CON-2
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II.
(Continued)
•
Safety Valve
A safety valve is an automatic pressure-relieving
device actuated by the static pressure upstream
of the valve, and characterized by rapid opening
or pop action. It is used for steam, gas or vapor
service.
•
Set Pressure
Set pressure is the gauge pressure at the valve
inlet, for which the relief valve has been adjusted
to open under service conditions. In liquid service,
set pressure is determined by the inlet pressure
at which the valve starts to discharge. In gas or
vapor service, the set pressure is determined by
the inlet pressure at which the valve pops.
•
Simmer
Simmer is characterized by the audible passage
of a gas or vapor across the seating surfaces just
prior to "pop". The difference between this "start
to open pressure" and the set pressure is simmer,
and is generally expressed as a percentage of set
pressure.
•
Valve Trim
Valve trim includes the nozzle and disc.
III. Introduction
A safety relief valve is an automatic pressure actuated
relieving device suitable for use either as a safety valve
or relief valve, depending on application.
Safety relief valves are used on hundreds of different
applications, including liquids and hydrocarbons;
therefore, the valve is designed to meet many
requirements. The 1900 series valves included in this
manual can
only be used to meet Section VIII
requirements. It cannot be used on ASME Code
Section I steam boilers or superheaters, but may be
used on process steam.
IV. Design Features and
Nomenclature
•
Cap and Lever Interchangeability
Many times it is necessary to change the type of
cap or lever in the field after a valve has been
installed. All flanged Consolidated
®
Safety Relief
Valves are designed so they can be converted to
any type of lever or cap desired. It is not necessary
to remove the valve from the installation, nor will
the set pressure be affected when making such a
change.
•
Design Simplicity
Consolidated Safety Relief Valves have a minimum
number of component parts. This results in a
savings by minimizing spare parts inventory and
simplifies valve maintenance.
•
Nomenclature Related to Design Features
Applicable nomenclature of the components of
Type 1900 valves, including those with design
options for bellows O-Ring seat, and liquid trim and
Thermodisc, is identified in Figures 1 thru 6 on
pages 6 and 7.
•
Simple Blowdown Adjustment
The Consolidated single blowdown ring design
makes it possible to set and test a valve that has
been in service when it cannot be set on line and
must be taken to the customer's shop. The ring can
be positioned so that the set point can be observed
although the volume of the testing media is very
low. After the set pressure has been established,
proper blowdown can be attained by merely
positioning the ring in accordance with the adjusting
ring position shown in Tables 12-14 (as appropriate),
on page 34 of this manual.
•
Valve Interchangeability
A Standard Consolidated Safety Relief Valve may
be converted to the bellows type, the O-Ring seat
seal type, etc. and vice versa. This requires a
minimum number of new parts, and results in lower
costs should conversion be required.
