Viking Johnson MaxiStep Reducing Coupling DN50/65-DN225/250

One coupling that joins two different pipe sizes

The Viking Johnson MaxiStep is a reducing, or stepped, coupling in the MaxiFit range. It joins pipes of two adjacent sizes, for example 100 mm to 125 mm nominal, in a single bolted joint, which removes a separate reducer and a pair of couplings from the design. Each end has its own wide OD range: the DN100/125 size takes 107 to 132 mm pipe on the small end and 132 to 158 mm pipe on the large end.

Construction is ductile iron to BS EN 1563 (EN GJS-450-10) with Rilsan Nylon 11 coating, a EPDM or nitrile gasket pair (a different gasket mould for each end) and M12 bolts. Ten stepped sizes from 50/65 to 225/250 are listed. As with MaxiFit, the coupling does not resist end load from internal pressure, so the line needs external restraint.

MaxiStep technical specification

Dimensions from the datasheet (OD ranges and diameters in mm; Ai and B are the end-ring diameters at the small and large end; L = overall length; A x T = sleeve length x thickness).

Why use a stepped coupling

• One joint instead of a reducer plus two couplings, which shortens the installed length and cuts the number of leak paths.
• Each end keeps the wide OD tolerance of the standard MaxiFit, so mixed pipe materials such as ductile iron to steel are accommodated.
• Sizes are consecutive in the nominal series, for example 125/150, so larger changes need more than one step or a conventional reducer.
• Setting gap is 20-40 mm on DN50/65 to 125/150, and 25-50 mm on the larger sizes.

How to specify it

Quote both pipe outside diameters, not only the nominal sizes. A 100 mm to 125 mm connection might be 107 to 132 mm on one side and 132 to 158 mm on the other, which is the range of the 100/125 size; a pipe with an OD outside either range needs a different size. Pick the gasket by service: EPDM grade E for potable water, nitrile grade G for gas lines up to 6 bar; stainless fasteners are an option for damp or corrosive chambers. Two gasket mould numbers appear for each size, one for the small end and one for the large end, which helps when ordering spares. No single order code is printed, so an enquiry should list the size pair plus the gasket and fastener choices.

Fitting guidance

• Pull the M12 bolts up evenly in a cross pattern to the 55-65 Nm torque range, using a 19 mm spanner.
• Add thrust blocks or similar anchoring outside the coupling, since it carries no pull-out load from line pressure.
• Check the OD of both pipe ends before fitting; each end only seals inside its own range.
• On lines running hotter than 60 C, plan a later re-torque of the bolts, which the datasheet flags.

Typical applications in Oman and the GCC

Stepped couplings appear in network upgrades where a new main has a different nominal size from the old one, in pump station pipework with mixed-size suction and delivery lines and in cooling water extensions. They are usable on water or gas within the printed ratings. Confirm the soil, water quality and temperature for your site; the maker limits the standard EPDM and nitrile gaskets to +90 C.

Selection and installation notes

Pipe couplings and clamps must be chosen from the actual pipe outside diameter, the pipe material, the working pressure and the joint movement expected, so measure the pipe before ordering and compare the reading with the size range on the data sheet. Clean the pipe surface and remove dirt, scale and sharp edges, mark the insertion depth, centre the coupling over the joint and tighten the bolts evenly in a cross pattern to the torque in the installation instructions. Check the joint again after the line has been pressurised, and do not use a coupling outside its stated pressure rating.

For a stepped coupling, check the outside diameter of both pipes and confirm that each end is inside its own size range.

Information needed for a quotation

Send the full model code, the quantity, the delivery location in Oman or the GCC, the intended use and any accessories needed, so that the complete package can be quoted together.

Documents and supply information

The manufacturer data sheet is attached to this page and should be read together with the project specification and the site risk assessment before a purchase is confirmed. Ratings, standards and dimensions are quoted as printed on that sheet. Lead time, stock position and certificates available with the shipment are confirmed in the quotation, and we supply to Oman and the wider GCC region for industrial, utility and building services projects.

Related items and documents

Related Viking Johnson items sit in the pipes and fittings category, including MaxiFit and MaxiDaptor. You can download the datasheet here, and Seven Star LLC will price your pair of pipe sizes.