FIELD OF INVENTION
The present invention relates to an unique robust restraint joint for a ductile iron
(DI) pipe for transporting water in both straight and bend configuration combating an
axial separating force. More particularly, the invention relates to a restraint joint with
restraint mechanism to keep the DI pipes intact against axial thrust at bends, tees, and
dead ends during water supply.
BACKGROUND OF THE INVENTION
The Ductile Iron (DI) pipes are used for water transmission and distribution for
very long distances. Normally, the DI pipes are connected with each other using flexible
push-on joints, which are flexible to allow pipe line directional changes. However, push-
on joints are not suitable for high pressure water supply lines, which experience large
amount of axial thrust especially at bends, tees, dead ends etc., and require a restraint
mechanism to keep the DI pipes intact. Restraint joint is also necessary for laying DI
pipes on slope, like in hilly terrain.

To provide resistance to the thrust forces, generally thrust blocks are used,
where the soil bearing capacity is good, though it is not practical in all situations. In
hilly areas and/or in severe directional changing scenario, mechanical joint, flanged
joint, restraint joints, ball and socket joints etc., are required for DI pipes to avoid the
joint separation due to the thrust forces.
The DI pipes are subjected to type test according to ISO 2531. The tests include
application of hydrostatic pressure, internal (positive and negative), external and cyclic
internal hydrostatic pressure application under specific conditions. The restraint joints
are also subjected to type test as described in ISO 10804, where they undergo axial
restraint, bending, shear and cyclic loads.
Restraints joints offer flexibility and are available in wide variety of design as per
the standards and manufacturer specifications. Most of the available design include
socket and spigot joints along with the bolts, rubber seals and weld bead on the spigot
end. Anchor gaskets are also used as internal restraint joints. However, anchor gaskets
are not suitable for the above ground applications as they are subjected cyclical
movement, which results in Poor performance of the gasket.

Simple flexible push-on joints are generally supplied with separate clamp
arrangements, fitting on the existing design of the DI pipes. Most of these designs are
complicated to assemble during the field installation. The joint components are
generally full circumferential and often create interference issues while assembly.
Assembly procedure often requires careful handling of the pipe and joint components to
achieve the required functionality of the DI pipe and restraint joint. The design has to
be robust to deal with large axial separating forces during water transportation in both
straight configuration and also in bend configuration whenever there is a change in the
direction of the pipe layout.
There are several design variations for the restraining purpose of DI Pipes.
Michael & Randall in US 20090273184 developed a combined system for sealing and
restraint for as-cast DI Pipes. Billy et al also developed a bell and plain end pipe joint,
according to US 4540204A that has a series of locking segments. Randall, as disclosed
in US 5197768A developed locking member that works on a pipe joint of bellow and
spigot type. Apart from self-restraint joints, there are mechanical joints as developed by
William et al as disclosed in US 7207606 B2.

OBJECTS OF THE INVENTION
Therefore, it is an object of the invention to propose an unique robust restraint
joint for a ductile iron (DI) pipe for transporting water in both straight and bend
configuration combating an axial separating force, which is capable of withstanding high
axial thrust and bending, shear and cyclic loads.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1. Complete Assembly of the DI Pipe with Restraint Joint – Vertical Gland
Position
Figure 2. Complete Assembly of the DI Pipe with Restraint Joint – Horizontal Gland
Position
Figure 3. Cross section of the Assembly and details of the Restraint Joint connections
Figure 4. Cross Section view of the Contacts Involved in Restraint Joint
Figure 5. Single Gland View & Assembly
Figure 6. Gland Cross Section Details & Key Features
Figure 7. Bolts on the Gland Flange Region
Figure 8. Split Locking Ring and Detailed View
Figure 9. DI Pipe and the weld bead towards the spigot end
Figure 10. Exploded view of the Restraint Joint DI Pipe assembly
Figure 11. DI Pipe is bent by 2.5 degrees

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
The main objective of the present design is to develop a unique robust restraint
joint fulfilling the requirements specified in type test of restraint joint [7]. The
developed design offers easy assembly method of the restraint joint at the site/field as
there are two halves of the gland are assembled from sideways and are joined with the
help of bolt and nuts. The design is termed as split gland design, which includes two
semi circumferential glands and a split locking ring as the important components. Since,
the restraint joint comes in two halves, the positioning could be decided based on the
field space constraints. Two possible configurations are shown in Figure 1 & Figure 2.
The design also provides flexibility for the pipe to bend to accommodate the change in
the direction during the pipe laying.
Important Components of the Restraint Joint – Split Gland
1. Collar Height at the Spigot End to bear the axial separating forces
2. Two semi circumferential Glands (connected together with the help of bolts)
3. Single Piece Locking Ring (Split)
4. Weld Bead
5. Bolts (at top and bottom)

Various components involved in split gland restraint joint are shown in Figure 3.
The design consists of two glands, locking ring and bolts. Glands and locking ring could
be manufactured from SG cast iron with SG400/18, SG400/18L, SG350/22 and
SG350/22L.
Suitable standard bolts could be used to assemble the two glands [Figure 7]
withstanding the high pressures generated while restraining.
Suitable welding electrodes should be used and welding procedure to be followed
for the weld bead on the DI Pipe spigot end [Figure 9].
Key Features of the Design:
One of the important requirements of the design is to have a circumferential
weld bead (W) to arrest the movement of the locking ring (R), which is in contact with
gland (G) and thereby with socket collar (C1).
Socket collar height (H), which is part of the DI Pipe is very crucial feature in the
design as it withstands the required axial restraining forces.
The bulk of the design includes Gland (G), which transfers the axial thrust loads
between spigot end of pipe (P2) to the socket end (P1) of another DI pipe, thus
forming the joint, through locking ring (R) and weld bead (W) [Figure 3]. Figure 4

shows the cross sectional view of the assembly and Figure 5 shows single gland and
assembled glands. The features that form the gland are highlighted in Figure 6 along
with their functionality.
Key Features:
D1 is the core part of the gland that runs semi circumferential and directly
connects with socket collar (S) and locking ring (R) on the two different ends. The
contact area (C1) connects with socket collar (S) whereas, the spherical surface (C2)
contacts with locking ring (R). Towards the socket end (P1) the gland (G) forms a firm
connection with socket collar (S) to transfer the thrust loads. The cylindrical surface
(F2) is provided to accommodate manufacturing tolerances of the DI pipe casting. The
feature, F3, on the contact (C2), is a spherical surface and provides the flexibility for
the spigot end of the DI Pipe to rotate without interference. The locking ring is in
contact with weld bead (W) & spigot end (P2). During the pipe bending, the relative
motion is provided between the spherical face (F8) of locking ring (R) and spherical
face of gland (F3). Towards the locking ring end the contact region (C2) is supported by
a small step (F4) to strengthen the contact region.
D2 is the flange region on the Gland (G) and provides the space for the bolts (B),
which are used to assemble the glands. All the bolt holes and nut holes will be part of
the flange (D2). The fillet feature,(F5), between the D1 and D2 regions is to strengthen
the gland as shown in Figure 5.

Locking ring (R), as shown Figure 8, is split (F6) at one location in
circumferential direction to allow the snap through fit on the weld bead (W) at spigot
end (P2) during the assembly process. Similar to F4 a small step, F7 is provided to
strengthen the locking ring (R) under the axial thrust loads. The top surface of the
locking ring (R) is given suitable profile (F8) to ensure spherical contact between the
ring (R) and gland (G).
Figure 9 shows the weld bead (W) on the spigot end (P2) and the cross sectional
details. It is preferred to achieve a flat normal face on one side of the weld bead (W) to
provide a good contact with the locking ring (R).
Assembly Procedure:
1. The assembly procedure starts with weld bead (W) on the DI Pipe. The weld
bead (W) can be made at the pipe manufacturing facility.
2. The locking ring (R) is snapped through the weld bead (W) onto the spigot end
(P2) of the DI Pipe. Locking ring (R) connects with the weld bead (W) under axial
separating load.
3. The standard DI pipe assembly can then be followed, which includes the gasket
insertion and pushing on the socket end (P1) of the DI Pipe on to spigot end (P2) of
another pipe.

4. After the DI pipes are assembled, the two pieces of the glands (G) should be
passed from the sideways, so that they sit on the socket collar (S) on one side and with
locking ring (R) on the other side [Ref Figure 10].
5. The glands are then positioned and assembled with the help of the nut and
bolts. Figure 10 shows the exploded view of the complete assembly.
The design provides slackness and loose contact of the gland (G) with locking
ring (R) just after the assembly (before the application of axial separating forces). This
is important as the design should accommodate for the dimensional deviations during
the manufacturing processes.
Upon the application of the axial separating forces, the locking ring’s spherical
contact face comes in contact with gland’s spherical face. The load transfer path would
be through spigot end (P2) of the DI Pipe, weld bead (W), locking ring (R), gland (G)
and socket collar (S) of the other DI pipe.
Normally, DI pipes without restraint joint offers approximately 5 deg bending.
However, as per the requirements of the restraint joint, the bending angle possible
should be lower than what is possible without the restraint joint (typically it is around
2.5 degrees), i.e., 2.5 deg. The present design is developed to accommodate the
bending as shown in Figure 11 so that there is no interference between restraint joint

(J) and DI pipes. The locking ring (R) in combination with the spigot end (P2) of the DI
pipe provides the relative motion along the gland spherical contact surface to
accommodate bending (F3).
The design arrangement can be extended to all other sizes of the DI Pipe.
Relative Dimensions of the Restraint Joint:
D – Diameter of the DI Pipe:
WG – Width of the Gland: Close to D/2.5 and higher
HG – Height of the Gland: Close to D/5 and higher
WGF – Width of the Flange on the Gland: Close to D/7 and higher
HGF – Height of the Flange on the Gland: Close to D/7 and higher
TG1 – Thickness of the Gland near socket region: Close to D/40 and higher
TG2 – Thickness of the Gland near socket region: Close to D/12 and higher
TG3 – Thickness of the Gland near socket region: Close to D/10 and higher
WL – Width of the Locking Ring: Close to D/10 and should avoid the
interference with the Gland and weld.
HGF – Height of the Locking Ring: Close to D/12 and higher
HWB – Height of the weld bead, should be greater than 3 mm and should not
create issues with welding and assembly.
DB – Bolt size, Radius of the bolts should be greater than 4mm radius and
depends on the number of bolts and the grade

WE CLAIM
1. A restraint joint arrangement for ductile iron (DI) pipecomprising:
a first pipe with a spigot end (P1) and a second pipe with a socket end (P2);
the socket end (P2) of the second pipe comprising a socket collar (S) with an
extended height (H);
the socket end (P2) further comprising a gasket, the gasket being configured to
be inserted inside the socket end (P2) by being compressed to offer leakage proof and
resistant to pipes separation;
the spigot end (P1) of the first pipe being configured to be inserted into the
socket end (P2) of the second pipe;
a gland (G) positioned at the spigot end (P1) with a hook, the hook being
configured to get entangled with the extended height while joining the first pipe and
the second pipe;
the first pipe further comprising a locking ring (R) positioned circumferentially at
the spigot end (P2), the locking ring (R) being configured to provide surface to the
gland (G) for grip; and
the first pipe also comprising a weld bead (W) at the spigot end (P1) welded
circumferentially across the spigot end (P1) to restrict the movement of the locking ring
(R) and thereby the gland (G).

2. The restraint joint arrangement for ductile iron (DI) pipe as claimed in claim 1,
wherein the gland is split into two a semi circumferential glands (G1, G2).
3. The restraint joint arrangement for ductile iron (DI) pipe as claimed in claim 2,
wherein the circumferential glands (G1, G2) comprise nut bolt arrangement to fix them
together over the socket (P2) and the spigot (P1).
4. The restraint joint arrangement for ductile iron (DI) pipe as claimed in claim 1,
wherein the gland is made by any of group of SG cast iron SG400/18, SG400/18L,
SG350/22, SG350/22L.