Process Safety Beacon published by CCPS. Shared by the developers of the near miss, incident & accident reporting app 'SARA' (Simple Accident Reporting App). To find out more please visit www.AltremisAppVenture.com

1. CCPS Process Safety Beacon Messages for
Manufacturing
An AIChE Industry Personnel
Technology Alliance
February 2002
A little “nothing” can really be deflating!
Here’s what
happened……
VACUUM is a powerful force!
When steam cleaning COMMON causes of vacuum damage to tanks include:
the interior of a railcar • The vessel has insufficient strength to withstand a vacuum; a vessel with a 50
most of the air was
psig (or higher) ASME pressure rating is frequently capable of withstanding a
displaced. When work
full vacuum;
was stopped at the end
of the day all valves • vacuum is created when liquid is transferred from a vessel or when hot vapor
were closed. As the car condenses, neither of which is replaced by air/nitrogen or other non-
cooled, the steam condensable material, and
condensed, creating a
vacuum, causing the • a vacuum relief system is not present or is not functioning properly.
railcar to collapse
Things to consider to prevent equipment damage from vacuum:
During painting, a tank’s
vacuum relief valve was • install a system to provide vacuum relief. As one of the pictures graphically
covered with plastic to demonstrates, railcars and trucks MAY NOT have this equipment. These
prevent potential devices will allow air to enter the vessel and prevent vacuum formation.
contamination of the • if installed, vacuum relief devices must be inspected and tested on a regula r
contents. When liquid basis. They are just as critical as pressure relief devices.
was pumped out the • understand which vessels in your department are not rated for full vacuum.
plastic covering These are the vessels vulnerable to vacuum related incidents,
prevented air/nitrogen • demonstrate caution whenever liquids are transferred or vapors are condensed
from replacing the liquid because of shutdown, maintenance, cleaning, etc..
volume. A vacuum
• be sure that the addition of air, nitrogen, or other vacuum breaking materials
developed leading to the are not impeded.
partial collapse of the
tank. WHENEVER vacuum relief systems are removed, covered, modified,
etc., special precautions are needed to prevent an incident !
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reproduction for the purpose of resale by anyone other than CCPS is strictly prohibited.
Contact us at ccps@aiche.org or 212-591-7319.