Body
Its spherical form of large radius allows for the stresses. turbulence and resistance to flow to be kept to a minimum.
BODY-BONNET JOINTS
Body-Bonnet Joints of check valves are machined as follows :
On 150 and300 classes ; male and Female.
On 600, 900 and 1500 classes : RTJ

Seat Rings
Seat ring are manufactured in two different ways, depending on the class and type of valves:
1) Screwed seat rings, bottom seated type lapped on both side.
They are dry assembled, with a controlled torque setting to t body.
2) Welded-in seat rings, designed in order to prevent any turbulence and avoid damages due to corrosion

Both are forged or rolled in one piece, for all dimensions. They are heat treated to obtain the requested surface hardness, and are perfectly cleaned before assembling.

Insert Seat Rings
These rings are manufactured with teflon or viton inserts, depending on fluid and service conditions.
They provide an elastometer primary seal. combined with a fire sale metal to-metal secondary seal, for temperatures from - 100oC (-144oF) to 204.4oC (400F).
Where maintenance is a potential problem the viton insert is in the form of a toroidal ring so that it can easily be removed END CONNECTIONS

Our standard production covers valves with :
Flanged ends (RF) that conform to ANSI B 16.5 and face to face dimensions that conform to ANSI B 16.10, with a raised face serrated finish or, on request, with any other of finish.
Butt-welding ends (BW) with end to end dimensions that conform to ANSI B 16.10.
Customer must specify the type of schedule required, or class of pipe, or diameter and bore.
Ring-joint flanged ends (RTJ) that conform to ANSI B16.5, with end to end dimensions ANSI B 16.10
Other Special end connections are supplied to customers’ special requirements.

Special Constructions
A) Outside lever and weight
    On request swing check valves can be furnished with an outside lever and weight. The object of the lever and On weight is either to balance the disc or give it     added weight. In balancing the disc the valve will open with a minimum of pressure. When the disc is weighted the valve will be very sensitive to a reversal of     flow.
B) Dashpot feature
    In case of intermittent use or in presence of thrusts, dashpot feature is highly recommended.
    In such instance the dashpot feature gradually causes the opening and closing of disc preventing therefore dangerous shocks.
C) Check valves with pneumatic safety control
    This is in the form of a simple pneumatic piston. In normal conditions of use, it pushes up the lever, thereby moving a special cam, that allows the disc to     move.
    Should there be no air in the cylinder, the spring allows the lever, and hence the disc to descend, thereby assuring that encloses before any inversion of flow.