Best Stainless Steel Sequence Valve Supplier & Manufacturer

A sequence valve is a pressure-operated, normally closed valve designed to direct pressurized hydraulic fluid to a secondary circuit or actuator only after a primary circuit has achieved a preset pressure threshold. Inside the valve, inlet fluid acts on the cross-sectional area of a spool or pilot poppet against an adjustable spring. Once pressure overcomes the spring preload, the spool shifts open, permitting flow to Port 2. Fabricating the body and internal moving parts from 316L or Duplex stainless steel ensures these critical tolerances remain immune to chemical oxidation, pitting, and fluid-induced erosion over millions of cycles.

Austenitic stainless steels like 304 and 316 have an inherent tendency to cold-weld (gall) when sliding against identical alloys under high contact pressures. To eliminate this phenomenon, Micro Precision employs three proprietary methods: (1) dissimilar material pairing, such as utilizing Nitronic 60 (UNS S21800) spools inside 316L housings; (2) specialized vacuum PVD coatings, including Diamond-Like Carbon (DLC) or chromium nitride (CrN) that lower the coefficient of friction below 0.1; and (3) precision cryogenic hardening and high-precision diamond honing to achieve surface roughness below Ra 0.08 μm.

Standard sequence valves restrict flow from Port 2 back to Port 1 because backpressure attempts to seat the valve. However, our stainless sequence valves are predominantly supplied with integrated reverse-flow check valves (also called counterbalance sequence designs). When the system reverses direction, fluid bypasses the main spool via a stainless poppet and spring check assembly, allowing free return flow with negligible pressure drops (ΔP < 1.5 bar).

Direct-acting sequence valves use fluid pressure acting directly against a heavy mechanical spring to displace the spool. They offer ultra-fast response times (< 8 ms) and low internal leakage, making them ideal for compact clamping circuits up to 60 L/min. Pilot-operated sequence valves utilize a smaller pilot poppet stage that vents oil from above a main balanced spool. This two-stage architecture allows precise pressure setting control, low pressure-override characteristics, and smooth performance under high flow rates reaching 350 L/min and operating pressures up to 420 bar.

If a sequence valve is internally drained, any backpressure built up in the secondary circuit (Port 2) acts directly on the spring chamber, adding directly to the cracking pressure on a 1:1 basis. This causes unpredictable sequence timing. An external drain port vents the spring chamber directly to the reservoir at atmospheric pressure, completely isolating the set point from downstream resistance and ensuring strictly repeatable sequence pressures.

To furnish an exact proposal within 24 hours, our engineering department requires: (1) working flow rate (L/min or GPM); (2) minimum and maximum adjustable cracking pressure range (bar/PSI); (3) hydraulic fluid chemistry (mineral oil, water glycol, Skydrol, ester-based); (4) stainless alloy preference (304, 316L, Duplex 2205); (5) mounting configuration (screw-in cartridge cavity, subplate CETOP, or inline threaded ports); and (6) drain circuit preference (internal or external).