Dodge StratoLink D71 API 610 Disc Coupling

API 610 disc coupling with a unitised, drop-out disc pack

The Dodge StratoLink D71 is a metallic disc coupling that Dodge launched as the first member of its StratoLink line and describes as an API 610 disc coupling. A center member assembly with two unitised, scalloped disc packs sits between two hubs, so torque passes through the flexing discs without lubrication. The drop-out spacer design lets the center member be removed for maintenance without moving the connected machines, and a patented bushing engagement system draws the disc pack into position by tightening the hardware, which Dodge says avoids driving bolts into place and makes rebuilds up to two times faster than with loose disc packs.

Hubs, adapters and the center member are 4140 alloy steel. Dodge states an average of 26 percent more torque capacity than existing designs, an average of 11 percent larger bore capacity and up to 24 percent lower weight, and it balances the coupling to AGMA Class 9. The center member assembly is stated to be a drop-in interchange for Rexnord Thomas Series 71 hubs; the names Rexnord and Thomas belong to their owners and are used only for identification.

Technical specifications

Ratings by size

From the Dodge brochure (torque in lb-in, weight in lb with standard length hubs and maximum bore):

Installation and alignment

The Dodge instruction manual MN4078 sets out seven steps: inspect parts, fit keys, mount the hubs flush with the shaft ends (by interference fit with heating to 350-450 degF, never above 450 degF, or by clearance fit with set screws), set the shaft spacing to the DBSE or C dimension, align axially, angularly and in parallel, install the center member with the compression fasteners, then verify the disc gap N. For size 300 with 5.5 inch DBSE, for example, the installation limits are 0.009 inch TIR parallel (offset P 0.004 inch), 0.013 inch angular and plus or minus 0.030 inch axial, and the disc gap N should read 0.427 to 0.442 inch. Hub and adapter fasteners are tightened in oiled condition; for size 300 the disc pack fasteners are M8 x 14 at 27 Nm.

Confirm before ordering: required torque with service factor, hub type and bore, DBSE (3.5 to 12 inch standard values are listed), balance requirement and the existing hub series if you are retrofitting.

Selection checks before the coupling is specified

A disc coupling for a process pump is chosen from the duty of the driven machine, not from the motor alone. Collect the motor power and speed, the pump type and service, the shaft diameters and keyway details on both sides, and the distance between shaft ends that the spacer must bridge. The size table above lists the six-bolt and eight-bolt sizes; the correct one follows from the required torque with an appropriate service factor and from the bore each hub must accept. Where the coupling replaces an existing Thomas Series 71 unit, record the existing hub dimensions so that the drop-in interchange of the center member can be confirmed on the drawing before the order is placed.

If the pump is built to API 610, the purchaser’s data sheet usually states the coupling requirements, including balance, spacer length and any guard specification. Share that data sheet with the quotation request so the offer can be checked against it line by line.

Commissioning the drive train

After the hubs are mounted and the machines are aligned, the center member is fitted and the hardware is tightened in the sequence and to the values given in the Dodge installation instructions. The bushing engagement system draws the disc pack into place as the bolts are tightened, so there is no need to force the bolts with a hammer. Rotate the shaft by hand to check that nothing binds, confirm that the guard is installed, and then run the set while checking vibration and bearing temperatures against the site acceptance values. A record of the final alignment readings and bolt torques is worth keeping with the pump file; it saves time at the next overhaul.

Effects of heat and sand

Pump houses in Oman, particularly at coastal and desert sites, see high ambient temperatures and wind-blown dust. Thermal growth of the pump and motor casings can shift alignment between cold and running conditions, so follow the pump manufacturer’s guidance on hot alignment offsets where it applies. The coupling itself needs no lubrication, which removes one source of dust contamination, but the guard should still be kept closed and sealed against sand build-up.

Routine inspection and disc pack replacement

During planned stops, look at the disc packs through the guard openings or with the guard removed under a proper isolation. Signs that need attention include cracked or deformed discs, fretting marks, loose hardware and changes in the running vibration pattern. Because the center member drops out without moving the pump or motor, a worn pack can be exchanged by removing the spacer assembly, fitting the replacement and tightening the hardware again. Check the alignment whenever the machines have been disturbed, since misalignment beyond the coupling limits is the most common cause of early disc fatigue.

Documents and quotation

The attached PDF is the Dodge StratoLink D71 instruction manual MN4078. The ratings table comes from the Dodge StratoLink brochure, which is too large to host here. Related drive items are listed under Electric Motors and Gear Units. Send the machines, power, speed, shaft sizes and spacing for a quotation.