Shopping Cart
Looking for energy efficiency: Industrial plants with many pipes
7 min read

Maintaining pressure: Flow losses of industrial valves

The movement of fluid in hydraulic systems creates resistance caused by the friction of the fluid at the pipe wall, by deflections and, last but not least, by the valves fitted. Find out what factors are decisive for the efficiency of a system.

The movement of fluid in hydraulic systems creates resistance caused by the friction of the fluid at the pipe wall, by deflections and, last but not least, by the valves fitted. Find out what factors are decisive for the efficiency of a system.

Pumps need a lot of energy without consuming it.

According to a survey conducted by the Fraunhofer Institute for the EU Commission, 12.6 % of the entire energy consumed in the EU is used for driving pumps, with pumps in industry making up the lion's share. Modern variable speed high-efficiency motors and flow-optimised pump hydraulic systems offer enormous saving potentials. However, pumps that transport liquids in industrial plants always just form one part of larger overall systems. Such systems also especially comprise pipes and valves. The question is: Is this somewhere opportunities for increasing efficiency may be found – so pumps can be dimensioned smaller or run at a lower rotational speed? To provide a direct answer: Yes, it is. By reducing flow losses.
Strictly speaking, it is incorrect to assume that pumps use a lot of energy – the pumps themselves consume only a relatively small share. Quite the opposite: It is the pump's task to put energy into a system, in the form of the fluid's kinetic energy. In actual fact, the energy is only consumed in the system. Assuming that a pump has got an efficiency of up to 90 %, the actual energy consumed by the pump itself is only 10 % – the remaining energy is transferred to the system, where it is consumed. See the illustration.
Schematic: Pressure loss in a piping system

The schematic clearly illustrates that the differential pressure built up by the pump – the energy pumped into the system – slowly decreases while passing through the pipes and fitted valves.


Where are the true energy guzzlers hiding?

When a fluid flows through a pipe, pressure losses are inevitable. First of all, they are caused by friction between the fluid and the pipe wall: The rougher the inside of the pipe, the higher the friction and, with that, the pressure loss. The material (e.g. metal, plastic or clay) as well as possible deposits and oxidation in the pipe play a role. Secondly, friction effects also develop within the fluid due to the fluid viscosity (internal friction). The internal friction effect increases with the flow velocity of the fluid. Plant designers can significantly influence the losses from flow velocity by using larger pipes. Note: The flow velocity is squared in the pressure loss calculation.
The main cause of flow and pressure losses, however, are vortices and flow separation. Simply put: Wherever fluid is hindered from continuing its even flow, energy is lost. A piping system is not made up of a single, straight pipe. Usually, such a piping system comprises several pipe bends (elbows), branches, reductions/increases in cross-section, measuring instruments, strainers and, naturally, valves (from Open/Closed valves to control valves). Each one of these components causes some pressure loss and therefore energy loss. 
These pressure losses are indicated by the loss coefficient ζ – zeta. This is a dimensionless unit for the pressure loss of a component (e.g. valve). The larger the zeta value of a valve, the higher the pressure loss. To help with the selection, valve manufacturers also provide the Kvs value, also known as flow coefficient, of the fully open valve. The flow coefficient is the flow rate of water at 20 degrees Celsius that causes a differential pressure of one bar in the valve.
When adding up all pressure losses in the different piping system elements, a system curve of the piping can be drawn. The system curve forms the basis for calculating the required head of the pump as a function of the flow rate. You can imagine that in very large systems with several hundreds of valves, many deflections and long pipes, large amounts of energy will be lost.

What role do valves play in the pressure loss of a piping system?

As the wall area within a valve is very small compared to the overall piping system, wall friction losses in a valve can generally be ignored. The lion's share of pressure loss (the resistance coefficient zeta ζ) is caused by vortex formations, flow separation and secondary flows. The flow resistance of valves primarily depends on how much the fluid is deflected when passing through the valve, whether the cross-section is reduced and whether vortices form at the edges.
Valves are categorised according to their design features into the basic types of globe, gate, butterfly, ball or plug and diaphragm valves, and according to the functions they perform, i.e. shut-off valves, safety valves, control valves and check valves or strainers. A look at the internal design of the different types quickly shows that their flow passages vary significantly.
Schematic of the functionality of a gate valve, type KSB ECOLINE GT 40

This simple gate valve of type KSB ECOLINE GT 40 demonstrates that the fluid flow is hardly disturbed at all in fully open valve position. The fluid can almost pass through freely.


Schematic of the functionality of a shut-off valve, type KSB BOA-Compact

This BOA-Compact shut-off valve with slanted-seat design and vertical bonnet has also got a hydraulically optimised port. However, a minor pressure loss may be caused by the reductions in cross-section and by vortices. The obturator being designed in the special shape of a throttling plug makes this valve an excellent match for throttling and control tasks.


Schematic of the functionality of a bellows-type globe valve, type KSB BOA-H

This bellows-type globe valve of the type KSB BOA-H clearly illustrates what path the fluid has to take through the valve. The flow is deflected at several points. This flow deviation results in a certain flow resistance but also provides the valve with a good design for throttling and control tasks.


Table with zeta values at the example of some KSB valves

The table shows the zeta values of different KSB valves of different nominal sizes (for BOA-W the values refer to the previous type series; the current values are better). The difference in resistance of the type series is due to their individual design types. Generally speaking, the simple connection between a low zeta value and a high energy efficiency mainly applies to shut-off valves. For throttling or control valves, integrating additional resistances is desirable or essential.

KSB offers the right valve solution for every application.

As a full-range supplier for the valves sector we offer a broad range of different designs. Alongside globe valves, gate valves, butterfly valves, ball valves, diaphragm valves and control valves, KSB's valve product range also includes actuators, positioners and strainers. No matter how different our products are in design, they all benefit from our 150 years of experience and our mission to always develop the best solution for our customers. 
Especially in times of strongly increasing energy costs, efficiency is gaining more and more in significance – in complex industrial applications even more so than in building services. Pressure losses are less relevant in building services as the flow velocity is relatively low at 0.7 m/s. In industry, flow rates can reach up to 4 m/s, which explains the trend towards considering the entire system's energy consumption in this field.
Our engineers develop products with a focus on several points: Maximum operating reliability and longevity naturally take centre stage. At the same time, the valves are hydraulically optimised to the maximum extent possible. Our BOAX or ISORIA butterfly valves, for example, are fitted with particularly thin discs to keep resistance to a minimum. Being economically efficient is the third criterion our products have to meet. Not everything that is technically possible makes sense from a commercial point of view. This is where an optimum has to be found without compromising on quality.
Product development at KSB: The previous BOA-W compared to the current BOA-Compact and BOA-SuperCompact

A clear development towards a higher efficiency: On the left, you can see a no-longer-current soft-seated valve of the type BOA-W (previous type series), in the middle a BOA-Compact and on the right the especially efficient and compact valve of the type BOA-SuperCompact.


KSB generally places a high value on offering products of the highest possible efficiency – no matter if they are giant motors for driving heavy-duty pumps or small butterfly valves. Our aim is to always use resources as sparingly as possible and leave the smallest possible CO₂ footprint.

Suitable products

BOA-Compact

BOA-Compact
Documents

Globe valve to DIN/EN with flanged ends, short face-to-face length to EN 558/14, slanted seat design with vertical bonnet, single-piece body, EPDM-encapsulated throttling plug, soft main and back seat, position indicator, locking device, travel stop, insulating cap with anti-condensation feature; maintenance-free, full insulation possible.

Details

BOA-H

BOA-H
Documents

Bellows-type globe valve to DIN/EN with flanged ends, with on/off disc or throttling plug, standard position indicator with colour coding for identification of valve design, replaceable valve disc; bellows protected when valve is in fully open position; seat/disc interface made of wear and corrosion resistant chrome steel or chrome nickel steel.

Details

ISORIA 10/16

ISORIA 10/16
Documents

Centred-disc butterfly valve with ISO 5211 compliant square shaft end, sealed by elastomer liner, with lever or manual gearbox, pneumatic, electric or hydraulic actuator. Wafer-type body (T1), semi-lug body (T2), full-lug body (T4) or U-section body with flat faces (T5). Body types T2 and T4 are suitable for downstream dismantling and dead-end service with counterflange. Connections to EN, ASME, JIS.

Details

SISTO-20

SISTO-20
Documents

Weir-type diaphragm valve to DIN/EN with flanged ends, threaded socket ends or socket weld ends, in straight-way pattern; shut-off and sealing to atmosphere by supported and confined diaphragm; body with coating or lining, position indicator with integrated stem protection. All moving parts are separated from the fluid by the diaphragm. Maintenance-free.

Details

NORI 40 ZXLF/ZXSF

NORI 40 ZXLF/ZXSF
Documents

Globe valve to DIN/EN with flanged ends (ZXLF), butt weld ends or socket weld ends (ZXSF), with gland packing, with on/off disc or throttling plug, non-rotating stem, integrated position indicator, seat/disc interface made of wear and corrosion resistant chrome steel or chrome nickel steel.

Details

SERIE 2000

SERIE 2000
Documents

Dual-plate check valve with single-piece, wafer-type body made of lamellar graphite cast iron, nodular cast iron, steel or stainless steel; metal/elastomer-seated or metal/metal-seated, maintenance-free, connections to EN, ASME or JIS.

Details

Matching services

Energy efficiency consulting (Fluid Future) for pumps and valves

Energy Efficiency Consulting

Optimise your system’s energy efficiency in four steps using FluidFuture®. KSB’s systematic approach ensures maximum energy savings.

  • Systematic analysis
  • Clear recommendations for action
View services
SES System Efficiency Service

SES System Efficiency Service

Pumps that are not optimally matched to the system consume too much energy. Thanks to SES System Efficiency Service from KSB, this doesn’t have to be the case.

  • Energy efficiency analysis
  • Damage analysis
View services

Don’t hesitate to contact us.

Would you like further information on KSB? Or have you got any questions surrounding our pumps, valves, services and spare parts? Just contact us. We would love to talk to you.

Find your contact

Stay up to date with the KSB Newsletter.

Want to make sure you never miss the latest news? With the KSB Newsletter you will receive information on our products and solutions, current promotions and events as well as fascinating insights into the world of KSB.

Sign up for the KSB Newsletter(opens in a new tab)