Glossary H-I-J-K-L-M-N

H

HEADROOM: Normally the distance from the saddle of the hook to the bottom of a single beam or to the top of the crane on a double girder.

HELICAL GEARING: A gear typified by teeth cut in a helical pattern.

HOIST: A machinery unit that is used for lifting and lowering a load.

HOLDING BRAKE: A brake that automatically prevents motion when power is off.

HOOK APPROACH: The minimum horizontal distance between the center of the runway rail and the hook.

HMI: Hoist Manufacturer’s Institute

I

IMPACT ALLOWANCE: Additional hook load assumed to result from the dynamic effect of the live load.

INTERLOCKING CRANE: A crane equipped with a device to hold alignment between the crane girder and a spur or another crane girder.

INVERTER (VARIABLE FREQUENCY DRIVE): A method of control by which the fixed line voltage and frequency is changed to a three-phase system with infinitely variable voltage and frequency.

J

JIB CRANE: A crane characterized by a boom rotating  about a fixed mast. Usually incorporates a trolley hoist.

K

KSI: Kips per square inch - measurement of stress intensity.

KIP: A unit of force equivalent to 1000 pounds.

KNEE BRACE: The diagonal structural member joining the building column and roof truss.

L

LIFT: Maximum safe vertical distance through which the hook, magnet or bucket can move.

LIFTING DEVICES: Buckets, magnets, grabs, and other supplemental devices, the weight of which is to be considered part of the rated load, used for ease in handling certain types of loads.

LIMIT SWITCH: A device designed to cut off the power automatically at or near the limit of travel for the crane motion.

LINE CONTACTOR: A contactor to disconnect power from the supply lines.

LIVE LOAD: A load which moves relative to the structure under consideration.

LOAD CARRYING PART: Any part of the crane in which the induced stress is influenced by the load on the hook.

M

MAGNETIC CONTROL: A device or system of devices having all basic functions operated by electromagnets.

MAIN LINE CONTACTOR: A magnetic contactor used in the incoming power circuit from the mainline collectors.

MAIN LINE DISCONNECT: A manual switch which breaks the power lines leading from the main line collectors.

MASTER SWITCH: A manually operated device which serves to govern the operation of contactors and auxiliary devices of an electric control.

MATCH MARKING: Identification of non-interchangeable parts for reassembly after shipment.

MMA: Monorail Manufacturer’s Association.  Specifications characterized by the use of Patented Track.

MONORAIL: A single beam supporting a trolley and hoist.  Can be straight or curved.

N

NEC: National Electric Code.

NEMA: National Electrical Manufacturers Association

NEMA 1: Indoor. Protects against accidental contact.

NEMA 3R: Outdoor. Rain tight.

NEMA 12: Indoor. Dust, dirt, dripping liquid tight.

NEMA 4:   Outdoor. Hose directed water tight.

NEMA 4X: Outdoor. NEMA 4 Corrosion Resistant.

NEMA 7: Indoor hazardous locations. For Class I, Groups A, B, C, or D. Vapors

NEMA 9: Indoor Hazardous locations. For Class II, Groups E, F and G.  Dust