minimum size connections (20 mm is considered adequate for pumps). The header may be routed to a gravity drain drum (with recovery to the process by pump or gas pressurization), or to a pumpout pump returning to the process, or in the case of sulfuric acid, to an acid blowdown drum. 

Relief valves vented to the atmosphere should have tail pipes equal to or larger in diameter than the relief valve outlet that extend vertically a minimum of one foot above building eaves, or eight feet above adjacent platforms on operating areas. The tail pipes should be provided with a drain located such that the exhaust through the drain hole does not impinge on vessels, piping, other equipment or personnel. 

In one incident, a man was draining water, through a 2-in.-diameter line, from a small distillation column rundown tank containing benzene. He left the water running for a few minutes to attend to other jobs. Either there was less water than usual or he was away longer than expected. He returned to find benzene running out of the drain line. Before he could close it, the benzene was ignited by the furnace which heated the distillation column. The operator was badly burned and died from his injuries. 

Two drain points were choked and one isolated. In addition, the change in diameter of the main provided an opportunity for condensate to accumulate. The main should have been constructed so that the bottom was straight and so the change in diameter took place at the top. 

Branch lines transfer oil from a ring main circuit to the oil-burning equipment. Where a residual oil fuel is to be used, there will be some cooling of the oil immediately adjacent to the pipe surfaces and this will show as a small increase in viscosity. To keep this variation to a minimum and so prevent any difficulties in atomization at the oil burner, care should be taken over the length and diameter of branch lines. Provision should always be made to isolate and drain branch lines. 

Internal diameter D < 10.4L(D < L/8) where D is in mm (in). Provision should always be made to isolate and drain branch lines. 

A length of 150 mm (6 in) main carries steam at 17 bar (2501b/in ). Drain points are located at 45 meters (150 feet) intervals, with collecting legs 100 mm (4 inches) diameter x 700 mm (28 inches) long. The main is brought up to pressure from 21°C (70°F) in 30 minutes. 

It is clear that in most cases other than very large distribution mains, in TD traps are sufficiently large. With shorter distances between drain points, or smaller diameters, then i in low-capacity traps more than meet even start-up loads. On very large pipes it may be worth fitting I in traps, or two in traps in parallel. Low-pressure mains often are drained through float/thermostatic steam traps, and these traps are now available for use at much higher pressures than formerly, where it is known that waterhammer will not be present. 

The downstream pressure-sensing pipe of each valve is connected to a straight section of pipe 10 diameters or 1 meter downstream of the nearest tee, elbow or valve. This sensing line should be pitched down, to drain into the low-pressure line. If it cannot drain when connected to the top of this line it can often be connected instead to the side of the pipe. The pipe between the two control valves must be drained through a steam trap, just as would the foot of any riser downstream of the pressure-reducing station. 

Features should be arranged so that moisture and dirt are not trapped. Where this is not practicable consideration should be given to the provision of drainage holes of sufficient diameter, located so that all moisture is drained away (Fig. 9.14). 

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