FIELD OF INVENTION
The present invention relates to a system and method of monitoring brake wear for
vertical hydro generators and motors. More particularly, the invention relates to a
system that continuously displays the current amount of wear in the brake pads of
each individual brake unit.
BACKGROUND OF INVENTION
Hydro generators/motors are large and usually vertical rotating machines. A
spinning hydro generator/motor is stopped using a combination of various methods
including electrical braking, hydraulic braking, and mechanical braking. The
mechanical braking is done by braking units placed below the rotor. These units are
also used for jacking purposes.
OBJECTS OF THE INVENTION
Therefore, it is an object of the invention to propose a system and method of
monitoring brake wear for vertical hydro generators and motors which is capable of
continuously monitoring wear on the brake pad.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Fig.1 - Shows various items of the system assembled for monitoring brake
wear of brake pads.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
The brake/jack units (5) consist of a piston-cylinder assembly with brake pads (6)
attached to the piston. When air at sufficient pressure is pumped into the cylinder,
the piston (7) moves and pushes the brake pads (6) against a brake track on the
rotor. The resulting friction between the pad and the track helps the rotor to slow
down and eventually stop. This friction also results in the gradual wearing of the
brake pads (6). The jacking of an idle rotor is done by pumping oil at a much
higher pressure into the cylinder instead of air.
The principle of the proposed system is that the change in the distance the piston
has to move during braking over a period of time indicates the wear in the brake
pad (6) over that period of time. Due to brake wear, the brake piston moves farther
to come in contact with brake track and the system measures this additional
movement using a displacement sensor (3) to measure the distance between a
fixed point and a reference point that moves along with the brake piston.
The proposed system isn’t integrated into the brake/jack unit. This allows the
system to be retro-fitted on older machines without having to replace the
brake/jack units.
The brake wear monitoring system consists of following items. See figure 1 for the
complete arrangement.
1. Driving plate (2): This plate connects the brake piston (7) to the reference
plate (1). When the piston (7) moves upwards, this plate pushes the
reference plate along with it. However, it doesn’t push the reference plate
(1) downwards when the piston (7) returns to its original position.
2. Reference plate (1): This item is moved upward along a shaft by the
driving plate. A ratchet mechanism prevents it from moving in the other
direction, thus at any given time, its position indicates the maximum
distance the piston has moved during braking up to that time since the last
reset.
3. Shaft (8): The reference plate and a displacement sensor are mounted onto
the shaft, which is in turn mounted on a hydraulic actuator.
4. Displacement sensor (3): This sensor is mounted onto a fixed position on
the shaft and is used to measure the distance from that position to a point
on the reference plate.
5. Hydraulic actuator (4): The hydraulic actuator ensures that the
components mounted on it (the shaft, the displacement sensor, and the
reference plate) are all lifted out of the way of the driving plate during
jacking operations. The actuator shall be single-acting if the brake/jack unit
is single-acting and double-acting if the brake/jack unit is double-acting. This
is to ensure that its piston retracts when and only when the piston in the
brake/jack unit retracts.
6. Brake/Jack unit (5):This unit is made of a piston-cylinder assembly with
brake pads (6) attached to the piston (7).
The reference plate and displacement sensor are mounted on a shaft, which is in
turn mounted on a hydraulic actuator (4) that operates in tandem with the
brake/jack unit (5) whose brake pad wear is to be monitored.
WE CLAIM
1. A system of monitoring brake wear for vertical hydro generators and motors
comprising;
a brake/jack units (5) comprising a piston-cylinder assembly with brake pads
(6) attached to the piston, the said piston disposed for moving and pushing;
a hydraulic actuator (4) operating in tandem with the brake/jack unit (5) for
monitoring brake pad (6) wear, the said hydraulic actuator having a shaft (8)
mounted on it, the said shaft having a reference plate (1) and a displacement
sensor (3) mounted on it;
a diving plate (2) connecting the brake-piston to a reference plate (1) for
moving the said reference plate (1) along a shaft (8);
a shaft (8) mounted on the hydraulic actuator (4), the said shaft having the
reference plate (1) and a displacement sensor (3) mounted on it; Characterized
in that,
the displacement sensor is disposed in the system for measuring the
distance between a fixed point and a reference point indicating movement of
the brake piston (7) to come in contact with brake track, wherein the said
distance traverse indicates the brake wear for a period of time.
2. A method for the system as claimed in claim 1, comprising;
pumping air at sufficient pressure into a cylinder to move the piston to push
the brake pads (6) against a brake track on a rotor; wherein the displacement
sensor (3) mounted on a fixed position on a shaft (8) measures the distance
moved by the piston from that fixed position to a point on a reference plate to
indicate the brake wear for a period of time.