Viking Johnson MaxiFit Wide-Tolerance Pipe Coupling DN40-DN300

Wide-tolerance ductile iron coupling for water and gas pipelines

The Viking Johnson MaxiFit is a bolted, wide-tolerance pipe coupling. One sleeve and two end rings pull a gasket onto each pipe end, so a single size covers a band of outside diameters. DN40 takes pipes from 47.9 to 59.5 mm OD, and DN300 takes 315 to 349 mm. The datasheet lists a standard-sleeve range and a long-sleeve MaxiFitXtra range, plus matching MaxiCap end caps and a MaxiFit Plus option with a threaded outlet.

The sleeve and end rings are ductile iron to BS EN 1563 grade EN GJS-450-10 with a Rilsan Nylon 11 coating, and the bolts are Sheraplex coated. The coupling joins plain pipe ends without welding, which is why it is a common choice for repairs, tie-ins and connections between mixed pipe materials. This is an unrestrained coupling: the datasheet states that MaxiFit does not resist end load from internal pressure, so the pipework needs external restraint.

MaxiFit technical specification

MaxiFit standard sleeve, dimensions from the datasheet (OD range in mm, M = diameter, L = overall length, A x T = sleeve length x thickness, weight in kg).

MaxiFitXtra long sleeve (same diameters and gaskets, longer sleeve for a wider setting gap).

Features taken from the datasheet

• Setting gap of 20 to 40 mm on DN40 to DN150 standard sleeves, and up to 140 mm on the MaxiFitXtra, which allows for pipe movement or a closing piece.
• MaxiCap end caps (DN50 and above) and a MaxiFit Plus threaded outlet (1 to 2 inch, DN50 to DN150) share the same family.
• Potable water contact approvals as printed: Rilsan Nylon 11 WRAS, DVGW, W270, ACS and KIWA; EPDM gaskets WRAS; the MaxiFit range as a finished product holds KIWA certification against the UK water fittings regulations.

Selection and ordering guide

Order by nominal size, but check the measured pipe outside diameter against the OD range column rather than the nominal bore alone. Choose the MaxiFitXtra when the gap between pipe ends needs to be long, such as a repair where a damaged section is cut out. Choose EPDM for water, or nitrile when the medium is gas, since the datasheet gives 6 bar for gas against 16 bar for water. Specify stainless bolts and nuts if the coupling will sit in a wet chamber or under groundwater. The gasket mould number in the table identifies the spare gasket, and the datasheet also notes that applications with fluctuating or elevated temperatures above 60 C may need bolts re-tightened as part of a maintenance schedule.

The datasheet does not list a single order code string, so please quote the nominal size, sleeve type (standard or Xtra), gasket material, bolt material and any outlet or end cap needed so that the exact configuration can be confirmed with the maker before ordering.

Installation notes

• Tighten all M12 bolts to 55-65 Nm with an A/F 19 mm spanner, working across the coupling in stages so both end rings seat evenly.
• Because MaxiFit does not resist end load, anchor the line with thrust blocks or restraint hardware where the pipe is under pressure.
• Keep the pipe ends within the stated OD range and inside the setting gap limits; the 6 degree angularity figure applies at maximum pipe OD and can be larger on smaller pipe diameters.
• For hot service above 60 C, include bolt re-tightening in the maintenance routine as the datasheet advises.

Where it is used in Oman and the GCC

Municipal and industrial water networks, cooling water headers, fire water ring mains and desalination plant pipework all need couplings that tolerate pipe outside diameter variation. MaxiFit fits mixed-material tie-ins and repairs on these lines. Gas use is limited to 6 bar and should be confirmed with the maker.

Related items and documents

Related Viking Johnson items include the pipes and fittings range, MaxiDaptor flange adaptors for flanged connections and MaxiStep reducing couplings for changes in pipe size. The official datasheet is attached, and Seven Star LLC can quote against your size list. Please confirm pipe material, OD and working pressure before ordering.