High pressure tube unions

Frequently Asked Questions

How does the DILO seal principle function?

It is a seal principle without intermediate tightening compound in form of tongue and groove with little depth of immersion. This principle guarantees permanent tightness at high static and dynamic alternating stresses. Sealing is effected by direct contact with the sealing profiles of the tongue and groove parts. 

Up to which pressure can DILO high pressure unions be used?

The standard program covers a pressure range of up to 320 bar. Special versions for pressures up to 600 bar or 1.000 bar are available on request. 

How to identify DILO unions?

On the face of the clamping nut the following markings can be identified:

  • Series and pressure stage (e. g. M1, J1, M2,....)
  • Nominal diameter of the union (e. g. 25)
  • Material mark (A, C or D)
  • DILO logo
  • the last 3 digits indicate the batch number of the raw material

Blanking disks are not marked due to risk of damage. 

In which material are DILO unions available?

DILO unions are available in 1.0460 (A), 1.4571 (C) or 1.7335 (D) material.

DILO unions are available in 1.0460 (A), 1.4571 (C) or 1.7335 (D) material.

DILO unions can be supplied for precision steel tubes in accordance with DIN EN 10305 and for steel tubes according to DIN EN 10220. If the internal diameters between tube and weld-on stub differ from each other the welding part can be supplied with an adjusted tube wall thickness for aligned laying of tubes.

For which thread types are DILO screw-in tube unions available?

DILO screw-in tube unions are available for metric threads according to DIN13, Whitworth tube threads according to DIN/ISO 228 and American conical threads NPT according to ANSI/ASME B1.20.1.

What is the design of the DILO union?

A straight DILO union always consists of three individual parts. It is equipped with a weld-on stub (part 1) and a clamping nut (part 2). The third individual component is variable. It can be a weld-on thread stub or a screw-in thread stub. 

What to do if you do not find the requested union in our catalogue?

Please contact our sales managers. They will be pleased to offer you customer specific solutions. 

What to do if a DILO union can no longer be identified by means of the marking?

In this case please verify the outside diameter of the weld-on stub as well as the thread of the screw-in stub and the necessary pressure range. 

What are the advantages of DILO high pressure unions?

  • DILO unions are used where systems have to be overhauled regularly or where critical operating conditions exist.
  • They guarantee a tightness of 1x10-8 mbar x l/s.
  • DILO high pressure unions can also be used for all media dependant on the material selected.
  • DILO tube unions can be loosened and re-connected as often as desired with the same level of gas tightness
  • DILO unions are resistant to vibration without any additional protection.
  • Complete interchageability of pieces of the same type is guaranteed.
  • Little depth of immersion allows easy assembly and disassembly. 

How are DILO unions treated prior to despatch?

Unions made of ferritic material (1.0460, 1.7335) are purified and oiled. Unions made of austenitic material (1.4571) are purified prior to despatch. 

By which assessments is the quality of DILO unions guaranteed?

  • With DIN EN 10204 (3.1) certificates including the chemical and mechanical values on the raw material used
  • Certification in accordance with ISO 9001:2008
  • Certificate on the quality assurance in accordance with KTA 1401
  • 2.1. Test report

Why are blanking disks necessary and how to assemble them?

Blanking disks are inserted between the weld-on stub part 1 and the weld-on thread stub part 3 or screw in stub part 5 and are tightened by means of the clamping nut. Thus, enabling pressure or leak tests of a plant component without any problems. Blanking disks with borings (throttle disks) can be inserted in order to set the media supply. 

Are DILO unions also suited for hydrogen application?

Yes, they are. Thanks to its metallic seal DILO unions are well-suited for hydrogen application. Corresponding references are available. Please contact our sales managers. They will be pleased to offer you a solution for your special application. 

How does the max. admissible pressure behave at high temperatures?

The max. admissible pressure is reduced at high temperatures. The pressure level overview for DILO high-pressure tube unions gives the permissible pressure (bar) depending on the operating temperature (°C).

What is the difference between the M and J series from DILO?

Precision steel tubes in accordance with DIN EN 10305 are used for the M series, steel tubes in accordance with DIN EN 10220 are used for the J series.