Distance Pieces

Another variation is the tandem cylinder. The tandem cylindet arrangement again allows two stages of compression on the same compressor throw but uses two double-acting cylinders separated by a second distance piece. This arrangement is usually used in low rod load applications where higher capacity is required. 

AUCTION VALVES AT ENDS OT CYLINDER ARE STATIONARY, DO NOT MOVE 

A two-compartment distance piece may be used for toxic gases, but it is not very common. In this configuration, no part of the rod enters both the crankcase and the compartment adjacent to the compressor cylinder. That is, even if there were one failure, the crankcase oil cannot be contaminated with the toxic gas. 

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Most other rotor parts in gas turbines are individually forged. This includes compressor wheels, spacers, distance pieces, and stub shafts. All are made from quenched and tempered low-alloy steels (Cr-Mo-V or Ni-Cr-Mo-V) with the material and heat treatment optimized for the specific part. The intent is to achieve the best balance of strength, toughness with ductility, processing and nondestructive evaluation capability, particularly when it is recognized that some... 

In reciprocating compressors, the use of explosion-relief devices must be stated if desired. The type and style of distance piece must be specified together with the connections for the collection and disposal of leakage gas. API 618 gives a rather complete coverage of all options. 

A distance piece provides the separation of the compressor cylinder from the compressor frame as shown in Figure 11-9. At the top of the figure is a standard distance piece. 

Long single-compartment distance piece (sufficient length for oil siinger travel)... 

Figure 11-9. API type distance pieces. (Reprinted with pennission from API, Sid. 618, 3rd Ed., Feb. 1986.)...

DISTANCE-PIECE OPENING provides free access to packing. 

Figure 12-2Q. Cast or nodular iron cylinders for pressures to 1,500 psi. Note double distance-pieces (left, vented or purged, to prevent oil and process gas from leaking past the shaft and right-end fixed clearance pocket). (Used by permission Bui. 85084, 1992. Dresser-Rand Company.)...

B) A Two-compartment or double distance piece arrangement (in-board distance piece of sufficient length for oil slinger travel). 

Figure 12-2T. Medium- or high-pressure, double-acting cylinder with flanged liner. The liner is locked in place by a flange between head and cylinder barrel. A step on the liner O.D. permits easy insertion. The cylinder may be made of cast-iron, nodular iron, or cast steel, depending on operating pressure. Note Optional two-compartment distance piece (type D) designed to contain flammable, hazardous, or toxic gases is illustrated. (Used by permission Bui. 33640, June 1985. Dresser-Rand Company.)...

Distance piece allows access to packing and oil-wiper rings. 

Distance Piece or Cross Tube (Kreuziohc, in Ger). This device was used in Germany when a proplnt charge of semi-fixed artillery ammunition was shorter than the cartridge case. The piece consisted of one or several tubular sticks of... 

Distance piece or cross tube 5 D1508—D1509... 

Fig. 6.6. Cross-section through heart of cone-and-plate system. (C) cone, P) plate, (1F1, IV2) windows, (M) reflection prism, [Z) cover, (F) filling hole, handle, (K) distance piece. Part E and V are explained in the text. AA, axis of rotation LL light propagation (77)...

The specimens treated with an anti-corrosion coating were placed one after the other on two threaded rods as described below. PTFE distance pieces were placed between the specimen to ensure defined crevice conditions. The complete package of specimens (Figure 11.74) was screwed up firmly at the end of the threaded rods and then placed in a beaker of FeClj solution (Figure 11.75). The threaded rods and bolts were made of rust-resistant steel. ... 

Figure 11.74. Specimen package in accordance with ASTM G-48 with PTFE distance pieces to create define crevices [120],...

After removal of the specimen package from the test solution, all specimen displayed, on the upper side only, damage to the coating and corrosion of the metal plate underneath the coating. This corrosion evidently took place at the attachment site of the PTFE distance piece. 

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