Flow control, pressure, and shut-off valves

Flow control valves (e.g. flow control or throttle valves) regulate the flow rate by restricting the cross-sectional area of the passage, allowing precise control of actuator speeds – comparable to a water tap.

Applications:

• Hydraulics: controlling the movements of cylinders and motors
• Pneumatics: regulating the air volume
• Process industry: dosing of liquids and gases

Versions with pressure compensation are load-independent and ensure constant movements despite changing loads.

Pressure relief valves limit or control the system pressure. They open when a set value is exceeded and divert the medium to reduce overpressure.

Applications:

• Protection of pumps, pipelines, and system components
• Overpressure protection in boilers, pressure vessels, hydraulic systems, refineries, and chemical plants

They react very quickly (often within milliseconds) and provide a reliable safety function.

Shut-off valves completely block or open a flow path. A special type are check valves, which prevent backflow and allow flow in only one direction.

Applications:

• Chemical and petrochemical industries
• Power generation
• Water and wastewater treatment
• Food, beverage, and pharmaceutical industries
• Utility systems as well as heating, ventilation, and air conditioning (HVAC)

They offer high operational safety, simple shut-off functionality, and prevent unwanted backflow/mixing.

The choice of material depends on medium, pressure, temperature, and application:

• Flow control valves: Steel, stainless steel, brass; in some cases plastics for special media
• Pressure relief valves: Alloyed steels, stainless steel, or bronze for high pressure/temperature requirements
• Shut-off valves: Cast iron, steel, stainless steel, plastics, or brass – depending on the medium (water, oil, chemicals, gases)

Criteria relevant for performance and safety:

• Operating and maximum pressure
• Flow rate/capacity
• Medium and material compatibility
• Temperature range
• Connection dimensions and installation position
• Response time (especially for pressure valves)
• Certifications/standards (e.g. ATEX, ASME, DIN)

Workmanship and maintenance are crucial for reliability and service life:

• Workmanship: Wear-resistant internal parts, precise adjustment mechanisms, high tightness
• General maintenance: Regular inspections significantly extend service life
• Flow control valves: Visual inspection, functional testing, occasional seal replacement
• Pressure valves: Annual servicing/testing for long-term functional safety
• Shut-off valves: Low-maintenance; check tightness, ease of operation, and corrosion resistance

Depending on type, material, operating cycles, and care, service life is often several years to over a decade (hydraulic valves approx. 5–10 years, pneumatic valves sometimes longer).

The shop offers various flow control, pressure relief, and shut-off valves with the following typical data:

• Pressure relief valves (PRV): G 1/2" and G 3/4"; max. flow rates 70–90 l/min; operating pressures up to 300 bar; adjustable ranges approx. 80–300 bar. Special shock valves for hydraulic motors (e.g. Danfoss OMP/OMR) with similar values.
• Throttle check valves: Threads G 1/4", G 3/8", G 1/2", G 3/4"; fine adjustment; max. flow rates 15–80 l/min; operating pressures up to 350 bar (for G 3/4" up to 280 bar).
• Counterbalance valves: Double-acting, partly for specific motors (e.g. CPM/CPRM) and with brake release port; max. flow rate 50 l/min; operating pressure 350 bar; pilot ratio 1:4.5.
• Check valves: In-line design and double pilot-operated versions; threads G 3/8" to G 1/2"; max. flow rates 30–70 l/min; operating pressures up to 350 bar; cracking pressures 0.5–4.5 bar.
• Fast-traverse/differential valves: Example: differential valve in in-line design; max. flow rate 160 l/min; operating pressure 350 bar; adjustable range 60–350 bar; recommended filter fineness 30 µm.