| valence |
the tendency of elements to form compounds
through a shift of electronic structure. |
| valence effect |
in general, the higher the valence of an ion,
the greater the loss of stability to emulsions, colloidal suspensions, etc., these
polyvalent ions will impart |
| valve |
a device used to control the rate of flow in a
line to open or shut off a line completely, or to serve as an automatic or semiautomatic
safety device. Those used extensively include the check valve, gate valve, globe
valve, needle valve, plug valve, and pressure relief valve. |
| vaporproof |
not susceptible to or affected by vapors.
For example, an electrical switch is made vaporproof so that a spark issuing from
it will not cause an explosion in the presence of combustible gases (vapors). |
| V-door |
an opening at floor level in a side of a
derrick or mast. The V-door is opposite the drawworks and is used as an entry to
bring in drill pipe, casing, and other tools from the pipe rack. The name comes from
the fact that on the old standard derrick, the shape of the opening was an inverted V. |
| vee ring |
an elastomer (seal) energized by pressure |
| velocity |
1. speed. 2. the timed rate of linear motion. |
| velocity
safety valve |
a storm choke |
| V-G meter |
see direct-indicating viscometer, vibrating
screen; see shale shaker. |
| viscometer |
a device used to determine the viscosity of a
substance. Also called a viscosimeter. |
| viscosimeter |
see viscometer. |
| viscosity |
a measure of the resistance of a fluid to
flow. Resistance is brought about by the internal friction resulting from the
combined effects of cohesion and adhesion. The viscosity of petroleum products is
commonly expressed in terms of the time required for a specific volume of the liquid to
flow through a capillary tube of a specific size at a given temperature. |
| viscous flow |
see laminar flow. |
| viton |
a fluoroelastomer capable of sealing in sour
gas, volatile adj: readily vaporized. |
| volatility |
the tendency of a liquid to assume the gaseous
state. |
| vug |
1. a cavity in a rock. 2. a small cavern, larger than a pore but too small to contain a
person. Typically found in limestone subject to groundwater leaching. |
