Tail pipe

All lation. The combination of olefins with paraffins to form higher isoparaffins is termed alkylation (qv). Alkylate is a desirable blendstock because it has a relatively high octane number and serves to dilute the total aromatics content. Reduction of the olefins ia gasoline blendstocks by alkylation also reduces tail pipe emissions. In refinery practice, butylenes are routinely alkylated by reaction with isobutane to produce isobutane—octane (26). In some plants, propylene and/or pentylenes (amylenes) are also alkylated (27). 

The relief valve must be installed so that gases are routed to a sale location. In small facilities and remote locations this is accomplished with a simple tail pipe, which points the discharge vertically upvsard anlower flammable limit in approximately 120 pipe diameters. Liquids may fall back on the equipment. 

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. 

Public concerns about air quality led to the passage of the Clean Air Act in 1970 to amendments to that act in 1977 and 1990. The 1990 amendments contained seven separate titles covering different regula-toiy programs and include requirements to install more advanced pollution control equipment and make other changes in industrial operations to reduce emissions of air pollutants. The 1990 amendments address sulfur dioxide emissions and acid rain deposition, nitrous oxide emissions, ground-level ozone, carbon monoxide emissions, particulate emissions, tail pipe emissions, evaporative emissions, reformulated gasoline, clean-fueled vehicles and fleets, hazardous air pollutants, solid waste incineration, and accidental chemical releases. 

Condenser tail pipes, used tvith any condenser, are sealed with a 34-foot leg into a sump, or with a condensate pump operating under vacuum on suction. With surface-type condensers, the level may be sealed in a receiver with a float or other type of level control. 

Figure 4-401 shows how a retrievable packer with a tail pipe can be used to precisely spot the cement slurry at the location of the perforations. 

SOUEE2ING AU PEPPOPATIONS AFTEP SETTING TAIL PIPE AND PACKER ABOVE THE CEMENT... 

Figure 4-401. Retrievable packer with tail pipe [161].

The perforation wash tool is retrieved and the packer run in the hole with a work string, set at the desired depth and tested. An annular pressure test of 1,000 psi is usually sufficient. The packer is run with or without a tail pipe, depending on the operation to be performed. If cement is to be spotted in front of the perforations, a tail pipe that covers the length of the zone plus 10 to 15 ft must be run with the packer. 

A spearhead or breakdown fluid followed by the cement slurry is circulated downhole with the packer by-pass open. This is done to avoid the squeezing of damaging fluids ahead of the slurry. A small amount of back pressure must be applied on the annulus to prevent the slurry fall caused by U tubing. If no tail pipe has been run, the packer by-pass must be closed 2 or 3 bbl before the slurry reaches the packer. If the cement is to be spotted in front of the perforations, with the packer unset, circulation is stopped as soon as the cement covers the desired zone, the tail pipe pulled out of the cement slurry and the packer set at the desired depth. The depth at which the packer is set must be carefully decided. 

If tail pipe is run, the minimum distance between perforations and packer is limited to the length of the tail pipe. The packer must not be set too close to the perforations as pressure communication through the... 

Two-plug method is a rather new method and requires the use of the telltale catcher sub (Dowell Schlumberger) to set a cement plug in a well at a rather precise location with minimum contamination. The tell-tale catcher sub is made up to the lower end of a drillpipe string. The sub also has an aluminum tail pipe, a bottom wiper plug (which carries a dart) and a top wiper plug. The sub on the drillpipe is lowered to the depth desired for... 

Heat loss in the exhaust pipe from the exhaust manifold to the converter can also be analyzed by Eq. (30). The flow is turbulent, and Nu depends on (Re)2/S. Assuming a tail pipe that is 3 ft long, and a Reynolds number of 30,000, the results of the computation are also shown in Table VII. Due to the low surface area, only 20% of the temperature above the wall temperature would be lost through the walls, and 80% would arrive at the converter inlet. As the gas velocity increases, heat loss through the... 

Chan, C.-C., C.-K. Nien, C.-Y. Tsai, and G.-R. Her, Comparison of Tail-Pipe Emissions from Motorcycles and Passenger Cars, J. Air Waste Manage. Assoc., 45, 116-124 (1995). 

Vermeulen RJ (2006) The effects of a range of measures to reduce the tail pipe emissions and/ or the fuel consumption of modem passenger cars on petrol and diesel. TNO report IS-RPT-033-DTS-2006-01695. TNO Science and Industry, Delft... 

This illustrates why a conventional SRV is best suited for simple discharge via a tail pipe into atmosphere. Its ability to tolerate built-up backpressure is very limited. 

When discharging to atmosphere via a vertical-rising tail pipe, recommended avoid using a flat-ended tail pipe, as shown in Figure 6.17. It is best to provide a 45 ° angle ending to the tail pipe to reduce built-up backpressure, reaction forces and noise while discharging. 

As a general rule, the length of the tail pipe should never exceed 12 times the pipe diameter. 

So P2 is not atmospheric and, as can be deducted from both formulas, the discharge reaction forces decrease if the discharge pipe is made larger (d2 increases, therefore P2 decreases, and P2 is proportional with the reaction force F). Based on the same principle, the reaction forces also decrease if, for instance, the exit to atmosphere through a tail pipe is scarf cut at an angle, because this results in an enlarged, oval exit area. 

Even though the reaction force due to the exhaust jet to atmosphere is significantly greater than the change in momentum component, the API makes no distinction for SRVs discharging into a closed header system compared with discharging through a tail pipe or direct to atmosphere. 

Depending on the calculated reaction forces, it is recommended to brace the discharge piping or tail pipe (Figure 6.24). 

Figure 6.25 shows the preferred tail pipe configuration to atmosphere in order to minimize the bending moment at the base of the SRV inlet riser. 

A tail pipe to atmosphere must be configured to eliminate or minimize the bending moment on the nozzle connection. It is important to note that the preferred type of stress on the inlet piping is compression, not tension as caused by bending. 

Another phenomenon caused by reaction forces, but one that is usually neglected, is the installation of a threaded SRV with tail pipe (Figure 6.27). If the outlet tail pipe is tilted in the wrong direction, it can cause the SRV to rapidly unscrew at the inlet when it relieves, making it come off and go airborne. 

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