MS Dismantling Joints

Dismantling Joints play a decisive role in the design and layout of pipelines and valves. They are an essential aid during the installation and removal of pipe sections and valves. Without a dismantling joint offering longitudinal adjustment, it is almost impossible to insert a valve exactly into a pipe section. Thanks to this adjustability of the dismantling joint, the valve can be fitted next to the dismantling joint, and the dismantling joint can be to set to the exact length required prior to being securely connected to flanges.

The reverse sequence is used for dismantling, where readjustment of the length of the dismantling joint creates enough space to loosen and remove the valve. In both cases, the dismantling joint guarantees fast installation and removal, thus contributing to increased efficiency and reducing site operations and down time. The procedure is similar where pipe sections have to be fitted together. Certain types of dismantling joints are also suitable for use without restraint in flexible pipelines. Finally, dismantling joints can be used to fill gaps e.g. where a pump installed in a fixed position has to be connected to a pipe protruding from a wall.

MS Dismantling Joints

The Design Principle

Even if there are numerous versions of dismantling joints available for different applications, the basic principle is always the same:

  • The flange adaptor is located on one side of the dismantling joint. It is connected securely to the pipe or valve via the flange. Flange bore holes corresponding to the respective pressure rating or standard are available.
  • The F-piece (flanged spigot), which has a flange at the other end of the dismantling joint for connection in the other direction, is pushed into the flange adaptor.
  • For the installation and removal of valves with longitudinal adjustment of maximum ± 25 mm, these two parts can be pushed against one another so that the dismantling joint can be inserted between the pipe sections or pipeline and valve.
  • When the nuts are tightened, the gasket is compressed between the follower (end-ring) and the central ring and pressed against the pipe of the F-piece. The high-quality rubber gasket ensures that the system is always leaktight on tightening of the nuts.
  • Threaded tie-rods are used for the subsequent restraining and flange connection, depending on the type of dismantling joint used. At the same time, they also serve to transfer the forces occurring on one side of the dismantling joint to the other side.

INSTALLATION INSTRUCTIONS

Style DJ400 14"-72" Dismantling Joints

Step 1 Check the DJ400 parts to ensure no damage occurred during transit and that no parts are missing.
Step 2 Check the mating flanges to insure that it matches the drilling of the DJ400. They must be parallel and aligned axially.
Step 3 Remove the tie-rods from the DJ400 and loosen the end ring bolts to allow the spool piece to move freely within the Flange Coupling body.

Step 4 Move the DJ400 into position between the mating flanges. Insert the flange gasket between the flange faces (not provided). Using flange bolts, fasten the flanged coupling end of the dismantling joint to one of the mating flanges. Depending on the situation, the tie-rods might need to be inserted concurrently with the flange bolts.


Step 5 Attach the flanged spool to the opposite mating flange in your system and fasten together with flange bolts. Make sure the spool piece is inserted at least 2 inches inside of the Flange Coupling body.


Step 6 The pipe spool piece should be concentric with the flanged coupling after bolting the flanges. If the flanged coupling was completely disassembled, make sure the beveled edge of the gasket matches the beveled end of the flanged coupling. Slide end ring into position and hand tighten the end ring bolts.


Step 7 Insert tie-rods. (NOTE: Without the tie-rods in place, the fitting is NOT RESTRAINED.) Each tie-rod will have a total of 4 nuts when assembled. While inserting the tie-rod, thread the nuts into position. The tie-rod must pass through the flanges on each end of the dismantling joint. Make sure the tie-rod lengths are equal. Tighten the nuts that secure the flanges BEFORE torquing the nuts on the end ring to complete the installation.


Step 8 Evenly tighten the bolts around the end ring by diametrically alternating opposite positions at appproximately 25 ft-lb increments until the recommended torque is achieved. Wait ten minutes and then retorque. Recomended torque for end rings is 60-70 ft-lbs.


PRECAUTIONS

  • Check flanges to make sure you are using the correct size DJ400; also check the length of DJ400 to make sure it will fit in the space allocated.
  • Make sure no foreign materials lodge between gasket and spool.
  • Avoid loose fitting wrenches, or wrenches too short to achieve proper torque.
  • Keep threads free of foreign material to allow proper tightening.
  • Take extra care to follow proper bolt tightening procedures and torque recommendations. Bolts are often not tightened enough when a torque wrench is not used.
  • Pressure test for leaks before backfilling.
  • Backfill and compact carefully around pipe and fittings.
  • When reinstalling parts with stainless steel hardware, there may be a loss in pressure holding ability due to worn or damaged threads during the original installation.

COMMON INSTALLATION PROBLEMS

  • Bolts are not tightened to the proper torque.
  • Rocks or debris between spool and gasket.
  • Dirt on threads of bolts or nuts.
  • Not enough pipe insertion.
  • Incorrect mating flange.