F
OR
M
ODELS
: JGI, JGM, JGN, JGP
AND
JGQ
S
ECTION
5 - M
AINTENANCE
PAGE 5-46
Compressor Cylinder Re-Boring & Bore Restoration
Guidelines
Compressor cylinder re-boring and bore restoration guidelines are to be followed for cylinder
maintenance to provide efficient, cost-effective operation:
1.
If the cylinder bore surface is blemished or gouged, affecting efficiency or caus-
ing rapid ring wear, or is more than 0.001 inches per inch of cylinder bore diam-
eter (0.001 mm/mm) out of round or tapered, the cylinder body should be
replaced or the bore restored to the guidelines below.
2.
It is essential that a cylinder has counterbores to allow for ring over-travel, or
future wear would make piston removal very difficult. Ariel compressor cylinders
are provided with counterbores that are 0.050 inches (1.27 mm) larger than the
nominal cylinder bore. The maximum over-bore on an Ariel cylinder bore diam-
eter is 0.044 inches (1.12 mm) larger than the nominal bore diameter, provided
the new main bore is concentric with both counterbores, leaving 0.003 inches
(0.08 mm) minimum steps to the counterbores.
3.
If the cylinder is bored more than 0.020 inches (0.51 mm) larger than the nomi-
nal bore diameter, a special oversize wear band and/or sealing rings may be
required depending on pressures and gas conditions. This is more applicable for
light gases, such as Hydrogen. Oversize wear bands and piston rings are not
available from Ariel. See Section 1 (Ariel Technical Manual) for maximum ring
end gaps.
4.
In a given cylinder class, a smaller-bore cylinder can be re-machined to the
larger-bore diameter and counterbores. (New piston, piston rings, wear band if
applicable, re-stamping cylinder data tag, and hydro-testing are required).
Re-boring can expose internal casting shrinkage, which would render the cylin-
der body unusable.
NOTE: CAUTION: ANY RE-MACHINING OF THE COUNTERBORES IN ORDER TO
RESTORE THE BORE OF A SMALLER-BORE CYLINDER OF A GIVEN CYLINDER
CLASS REQUIRES HYDRO-TESTING THE CYLINDER BODY AT 1.5 TIMES THE MAWP
RATING ON THE CYLINDER DATA TAG BY A QUALIFIED FACILITY, BEFORE
RETURNING THE CYLINDER TO SERVICE.
5.
Cylinder design is based on the 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,
the cylinder should either be replaced or reconditioned. Reconditioning may
include aftermarket application of metal spray. Ariel does not provide this ser-
vice. Contact Ariel for a copy of Reference ER-40 "Thermal Spraying Compres-
sor Cylinder Bores to Return to OEM Dimensions" for additional information.
6.
Any re-boring operation will remove the hard nitrided layer in ductile iron cylin-
ders, which is provided to extend the service life of the bore. The user should
determine the cylinder bore hardness required for the application. To maintain
the OEM hardness level, re-machined iron bore surfaces should be hardened
after finish machining by nitriding or other hardening process that does not result
in distortion or changes in the bore that are detrimental to operation of the com-
pressor. Resulting bore hardness is to be taken into consideration when metal
spraying. Contact Ariel for assistance on cylinder bore hardness requirements.
7.
Cylinder re-boring and bore restoration must be done by qualified suppliers and
