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When a project calls for clean steam — whether it’s a hospital sterilization system, a pharmaceutical lab, or a food processing facility — the equipment has to perform under pressure, literally. The DHT SS Series Unfired Steam Generator (USG) is engineered to do exactly that, and it’s a product we’ve been excited to bring to our customers in New York and New Jersey.

The SS Series reflects where clean steam generation is heading: tighter pressure control, smarter controls integration, and a fully factory-packaged design that takes complexity off the jobsite.

What Makes It “Unfired” — and Why That Matters

An unfired steam generator doesn’t burn fuel directly. Instead, it uses an existing energy source — either steam or high-temperature hot water — to generate clean secondary steam through a heat exchanger. This distinction matters for two reasons: it significantly reduces the regulatory and safety burden compared to fired boilers, and it produces clean steam with all-316 stainless steel wetted surfaces, which is essential in contamination-sensitive environments.

Key energy input specs:

• Primary steam supply: up to 150 PSIG
• High-temperature hot water supply: up to 450°F
• Clean steam output: up to 90 PSIG (consult factory for higher pressure)
• Adjustable pressure control: 10–100 PSI standard; 35–200 PSI for high-pressure steam applications
• Electrical: 110V / 1Ph / 60Hz, 4-amp full load draw

Pressure Control and Controls Architecture

Accurate, responsive pressure control is central to the SS Series design. A durable pressure transmitter sends a 4–20 mA signal directly to an advanced PID controller, which drives a fully modulating, fast-acting control valve. This closed-loop configuration allows the unit to track varying demand loads precisely — important in applications like sterilization cycles where pressure stability directly affects process outcomes.

Controller specifications:

• Display: 4.3-inch TFT color touchscreen, 480 × 272 px, 16M colors; 1/8 DIN LCD backup interface
• Native BMS protocols: Modbus IP and BACnet IP (no external gateway required)
• Legacy support: RS-485 via optional communications gateway
• Enclosure: NEMA 4, UL listed; 12”H × 10”W × 6”D
• Memory: 8GB; backlight rated for 50,000-hour service life
• Features: data logging, fault logging, real-time trending and graphing, brightness control (16 levels)

ASME Compliance and Standard Package

Every SS Series vessel is ASME B&PV Code Section VIII, Division 1 stamped and National Board registered, with U Stamp and UB Stamp options available.

Standard package includes:

• Magnetic level controller
• Internal steam separator
• High-pressure cutoff and low-water cutoff
• ASME pressure relief valve
• Vacuum breaker
• Manual blowdown valve + automatic blowdown valve on timer
• Fiberglass insulation with 22-gauge galvanized steel jacket
• Carbon steel support skid base

Optional upgrades:

• Total dissolved solids (TDS) monitor for surface blowdown
• Automatic blowdown timer with motorized valve
• Economizer for condensate sub-cooling
• Centrifugal boiler blowoff cooler

These options are particularly relevant on projects with stringent water quality requirements or where operational efficiency targets demand tighter condensate management.

Packaging and Installation

The SS Series ships fully assembled and pre-piped — all components mounted and connected before the unit leaves the factory, requiring only single-point service connections on-site. This factory-packaged approach reduces installation time, minimizes field coordination, and lowers the risk of piping errors.

Installation flexibility:

• Available in vertical or horizontal configurations
• Designed for both new construction and retrofit applications
• Supports single or multiple-unit installations

Application Fit

The SS Series is well suited for any facility that requires clean steam for process, sterilization, or humidification:

• Hospitals and medical centers
• Pharmaceutical and bio-medical research laboratories
• Universities and nursing homes
• Hotels and apartment buildings
• Food processing and commercial laundries
• Art museums (humidity control for preservation environments)

Warranty

• Tube bundle: 3 years
• Shell: 5 years

We work closely with the DHT team on submittals, specifications, and startup coordination across New York and New Jersey. If you’re designing a clean steam system or evaluating options for a retrofit, we’re glad to walk through the technical details with you.

Contact the Wales Darby team to discuss your project.

Get in touch! Reach out to us at engineering@walesdarby.com