KLINGER Innovation

Rugged and Capable: Ball Valves for District Heating

The Monoball KHO from KLINGER Fluid Control has been designed to withstand the challenging conditions of district heating applications. Durability, reliability and robustness are of the essence here.

Being part of the critical infrastructure, district heating must work reliably at all times. Prolonged outages or maintenance downtimes in the decentralized generation and distribution of thermal energy are unacceptable, especially in the winter months. In meeting the many challenges that district heating poses for materials and machines, developers rely on components that have been designed to withstand the arduous conditions deep underground. This includes the range of Monoball KHO ball valves from KLINGER Fluid Control.

The Monoball KHO is available in a wide range of versions.

Contacts mentioned in the article:

Gerhard Gruber, Application Engineer at KLINGER Fluid Control

District heating: a stress test for valves

“Although the layout of district heating networks varies from country to country, their basic structure is the same everywhere. This means that the Monoball KHO can be used everywhere,” says Gerhard Gruber. As an application engineer at KLINGER Fluid Control, he is familiar with the many demands placed on valves used in district heating networks.

“Hot water flows in the pipework in a closed circuit. It is heated using biomass, natural gas, waste incineration or electricity. The heat acts on the pipework, causing it to expand and contract. This, in turn, causes tensile, compressive or bending stresses on the pipe unions and valve body.”

Gerhard Gruber, Application Engineer at KLINGER Fluid Control, knows what valves for district heating must be capable of.


Added to this thermal stress are the forces exerted by the water itself, which flows through the system at high pressure.


Smooth flow

The KLINGER Monoball KHO has an exceptionally robust design capable of withstanding these stresses. All body components are cast from carbon steel, and their seams are welded across their entire contact surface. This reduces the risk of crevice corrosion and allows the body to compensate even large temperature variations as well as the forces acting on it from the pipework. “The more robust the valve body and the more meticulously welded the seams, the more durable the entire system,” says Gerhard. Computer simulations that show the forces acting on the body illustrate the withstand capability of the Monoball KHO. The straight internal geometry of the ball itself aids a smooth, turbulence-free flow: The cylindrical bore keeps the pressure drop to a minimum, and the stainless-steel components are resistant to both chemicals and mechanical loads.

In this computer simulation, strong forces act on the valve. But the stress-optimized body design ensures that the internal stresses in its more delicate areas (blue and green regions) remain low.

Avoiding costly maintenance work

This is important in district heating because not all water is the same. “The water circulating in the networks has been conditioned and is not the same as tap water. It has been softened, desalinated, de-ionized and treated with various additives that make it usable for longer periods. In older systems, the water may, over time, turn opaque with suspended solids,” says Gerhard. These solids can clog the valves, causing blockages and the need for maintenance – a costly undertaking, as the valves in district heating networks are usually housed in maintenance shafts or buried underground and therefore difficult to access. So a blockage, let alone a leakage, are invariably associated with high costs.

District heating valves are often located in maintenance shafts and difficult to access.

Low operating costs

To maximize its leaktightness, the Monoball KHO features a system of gaskets and seals that is at the same time elastic, robust, and capable of withstanding contamination and pressure surges. It has both the best leakage classification, A, and a long service life. As pressure can be applied in both directions, it can moreover act as a bidirectional flow valve. The seal system does not reduce the flow rate, ensuring that the medium can flow through unimpeded and without turbulence. “This reduces the work the pump has to do to keep the medium moving through the valve. And that, in turn, helps save energy. The bottom line: lower operating costs for the customer in the long term,” says Gerhard.

Ball valve maintenance

Given that district heating networks have an expected service life of several decades, these savings add up over the years. But the systems’ considerable lifespan also impacts the functionality of the valves themselves. As Gerhard explains, the ball valves in district heating networks are only operated infrequently, usually once a year. The Monoball KHO therefore comes with a functional guarantee that covers, among other things, freedom blockages and a constant actuating torque. Despite this, KLINGER Fluid Control recommends operating the valve at least once a year.

Fit for the long-haul

The Monoball KHO can be operated either by hand or using mechanical, electric or pneumatic actuators. Connected to the actuator with flexible drive extensions, the valves can also be installed in hard-to-reach places or underground. The Monoball KHO complies with the EN 488:2020 district heating standard for underground use, which specifies the testing requirements for composite casings and valves for buried networks. To ensure its valves’ compliance, KLINGER Fluid Control has built its own test bench. “In these, we try to deform the products. We pull on them, compress them, bend them, all with the forces specified in the standard,” says Gerhard. These are the same forces that may act on the valves in decades-long use deep underground. With these tests, KLINGER Fluid Control ensures that its Monoball KHO valves will work reliably under these conditions in the long-run.

KLINGER Fluid Control was one of the first companies to set up an EN 488 compliance test bench.

Frequently asked questions (FAQ)

In which areas of district heating can the Monoball KHO be used?

The Monoball KHO can be used both above ground and underground in heat generation plants, in substations, and in the primary and secondary networks.

In what designs is the Monoball KHO available?

The standard versions cover the nominal diameter range DN15 to DN125 or 20R25 to 150R125, with pressure ratings of PN16 and PN40. The ISO TOP flange version has an EN ISO 5211 compliant top flange. A version with a threaded ISO 228-1 connection with cap and chain, and with a weld end that complies with AGFW FW401 Part 5 is also available. The Monoball KHO-U for buried installation is available with a nominal diameter ranging from DN25 to DN250 or 32R25 to 300R250. All models can be fitted with insulation.

Connect with us

We appreciate your feedback:

Go back

Zum Seitenanfang navigieren