Viscometer
AssigneeOntario Research Foundation
InventorEdmund G. F. Sweet
Life of this patent
Estimating the term…
Abstract
A method and apparatus are provided for measuring the viscosity of a fluid medium such as drilling mud. A rotary member is mounted within a housing for free rotation and viscous drag means applies a torque-induced rotation to the rotary member. The rotary member has a portion moving adjacent to a fixed surface but out of contact with the fixed surface, thus defining a fluid cavity in which the fluid medium to be tested can be placed, in order to be sheared by relative movement between the portion and the fixed surface. Means are provided to measure the rotational speed of the rotary member, whereby the geometry of the fluid cavity and the nature of the viscous drag means can be used in a determination of the viscosity of the fluid medium to be tested.
Claims31
An apparatus for measuring the viscosity of a fluid medium, comprising:
- means for rotating a first member at an accurately known rate,
- a freely turning rotary member having an axis of rotation and having a first portion adjacent said first member but out of contact therewith,
- a first fluid cavity between said first member and said first portion,
- a fluid being located in said first fluid cavity such that rotation of the first member will place torque on said rotary member thus seeking to induce rotation therein,
- the rotary member having a second portion moving adjacent a fixed surface but out of contact therewith,
- a second fluid cavity between said second portion and the fixed surface into which can be placed said fluid medium of which the viscosity is to be measured,
- and means to measure the rotational speed of the rotary member.
A method of measuring the viscosity of a fluid medium, comprising the steps of:
- using viscous drag means for applying a torque-induced rotation to a rotary member, in such a way that the torque on the rotary member can be known,
- placing the fluid medium in a fluid cavity defined between a portion of the rotary member and a fixed surface,
- determining the torque applied to the rotary member through the viscous drag thereon from a prior calibration,
- and determining the viscosity of the fluid medium from the geometry of the fluid cavity, the known torque on the rotary member, and the rotational speed of the rotary member.
A method of determining the viscosity of a fluid medium, comprising the steps:
- rotating a first member at a given rate,
- using viscous drag to cause the rotating first member to rotate a rotary member about an axis of rotation thereof,
- providing a fluid cavity between a portion of the rotary member and a fixed surface and placing the fluid medium therein, and
- measuring the rotational speed of the rotary member,
- whereby the geometry of the fluid cavity, the rotational speed of the rotary member, and a precalibrated relation between torque on the rotary member and the slip between the latter and the first member allow a calculation of the viscosity of the fluid medium.
A method of measuring the gel strength of a thixotropic liquid, comprising the steps of:
- providing a first member adapted to be rotated at a variable, known rate,
- providing viscous drag means to cause the rotating first member to attempt to rotate a rotary member about an axis of rotation thereof,
- providing a fluid cavity between a portion of the rotary member and a fixed surface and placing the thixotropic liquid therein,
- accelerating the first member at maximum gradient,
- when the rotating first member reaches a rotational speed which equates to a shear rate of 5.11 sec..sup.-1, measuring the differential speed between the first member and the rotary member,
- and using the geometry of the fluid cavity, the rotational speed of the rotary member, and a precalibrated relation between torque on the rotary member and the slip between the latter and the first member to calculate the gel strength of the thixotropic liquid.
A method of determining the gel strength of a thixotropic liquid, comprising the steps:
- providing a first member which can be rotated at a known, variable rate,
- providing viscous drag means to permit the rotating first member to rotate a rotary member about an axis of rotation thereof,
- providing a fluid cavity between a portion of the rotary member and a fixed surface and placing the thixotropic liquid therein,
- gradually increasing the rotational speed of the first member from 0, and measuring the rotational speed of the rotating first member when the rotary member begins to rotate.
Dependencies are inferred from the claim text.