Piston sealing

Because most axial compressors are in air service, most are equipped with labyrinth type end seals. There are no interstage seals in the machines with unshrouded stator blades. The balance piston seal, a labyrinth type, is the only internal seal. There is no reason that axials cannot use some of the other seals as described in Chapter 5, such as the controlled leakage or the mechanical contact type, if the gas being handled by the compressor needs a more positive seal. If there is any prob-... 

They are normally limited to a maximum inlet temperature of 250 °C by the "D" ring piston seals. 

Piston sealed by two single-piece snap rings. Rod threaded and locked into piston. 

Development of Self-Lubricating. Piston-Seal Materials for High-Pressure, Oil-Free Air Compressors , Rept No PAS-75-21, Naval Ship R D Center, Annapolis (1975) 3) T. Toshiaki ... 

Caliper piston seal SBR Heat resistance, Ufe EPDM ... 

Piston meters, reciprocating, 11 655 Piston seals, in high pressure apparatus, 13 415... 

Comparison of the retention behaviour in 50% aqueous DMF and acetonitrile (Figure 4.3D) indicated that DMF is a selective modifier for the separation of alkanols ( , 1-6) and PAHs (11-16) and of aromatic and aliphatic compounds. Unfortunately, DMF is too aggressive as a solvent and attacks organic polymer piston seals in the pump and, therefore, highly concentrated solutions cannot be used as an eluent. 

Always turn on piston seal wash feature to prolong seal life. 

Never let buffers sit immobile inside pumps or columns. They can precipitate and cause severe damage to the piston and the piston seal. 

LC pumps—replace or clean piston seals, pistons, in-line filter, solvent filter sinkers and check valves. 

Annual preventive maintenance, in which most wearable items such as pistons, seals, lamps, and filters are replaced, is to be scheduled before calibration. 

Left, Cross section Right, Piston seal Detail (X) 7, Cylinder bushing 8, Labyrinth twin-rings 9, Labyrinth guiding ring. 

It is especially difficult to seal pistons with reciprocating motion. Piston rings are suitable as piston seals in piston compressors up to 1500 bar. Above 200 bar, lubrication is generally required. 

The maintenance and installation of piston seals requires a great deal of experience the necessary flushing- and lubricating systems are sometimes quite complicated. Frequently, the optimal design (3000 to 8000 h lifetime) must be determined empirically. 

Cautionary note A number of the HPLC methods listed in this chapter use phosphate buffers as solvents. It should always be remembered that phosphate salts are very abrasive to piston seals and pistons. If using these systems, always remember to wash out the aqueous pump thoroughly with water at the end of a run. If this operation is not carried out, the piston seal lifetime will be significantly reduced and in some cases, if left too long, pistons can stick and possibly fracture, which will be expensive to repair/replace. 

The POSRV consists of two basic components a main valve, which provides the capacity, and a pilot, which controls the main valve. In normal operation, the pilot allows the system pressure (P) to act upon the top of the piston. The unbalanced piston assembly is increasingly forced down onto the nozzle with increasing system pressure due to the piston seal area (AD) being larger than the seat seal area (AN). The surface (AD) on top of the piston on which system pressure arts is approximately 30% greater than the seat area. So the closing force (F = PAD) increases as pressure rises (Figure 5.33). 

In case of pilot valve, check the piston seal and other soft goods within both pilot and main valve Change all soft goods. 

Figure 3.5 Reciprocating-piston pump head showing the check valves, piston, seal, and pulse damper. (Adapted from Ref. 1 with permission.)...

A cutaway drawing of the rotating-cylinder reactor is shown in Fig. 35. The mechanical aspects of the reactor system were designed to provide temperature control, fluid containment, and process measurements. The apparatus consists of a stainless steel (SS) holder and glass cylinder in which rides an SS piston, sealed by two Viton O-rings. Piston movements is monitored by a linear variable differential transformer (type 250 HCD, Schaevetz Engineering) attached to the piston and fixed relative to the cylinder. 

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