SensoControl measuring connections for easy connection of pressure circuit and measuring device

SensoControl Test Ports for Easy Connection of Pressure Circuits and Measuring Devices

Test ports from SensoControl reliably connect pressure circuits and measuring devices in high, low, and vacuum pressure systems. They primarily serve for pressure-related connection for measurement, for bleeding cylinders and hydraulic systems, and for sampling. Typical applications include hydraulic test benches, industrial machine controls, laboratory test stations, and mobile measurement vehicles. The design depends on the medium, operating pressure, temperature range, and compatibility with measuring devices, as well as the installation situation and sealing system.

Materials and Corrosion Resistance

For SensoControl test ports, predominantly stainless steel (1.4301/1.4404) and brass are used. Stainless steel is preferred for aggressive media, high demands on hygiene or chemical resistance, and elevated temperatures. Brass is more economical, sufficiently resistant to mineral oils and air, and offers good machinability for fine threads and precision bores. Plastics such as PTFE or PEEK are used for internal seals when chemical resistance and low adsorption are required. Surface treatments like nickel plating or passivated stainless steels reduce wear and oxidation in humid environments.

Designs and Connection Variants

Test ports are available in compact block designs, angled designs, and as straight elements with an integrated valve. For connection to sensors and measuring devices, standardized thread sizes (e.g., G1/4, G1/8, 1/4 NPT) as well as quick couplings, screw connections, and hose connections are available. In-line modules with shut-off and drain functions allow easy disconnection of the measuring device without pressure loss in the system. For pressure switches or electronic pressure sensors, variants are available with and without pressed-in sealing washers, with conical or cylindrical threads, and with suitable clamp or crimp connections for cables.

Seals, Damping, and Leak Rate

The sealing technology defines measurement uncertainty and long-term stability. Elastomers such as NBR and FKM are used for general hydraulic applications; FKM (Viton) is used at higher temperatures and with more aggressive oils. PTFE seals minimize friction and hysteresis-dependent measurement errors; POM inserts offer wear resistance under mechanical stress. For critical measurements, the permissible leak rate is specified and must include proof of tightness over lifetime cycles. During installation, clean mating surfaces and correct tightening torque of the threads are crucial, as overtightening damages the seal and causes micro-leaks.

Technical Specifications and Selection Criteria

The selection of a test port depends on operating pressure, nominal flow rate, temperature range, medium, and compatibility with the measuring device and piping system. For continuous pressure monitoring in high-pressure hydraulics, connections with nominal working pressures ≥ 350 bar and minimal inherent flow should be chosen. For low-pressure and vacuum applications, connections with integrated vacuum seals and non-return valves are used. Further criteria include dead volume (relevant for rapid pressure changes), repeatability of the connection, and electromagnetic compatibility for integrated sensors.

Connection and Installation Instructions

Before installation, the sealing surface must be cleaned and checked for damage. Threads must be cleanly cut according to standards; for threads with a sealing function (cylindrical or conical), the recommended sealants must be used. For connections with a screw ring, ensure correct alignment of the cable routing to avoid bending stress and torsion of the connection. For repeated measurements, a bleed port near the measuring device is recommended to remove air bubbles. For high-frequency measurements, ensure minimal dead volume and short connection lengths to minimize pressure waves and resonances.

Practical Examples

Example 1 — Hydraulic Test Bench for Drive Elements: To monitor system pressure, a SensoControl G1/4 stainless steel test port with an integrated shut-off valve is installed directly on the test cylinder. A short, rigid connection leads to the differential pressure sensor. Before commissioning, the system is filled with oil, bled via the test port, and the valve is then closed. The test ports minimize dead volume, allowing precise detection of rapid pressure peaks.

Example 2 — Bleeding Industrial Cylinders: For a pneumatically controlled production cylinder, an angled test port is used to ensure easy accessibility in confined installation spaces. The port features an integrated fine sieve and a hand-operated bleed valve. During maintenance, the cylinder can be quickly bled without having to remove pressure lines.

Example 3 — Sampling in Oil Circuits: For regular oil analyses, a test port with a sampling tap is mounted directly before the filter. The brass version with PTFE seal allows clean, residue-free sampling. The sample quantity is precisely dosed, as the test port has a defined dead volume and reproducible flow characteristics.

Further practical applications, technical drawings, and installation instructions can be found on our technology page and in specific application examples: Technology, Application Examples.

Maintenance, Service Life, and Replacement Intervals

Regular visual inspection for corrosion, damage, and leaks is mandatory. Replacement intervals depend on operating cycles, media exposure, and temperature cycles. Elastomer seals should be checked first due to wear; for aggressive media, a semi-annual seal check is recommended, for moderate loads, annual inspections. If leaks are detected, the connection including the seal must be replaced, as rework increases measurement uncertainty. Spare parts should be factory-approved to avoid material and manufacturing deviations.

Standards, Test Procedures, and Documentation

Test ports must comply with relevant standards and test procedures (e.g., ISO, DIN EN, VDMA requirements for pressure components). Test protocols for tightness, flow, and material origin increase the validity of measurements. For metrological traceability, calibration instructions and interface descriptions must be provided. Documents should include information on material, temperature range, permissible maximum pressure, thread type, and sealing system.

Compatibility with Measuring Devices and Measurement Chains

The interaction between the test port, connection line, and measuring device influences the measurement result. Electromechanical sensors require galvanic isolation or equipotential bonding connections when conductive media are measured. For pressure transmitters, the permissible connection capacitance must be observed; long capacitive lines can alter measurement behavior. For digital sensors with integrated electronics, EMC-compliant shielding and suitable connectors should be used.

Selection Guide Summarized

• Choose material according to medium and temperature, seal according to chemical resistance and pressure requirements, design according to installation situation and measuring device.

FAQs

1. Which seal is suitable for hydraulic oil at 80 °C?
For mineral oils up to approximately 120 °C, FKM (Viton) is recommended. For prolonged thermal stress or aggressive additives, check PTFE-based seals or specified high-temperature elastomers.

2. How do I reduce dead volume and metrological delays?
Use short, rigid connections and test ports with small internal volume and smooth flow paths. Avoid unnecessary intermediate adapters and kinks; choose connections with an integrated shut-off valve to minimize MS connections.

3. When is stainless steel absolutely preferable to brass?
Stainless steel is absolutely necessary for corrosive media, contact-critical measurements (e.g., food, chemical analyses), higher temperatures above the operating limits of brass, or when galvanic corrosion between components must be excluded.