Tubing Failures (English) - AIChE

cypriotcamelΠολεοδομικά Έργα

29 Νοε 2013 (πριν από 3 χρόνια και 8 μήνες)

69 εμφανίσεις

Process Safety Moments from CCPS

Date: June 2012

Issue Number: 002

AIChE © 2010. All rights reserved. Reproduction for non
-
commercial,
educational purposes is encouraged. However, reproduction for the
purpose of resale by anyone other than CCPS is strictly prohibited.

Mechanical Integrity of
Tubing

2

Mechanical Integrity of Tubing

Tubing, including metal tubing, and also tubing
made of plastic, rubber, and other materials, is
commonly used in process plants, for example:


For instrument connections


To flush pump and agitator seals


For other applications with small flow requirements

Where do you use tubing in your plant?

3

Incident 1


A ½
-
inch stainless steel tube between a glycol
pump and a process vessel failed at a fitting
near the process vessel.


The resulting leak sprayed onto a reboiler and
ignited causing significant equipment damage.


The tubing failure was concluded to be the
result of vibration caused by the glycol pump.

4

Incident 2

1
-
in SS tube to a gas scrubber failed at nut and
ferrule compression fitting

Resulting gas leak ignited but self
-
extinguished
without major damage

Exact cause not determined


Pressure charts showed over
-
pressure before the incident


Tubing possibly damaged or weakened during storms in previous hurricane season


5

Incident 3

Gas leak from ½
-
in tubing for pump seal
was detected during LNG plant startup

Repairs done by unqualified technician

When the plant re
-
started, tubing failed
completely causing an LNG leak and fire



6

Found during a plant inspection

6

7

Found during a plant inspection

7

8

Found during a plant inspection

8

9

What can you do?

Review
procedures
for installation, inspection, and maintenance of
tubing
.


Remember


tubing may not be as durable as pipe and may be more
easily damaged. Avoid impacts to tubing and tubing connections
.

Report damaged
or leaking tubing
observed in the plant
and
ensure
it is
repaired.

Use qualified personnel to install
and repair
tubing.

Use proper
tools for installation and maintenance of tubing.

Use correct
components


tubing, ferrules, nuts, and
fittings
-

do
not
mix components from different manufacturers.


Ask
your tubing
supplier
to
provide information on proper installation
and maintenance of their product
.

9

10

Safety precautions from a supplier*


Do not bleed system by loosening a fitting nut or fitting plug.


Do not assemble and tighten fittings when the system is pressurized.
Always depressurize a system before adjusting the tightness of a
tube fitting connection, or before disassembling tubing.


Make sure that the tubing rests firmly on the shoulder of the tube
fitting body before tightening the nut.


Use the correct tool for gap inspection gauge to ensure sufficient
pull
-
up upon initial installation.


Always use proper thread sealants on tapered pipe threads.


Do not mix materials or fitting components from different
manufacturers


tubing, ferrules, nuts, and fitting bodies.


Never turn fitting body. Instead, hold fitting body and turn nut.


Avoid unnecessary disassembly of unused fittings.

* Ref.: Extracted from a compression tube fitting manufacturer installation guide


ask your
tubing supplier for their recommendations.

11

References

May 2012 CCPS
Process Safety Beacon
.

US Department of the Interior, Minerals
Management Service, Gulf of Mexico OCS
Region, Safety Alert No. 248, “Stainless Steel
Tubing
-
Related Fires,” December 28, 2006.

Contact your tubing supplier for information.

11

12

CCPS Process Safety Moment No. 001

12

Get more information:


CCPS books and resources on mechanical integrity:


Guidelines for Mechanical Integrity Systems (2006)

(
available from CCPS/Wiley
, or electronically from
Knovel Corporation
)


CCPS Member Companies:
Volunteer to Serve on a CCPS
Committee


Not a CCPS Member Company?
Learn about the benefits


CCPS Web Site:
www.aiche.org/ccps