Glossar

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Adjustment Ratio

The adjustment ratio is the proportion of the max. and min. volume flow to be controlled for a control valve. As a general rule, the adjustment ratio is ratio is approx. 10:1, however, it may be significantly larger for small valves.

 

Back Pressure Regulator Valves | Short Form: UV

The back pressure regulator valve (inlet pressure regulating valve) limits the pressure upstream of the valve to an adjusted (but changeable) nominal value. The back pressure regulator always drains the corresponding quantity of the fluid needed to reach the set value.

 

Balanced Valve

On a balanced valve, the forces acting on the cone are compensated on an equally sized release surface through the inlet or outlet pressure. Thus the valve features considerably better regulating properties.

 

Bleeding

Bleeding describes the process by which gas is discharged from the plant (pipeline) in a controlled manner through a bleeding valve. It is intended to enhance the safety and efficiency of the plant.

 

Buoyancy Force

The buoyancy force of a float is equivalent to the mass of the fluid displaced by it. As a general rule, the buoyancy forces indicated by Mankenberg refer to water.

 

Combined Venting and Bleeding Valve | Short Form: EB

Combined venting and bleeding valves have two functions, a start-up bleeding valve and an operating bleeding valve. Depending on the manufacturer, they are single devices placed in one housing or optimised solutions.

 

Combined Venting and Bleeding Valve with Vacuum Valve | Short Form: EB with VV

Combined venting and bleeding valves with a vacuum valve are operating bleeding valves with an integrated pressure-controlled vacuum breaker. They are installed in vacuum-vulnerable pipelines. The small bleeding performance of the operational air release reduces the risk of pressure surges.

 

Commuting Line

The commuting line is a compensation line for the cold condensate in steam traps. It allows the escape of the gas enclosed in the steam trap and thus creates space for the condensate.

 

Control Deviation

The control deviation indicates the extent of the variations. In the range from 10 % to 70 % of the possible flow rate, the pressure variation and the set value (psoll) must not vary more than + 10 %.

 

Control Line

The control line takes the inlet and outlet pressure to be regulated from the pipeline (at a location with low turbulences) and transfers it to the control unit. Thus the use of external control lines can contribute to a more stable behaviour of the control valve. Not every pressure regulating valve needs a control line. The control line can also be used to adjust pressures at locations remote from the valve.

 

Control Unit

The control unit transfers the pressure to be regulated to the pressure regulating valve mechanism. The pressure acting on the control surface closes (pressure reducing valve) or opens (back pressure regulator) the valve against the spring force.

Three construction types can be distinguished:

» Diaphragm

» Piston with O-ring and other seals

» Bellow

 

Corrosion by Contamination

Is caused by ferrous deposits and brings about a contamination.

 

Crevice Corrosion

Occurs in a design-related enclosed hollow space of the equipment and in a chloride-containing environment

Can be prevented through avoiding enclosed hollow spaces already during the design phase.

 

Designation Line

The designation line includes information regarding valve type, connection size, rated pressure level at the inlet side, version, KVS value, elastomer code, control range, cone seal and material.

 

Differential Pressure | Δp

The differential pressure defines the pressure difference between inlet and outlet pressure. If pressure ranges are indicated, the smallest pressure difference is applicable for the design of the valves (calculation of the Kv value).

 

Differential Pressure Control Valve | Short Form: DV

Depending on the task, the differential pressure control valves are either pressure reducing valves or back pressure regulators, whose reference pressure is not the atmosphere but the system pressure in another section of the plant.

 

Double Seat

The double seat is a variant to increase the Kv value of a valve by installing two parallel seats instead of one. At Mankenberg, regulation is made through two cones that are firmly attached to each other.

 

Drain Control Valve | Short Form: NV (Level Control Valve)

Drain control valves are level regulating valves which limit the flow of fluid out of a vessel. As the float sinks, the valve is closed.

 

Float Valve | Short Form: NV (Level Control Valve)

The float valve, also called level control valve, is a float-controlled valve.

 

Float Weight

The float weight is the mass weight of the float. It is required for the closing or opening of float-controlled valves. It can be increased for some floats through filling them with sand and adapting them to the operating conditions.

 

Flow Controllers | Short Form: MR

Flow controllers are self-actuated regulating valves that control the volume flow by maintaining constant the differential pressure through an orifice.

 

Flow Velocity | v

The flow velocity (v), or stream velocity, is the velocity of a flow, a directed movement of particles or media. Depending on the medium, certain velocities are permitted. Consequently, the flow velocity and the resulting pressure loss serve as a basis for the design of the pipelines.

 

Gas Spring Cap

The gas spring cap is an alternative setpoint adjuster for pressure regulating valves. Unlike spring-loaded or weight-loaded valves, such regulating valves with gas spring cap are suitable for connection to an existing process control system (PLS). Therefore, they are generally used in cases, where the set value must be frequently changed (for example batch processes in the foodstuffs industry).

 

General Corrosion

The passive layer is completely destroyed, his type of corrosion depends on the consistency of the fluid. Can be avoided by optimally selecting the material with respect to the medium.

 

 

Hard Facing

It is recommended that the cone for pressure regulating valves for liquids and with a pressure drop of approx. > 25 bar is designed with a hard facing layer. This will prevent early wear and tear due to cavitation.

 

High Point

The high point is a local or the absolutely highest point of a pipeline. These points are especially important in piping engineering because they may be ideal points for bleeding as well as points of origin of vacuum shocks.

 

I/P converter

The I/P converter transforms an electrical input signal into a pneumatic output signal and, depending on the level of the pressurised gas (control air pressure), it sends a pneumatic signal in order to display different control ranges.

 

Inflow Regulator | Short Form: NV (Level Control Valve)

Inflow regulators are level control valves that limit the intake of a liquid in a vessel. As the float rises, the valve closes.

 

Inlet Pressure | p1

The inlet pressure indicates the pressure upstream of the valve.

 

Installation

As a basic principle, pressure regulating valves should be installed in horizontal pipelines, however, a vertical line is also possible for gases. If the valve is installed horizontally into a vertical line, this may result in regulating inaccuracies and increased wear and tear.

Gases

Installation is possible with the spring cap pointing upwards or downwards or in vertical lines

Liquids

Installation with the spring cap pointing downwards. Thus gas cushions are avoided that may cause the valve to oscillate.

Steam

Installation with the spring cap pointing downwards to protect the diaphragm from overheating by means of a condensate guard. A steam dryer (liquid separator) should be installed on the upstream side.

 

Intergranular Corrosion

Diffuses from the grain boundaries in heat-sensitized areas, the chromium degrades and impairs the passivating effects.

Can be avoided by selecting low-carbon steel types.

 

Intermediate Piece

The intermediate piece is an extension of the valve body for steam applications. The intermediate piece creates the required space for a water trap, which protects the diaphragm from the high steam temperatures.

 

Kv Value (Application) | Kv

The Kv value (m³/h) is a measure of the achievable flow rate of liquids or gases through a valve and is used to select and dimension the valves. It is calculated on basis of the operating conditions of the application.

 

Kv Value (Valve) | Kv

The flow coefficient Kv (m³/h) is the specific volume flow of a valve at a determined lift.

Conditions: Pressure loss across the valve 1 bar, medium water 5 - 40 °C.

 

Kvs Value | Kvs

The required Kv value is calculated on basis of the given operating conditions of an application and is augmented by 30 % in order to ensure that the selected valve always operates within its optimal performance range. The resulting Kvs value should be smaller than the Kv value of the used valve.

 

Leakage Line

In case of toxic or hazardous media, the leakage line installed at the valve drains the medium safely.

 

Lever Transmission

The lever transmission is the proportion between the length of the float lever and the lever of the valve cone at / in a float-controlled valve.

 

Lifting Lever

The lifting lever is a mechanical device to manually open safety valves for a functional test.

 

NACE

National Association of Corrosion Engineers is an American association of engineers and other experts with the aim of finding solutions for problems caused by corrosion.

 

Nominal Pressure

The nominal pressure is the design pressure of the plant and/or component.

 

Nominal Value

The nominal value is the value set on the valve that must be controlled.

 

Norm Cubic Metre | Nm³/h

The norm cubic metre (Nm³/h) is a volumetric unit to describe a quantity of gas. It indicates the volume of a gas at normal conditions for 1 bar (abs.) at a temperature of 20 °C.

 

Operating Pressure Range

The operating pressure range indicates the range within which a valve can be used. Thus the valve function is ensured within this range.

Example:

The indication pressure range 0-6 bar means for a bleeding and venting valve: the valve can be used for this system pressure range and will function.

 

Operating Pressure

Operating Pressure is the pressure prevailing throughout the plant.

 

Outlet Pressure | p2

Outlet pressure is the designation for the pressure prevailing downstream of the valve.

 

Ozone-resistant Design

The valve is designed for use in an ozone-laden atmosphere (use of special materials).

 

Pilot-actuated Control Valves | Short Form: RP

As a general rule, pilot-actuated control valves are larger-sized valves with high volume flow that are controlled by a smaller pilot valve. This pilot also determines the function and the reduction ratio of the valve unit.

 

Pipeline Extension

A valve is often sufficiently dimensioned for a certain application with regards to the KV(S) value, but might be too small in respect of the nominal diameter and the resulting flow velocities. Too high flow velocities result in noise, pressure rise and wear and tear. In such a case, the flow velocity can be reduced to an admissible value thanks to the pipeline extension.

 

Pitting Corrosion

Can be avoided by selecting molybdenum-containing steel types.

 

Pitting Index | PREN

The PREN index is a measure of the corrosion resistance of stainless steel alloys.

PREN = 1 x %Cr + 3,3 x %Mo + 16 x %N

 

Pressure Drop | Δp

The pressure drop defines the pressure difference between inlet and outlet pressure. If pressure ranges are indicated, the smallest pressure difference is applicable for the design of the valves (calculation of the Kv value).

 

Pressure Maintaining Valve

The pressure maintaining valve (inlet pressure regulating valve) limits the pressure upstream of the valve to an adjusted (but changeable) nominal value. The back pressure regulator always drains the corresponding quantity of the fluid needed to reach the set value.

 

Pressure Range

The pressure range indicates the range within which a valve can be used. Thus the valve function is ensured within this range.

Example:

The indication pressure range 0-6 bar means for a bleeding and venting valve: the valve can be used for this system pressure range and will function.

 

Pressure Reducing Valve | Short Form: DM

Pressure reducing valves reduce a high, fluctuating inlet pressure to a lower and stable outlet pressure. They are open in unpressurised condition and closed with rising outlet pressure.

 

Pressure Regulating Valve

Pressure regulating valve is the general term for any form of valves that regulate the pressure.

 

Pressure Regulator

See pressure regulating valve

 

Pressure Relief Valve | Short Form: SR

Pressure relief valves protect pipelines from dangerous dynamic pressure changes (pressure surges).

 

Reduction Ratio

The reduction ratio is the quotient of inlet and outlet pressure. Due to its design, every pressure reducing valve has a maximum reduction ratio.

Example:

Reduction ratio 20:1 (the data sheet of the control valve indicates 20)

The nominal value for the outlet pressure of 1.2 bar is the highest admissible pv = 20 x 1.2 bar = 24 bar

 

Safety Valve

Safety valves protect plants or plant components from inadmissible excessive pressures by responding quickly at a pre-set inlet pressure and discharging the fluid from the system

 

Sea Water-resistant Materials

All steel types having a PREN index > 33 are classified as sea water resistant materials.

 

Seat Leakage

The permissible seat leakage indicates how much water may flow through a closed valve during the final test on the test bench. Since control valves are always regulated through a fine balance of forces, a minor leakage is permitted. The corresponding quantities and test methods are internationally standardised.

 

Seat Tightness

See Seat Leakage.

 

Self-acting Valve

The valve operates independently. No additional energy supply is required (no power supply lines, no compressed air lines etc.).

 

Separator | Short Form: AS

Separators separate media of different states of aggregation.

 

Setting Range

The setting range indicates the range within which a valve can be set.

Example:

The indication setting range 4 - 6 bar means for a pressure reducing valve: the outlet pressure can be set between 4 and 6 bar back pressure regulating valve: the inlet pressure can be set between 4 and 6 bar

 

Silicone-free Design

Valve design without the use of silicone-containing sealants and lubricants.

 

Sour Gas Directive

The Sour Gas Directive is a guideline for the selection of materials for the use in atmospheres containing H2S.

 

Standard Cubic Metre | Sm³/h

The standard or norm cubic metre (Nm³/h) is a volumetric unit to describe a quantity of gas. It indicates the volume of a gas at normal conditions for 1 bar (abs.) at a temperature of 20 °C.

 

Start-up Venting and Bleeding Valve | Short Form: EB

The start-up bleeding valves bleed plants with low internal pressure during start-up or filling. The float acts directly onto the cone. Such valves have a large seat diameter to ensure fast bleeding at a pressure below 0.1 bar. During operation they are kept closed by the internal pressure of the vessel. In case of a suddenly occurring vacuum the valves open and compensate the pressure. Thus damages caused by a vacuum will be avoided.

 

Steam Trap | Short Form: KA

The steam trap discharges liquids from steam or gas systems

 

Stress Corrosion Cracking

Occurs in a chloride-containing environment, when the equipment is exposed to high stress, for example.

Can be avoided by selecting a suitable stainless steel.

Transcrystalline or intergranular crack path at sensitized microstructures.

 

Temperature Limits

Temperature limits show the minimum and maximum operating temperature of a valve. As a general rule, they can be determined based on the used elastomers and the fluid taken as a basis for the calculation.

 

Tightness of the Valve

The permissible seat leakage indicates how much water may flow through a closed valve during the final test on the test bench. Since control valves are always regulated through a fine balance of forces, a minor leakage is permitted. The corresponding quantities and test methods are internationally standardised.

 

Vacuum Breaker | Short Form: VV

The vacuum breaker is used to protect processes from inadmissible high vacuums. Vacuum breakers are set to a differential pressure to the atmosphere, they open when this value is reached and let air flow into the system.

 

Vacuum Control Valve | Short Form: VV

The vacuum control valve controls the negative pressure within pipelines, vessels and similar plants upstream and downstream of the valve.

 

Valve Cone

The valve cone is a movable component in the valve, that rests on the valve seat. Owing to the cone stroke the valve opens, is throttled or closed.

 

Valve Seat

The valve seat is the apron for a defined cross-flow aperture in the valve, through which the medium to be regulated has to flow.

 

Venting

Venting describes the process by which air is induced into the plant (pipeline) in a controlled manner through a bleeding valve. It is intended to prevent the creation of a vacuum in the plant.

 

Venting and Bleeding Valve | Short Form: EB

The venting and bleeding valves are used for supplying / discharging air in pipelines, see Venting and Bleeding.

 

Venting and Bleeding Valve for Continuous Operation | Short Form: EB

The continuous bleeding valves are used to evacuate the air accumulating during operation. They are provided with a lever transmission thus they also operate at very low or very high pressures. If air intake is to be avoided the outlet must be provided with a non-return valve. In such a case they will act as bleeding valves without venting function.

 

Water Trap

The water trap protects the diaphragm in steam control valves from overheating. The water trap must be created by filling water into the device prior to commissioning. During operation the water trap is maintained by cooling the steam at the valve side itself.

 

Working Cubic Metres | m³/h at x bar(g)

The working cubic metre (m³/h at x bar(g)) is a volumetric unit to describe a gas in the operating condition, i.e. at operating pressure and operating temperature. Attention: When this unit is applied, always indicate the used reference pressure and reference temperature.

 

Weiterführende Informationen

The Mankenberg Order Service

New - Guidebook

guidebook "Self-acting Control Valves"

 
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