Heavy Duty Balanced Opposed Compressors - Ariel Corporation

FOR MODELS: JGZ AND JGU SECTION 5 - MAINTENANCE
can make a seal that takes some time to vent. If gas is trapped behind the piston, the VVCP
can be adjusted when the cylinder is pressurized, but difficult to turn when cylinder is vented.
This problem is corrected by disassembling the VVCP and cleaning.
To adjust volume, loosen stem locking handle (or locknut), so that stem is free to turn. Turn
stem by use of adjusting handle on outboard end of shaft (or wrench flats). Turn clockwise to
load; counterclockwise to unload the compressor cylinder. See the VVCP instruction plate on
the equipment for the dimensional positions for fully closed (load) and fully open (unload).
Reference Section 1 for an illustration. Re-tighten stem locking handle (or locknut) to hold
stem in place.
Compressor Cylinder Re-Boring and Bore Reconditioning
Guidelines
Cylinder Re-Boring
If the cylinder bore surface is blemished, gouged, or more than 0.001 inches per inch of
cylinder bore diameter (0.001 mm/mm) out of round or tapered, or if it affects efficiency or
causes rapid ring wear, replace the cylinder body or restore the bore to the guidelines below.
1. A cylinder requires counterbores to allow ring over-travel, else future wear makes piston
removal very difficult. Ariel compressor cylinders ship with counterbores 0.050 inches
(1.27 mm) larger than the nominal cylinder bore. The maximum over-bore on an Ariel cylinder
bore diameter is 0.044 inches (1.12 mm) larger than nominal, provided the new
main bore is concentric with both counterbores, leaving 0.003 inches (0.08 mm) minimum
steps to the counterbores.
2. Cylinder bore diameters more than 0.020 inches (0.51 mm) larger than nominal may
require a special oversize wear band and/or sealing rings, depending on pressures and
gas conditions. This applies more to light gases, such as Hydrogen. Ariel offers no oversize
wear bands or piston rings. See Ariel Technical Manual, Section 1 for maximum ring
end gaps.
3. In a given cylinder class, a qualified machine shop can re-machine a smaller bore cylinder
to the larger bore diameter and counterbores. It requires a new piston, piston rings,
wear band (if applicable), cylinder data tag, and hydro-testing. Re-boring may expose
internal casting shrinkage, which renders the cylinder body unusable.
CAUTION: Any counterbore re-machining to restore the bore of a smaller bore
cylinder of a given class requires a qualified facility to hydro-test the cylinder
body. Test at 1.5 times the cylinder data plate MAWP rating before returning the
cylinder to service.
4. Cylinder design is based on wall thickness at the counterbores of the larger cylinder bore
for any given cylinder class. Therefore, the larger bore cylinder counterbores of a cylinder
class cannot be machined larger. In this case, either replace or recondition the
cylinder. Reconditioning may include aftermarket application of metal spray. Ariel does
not provide this service. See "Cylinder Bore Reconditioning by Thermal Spraying" below
for additional information.
5. Cylinder re-boring removes the nitrided layer (if applicable) that extends bore service life.
The user should determine the cylinder bore hardness required for the application. To
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