The FOX HST-Plastic Series Diaphragm Pulsation Damper is an advanced technical solution for pulsation control within hydraulic circuits. Designed to maximise flow stability, this damper requires a nitrogen pre-charge pressure between 60% and 80% of the working pressure, a value that must be calculated in close relation to the type of pump used and the operating temperature of the system. The component offers a recommended compression ratio of 2.5 (P2/P0), with a maximum operationally tolerated limit of 4. It is important to emphasise that the mechanical life of the device, strictly measured in number of cycles, is always inversely proportional to the increase in this compression ratio.

Construction Features and Materials

The versatility of the series lies in the wide range of materials available for the internal diaphragm, including technical options such as NBR, HNBR, EPDM, FPM, HYTREL and Alcryn, ensuring maximum chemical and mechanical compatibility with various operating fluids. The nitrogen charging valve supplied in the standard configuration features a 5/8″ UNF connection. The construction design of the damper allows installation in both horizontal and vertical orientation; however, in the latter case, it is essential that the nitrogen valve faces upwards to ensure correct operation. The standard maximum working pressure (PS) of the component is 10 bar, while the test pressure (PT) corresponds to the PS value multiplied by the safety coefficients 1.43 or 1.5.

Variants and Operating Temperatures

The construction versions of the outer body are available in different polymer variants, each specifically designed to tolerate strict operating temperature ranges:

  • The standard version identified as HSTP, made of PP (Polypropylene), is fully suitable for operating temperatures between 0°C and +70°C.

  • The HSTPVC variant, made of PVC-U material, reliably covers a temperature range from -5°C to +50°C.

  • The model designated HSTPVCC, made of PVC-C, raises the maximum supported temperature threshold, operating safely between -5°C and +60°C.

  • For the most extreme thermal conditions, the HSTPVDF version in PVDF handles temperatures from -20°C to +80°C without critical issues.

Connections, Options and Regulatory Compliance

In addition to flexibility in the choice of construction materials, the entire range offers various advanced hydraulic connection solutions. Versions equipped with an integrated flange connection or with a flange compliant with strict international ANSI B16.5 and UNI/DIN standards are available. To meet specific system requirements, configurations with special connections can always be requested. In order to drastically reduce management costs and machine downtime, the line includes fully maintenance-free variants, identified by the dedicated HSTP-SMF code. In addition, for applications requiring higher resistance, a high-pressure construction version capable of continuous operation up to 15 bar is available upon request. Finally, to fully comply with global safety directives, the product can be supplied in accordance with top-level certifications such as CE (2014/68/EU-PED), KOSHA, SELO, EN 14359, PD5500, EN 13445, DOSH, NR-13, AS1210/4343, ARH, BV, Lloyd’s/ABS, DNV/RINA and CU-TR 032/2013.

Summary technical table of the main features