A–B–C–D–E–F–G–H–I–J–K–L–M–N–O–P–Q–R–S–T–U–V–W–X–Y
Tee Piece
A pipe or tubing fitting with a side outlet at right angles. Resembles a T.
Tensile Strength
The maximum amount of tensile stress (ultimate strength) that a material can withstand before failure or rupture occurs. It is the maximum stress developed in a material in a Tensile Test.
Tensile Test
A test performed on a specially machined specimen taken from material in its delivered condition to determine physical properties e.g. yield strength, ultimate strength and percent elongation.
Tension Test
Same as Tensile Test.
Test Certificates
Documents provided by a manufacturer certifying that required tests were performed.
Thermal Relief Valve
For relieving pressure in vessels/tubing due to temperature changes.
Throttling
The intentional restriction of flow by partially closing or opening a valve. A wide range of throttling is accomplished automatically in regulators and control valves.
Through Conduit
An expression characterizing valves when in the open position wherein the bore presents a smooth uninterrupted interior surface across seat rings and through the valve port thus affording minimum pressure drop. There are no cavities or large gaps in the bore between seat rings and body closures or between seat rings and ball/gate. Consequently, there are no areas that can accumulate debris to impede pipeline cleaning equipment or restrict the valve’s motion.
Thrust
A force transmitted by an actuator to a valve through the valve stem expressed in Newtons or Pounds.
Thrust Expressions
- STO Start-To-Open – Thrust required to move the valve from closed
- ETO End-To-Open – Thrust required to fully open the valve
- STC Start-To-Close – Thrust required to move the valve from open
- ETC End-To-Close – Thrust required to fully close the valve
Note : Always check whether the valve is standard acting (stem down to close) or reverse acting (stem up to close).
Top Entry Ball Valve
A two-piece body valve, which is designed and constructed to allow for installation of the valve internal parts into the valve body, with the valve installed into a pipeline. By removing the bonnet, all the valve parts can be removed and re-installed with the use of special tooling. It is specifically designed for in-line maintenance activities.
Topworks
Topworks refer to the dimensional configuration of a valve's stem and bonnet. Valve topworks drawings are needed by the valve/actuator mounting kit manufacturer so that they can correctly design the valve mounting hardware used to couple the valve and actuator together.
Torque
The turning effort required to operate a valve. Usually expressed in pound∙feet or Nm and referred to the stem nut handwheel or operator pinion shaft.
Torque Expressions
- BTO Break-To-Open – Torque required to move the valve from closed
- RTO Run-To-Open – Torque required to travel
- ETO End-To-Open – Torque required to fully open the valve
- BTC Break-To-Close – Torque required to start to move from open
- RTC Run-To-Close – Torque required to travel
- ETC End-To-Close – Torque required to close the valve
Torque Output
The torque output of an actuator normally expressed in Nm, inch/pounds or foot/lbs.
Torque Switch
An electrical device on a motor operator which cuts off power to the operator when allowable torque is exceeded, thus preventing damage to the valve and/or the operator.
Torsion Spring
A coiled spring which exerts a force by twisting about its axis rather than by compression or elongation.
Transition Piece
A length of pipe that is welded to a valve hub or closure. Generally provided by the customer, it serves as a transition from the customer’s piping to the valve to compensate for differences in material or size.
Transmission Line
A main pipeline transporting oil or gas from wells or storage fields to refineries, loading docks or distribution companies.
Trim
Those parts (and their materials) of a valve assembly excluding the valve body, bonnet assembly, which are exposed and in contact with the line medium. Usually consisting of, but not limited to the seat rings, valve ball obturator and stem.
Triple Eccentric Butterfly Valve
A particular design of a butterfly valve where the stem is located behind the disc below the centreline of the disc and its cone axis is offset from the centerline of the disc. This particular design is capable of a very tight shut-off at temperatures well above 1,000°F (530°C).
Trunnion
That part of a ball valve which holds the ball on a fixed vertical axis and about which the ball turns. The torque requirement of a trunnion-mounted ball valve is significantly less than that for a floating ball design.
Turbulent Flow
The random flow of a fluid in which the velocity at a certain point in the fluid varies irregularly.
Turns to Operate
The number of complete revolutions of a handwheel or the pinion shaft of a gear operator required to stroke a valve from fully open to fully closed or vice versa.