Single- and double-layer measuring bellows

Bellows is a thin-wall metal pipe with corrugated (undulated) lateral surface.– page 119 of the Catalog

Purpose

Single- and double-layer metallic measuring bellows are intended for operation as elastic sensible elements in measurement equipment and devices for monitoring and control of various designs, and serve for conversion of the pressure measured into displacement, and used as an expansion joint (bellows expansion joint) and a phase separator in various bellows units.

General specifications

The bellows are manufactured of: alloy grade 36НХТЮ, beryllium copper grade БрБ2, stainless steel 12Х18Н10Т, and brass grade Л-80.

We manufacture over 200 typical sizes of measuring metal bellows with diameters of 9 to 190 mm with a wall thickness of 0.08 to 0.25 mm, suitable for operation in atmospheres causing no metal corrosion at temperatures:

213 to 473 K (-60...+200°С) – for bellows made of alloy grade 36НХТЮ;

213 to 373 K (-60...+100°С) – for bellows made of beryllium copper grade БрБ2 and of low brass grade Л-80;

373 to 673 K (-200... +400°С) – for bellows made of stainless steel grade 12Х18Н10Т.

Single- and double-layer measuring bellows, their general characteristics

Bellows is a corrugated tube with thin walls. More often, they are made of metallic (steel, brass, bronze) materials. Bellows surface can be extended or compressed along the axis, curved in any direction or offset. Such deformation occurs under the action of differential pressure and temperature, and also due to force impact (mechanical exposure). This property of bellows allows for protection of the pipeline integrity.

There are single-layer bellows, double-layer bellows and multi-layer bellows. Thickness of each layer varies per each typical size of the element. Single-layer bellows, as a rule, are manufactured of thin-wall stainless steel.

Reinforced corrugated tubes are also used in production.
Wide range of operating temperatures (-260…+ 530°C),corrosion resistance to many atmospheres (from drinking water to inert gas), simplicity and reliability of operation define wide use of bellows in various industrial sectors.

For example, in pneumatic and hydraulic automatics, single- and double-layer bellows are used as elastic sensible elements of pressure and temperature transmitters. This type of bellows is used for media separation.

Multi-layer bellows are widely used in connection of pipelines in oil and gas industry, nuclear industry, in power engineering, civil construction and machine engineering.

Bellows expansion joints serving for prevention of pipeline rupture under the action of external factors (differential temperature or pressure), are often used in pipelines. Such expansion joints are almost irreplaceable for hot water supply, various heating equipment. Installation of bellows to the valves of structures shall not only considerably prolong its service life, but also increase its leak-tightness.

Bellows is a quite elastic corrugated envelope more often manufactured of various metals. They can be single- or multi-layer. Double-layer bellows have the same thickness as single-layer ones, but they withstand higher loads. They are divided into seamless and welded.

Bellows can operate in aggressive media, withstanding the impact of adverse factors, cryogenic liquids. Metallic bellows are adapted for exposure of high pressure and can withstand up to 7 MPa. Double-layer bellows are used in pipeline equipment in order to ensure sealing, as flexible joints, phase separators. They are used as sensible elements of all types of transmitters, receiving the changes in gas or liquid pressure, respond to temperature difference of the medium.

They are distinguished by elasticity, high strength and rigidity. It is necessary to note, that metallic double-layer bellows are not almost subjected to deformations, but can withstand axial and torsional oscillations. At our plant we use various technologies for production of metallic bellows, having sufficient chemical resistance to organic liquids and distinguished by gas impermeability.

If there is a thin wall ensuring a slight rigidity, metallic bellows have a quite long stroke. During the installation of bellows, it is necessary to consider vibration which shall affect the seal, as each seal has its natural oscillation frequency. Natural oscillation frequency of bellows shall be higher than the forced frequency.

Flexible metallic double-layer bellows are very elastic. Application of bellows for sealing axial mechanical seals increases sliding velocity up to 100 m/s.Metallic bellows ensure good sealing to vacuum systems from vibrations.

It is recommended to purchase these products from reliable suppliers, that cooperate directly to manufacturers. For example, at our plant there is a department that deals with bellows sales. You can consult an expert on any issues of interest.

Component list

Example of ordering as per GOST 21482-76

Bellows with the outside diameter 28 mm, number of corrugations 10, wall thickness 0.12 mm, made of material 36НХТЮ as per GOST 21482-76:

Bellows 28х10х0.12 – 36НХТЮ GOST 21482-76.– page 120 of the Catalog

Example of ordering as per GOST 22388-90

Bellows with the outside diameter 16 mm, number of corrugations 12, wall thickness 0.12 mm, version 1:

Bellows 16-12-0,12-1 GOST 22388-90.