Clearance

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clearance

1. 
a. the disposal of merchandise at reduced prices
b. (as modifier): a clearance sale
2. the act of clearing an area of land of its inhabitants by mass eviction
3. Dentistry the extraction of all of a person's teeth
4. a less common word for clearing

Clearance

 

the maximum profile of an object. As applied to transport vehicles and the moving parts of stationary machines, clearance is determined on the basis of their safe movement among other machines and structures. Outside the clearance, which permits the movement of machines in different directions, it is possible to erect structures and set up machines, lathes, and the safety zone for people. For example, the clearance of a moving train is the maximum profile in a plane perpendicular to the axis of the railway track beyond which no part of a locomotive or car should project when in working order. A railway clearance gauge is the maximum profile in a plane perpendicular to the axis of the railway track within which no parts of structures and equipment should extend. Meeting these clearances ensures the safe movement of trains in tunnels, on bridges, and under over-bridges. Underbridge clearance is the profile of the clear opening under a bridge between the bottom of its span structure and the estimated navigable level in height and between the supports of the span in width.

REFERENCES

Evgrafov, G. K., and N. N. Bogdanov. Proektirovanie mostov. Moscow, 1966.
Evgrafov, G. K., and N. N. Bogdanov. Zheleznye dorogi. Moscow, 1968.
Evgrafov, G. K., and N. N. Bogdanov. AvtomobiV. Ekspluatatsiia i remont. Entsiklopedicheskii slovar’-spravochnik. Moscow, 1968.

I. A. IVANOV


Clearance

 

the distance from ground level (plane of reference) to the lowest structural member of a motor vehicle, excluding the wheels; one of the parameters that determine the operational trafficability of motor vehicles.

The minimum permissible clearances established in the USSR are 200 mm, 240 mm, 260 mm, and 270 mm for fully loaded trucks with carrying capacities of 1.5 tons, 3 tons, 5 tons, and 8-12 tons, respectively, and 240-270 mm for buses, depending on their length and purpose.

clearance

[′klir·əns]
(engineering)
Unobstructed space required for occasional removal of parts of equipment.
(mechanical engineering)
In a piston-and-cylinder mechanism, the space at the end of the cylinder when the piston is at dead-center position toward the end of the cylinder.
The ratio of the volume of this space to the piston displacement during a stroke.
(mining engineering)
The space between the top or side of a car and the roof or wall.
(navigation)
The clear space between a vessel and an object such as a navigation light, hazard to navigation, or another vessel.
A specific message from air-traffic control to a pilot of an aircraft allowing him to proceed in accordance with the flight plan which the pilot had filed, or with some modification of the original plan.
In the instrument landing system, the difference in the depth of modulation which is required to produce a full-scale deflection of the course deviation indicator needle in any flight sector outside the on-course sectors.
(ordnance)
Elevation of a gun at such an angle that a projectile will not strike an obstacle between the muzzle and the target.
(petroleum engineering)
The annular space between down-hole drill-string equipment, such as bits, core barrels, and casing, and the walls of the borehole with the down-hole equipment centered in the hole.

clearance

1. Open space between two elements of a building to aid in proper placement, to compensate for minor inaccuracies in cutting, or to allow unobstructed movement between parts.
2. The space or distance allowed for anchorage or erection processes or to accommodate dimensional variations in the building structure.

air traffic control clearance

Authorization for an aircraft to proceed under conditions specified by an air traffic control unit (ICAO). This is to prevent collisions between known aircraft. The pilot-in-command of an aircraft must not deviate from the provisions of VFR (visual flight rules) or IFR (instrument flight rules) air traffic clearance except in an emergency or unless an amended clearance has been obtained. Additionally, the pilot may request a different clearance if he or she has information available that makes another course of action more practical or if aircraft equipment limitations or company procedures forbid compliance with the clearance issued. Pilots may also request clarification or amendment, as appropriate, any time a clearance is not fully understood or is considered unacceptable because of safety. Controllers should, in any such instance and to the extent of operational practicality and safety, honor the pilot's request. The pilot is responsible for requesting an amended clearance if ATC issues a clearance that would cause him or her to deviate from a rule or regulation, or, in the pilot's opinion, would place the aircraft in jeopardy. Normally, only the word clearance is used, and it may be prefixed by words such as start-up, taxi, takeoff, departure, approach, or landing to indicate the particular portion of flight to which the ATC clearance relates. Also called an air traffic clearance.
References in periodicals archive ?
In addition, one patient in the 5000 microgram dose group showed total clearance of HBV DNA and HBeAg.
In the Masters' qualifi-ers held in Barnsley in December, Wilson had fired in a maximum 147 and a 136 total clearance on his way to beating Ricky Walden 6-2 .
Trump looked on course for an easy win when he stormed into a 4-1 lead with the help of a total clearance of 122 in the second frame.
WELSH Black cattle met an impressive trade at the annual show and sale in Abergavenny, resulting in a total clearance of the 41 lots on offer with an overall average of pounds 913.
Maguire made three centuries in the match, including a total clearance of 127 in the final frame.
A 130 total clearance was Hendry's emphatic response for 3-3 before Selby made it 4-3 by snatching a dramatic seventh frame on the black.
He completed the win with a total clearance of 143, beating Dumbarton's Marcus Campbell's 134 for the pounds 2000 high-break bonus.
Maguire had the momentum and in frame 21 he compiled a magnificent 131 total clearance ( his seventh ton of the tournament ( after Higgins had missed a red into the right black pocket.
2 chalked up a brilliant 141 total clearance during a sparkling 6-4 win over Stephen Lee - just days after arriving in Dublin faced with the prospect of losing his top-16 status.
I can't believe I missed the yellow, and should really have had a total clearance of 137," admitted Read, whose break knocked Simon Stockwell's 84 off the top perch.
However a slight change to his cue has worked in his favour and the Scotsman needed only 74 minutes to beat Shaun Murphy 6-0, completing victory with a total clearance of 144.
Mark Gray, of Peterborough, produced his highest break in professional competition, a 145 total clearance, in the final frame of his 5-3 victory over Rory McLeod.

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