Introduction

In chemicals, water treatment, oil and gas and power projects, the pneumatic actuator is the core of piping automation. Choose the right maker and a line runs steadily for a decade; choose wrong and you get inflated torque, ageing seals, frequent shutdowns and losses far beyond the price of the equipment. Zhejiang is a major cluster for fluid control equipment, and plenty of companies make actuators - but few build both the actuator and the valve themselves. This article covers two things: how double-acting and single-acting differ, and what a good manufacturer looks like.

1. Double-Acting vs Single-Acting: One Sentence Each

It is the most common procurement question, and the difference is one line: where does the valve go when the air fails?

  • Double-acting: both open and close are driven by air pressure. Simple, stable torque, relatively controllable air consumption - suited to most standard on/off and modulating duty

  • Single-acting: fitted with a spring return, so the valve returns to its safe position when air or power is lost - suited to emergency shut-off and other safety-critical duties

Getting this wrong has a direct cost: fit a double-acting unit on an emergency shut-off loop and, when the air fails, the valve simply stays where it is. That is not a performance issue - it is a safety issue.

In one line: air in normal operation, safe position on air failure → single-acting; pure on/off or modulating with stable air → double-acting.

2. Double-Acting Selection: Four Parameters, Not Just Bore

Bore is the outermost piece of information. Four parameters actually decide the model:

  • Required torque: set by media pressure, seat friction, differential pressure and safety factor; a catalogue range of 8-6000 N·m does not mean any model covers any duty

  • Air supply pressure: sites usually run 4-7 bar; real output torque must be recalculated at the site pressure, not the catalogue pressure

  • Air consumption: on high-cycle duty this drives compressor load and running cost directly

  • Cycle rate and stroke: 90° or 180°, and how many cycles per minute, decide the design and seal life

Give the maker all four and ask for a model matched to the calculated figures - that is the reliable route. Sending only "a DN80 ball valve" gets you a guess.

3. One Package: Actuator, Valve and Accessories from One Maker

The real headache is not finding products but stitching three suppliers together - an actuator from one, a valve from another, accessories from a third - with poor matching and constant commissioning faults.

  • Actuator range: rack-and-pinion (air-driven, remote on/off and angle adjustment) plus high-torque scotch yoke (for high-torque duty), across AT, AW, HG, linear-stroke and stainless steel series

  • Complete valves: pneumatic butterfly, ball, gate, control and shut-off valves, with actuator and body integrated, for water, gas, oil and corrosive media

  • Accessories: solenoid valves, limit switches and air filter regulators supplied together

  • Span: more than 100 series and models, torque 8-6000 N·m, for DN15-DN800, with hundreds of thousands of cycles under normal duty

  • Customization: body material, seal material, output torque and protection class adjusted to media corrosiveness, pressure and temperature class, explosion-proof requirement and installation space

4. Three Decades: From QGH to AT, AW and HG

Company age and technical depth are the most direct indicators of reliability.

  • 1989: technical work begins; founder Mr. Ji Zhongyong, seeing domestic projects depend on expensive, slow imported actuators, sets out to build a high-quality domestic product

  • 1997: the company is founded and launches the first QGH series, breaking the foreign monopoly

  • 1998: formally renamed Zhejiang Huaershi Auto-control Instrument Valve Co., Ltd.

  • 2004: second-generation GT series, and recognition as a Longwan district high-tech enterprise

  • 2007: Shanghai production base established, adding the DRSC and HG high-torque scotch yoke lines

  • Today: two bases, more than 20 national patents, national high-tech enterprise and technology-based SME; the patents come from in-house development, not badge engineering

5. Quality Control and Delivery: Where a Reject Rate Below 2% Comes From

  • Process: cylinders use a hard-anodized aluminium alloy process for wear and corrosion resistance; service life beats ordinary domestic products in the same duty, and seals age more slowly under severe corrosion and wide temperature swings

  • Everything in-house: both bases have full CNC equipment, and raw material intake, precision machining, assembly and commissioning, plus final air-tightness, torque and life testing, are all done in-house, with salt-spray, life and torque laboratories

  • Full inspection before dispatch: multiple inspection steps per unit, reject rate below 2%; actuator and valve developed and built together, so compatibility faults drop sharply

  • Certification: ISO9001, occupational health and safety, environmental management, plus SIL functional safety and CE on selected products - eight authoritative certifications

  • Delivery: standard models in 7-15 days, custom builds scheduled to order - against months for imports

6. Five Criteria That Shorten the Shortlist

  1. Fit: enough models, customization available, coverage of your industry duty

  2. Expertise: free duty assessment and selection support, and a clear explanation of how torque is calculated

  3. Stability: in-house laboratories, full pre-dispatch inspection, a real reject rate

  4. Value: purchase cost (commonly around 40% of imports) and lead time both ahead

  5. Service: on-site guidance, troubleshooting and spare parts that actually arrive

On site: municipal wastewater plants - butterfly valve and actuator packages for sedimentation tanks and dosing lines, cutting later maintenance costs by about 30%; chemical RTO waste gas treatment - explosion-proof ball valves and actuators for hazardous workshop duty; sheet metal and metallurgy piping retrofit - high-torque scotch yoke actuators replacing imports with the supply lead time halved. Products export to Russia, Southeast Asia, the Middle East and more than ten countries, serving chemicals, water treatment, oil and gas, metallurgy, power, pharmaceuticals and waste gas treatment.

Conclusion

Choosing an actuator maker is really choosing a long-term guarantee of stable operation. Company age, certification, in-house development, QC system, delivery and service - none can be skipped. And on double-acting versus single-acting, ask one question first: where must the valve sit when the air fails?

If you are comparing suppliers, or have a valve that needs an actuator, send us media, bore, pressure and temperature, explosion-proof requirement and air supply pressure - free duty assessment and selection, plus product data and technical parameters on request.

Zhejiang Huaershi Auto-control Instrument Valve Co., Ltd.

Since 1989 · 30+ years focused on pneumatic actuators and pneumatic valves

Website: www.hesvalve.com