Crane rail clip selection: from rail section to clip type and spacing

A rail clip holds a crane rail on its girder or soleplate and resists the sideways load from the crane wheels. The right clip has to fit the rail, carry the horizontal load and fit on the support. This guide sets out the method and the public rail geometry. It does not give clip capacities: those are each manufacturer's own test data, and any capacity we quote comes from the datasheet of the manufacturer whose clip we offer.

Step 1: identify the rail section

Most enquiries name a DIN 536 Part 1 rail. ArcelorMittal publishes these dimensions (head width, foot width, height, mass):

• A45: 45 mm, 125 mm, 55 mm, 22.1 kg/m
• A55: 55 mm, 150 mm, 65 mm, 31.8 kg/m
• A65: 65 mm, 175 mm, 75 mm, 43.1 kg/m
• A75: 75 mm, 200 mm, 85 mm, 56.2 kg/m
• A100: 100 mm, 200 mm, 95 mm, 74.3 kg/m
• A120: 120 mm, 220 mm, 105 mm, 100.0 kg/m
• A150: 150 mm, 220 mm, 150 mm, 150.3 kg/m

American CR rails are listed on the same page, for example CR104 (63.5 mm head, 127 mm foot, 127 mm high) and CR175 (108 mm head, 152.4 mm foot, 152.4 mm high). If the rail is unmarked or worn, measure the head width, foot width and overall height and send them.

Step 2: establish the horizontal load

Ask the crane maker for the horizontal wheel load. Where it is not known, Gantrail, a UK clip maker, says it often assumes 15% of the vertical wheel load, tells the customer so, and treats a figure below 15% with caution. In Europe the FEM rules give methods for calculating these forces.

Step 3: bolted or welded

Bolted clips are fixed with bolts through the girder flange; welded clips have a base welded to the girder. Gantrail notes that in some countries, notably Germany, welding to crane girders is not considered good practice, and that where welding is used a continuous weld around the base is better for fatigue. For its bolted clips it recommends grade 8.8 bolts, stating that grade 4.6 bolts give only 40% of the horizontal capacity.

Step 4: check the support width

The rail foot width plus the width the clips add on each side must not exceed the girder or soleplate width. Each clip datasheet states the dimension it adds to the rail foot. An A100 rail, for example, starts from a 200 mm foot before any clip is added.

Step 5: set the spacing

Gantrail states that clip spacing cannot be calculated, only checked by calculation in some cases, and gives this guide from experience:

• Normal applications: 600 to 650 mm
• Heavy duty, or where guide rollers apply side load: 500 mm
• Light duty: 800 mm

It reports that problems are often encountered when spacing goes beyond about 1 m. Rail stiffness also varies: Gantrail compares the A100 with a rail of similar head width and finds the A100 more than 40% stiffer sideways, which is why spacing does not follow from the head width alone.

Rails on concrete

On concrete, Gantrail's guidance is to use a continuous soleplate for wheel loads above 35 tonnes, heavy-duty applications and steelworks. Discontinuous mounting suits lighter applications, mostly below 15 tonnes, and needs the rail stress checked.

How rail clips are installed

The sequence below follows Gantrail's published fitting instructions for its 1 Series (welded base) and 3 Series (bolted) clips, which are read together with each clip's datasheet. Other makers' clips differ in detail: always work from the instructions for the clip you actually buy.

1. Rail and pad in position. The clips are fitted with the rail, and the pad if one is used, already in place on the support; Gantrail's 1 Series instructions start from that point. Gantrail's maintenance note stresses that misaligned rails affect crane safety and reliability, and calls for a survey where alignment problems are expected.
2. Welded base clips: mark out and weld the base. Position the base across the rail centreline using the dimension given on the clip datasheet, and along the rail to suit the project. Tack weld the ends and front face, then weld to the datasheet's weld detail. Gantrail's 1 Series datasheets call for a fillet weld all round with low-hydrogen electrodes, and say the weld closest to and parallel with the rail is omitted where there is no rail pad.
3. Bolted clips: fit the bolts and clip body. Pass the bolts through the holes in the support, place the clip over them with its rubber nose resting on the rail's bottom flange, and fit the special washer the right way up, as the instructions show.
4. Seat the clip against the rail. Move the clip into metal-to-metal contact with the edge of the rail foot, run the nut down and tighten it with a spanner. Tap the clip towards the rail with a hammer of about 1 kg along its slots, and tighten only until the rubber nose is compressed and the clip sits fully on its base. Do not apply full torque yet.
5. Torque to the clip maker's value. Tighten to the torque on that clip's datasheet. Gantrail gives a single value per clip rather than a range; for example, its datasheet for the 1116/15 welded clip states 125 Nm. Where impact wrenches are used, its technical note on nut tightening describes calibrating the wrench against a bolt tension meter and checking with a direct-indicating torque wrench.
6. Inspect the track in service. Gantrail recommends periodic inspection, at least once a year for any track in use and more often in heavy service, looking for sideways movement of the rail. It does not recommend routine re-checking of clip nut torque unless the rail has moved, because torque wrench readings can mislead and repeated checks can damage bolted connections.

What to send

1. The rail section, or its measured head width, foot width and height.
2. The vertical wheel load, and the horizontal load if known.
3. The support: steel girder (flange width and thickness) or concrete.
4. Bolted or welded, and whether a rail pad is wanted.
5. Runway length, the spacing you plan, quantity and destination.