Which cable protection conduit to choose: PA, PP or metal?

Step 1: which material suits the environment?

PA6 is the workhorse: impact resistant, self-extinguishing and affordable, usable from −40 to +105 °C. PA12 costs more but hardly absorbs moisture, stays flexible at −60 °C and tolerates oil and coolant better. PP is chemically the strongest but mechanically the weakest; use it in wash-down and plating lines, not in a moving run.

Choose metal conduit as soon as heat, sparks or mechanical damage are involved. A galvanised steel wound conduit with PVC jacket is sealed and robust; a stainless version without jacket handles higher temperatures but is not liquid-tight.

Step 2: closed, slit or split profile?

A closed conduit is the only one that achieves an IP rating, but cables must be pulled through. A slit conduit clips around an existing pre-terminated cable — handy for retrofits, but expect IP40 at most. Split hinged conduits sit in between and are splash-proof with a sealing lip.

• Closed: IP66 up to IP69K possible, pull cables in before mounting.
• Slit: retrofit mounting, no sealing claim, ideal for maintenance.
• Split with sealing lip: compromise for dust and splash water.

Step 3: which gland system belongs to it?

Conduit and gland form one system: the gland grips the corrugation of that specific brand. Choose plastic (PA) glands for standard use, nickel-plated brass for vibration and EMC requirements, and stainless for food or outdoor installations. Watch the thread type (metric M or PG) and the enclosure wall thickness.

What changes in a moving application?

On a robot arm or moving run the dynamic bend radius counts, not the static one: allow 1.5 to 2 times the static value. Use swivel glands at the moving end, let the conduit form a generous loop instead of a kink, and place strain relief just behind both glands so the corrugation is not pulled out of the clamp.