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

Measuring Ports for Pressure Monitoring: Direct Connection of Pressure Circuit and Measuring Device

SensoControl measuring ports connect measuring devices securely and reproducibly to high, low, and vacuum pressure circuits. The components are designed for pressure monitoring, sampling, and bleeding in hydraulic and cylinder systems. Typical applications include test benches, automated production machines, mobile hydraulic units, and maintenance workstations in the manufacturing industry. Crucial factors are leak-tightness, material compatibility, and ease of assembly in confined spaces.

Materials and Corrosion Resistance

Measuring ports are often made of brass, stainless steel (1.4301 / 1.4404), or aluminum. Brass offers a good compromise between cost, mechanical strength, and machinability, but has limited resistance to aggressive media and galvanic stress. Stainless steel is suitable for corrosive media, higher temperatures, and hygienically relevant applications; it minimizes wear during frequent assembly cycles. Aluminum reduces weight in mobile applications but is chemically less resistant than stainless steel. Material selection depends on the medium, pressure range, temperature, and environmental conditions; for hydraulic oils and mineral oils, brass is often sufficient, while for water, cooling lubricants, or saline environments, stainless steel is preferable.

Designs and Connection Variants

SensoControl measuring ports are available in compact inline designs, angled designs, and quick-coupling variants. Inline models allow for short measuring lines and low dead volumes; angled connections reduce installation space on cylinder heads and valve islands. Quick couplings accelerate repeated measurements without tools but pose a higher leakage risk if incorrectly selected. Important connection standards include BSPP, BSPT, NPT, and metric fine threads; in addition, cone, SAE, and O-ring face seal interfaces are found at special measuring points.

The following variants are relevant for a secure connection to the measuring device:

• various thread types (BSPP, BSPT, NPT, metric), quick coupling, SAE cones

Seal Types and Leak-tightness Requirements

Seals in measuring ports are made of NBR, FKM (Viton), EPDM, or PTFE. NBR is standard for mineral oil-based hydraulic fluids and offers good abrasion and tear resistance. FKM is required for higher temperatures and oil- or chemical-resistant applications. EPDM is suitable for water and steam applications but is not oil-resistant. PTFE seals offer chemical neutrality and low friction, and are used when contamination or high chemical resistance play a role. The sealing concept and insertion depth must be matched to the thread/connection to ensure repeatable leak-tightness during assembly cycles.

Temperature and Pressure Ranges

SensoControl measuring ports typically cover ranges from vacuum to several hundred bar. Permissible pressures depend on the material, geometry, and seal. Stainless steel versions achieve higher pressure resistance and are suitable for test benches with increasing pressure peaks. Temperature resistance is determined by the material and seal; PTFE and FKM seals allow operation over a larger temperature range, while NBR can become brittle at low temperatures.

Assembly, Maintenance, and Testability

Assembly is preferably carried out with a defined tightening torque to avoid seal damage and leaks. For installation positions with limited torque space, angled connections or union nuts with slots are advantageous. Maintenance includes regular visual inspection for corrosion, leak tests, and replacement of seals at prescribed intervals or after wear. For quality-relevant measurements, a calibration chain with short, directly connected lines and the use of high-quality quick couplings that minimize measurable dead volumes and internal leaks are recommended.

Connection to Measuring Devices: Cables, Lines, Adapters

The connection between the measuring port and the measuring device is made via test lines made of stainless steel flex, PTFE hoses, or metal-jacketed high-pressure lines. Stainless steel flex offers low dead volumes and high temperature and chemical resistance. PTFE hoses are lightweight, electrically insulating, and chemically inert. Adapters with firmly defined transition threads reduce inconsistencies in the measurement chain. For differential pressure measurements, symmetrical line routing must be observed to minimize pressure differences due to temperature or height differences.

Practical Application Examples

Example 1 — Bleeding a Cylinder: A waiting service technician connects an angled measuring port with a BSPP thread directly to the cylinder connection. After opening the connection, slow bleeding is enabled, while the oil from the bleed hole is guided through a transparent PTFE hose piece to the collection container. The metal housing of the connection prevents mechanical damage from hoses and allows repeated use without seal damage.

Example 2 — Sampling on a Hydraulic Unit: For oil sampling, an inline measuring port with a quick coupling is used. The technician takes the sample during ongoing operation without interrupting the pressure circuit by actuating the quick coupling. The sampling line consists of stainless steel flex to prevent the ingress of foreign substances. Subsequently, the coupling is closed pressure-tight, and the measuring point is fitted with a protective cap.

Example 3 — Pressure Testing in a Production Plant: At a test station, measuring ports with NPT threads are screwed onto test valves. Precision manometers are connected via short metal-jacketed lines. To ensure reproducible measurement results, all connections are screwed with a defined tightening torque, and the seals are visually inspected after each test cycle. If necessary, adapters are used to couple different thread types without increasing the dead volume.

Qualification and Safety Aspects

For safety-relevant measurements, pressure-related approvals, material certificates, and traceability of components are important. Documented test protocols for leak-tightness, tensile strength of threaded connections, and material testing (e.g., for sulfur content in stainless steel) should be available. In potentially explosive areas, electrically conductive versions of the measuring ports and antistatic hoses are preferable. Installation instructions must specify the correct tightening torques and suitable sealants.

Compatibility with Measuring Devices and Accessories

Measuring ports must be selected to be compatible with commercially available pressure gauges, data loggers, and calibration systems. Adapter catalogs for thread and seal transitions are helpful to reduce assembly times. Protective covers, caps, and mounting clamps extend the service life and simplify handling in harsh manufacturing environments. Further technical details and accessories can be found under Technology and in our Application Examples.

Selection Criteria for Procurement

When procuring, the following factors are prioritized: material suitable for the medium, suitable seal, thread or quick coupling requirement, permissible pressure and temperature range, dead volume, and repeatability of the connection. Also consider the frequency of assembly cycles and the environment (corrosion, contamination, explosion protection) to optimize material and seal selection. Replacement seals should be kept as consumables, especially for regular measurement intervals and mobile testing tasks.

FAQ

1. Which seal should I choose for mineral oil-based hydraulic fluids?
For mineral oil-based hydraulic fluids, NBR is the common choice, offering good resistance and abrasion resistance. For higher temperatures or chemical stress, FKM is preferable.

2. How do I avoid measurement errors due to dead volume?
Minimize dead volume through short, direct lines, stainless steel flex or PTFE hoses, and compatible adapters without additional cavities. Use inline connections with low internal volume and avoid unnecessary intermediate elements.

3. When is stainless steel absolutely necessary instead of brass?
Stainless steel is absolutely necessary for corrosive media, saline environments, higher temperatures, or when hygiene/chemical compatibility is required. For frequent assembly cycles, stainless steel also reduces wear on sealing surfaces.