Hydac HDA 44Z6-A-0100-G01-000 Flush-Membrane Transmitter

Flush-membrane transmitter for viscous, dirty or freezing media

The Hydac HDA 44Z6-A-0100-G01-000 (HYDAC part number 922532) is a pressure transmitter whose steel membrane sits flush with the process face. A conventional pressure port has a small bore that can block, fill with residue or freeze. Here the medium acts directly on the front membrane, and the pressure is passed to the measuring cell through an internal oil fill that is free of silicone.

HYDAC recommends it where media change regularly and residues could contaminate the next fluid, which makes it useful on viscous lines, paint and adhesive circuits, and process connections that need to be cleaned easily. This code has a 0 to 100 bar range, 4 to 20 mA output and a four-pole M12x1 plug.

Technical specifications

Choosing the thread option

The fourth block of the code selects the process connection. G01 is a G1/2 A thread to DIN 3852; G02 adds a front O-ring seal on G1/2; G04 is a G1/4 thread with front O-ring and G12 is a G1/2 thread with front O-ring and a cooling section for hot media. This item is the plain G01 version, so confirm that your port is machined for a G1/2 A flat seal before ordering. The flush design needs a mating bore with enough clearance for the membrane.

Handling and installation

Never touch or poke the front membrane with a tool, and do not pull the transmitter out of a bore while it is under pressure. Because the cell is oil-filled, the datasheet limits fluid temperature and requires a cooling-section variant when the medium is hotter than the standard range. Tighten to 45 N·m for G1/2 and keep the cable fitted with the IP 67 mating plug. The USA datasheet attached lists psi ranges with SAE and bar equivalents, so match the range to your process in bar.

Where cleaning-in-place or flushing is part of the process, check the cleaning agent against FKM and stainless steel, and confirm the seal selection with the supplier if the medium is aggressive.

A flush membrane leaves no pocket for viscous, crystallising or contaminated media to collect in, which is why such sensors are chosen for pastes, paints and dirty fluids. Confirm the wetted materials and the G1/2 sealing method against your process medium before ordering.

Selection checks for the HDA 44Z6 flush-membrane transmitter

Before choosing this code, compare the normal working pressure and the highest expected pressure peaks with the 0 to 100 bar range and the stated overload pressure. Pressure spikes from fast-closing valves, pump starts and pigging can exceed the steady reading by a wide margin, so a range with headroom above the normal value usually gives a longer service life than one sized exactly to it. Confirm that the receiving PLC or indicator accepts a two-wire 4 to 20 mA loop and can supply a voltage within the 8 to 30 V DC range after allowing for cable and barrier drops. Check also that the process temperature at the mounting point, not just in the tank, stays inside the fluid temperature limit; if it does not, the G12 cooling-section option described above is the one to discuss.

Wiring and commissioning

Use a shielded cable with an M12x1 four-pole mating connector, which must be ordered separately, and follow the pin assignment in the HYDAC datasheet. Ground the shield at one end only, normally at the control panel, to avoid loops. Before putting the line under pressure, power the loop and confirm that the reading at zero pressure is close to 4 mA. Then raise the pressure in steps, preferably against a reference gauge, and confirm that the PLC scaling matches the 0 to 100 bar span. Record the as-found readings so later checks have a baseline.

Maintenance and cleaning

The main maintenance task is keeping the membrane face clean and undamaged. When the transmitter is removed during a product change or shutdown, depressurise and drain the line first, then wipe the membrane with a soft cloth and a cleaning agent compatible with stainless steel and FKM. Do not scrape dried paint, adhesive or scale off the membrane with tools; soften it and remove it gently instead. Inspect the seal and the G1/2 thread, replace a damaged seal, and refit at the specified tightening torque. A periodic comparison against a calibrated gauge shows whether drift has developed.

Operating in Oman and GCC sites

Outdoor pipework in Oman can reach high surface temperatures in summer, especially on lines exposed to direct sun. Where possible, mount the transmitter on a shaded part of the line or fit a simple sunshade, and keep the cable away from hot surfaces. Dust and sand can collect around the M12 plug, so keep the mating connector fully screwed home and cap the socket whenever the cable is disconnected. In humid coastal plants and wash-down areas, the IP 67 rating only holds when the connector and its seal are correctly fitted, so check them after every maintenance visit. Store spare units in their packaging with the membrane protected until installation.

Documents and quotation

The flush-mount series datasheet is attached. Please state the medium, the process temperature and the thread you need. See also our pressure instrumentation range.