The following terms with corresponding definitions are used in this standard:
1.brake block: A removable element of the brake system, the working surface of which comes into frictional contact with the wheel tread surface.
2.composite brake block: A brake block manufactured by vulcanization under pressure in molds from a multicomponent mixture, including powdered mineral and other fillers, reinforcing fibers, and a polymer binder with a vulcanizing group.
3.composite brake block with inserts: A composite brake block in which, in addition to the composite material, one or more inserts made of a material different from the base are used.
4.brake block with metal consoles: A type of composite brake block with inserts, where the insert is made of cast iron and has more than two metal protrusions (consoles) on the non-working rear surface of the block, serving to secure the insert in the composite material of the block.
5.cermet brake block: A brake block manufactured by sintering a powder composite material under pressure with a metal back.
6.brake block back: The surface of the brake block with elements for attaching the block to the shoe, which transmits the braking force from the shoe.
7.metal back (solid metal frame): The load-bearing frame element of a composite or cermet brake block, which transmits the braking force from the shoe.
8.shoe: An element of the brake system that receives the braking force and transmits it to the brake block.
9.key: A fastening element of the brake block in the shoe, made in the form of a wedge with an angle ensuring self-locking.
10.central boss: A protruding element of the brake block, located at the center of its back, with a hole for the key to pass through.
11.side bosses: Guide structural elements located at the edges of the brake block back, intended for positioning the key in the block and the block in the shoe.
12.brake unit: A device for transmitting compressed air pressure acting on the cylinder piston or manual brake force to the brake blocks, which are pressed against the wheel tread surfaces during braking.
13.flange: An element of the brake block that covers the wheel flange but does not contact its top.
14.rejection size: An unacceptable value of defect parameters, at which the operation of the wheel pair of traction and trailing rolling stock is prohibited.
Brake blocks are distinguished by the type of rolling stock for which they are intended:
a)freight (B);
passenger (P);
locomotive (T);
motor-car rolling stock (MP);
b) the realized coefficient of friction:
high-friction block;
low-friction block (1);
c) design:
with a wire-mesh frame (WMF);
with a solid metal frame (SMF);
flanged (F);
for brake units (BU)
