Abstract: A concentration measurer for measuring the concentration of turbidities in object liquid by detecting the diffuse reflection light of a laser beam emitted to the object liquid, comprising a concentration detecting part formed by bundling a plurality of optical fibers for laser beam emission and a plurality of optical fibers for laser beam receiving. In this measurer, a body part having an emitter and a receiver for the laser beam and the concentration detecting part can be formed separately from each other, and the body part and the concentration detecting part can be connected by flexible optical fibers. By this measurer, a concentration up to a high turbidity concentration can be measured with high sensitivity and, when the concentration detecting part is formed separately from the body part, the concentration detecting part can be easily installed even in a restricted area and an adverse environment.

Abstract: This invention provides a cleaning method for removing sediment from the inner wall of the rotary drum of a horizontal drum-type centrifugal separator which comprises charging a plurality of solid cleaning medium pieces such as globules, balls, cubes, rods, springs etc., into the rotary drum, supplying a cleaning liquid to the rotary drum, rotating the drum, and discharging the sediment together with the cleaning liquid. The solid cleaning medium is charged into the rotary drum either before centrifugal separation or at the time of cleaning after centrifugal separation.

Abstract: A concentration measurement apparatus capable of accurately measuring the concentration of suspended matter in a liquid is provided.A transmitter 1 which transmits sound waves, light waves, or the like, and a receiver 2, which is disposed in opposition to this transmitter 1, are provided, small pipes 3 and 4, which enclose the transmitting surface position of the transmitter and the receiving surface position of the receiver, and which are opened in the direction of transmission and the direction of reception, respectively, are provided, and a mechanism for filling these small pipes with a clean liquid or gas is provided.The transmitting surface of the transmitter and the receiving surface of the receiver are not contaminated by means of the deposition or generation of suspended matter, so that it is possible to conduct the accurate measurement of the concentration in a constant manner.