Sensor fittings for detection of pressure drop

Signal Fittings for Pressure Drop Detection

Parker Legris signal fittings are used for reliable end-position sensing of cylinder pistons and for the detected recognition of pressure losses in pneumatic systems. Typical connection threads are 1/8", 1/4", 3/8", 1/2" and M5x0.8; the designs cover inline and angled installation, compact dimensions, and reinforced versions for continuous industrial use. Material selection, sealing principle, and electrical connection types determine performance: brass or stainless steel housings offer corrosion resistance and mechanical stability, while plastic-reinforced variants reduce weight and cost with lower thermal loads. NBR elastomer seals are suitable for standard applications up to approx. 80 °C; FKM/FPM seals extend the temperature and chemical range, and PTFE-coated seals offer additional resistance to aggressive media. The functionality is based on pneumatic pressure transmission in conjunction with an electrical or pneumatic switching output. Electrical signal fittings usually integrate reed switches, Hall sensors, or mechanically actuated microswitches, matched to switching frequency, switching voltage, and current. Reed switches are suitable for applications with low switching currents and offer galvanic isolation; Hall sensors allow higher switching frequencies and longer service life with robust EMC compatibility. For pneumatic signal outputs, the pressure state is directly converted into an airflow or pressure pulse, which offers advantages in purely pneumatic controls without electronics. Sealing and connection variants are crucial for tightness and response time. Thread seals are realized either with PTFE thread tape, form-fitting O-ring seats, or conical sealing surfaces. O-ring seats with Buna or Viton O-rings reduce leakage rates and simplify repeated assembly. For threaded applications in vibrating environments, self-locking variants or additional retaining rings are recommended. For robust industrial environments, conductive housings or coatings are possible to minimize static charge and EMC interference. Electrical connections are available as cable glands, M8/M12 connectors, or pre-assembled cables with open ends. Protection classes up to IP67 or IP69K are available for high-pressure cleaning and outdoor applications. The chosen protection class influences service life and reliability: for applications with cleaning cycles in the food or pharmaceutical industry, stainless steel housings with IP69K and FDA-compliant seals are preferable. For fault diagnosis and maintenance, clear markings and plug-in systems that allow serial or parallel feeding of multiple sensors are important. Signal fittings with LED displays offer quick local visual inspection; variants with switching delay or hysteresis reduce false alarms during short pressure fluctuations. In safety-relevant applications, components should be tested according to relevant standards and contain clear information on switching cycles, switching times, and operating temperatures.

Application Fields and Practical Integration

In production lines, signal fittings serve as end-position detectors for pneumatic cylinders to coordinate subsequent processes. If a system loses pressure, a control component (SPS/PLC) is informed via the signal fitting, which safely stops the production step or moves it to a defined state. In paint booths with explosion protection requirements, purely pneumatic signal outputs are often the better choice, as they do not introduce additional electrical energy into potentially explosive zones. A typical practical example: an assembly unit with pneumatic grippers uses cylinders with integrated Parker Legris M5x0.8 signal fittings to provide feedback on the gripping position. The sensors are electrically connected to the control system via M8 connectors; LED indicators on each cylinder allow quick visual checks during plant downtime. By using FKM O-rings and stainless steel housings, the system is reliably sealed in an oily lubrication environment and maintains high switching reliability over long operating times. Another concrete scenario: in a packaging machine, an angled signal fitting with a 1/4" connection thread reports the end position of a piston that extends a transport slide. The sensor is designed as a reed switch and integrated into the existing pneumatic control system with redundant evaluation. In the event of a pressure drop in the cylinder, the sensor fitting generates a switching signal that causes the PLC to move the machine part to a safe position and issue an error message. This combination minimizes production downtime and simplifies error analysis through clear error messages in the control system. For mobile tools and robot arms, compact signal fittings with 3/8" or 1/2" connections offer large flow cross-sections and lower pressure losses, ensuring short response times and precise piston positioning during fast cycles. With the correct selection of material and seal, temperature ranges from -40 °C to over 150 °C can be covered; special versions for vacuum applications are available if required.

Design, Installation, and Test Points

When designing, attention must be paid to the compatibility between the cylinder and fitting threads, as well as the required torque for a secure seal. Installation often requires a defined insertion depth and, if necessary, the use of flat gaskets or O-ring seats. Commissioning should include a pressure test under operating conditions to verify static and dynamic tightness. EMC tests and leakage rate tests according to defined test cycles increase operational safety. Maintenance instructions include regular visual inspection for damage, checking the seals, and, if necessary, replacing O-rings. For electronic sensors, diagnostic functions such as LED displays, current monitoring, and short-circuit protection are useful. Spare parts should be procured with identical material and sealing parameters to avoid softening or compatibility problems. Further technical details, specific product data sheets, and material specifications can be found on our technical page https://maku-industrie.de/technik. Practical application cases and possible integration scenarios are documented at https://maku-industrie.de/anwendungsbeispiele. The following criteria play a central role in selection:

• Thread size and type, material (brass, stainless steel 1.4301 / 1.4404), sealing material (NBR, FKM, PTFE), protection class (IP protection classes), switching principle (reed, Hall, mechanical), connection type (M8/M12, cable, screw connection), temperature range, and service life specifications.

Compatibility with Parker Legris Components

Parker Legris signal fittings are designed for easy integration into existing Legris pneumatic systems. The adapter geometries and threads comply with common standards, which facilitates retrofitting and interchangeability. Combinations with Legris quick couplings, hose connections, and cylinder mountings enable modular solutions for line automation. The data sheets contain precise information on tightening torques, sealing recommendations, and switching characteristics that must be considered during design.

Quality and Test Features

Important test features include leakage rate, switching cycle resistance, operating temperature, corrosion resistance, and EMC behavior. Components with appropriate certifications and material certificates facilitate integration into regulated production environments. For safety-related applications, a risk assessment including a redundancy concept and regular functional tests is mandatory.

FAQs

1. Which thread size should I choose: 1/8", 1/4", 3/8", 1/2" or M5x0.8?

The selection depends on the flow rate requirement, space conditions, and cylinder diameter. M5x0.8 is suitable for compact miniature cylinders and low flow rates; 1/4" is standard for many industrial applications; 3/8" and 1/2" are preferable for larger cylinders and high cycle rates to minimize pressure losses.

2. Which sealing material is best against oils and high temperatures?

FKM/FPM offers good resistance to oils, fuels, and higher temperatures up to approximately 150 °C. PTFE-coated seals further increase chemical resistance and temperature tolerance but are less suitable for dynamic applications without appropriate design.

3. When should I choose an electrical signal fitting instead of a pneumatic one?

Electrical variants are preferable when precise switching states need to be transmitted to a PLC, long cable runs, or complex logic functions are required. Pneumatic outputs are useful in hazardous areas when electrical components should be avoided or when the control system remains purely pneumatic.