![WIKA Model HPAC High-pressure connection adapters and couplings Nominal pressure of 15,000 ... 60,000 psi [1,034 ... 4,136 bar]](https://www.ics-schneider.de/wp-content/uploads/2023/02/fitting-1-350x350.jpg?x90648)
- One-piece design
- Laser marked for identification
- Large selection of materials and configurations available
- Customer-specific combination of adapters, fittings, valves and measuring instruments (instrument hook-up) on request
 Datasheet |
Loose Union for Gauges – Flexible Orientation & Stress-Free Installation
Loose unions allow rotatable, stress-free alignment of pressure gauges, digital gauges and diaphragm seals during installation. The separable nut/nipple design lets you set the exact viewing position without twisting the seal or stressing pipework—ideal for tight spaces and sensitive measuring points.
Available in brass and stainless steel 316(L) with common threads G 1/4, G 1/2 (BSPP), 1/4″, 1/2″ NPT and optional M20×1.5. Sealing concepts include flat gasket/O-ring (BSPP) or PTFE tape/paste (NPT). On request, we supply pre-assembled sets with gauge cock, snubber and instrument.
FAQ on Loose Unions for Gauges
Selection, thread standards, sealing, installation and typical use cases.
What is the advantage of a loose union versus a fixed fitting?
It lets you freely orient the display without twisting the sealing element. This avoids mechanical stress in the measuring chain and reduces leakage risk.
Which thread standards are available?
| Thread | Standard | Sealing | Note |
|---|---|---|---|
| G 1/4, G 1/2 (BSPP) | ISO 228 (parallel) | Flat gasket/O-ring at seat | Mating face must be flat |
| 1/4″, 1/2″ NPT | ASME B1.20.1 (taper) | PTFE tape or paste | No sealing face required |
| M20×1.5 | ISO metric | Usually flat gasket | Verify seat geometry |
Which materials are offered?
Brass for neutral media (air/water/oil) and 316(L) stainless steel for corrosive, hygienic or outdoor applications. Choose gasket materials per medium and temperature (NBR/FKM/EPDM/PTFE).
How do I install a loose union correctly?
- Confirm thread standard and sealing concept (BSPP/NPT/Metric).
- Screw the nipple into the mating part and seal it (O-ring/flat gasket or PTFE).
- Place the gauge, set the orientation.
- Tighten the union nut (torque per datasheet) and perform a leak test.
Does a loose union prevent twisting of diaphragm seals?
Yes. The rotatable connection prevents capillaries/membranes from being twisted or stressed—important for accuracy and service life.
Can I use a loose union with a snubber/cooling element?
Yes. Typical order: Process → shut-off valve/gauge cock → snubber → cooling element/siphon → loose union → gauge. This keeps the final orientation free until the last step.
Common mistakes to avoid
- Wrong standard (BSPP vs. NPT) → leakage.
- No flat face with BSPP → uneven sealing.
- Over-tightening the union nut → damaged gasket.
- No leak test after installation → later failures.
How do I pick the right gasket?
By medium and temperature: NBR (general purpose), FKM (oils/chemicals/temp), EPDM (water/hot water) or PTFE (chemically inert, high temp).
Are there pressure limits?
Yes, per pressure rating/PN and material. Check the datasheet; for high pressure, vibration or pulsation, consider adding a snubber and protective guard.
Does ICS Schneider supply pre-assembled solutions?
Yes. We can deliver complete measuring points with loose union set, gauge, cock, snubber/cooling element, including gaskets and a test report.