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 Compressor Cylinders  (Download Custom Cylinder Literature, Valve-in-Head Literature)

Most ACI water-cooled cylinders utilize slip-fit liners. Pistons are general multi-piece to facilitate rider ring installation. Piston rods are commonly produced from AISI 4140 heat treated materials and hardened in the packing area. The standard rod design utilizes a multi-through stud arrangement to minimize the torque required for assembly and disassembly of the piston from the rod. Valves are designed to suit the applications and are always non-interchangeable to prevent possible incorrect installation -- this is an API 618 requirement.

All ACI compressor cylinders and related gas containing components are subjected to hydrostatic tests at least 1½ times the maximum working pressure for at least 30 minutes. Other inspection procedures are applied on an as required basis.  Materials of construction are selected with respect to pressure rating, cylinder size, compression medium and other factors that might influence the suitability of a material for a given application. Exotic materials are available. ACI material specifications are based on referenced industry standards such as ASTM, ASME, SAE and AISI. Fasteners such as studs, nuts and bolts are of high grade materials. Studs and piston rods feature rolled threads.

Accessory equipment for compressors may either functionally duplicate OEM designs, be of a standard design, or a special ACI proprietary design when duplication is not the best engineering approach. ACI cylinder standard designs comply with API 618 standards.

The patented Four-Poster compressor cylinder design has been engineered specifically to meet critical gas transmission requirements. It is highly efficient and includes many mechanical innovations that improve serviceability and reduce maintenance downtown. The design also minimizes field installation costs, both in new and in reapplication situations. The cylinder can be applied to a wide range of integral engines, providing complete compressor spare parts standardization. In many reapplications, the Four-Poster can even be installed without disturbing existing drums and piping!
 

The Four-Poster cylinder utilizes a one-piece cast iron, or ductile iron, body. Four vertical valve pockets are provided, one at each corner of the body. Each pocket houses one suction and one discharge valve, separated by a diffuser cage. All valves load from the top and use a common horizontal loaded port, in line with the diffuser cage in each pocket, to provide communication between the valves and the main bore. Valve caps or clearance volume unloaders are installed over the valve pockets.

The vertical orientation of the valve pockets and top-mounted unloaders improve maintenance. Servicing requires only a small overhead crane, thus eliminating the need for special jacks or handling tools required on most other designs. The Four-Poster valve orientation maximizes safety for maintenance personnel.

Maintenance is further improved by virtue of the liner and rear head design. The liner is slip-fitted to the body bore, requiring only a moderate force for assembly or removal. The rear head is a plug-type design assembled through the front end of the cylinder. Thus, both the liner and the rear head, complete with packing case, can be removed or installed without removing the cylinder from the frame.

The piston and rod assembly is also designed for ease of maintenance. Multiple through-studs attach the piston to the flanged rod, permitting removal of the piston without disturbing the rod to crosshead attachment. Drake locknuts are used to safely secure the piston to the rod. Use of a segmented piston aids in the assembly of the stretch type non-metallic rider bands. The Four-Poster design is compatible with the use of ACI's patented ExactoTorque™ locknuts for safe, trouble-free attachment of the rod to the crosshead. This multi-jackscrew design provides precise prestressing of the rod with much less torque than is required with conventional hex nuts. It also improves safety for maintenance personnel by elimination of the use of a slugging wrench.