Steam Main Jargon Buster

Fail closed or 'normally closed'

Typically used to describe a valve actuator which needs compressed air (or similar) to be applied to it to open the connected valve. Therefore in a failure situation the valve would spring shut, or otherwise close.

Fail open or normally open

Typically used to describe a valve actuator which needs compressed air (or similar) to be applied to it to close the connected valve. Therefore in a failure situation the valve would open.

Fail safe

A term used to describe the requirement of a product or system to shut down in a safe manner under fault conditions.

Fail-in-place

A term used to describe the ability of an actuator to stay in position if the control signal fails.

Fault flow

Used for sizing a safety valve. The fault flow is the worst case flow that the safety valve should be sized to relieve.

Feedback control

A control algorithm or system in which the control output is calculated from measurements of the process output. Can be called 'closed loop control'.

Feedback potentiometer

This is used on an electrical actuator to provide a feedback voltage to indicate valve position.

Feedpump

In the case of a steam boiler this is the pump specifically designed to provide water into the steam boiler.

Feedwater

The name given to water being fed to the boiler. It consists of condensate return water (condensed steam which has become water that is returned back to the boiler feedwater tank from the process) mixed with treated make up water (raw water that has been treated).

Felt shower

This is used to humidify corrugated paper on a paper making machine or corrugator.

Fermentation

This is a chemical process normally associated with the brewing industry. Sugar is converted to alcohol by the addition of yeast enzyme to the conditioned wort.

Fieldbus

A digital control and instrumentation system in which each device has its own intelligence and communicates via a data highway.

Filter

A device for removing solids from the medium being fed through the filter.

Flange

A method for connecting pipes and other items. For pipes they are typically ring shaped, and form a rim at the end of a pipe.

Flange tables

These tables detail the outside, inside diameter sizes and bolt hole drilling patterns for standardised flanges.

Flash point

Defined as the lowest temperature at which a flame will propagate through the vapour of a combustible material to a liquid surface. It can also be defined as the minimum temperature at which the liquid produces sufficient concentration of vapour above it that forms an ignitable mixture with air.

Flash steam

Flash steam is a vapour of steam which is formed from hot condensate at a higher pressure, discharged as it flows to a lower pressure area. It is caused by the condensate containing more energy than it can hold at the lower pressure. This energy is given up by the condensate (water) in the form of flash steam. Flash steam is very valuable and can be used for a wide variety of purposes.

Flash vessel

A vessel located in a condensate return line that separates flash steam from the condensate water. The flash steam can be fed to a low pressure steam system. The condensate that comes out of the bottom of the vessel can be discharged to the condensate return tank and from there returned back to the boiler feedwater tank.

Float trap

A type steam trap that works by sensing the difference in density between steam and condensate. Typically it does this by using a ball float which is lifted by condensate to expose a valve opening, and the condensate is removed. Steam cannot lift the float so the valve stays closed when trap is full of steam.

Flowmeter

This measures the flow rate of steam, liquid or gas passing through the meter. It is for monitoring usage, cost accounting, and energy conservation.

Fouling

This is the deposition of a film or scale on a heat transfer surface of a heat exchanger. This causes increased thermal resistance to heat flow and therefore reduces the heat transfer capability.

Fouling factor

A measure of additional thermal resistance due to fouling of a heat exchanger.

Free float

A type of float steam trap. There is only one moving part in the trap, the float which is free to move up or down in the trap body (there is no lever or hinges). When condensate reaches the steam trap the condensate lifts the ball (float) and exposes the exhaust valve port, and the condensate can be removed. When steam reaches the trap, the ball/float is not lifted and stays on the exhaust port which means that no steam is discharged. The 'free float' range of steam traps is manufactured by TLV.

FT14

Model number for a float type steam trap manufactured by Spirax Sarco. (Please also see float trap).


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