ECOTROL® Rotary Control Valve 8C D / 6H D

The globe-style ECOTROL® uses a linear up-and-down stroke of stem and plug and is designed for large flow rates up to Kvs 7,000 m³/h and nominal sizes up to DN 700. The rotary control valve, by contrast, modulates flow through a rotary motion of the upper throttling disc and is dedicated to very small flows (Kvs from 0.01 m³/h) and high differential pressures. It delivers 100:1 rangeability (vs. 40:1–50:1 for the globe version), an inherent near-quadratic characteristic, and a quarter-turn actuator interface to DIN EN ISO 5210 F07. Body, end connections and most stem sealing options are identical – so an existing ECOTROL® globe valve can in many cases be converted to the rotary disc trim.

The trim consists of two lapped throttling discs. The lower disc is fixed in the valve body and contains one or two flow bores with radial V-shaped channels whose cross-section widens steadily – analogous to a V-port plug. The upper disc is coupled to the valve shaft and rotated by the quarter-turn actuator between 0° (closed) and 90° (fully open). A compression spring plus the line differential pressure press the discs together with a defined force, ensuring reliable shut-off. Depending on the rotation angle, a precisely defined cross-section of the V-channels is exposed to the flow.

Typical applications include the precise control of minimum and metering flows, handling of high differential pressures in a compact envelope, and service with abrasive, particle-laden or cavitation-prone media. The valve is frequently deployed in pilot and start-up lines, in chemical and petrochemical processes, in pharma and biotech plants, in boiler feedwater minimum-flow recirculation, and as a flow control element in pressure swing adsorption plants. It is also widely used in pilot plants and R&D installations as a high-precision flow trim.

The ECOTROL® rotary control valve is offered in two series. The 8C D series covers DN 15–50 (½″–2″) at PN 16–63 / ANSI Class 150–600 and is the all-rounder for standard applications. The 6H D series is engineered for high-pressure service at PN 100–250 / ANSI Class 900–1500 and is used wherever extremely high differential pressures have to be handled.

The permitted media temperature range is from –46 °C to +500 °C, determined by the combination of body material, stem seal and throttling-disc compression spring. With the standard 1.4310 spring, temperatures up to 300 °C are possible; with an Inconel X750® spring, up to 500 °C. A dedicated cryogenic version with extended bonnet (DEK5) is available for low-temperature service; an optional heating jacket with DN 15 PN 40 flange connections is also available.

The rotary control valve has an inherent, near-quadratic flow characteristic – ideal for fine control of small flow rates. The rangeability of 100:1 is significantly higher than that of typical globe valves. This makes it possible to maintain accurate control across very narrow flow bands without losing resolution at the lower end of the range.

Kvs values from 0.01 m³/h up to 1.00 m³/h are available, depending on the number of flow channels (one or two) and the characteristic curve (A or B). This covers virtually any small-flow control duty in practice; even micro-dosing tasks with Kvs below 0.1 m³/h can be accommodated without a custom design.

The standard throttling discs are hardened 1.4112 for general service up to 300 °C, or up to 400 °C with an Inconel spring. For galling-prone or highly abrasive media, Nitronic 60 is used. For maximum wear resistance under high differential pressure and aggressive media, throttling discs in tungsten carbide are available – rated up to 500 °C. Special materials can be supplied on request.

Bodies are supplied in cast steel (1.0619 GP240GH / A216 WCB), stainless steel (1.4408 G-X5CrNiMo19-11-2 / A351 CF8M), low-temperature cast steel (1.6220 G20Mn5 / A352 LCC) or creep-resistant steel (1.7357 G17CrMo5-5 / A217 WC6). The rotary control valve therefore covers cryogenic, hot and corrosive process conditions equally reliably.

The standard solution is a maintenance-free PTFE V-ring packing with a self-adjusting stainless-steel spring (EPDM or FKM profile rings, depending on medium and temperature). Optional adjustable gland packings in PTFE braided packing, reinforced graphite/Inconel or pure graphite are available – rated up to 500 °C. For cryogenic service, the PTFE V-ring packing is combined with the DEK5 extended bonnet.

Class IV to IEC 60534-4 is achieved as standard (max. 0.01 % of Kvs). Class V with lapped sealing surfaces is available on request. Because the throttling discs are pressed together evenly by spring force and line differential pressure, the shut-off tightness remains very stable over the valve’s service life.

The rotary control valve requires a quarter-turn actuator. The interface is built to DIN EN ISO 5210 F07 and accepts a backlash-free shaft coupling SW17. The standard solution is the pneumatic ARCATORQUE® 841 quarter-turn actuator; electric or hydraulic quarter-turn actuators can be fitted as alternatives. Important: the actuator should provide adjustable mechanical stops at both end positions, and the valve opens by anti-clockwise rotation.

The 8C D series is rated for a maximum differential pressure of 100 bar in the closed position, with a required actuator torque of 10 Nm (40 Nm permitted). The 6H D series handles up to 250 bar differential pressure with an actuator torque of 16 Nm. This makes the rotary control valve outstandingly suitable for high-pressure minimum-flow control and small-scale anti-surge duty.

Flanged connections to DIN EN 1092-1 or ASME B16.5, in RF and RTJ designs, are available as standard. Butt-weld ends to DIN EN 12627 / ASME B16.25 and extended weld ends (for reduced heat-affected zones) are available on request. This allows the valve to be installed in virtually any piping environment without custom adaptation.

Yes. The rotary disc trim is built on the same ECOTROL® body platform. An existing ECOTROL® globe-style control valve of the 8C or 6H series in the corresponding small sizes can therefore, in many cases, be converted to a rotary-disc solution by simply exchanging the trim and bonnet assembly. This saves capital cost, preserves the piping infrastructure and enables precise small-flow control without a complete new investment.

Every stroke involves a sliding motion of the upper disc against the fixed lower disc. Particles entering the sealing gap are moved tangentially out of the gap – in contrast to classical globe-valve kinematics, where dirt can settle into the seating surface. This self-cleaning action prevents fouling of the sealing surfaces and makes the rotary control valve particularly reliable on crystallising, polymerising or particle-laden media.

Recommended installation is in a horizontal pipe run with the actuator above the valve and in line with the flow arrows on the body. A straight pipe section of at least 10 × nominal diameter should be provided both upstream and downstream as a stabilisation zone. A bypass line with isolation valves and a strainer upstream of the valve are strongly recommended. The valve opens anti-clockwise – the actuator must be fitted with adjustable mechanical stops at both end positions. Thermal shock should be avoided: above a temperature differential of 300 K, the recommended ramp rate is no more than 2 K/min.

The full ARCA service portfolio is available for the rotary control valve as well: ARCAlaunch supports commissioning – including flushing services, ARCAcare covers preventive maintenance, ARCAsafe ensures spare-parts availability, ARCA24/7 guarantees telephone support around the clock, and ARCAknowhow delivers hands-on training. Sizing is performed in the ARCA-VENA software; via the ARCAonsite platform, all documents (equipment passport, data sheet, operating manual, spare parts, maintenance history) are available via QR code directly at the valve.

The ECOTROL® rotary control valve is designed in accordance with the Pressure Equipment Directive 2014/68/EU; the pressure-containing shell is engineered to EN 12516-2 / ASME B16.34, with seat leakage tested to IEC 60534-4. With respect to explosion protection, an ignition-hazard assessment to DIN EN ISO 80079-36 has demonstrated that the valve itself contains no inherent ignition source and is therefore not within the scope of the ATEX Directive 2014/34/EU (manufacturer’s declaration available). Optional designs to AD 2000, NACE MR0175 and oxygen service are available on request.