Modular Gas Valves: An Insiders’ Guide to Technology Breakthroughs

This article explains how OEMs and end users can take advantage of these new designs for a variety of vital applications.

DECIDING TO DOWNSIZE

Some major burner manufacturers have been able to achieve substantially smaller gas trains by using the new valves. This reduction in the size of components has resulted in savings of up to 30% of fuel train component costs. Here’s how that’s happening:

Downsizing via higher flow rates

Using computational fluid dynamics and finite element analysis software, mak¬ers using the new designs have enhanced a valve’s internal geometry and trim weight to maximize flow in as small a size as possible.

For example, a respectable 40% increase in flow rates over older technology has been achieved in solenoid gas valves, where the short stroke makes it difficult to make even minimal gains. In longer stroke electrohydraulic versions, a 100% boost in flow rate is possible (depending on pipe size).

Downsizing with small-footprint designs

Today’s space-constrained burners, boilers or makeup air heaters mean that smaller is usually better. For preassembled units, all elements of the gas train must fit through standard entryways. Even for trains assembled on site, users may need smaller footprints to free up space for production or to provide greater access to other parts of the heating equipment.

A major way in which valve manufacturers have enabled component downsizing is by pro¬viding flanged end connections for space-saving, face-to-face mounting. This eliminates the need for pipe nipples when joining two valves in series and provides the smallest face-to-face, double-valve footprint.

Downsizing despite low supply pressure

Designers of gas-fired combustion systems for use in many North American cities face a special challenge: low supply pressure. Across New York City, for example, many gas mains provide supply pressure under 10 inches of water column (IWC). In a typical installation, designers must balance the available supply pressure against the pressure drop or pressure the heating equipment and the related components in the fuel supply train consume.

Where supply pressure is minimal, designers must compensate either by including a gas booster device, which is an added expense to the customer, or by over-sizing piping and components in the gas train, adding considerable space, inefficiency and cost.

The high flow rates of modular gas valves require lower pressure drops. For example, at 2 IWC inlet pressure and 1 IWC drop, one of the newer 1½-inch gas valves could offer almost twice the flow of previous technology, which nets 3 million British thermal units per hour (Btu/hr) versus 1. 7 million Btu/hr.

CHOOSE THE MOST FLEXIBLE TECHNOLOGY

Modular gas valve purchasers can choose from two basic valve operating technologies and can mix and match the components for design. The two technologies include solenoid and electrohydraulic.

Solenoid valves work electromechanically with electrical current running through a solenoid coil to magnetically actuate valve opening or closing. Electrohydraulic valves work by converting electrical current into hydraulic flow to actuate opening or closing.

With configurations that include double solenoid, solenoid and electrohydraulic and double electrohydraulic, it is possible to fine-tune the valve array to fit precise application needs. Other advantages of modular gas valve designs include:

Simple installation and maintenance

Until recently, manufacturers of gas shutoff valves offered no choice in mounting options. Both monobloc and modular versions required adding adaptors to their flanges to connect to piping.

A new option is available with dual end connections. Where customers prefer to simplify subsequent valve removal, avoid pipe unions, and minimize maintenance downtime, the usual flange adaptors are available. However, for those who want to eliminate the expense of adaptors, valve bodies can also be internally threaded through national pipe thread taper for direct “hard-pipe” mounting.

Broad temperature ranges

Modular gas valves designed with wider ambi¬ent temperature ranges can reduce bloated inventories. The designs include products rated for operation down to -40°F (-40°C) and up to 140°F (60°C) for solenoid models and up to 150°F (66°C) for electrohydraulic valves.

Higher close-off pressures

In many locations, the gas supply entering a site is pressurized to about 30 psi. Additionally, a primary regulator and sometimes a secondary regulator upstream of the safety valve reduce the gas going to the gas train and heating equipment to 5 psi or below. Conventional modular gas shutoff valves usually carry maximum operating pressure differential ratings of 5 psi, which means they can safely open and close against that amount of line pressure. However, unexpected spikes in gas supply pressure hold the potential to rupture the regu¬lator’s diaphragm, which could lead to an overpressure condition and unsafe combus¬tion.

Incorporating valves with a close-off pressure rating greater than the building supply pressure eliminates the effort and expense of relief devices.

CONCLUSION

When selecting a modular gas shutoff valve for a given piece of combustion equipment, consider the flow rates, space requirements, mounting options, temperature ranges and close-off pressures. The right choice can reduce cost of ownership, reduce time and costs for installation and maintenance, decrease inventories and open up valuable space in your facility.

Gerry Longinetti is the industrial segment marketing manager of ASCO Numatics, a business unit of Emerson Industrial Automation (www.ascovalve.com). He is responsible for creating and executing marketing product strategies, as well as identifying new product solutions for customers in the combustion, engines & transmission, pumps, compressors, blowers, dust collectors, sterilizers, packaging, agriculture and machinery equipment industries. Reach him at gerry.longinetti@emerson.com

James Chiu is the industrial segment marketing product engineer of ASCO Numatics. He is responsible for identifying and introducing new product solutions for customers in the combustion, agricultural and gas generator equipment industries. Reach him at james.chiu@emerson.com