Double offset

Pipes in a compressor circuit should connect directly point-to-point. Bends instead of elbows cause less friction loss and less vibration. Angular branch connections eliminate hard tees and give a smoother flow. Double offsets for a directional change should be avoided. Intercoolers closely integrated with the machine minimize piping. Pulsation dampeners should be located on the cylinders without any interconnecting pipe. Knockout drums should be adjacent to the machine. Several after-coolers or exchangers in the circuit should be stacked as much as possible for a direct gas flow. Equipment in the circuit should be in process flow sequence. 

The common types of expansion bends are either fabricated or built-up. Fabricated bends may be of simple-17, double-offset-77 (Fig. 109), circle, or single-offset-77 shapes. Creased bends, though once used to some extent, have become less popular in recent years. Built-up bends are made in a number of configurations from welding elbows. 

The high performance butterfly valve operates like aU butterfly valves with a disk mounted in the middle of the valve that is rotated to open and close the valve. The high performance butterfly is designed with a more complex disk assembly often called "double offset." The first offset is done by locating the stem downstream of the centerline of the disk. This allows an unobstructed 360-degree sealing surface. The second offset moves the stem off the vertical axis of the disk. The combination moves the disk quickly away from the seat as the stem is rotated. This is done to reduce operating torque and extend seat life. 

The double offset option should only be utilized when the follower ring width, U, exceeds the 25% limit of the gasket width w . 

If to > w then the designer must decide whether a single or double offset is required. 

If the single offset exceeds. 25 w, then a double offset is required. 

Check width of ring for double offset w = to — 2 X offset... 

Style single offset, double offset, triple offset... 

Poly(ethylene oxide). Although AH j is more than double that of polyethylene, the effect is offset by an even greater increase for AS j. The latter may be due to increased chain flexibility in the liquid caused by the regular insertion of ether oxygens along the chain backbone. 

A double helix shortens mixing time but requires more power. The disadvantages of the higher torque requirement are freqiientlv offset bv the better mixing and heat transfer,... 

Select a tungsten carbide insert bit with no offset and conical or double cone inserts when drilling hard and abrasive limestone, hard dolomite, chert, pyrite, quartz, basalt, etc. Use bit type 7-4 to 8-3. 

Furthermore, the share cf crops lost to Insects has nearly doubled during the last 40 years (Table 1), despite a more than 10-fold increase in both the amount and toxicity of synthetic insecticide used (17-19). Up to the present time the increased insect losses, in terms of yields per hectare, have been offset by increased crop yields obtained through the use of higher yielding varieties and greater use of fertilizers and other energy-based inputs (20, 21). 

TABLE 1 Chemical shifts, offsets relative to the transmitter, calculated and observed double quantum frequencies for selected 13C resonances of strychnine (1)... 

As shown in Fig. 17, the BSFS, by a double adiabatic decoupling, is not only significantly reduced compared with that by a single adiabatic decoupling but it also becomes linear as a function of the offset as predicted by Eq. (102). This linear BSFS is corrected by the application of a dilated evolution time =[l+(/lnnS/A/)2]h. 

Fig. 17. The BSFS versus the offset S for a single (open circles) and a double adiabatic (filled circles) decoupling, respectively. By application of a dilated evolution time t = 1.00223/], the remaining BSFS, which is linearly proportional to the offset, is eliminated (filled diamonds). Reprinted from Ref. 47 with permission from Elsevier.

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