1/2“-24”RF FF RTJ 150#-2500# Stainless Steel 317 Duplex Stainless
What is a Flange face?
Different types of flange faces are used as the contact surfaces to
seat the sealing gasket material. ASME B16.5 and B16.47 define
various types of flange facings, including the raised face, the
large male and female facings which have identical dimensions to
provide a relatively large contact area.
Other flange facings covered by these standards include the large
and small tongue-and-groove facings, and the ring joint facing
specifically for ring joint type metal gaskets.
Raised Face (RF)
The Raised Face flange is the most common type used in process
plant applications, and is easily to identify. It is referred to as
a raised face because the gasket surfaces are raised above the
bolting circle face. This face type allows the use of a wide
combination of gasket designs, including flat ring sheet types and
metallic composites such as spiral wound and double jacketed types.
The purpose of a RF flange is to concentrate more pressure on a
smaller gasket area and thereby increase the pressure containment
capability of the joint. Diameter and height are in ASME B16.5
defined, by pressure class and diameter. Pressure rating of the
flange determines the height of the raised face.
The typical flange face finish for ASME B16.5 RF flanges is 125 to
250 µin Ra (3 to 6 µm Ra).
Raised Face height
For the height measures H and B of all described dimensions of
flanges on this website, with exception of the Lap Joint flange, it
is important to understand and remember the following:
In pressure classes 150 and 300, the height of raised face is
approximately 1.6 mm (1/16 inch). In these two pressure classes,
almost all suppliers of flanges, show in their catalog or brochure,
the H and B dimensions including the raised face height. (Fig. 1)
In pressure classes 400, 600, 900, 1500 and 2500, the height of
raised face is approximately 6.4 mm (1/4 inch). In these pressure
classes, most suppliers show the H and B dimensions excluding the
raised face height. (Fig. 2)
Flat Face (FF)
The Flat Face flange has a gasket surface in the same plane as the
bolting circle face. Applications using flat face flanges are
frequently those in which the mating flange or flanged fitting is
made from a casting.
Flat face flanges are never to be bolted to a raised face flange.
ASME B31.1 says that when connecting flat face cast iron flanges to
carbon steel flanges, the raised face on the carbon steel flange
must be removed, and that a full face gasket is required. This is
to keep the thin, bittle cast iron flange from being sprung into
the gap caused by the raised face of the carbon steel flange.
Ring-Type Joint (RTJ)
The Ring Type Joint flanges are typically used in high pressure
(Class 600 and higher rating) and/or high temperature services
above 800°F (427°C). They have grooves cut into their faces which
steel ring gaskets. The flanges seal when tightened bolts compress
the gasket between the flanges into the grooves, deforming (or
Coining) the gasket to make intimate contact inside the grooves,
creating a metal to metal seal.
An RTJ flange may have a raised face with a ring groove machined
into it. This raised face does not serve as any part of the sealing
means. For RTJ flanges that seal with ring gaskets, the raised
faces of the connected and tightened flanges may contact each
other. In this case the compressed gasket will not bear additional
load beyond the bolt tension, vibration and movement cannot further
crush the gasket and lessen the connecting tension.
Ring Type Joint gaskets
Ring Type Joint gaskets are metallic sealing rings, suitable for
high-pressure and high-temperature applications. They are always
applied to special, accompanying flanges which ensure good,
reliable sealing with the correct choice of profiles and material.
Ring Type Joint gaskets are designed to seal by "initial line
contact" or wedging action between the mating flange and the
gasket. By applying pressure on the seal interface through bolt
force, the "softer" metal of the gasket flows into the microfine
structure of the harder flange material, and creating a very tight
and efficient seal.
Most applied type is style R ring that is manufactured in accordance with ASME B16.20 used with
ASME B16.5 flanges, class 150 to 2500. Style 'R' ring type joints
are manufactured in both oval and octagonal configurations.
The Octagonal ring has a higher sealing efficiency than the oval and would be
the preferred gasket. However, only the oval cross section can be
used in the old type round bottom groove. The newer flat bottom
groove design will accept either the oval or the octagonal cross
Style R ring type joints are designed to seal pressure up to 6,250
psi in accordance with ASME B16.5 pressure ratings and up to 5,000
The RX type is suitable for pressures up to 700 bar. This RTJ is capable
of sealing itself. The outer sealing surfaces make the first
contact with the flanges. A higher system pressure causes a higher
surface pressure. Type RX is interchangeable with the standard
The BX type is suitable for very high pressures up to 1500 bar. This ring
joint is not interchangeable with other types, and is only suited
for API type BX flanges and grooves.
The sealing surfaces on the ring joint grooves must be smoothly
finished to 63 Microinches and be free of objectionable ridges,
tool or chatter marks. They seal by an initial line contact or a
wedging action as the compressive forces are applied. The hardness
of the ring should always be less than the hardness of the flanges.
Choice of material
The table below indicates the most commonly used materials for ring
- Soft iron
- Carbon steel
- SS (Stainless steel)
- Nickel alloys
- Duplex steel
The Tongue and Groove faces of this flanges must be matched. One
flange face has a raised ring (Tongue) machined onto the flange
face while the mating flange has a matching depression (Groove)
machined into it's face.
Tongue-and-groove facings are standardized in both large and small
types. They differ from male-and-female in that the inside
diameters of the tongue-and-groove do not extend into the flange
base, thus retaining the gasket on its inner and outer diameter.
These are commonly found on pump covers and Valve Bonnets.
Tongue-and-groove joints also have an advantage in that they are
self-aligning and act as a reservoir for the adhesive. The scarf
joint keeps the axis of loading in line with the joint and does not
require a major machining operation.
General flange faces such as the RTJ, TandG and the FandM shall
never be bolted together. The reason for this is that the contact
surfaces do not match and there is no gasket that has one type on
one side and another type on the other side.
With this type the flanges also must be matched. One flange face
has an area that extends beyond the normal flange face (Male). The
other flange or mating flange has a matching depression (Female)
machined into it's face.
The female face is 3/16-inch deep, the male face is1/4-inch high,
and both are smooth finished. The outer diameter of the female face
acts to locate and retain the gasket. In principle 2 versions are
available; the Small M&F Flanges and the Large M&F Flanges.
Custom male and female facings are commonly found on the Heat
Exchanger shell to channel and cover flanges.
Large Male&Female Flanges
Small Male&Female Flanges
Advantages and Disadvantages of T&G and M&F flange faces
Better sealing properties, more precise location and exact
compression af sealing material, utilization of other, more
suitable sealing and spezialized sealing material (O-rings).
Commercial availabillity and cost. Normal raised faced is far more
common and ready available both regarding Valves, flanges and
sealing material. Another complexity is that some rigid rules must
be applied to the piping design. Do you order Valves to be female
end both sides, or on one side maybe, in which case do you point
all male ends in the flow direction, or what. Same applies to any
flanged joint / vessel connection of course.
150 is what percent of 2500?
Solution for 150 is what percent of 2500:
15000:2500 = 6
Now we have: 150 is what percent of 2500 = 6
Question: 150 is what percent of 2500?
Percentage solution with steps:
Step 1: We make the assumption that 2500 is 100% since it is our
Step 2: We next represent the value we seek with $x$
Step 3: From step 1, it follows that $100%=2500$
Step 4: In the same vein, $x%=150$
Step 5: This gives us a pair of simple equations:
Step 6: By simply dividing equation 1 by equation 2 and taking note
of the fact that both the LHS
(left hand side) of both equations have the same unit (%); we have
Step 7: Taking the inverse (or reciprocal) of both sides yields
$Rightarrow x=6%$Therefore, 150# is 6% of 2500#.