Page 242 - The Tribology Handbook

Piston rings B17

METALLIC LUBRICATED RINGS

Selection of type and materials
Table 17.1 Types of piston rings and guidance on selection’

Ring 9% Description Ring trpe Description
z
STRAIGHT- The most simple ring can GROOVED Materials such as
FACED be chromium-plated on INLAID chrome, bronze and 2
RECTANGkULAR peripheral face to give ferrox are inlaid in 2 v:
Lilt
longer life multi-groove .$
configurations, e?
providing good scuff 2
resistance e
BARREL- Widely used as top EXTERNALLY - Combines gas sealing
FACED compression ring in STEPPED and oil control 4g
CHROMIUM- diesel and petrol engines. COMPRESSION functions, the step < a
PLATED Gives quick bed-in. good AND @
scuff resistance and long SCRAPER giving the ring a 2
torsional twist when
life. Has neutral oil 9 fitted
control characteristic
NAPIER
RECTANGULA + Various low-wear-rate
/ scuff-resistant materials,
such as electroplated
chrome, sprayed chrome,
molybdenum, etc. are set
SEMI-INLGID 9 into ring periphery. Very popular ring
/ Outer lands give edge SPRING
protection to deposited LOADED high-speed diesels.
m
material SLOTTED Main wall pressure is
OIL CONTROL derived from butting
d KEYSTON 2 A common top ring in helical coil expander.
diesel engines prevents BEVELLED Chromium-plated for 2
sticking due to carbon
formation fitted in
m groove with similar taper

3 SLOTTED A common form of bulk
TRPERFACED Normally between io to OIL CONTRO oil scraper with two
l$, gives quick bed-in
and combines gas sealing
and oil control features.
A witness land at
periphery is often added BEVELLED

DYKES Mainly used in high-speed
PRESSURE racing applications to
BACKED prevent blow-by due to
‘flutter’ under high STEEL (a) Combined spacer
inertia loading. Fitted in RAIL expander
6
a groove of similar shape MULTIPIECE ib) Separate spacer
,I
expander
INTERNAILLY . Step or bevel relief on (a)
STEPPED inner edge causes ring to These rings allow very
POSITIVE dish when fitted, giving high scraping
TWIST bottom edge contact and pressures to be
TYPE 7a good oil control applied with good
(b) conformability, and
NEGATIVE / / have chromium-
TWIST plated rails
TYPE
7b
* Basic ring types only shown above. Several features often combined in one ring design, e.g. 4, 7 and 2, giving internally stepped,
barrel-faced, chromium-plated, keystone ring.
B17.1