Chemical Engineering February 2016 - 53

isolation valves require highly reliable
shutoff and sealing capabilities
in order to prevent dangerous leaks
in harsh operating environments.
Application-specific materials may
prevent corrosion, but rolled threads
can help to ensure stronger seals
and connections.
Rolled threads are work-hardened
without the removal of material, so
the natural material grains are left
unbroken and continuous. As a result,
these threads have much higher
yield strengths and tighter tolerances
than that of cut threads. The uniform
thread geometry of rolled threads allows
parts to fit together better, with
fewer chances for sliding or loosening.
depending on the ductility of the
material, tolerances of rolled threads
can be as tight as ±0.015 mm.
These tight tolerances are ideal for
threaded valve joints and connections
that require reliable material isolation
and shut-off.
Production costs. As with material
selection, the selection of the machining
method can impact costs. The
thread-rolling process is much more
efficient than cutting, and in some
cases can result in 90% decreases in
production times. unlike the cutting
tools that must be sharpened and
reset periodically during machining,
the dies used for rolling can continue
production for long periods of time.
die lifetime is an important factor in
considering machining costs. Figure
5 shows an example of some internal
components from a high-pressure
fog valve that are constructed of 316
stainless steel. For such components,
the designer has the option to specify
full thread crest, if required. However,
if an application does not require full
thread crest, the costs will be lowered
because the die life is increased when
the crest is not full. This has no impact
on the effective portion of the thread.
Full thread crest was not specified for
the components in Figure 5.
The accuracy of rolled threads
is another factor that makes them
cost-effective, because the need to
frequently inspect threads for consistency
during production runs is
eliminated. This saves on costs of
labor. By rolling threads, the design
engineer will observe the exact same
thread geometry for the first part as
the last.
An understanding of the intended
functionality and operating environment
is significant in deciding on a
material for a small threaded part or
valve component in the CPI, but this is
only part of the process. going a step
further in the design of these components
by specifying the machining
method is another way of ensuring
that the part will operate at peak performance
when manufactured from
the desired material.
■
Edited by Mary Page Bailey
Author
Kenneth Rinier is the general
manager of Vallorbs Jewel Co.
(2599 Old Philadelphia Pike,
Bird-In-Hand, PA 17505; Website:
www.vallorbs.com; Phone: 1-717392-3978),
a precision parts machining
company that specializes
in small, complex components.
Rinier is a trade-school graduate
in precision machining, having
studied advanced blueprint reading, geometric dimensioning
and tolerances and lean manufacturing. He has
over 36 years of on-the-job experience at Vallorbs as a
Swiss screw machine operator, tool designer and fabricator,
quality-control supervisor and site manager.
NACE CORROSION RISK
MANAGEMENT CONFERENCE
MAY 23-25, 2016 * HOUSTON, TEXAS
HOUSTON MARRIO T T WESTCHASE
MANAGE RISKS.
REDUCE FAILURES.
The NACE Corrosion Risk Management Conference brings together
experts from oil & gas, pipeline, chemical process, power generation,
and infrastructure industries, to share knowledge and best practices in
corrosion risk management.
Attend to Learn How to:
§ Understand industry regulations and how
they impact risk management
§ Understand different risk assessment methods
and how to apply them to your industry
§ Understand the role corrosion science and
engineering plays in risk management
§ Allocate resources effectively to mitigate
unanticipated failures
REGISTER TODAY
Save $100 when you register by April 6
Go to corrosionrisk.nace.org
for more information
Circle 13 on p. 62 or go to adlinks.chemengonline.com/61492-13
ChemiCal engineering www.Chemengonline.Com february 2016
53
http://www.vallorbs.com http://corrosionrisk.nace.org http://adlinks.chemengonline.com/61492-13 http://www.Chemengonline.Com
Chemical Engineering February 2016

Table of Contents for the Digital Edition of Chemical Engineering February 2016
