Dwyer Magnehelic 2000 Differential Pressure Gauge

Overview

The Dwyer Magnehelic 2000 is the Series 2000 Magnehelic differential pressure gauge from Dwyer Instruments, a mechanical dial instrument that has become the reference tool for reading low air and gas pressures in ventilation, filtration and clean air systems. Dwyer offers it in 81 standard models and 27 options, so the same 4-inch gauge can show anything from a fraction of an inch of water column up to 30 psi, in inches, millimetres or centimetres of water, pascals or kilopascals, or air velocity units. It reads positive, negative (vacuum) or differential pressure and needs no electrical supply to operate.

Seven Star LLC supplies the Dwyer Magnehelic 2000 to facility managers, HVAC contractors and plant engineers throughout Oman and the GCC, backed by engineering support in Muscat. Because the gauge resists shock, vibration and overpressure and carries an IP67 rating, it suits plant rooms and rooftop air handlers in the Gulf climate as well as clean indoor spaces such as hospital theatres and pharmaceutical suites.

Operating Principle

The gauge senses pressure with a silicone rubber diaphragm that has an integrally moulded O-ring and is supported between front and rear plates. Pressure acting on the diaphragm moves a flat spring steel range spring. At one end of that spring sits a samarium cobalt magnet, and next to the magnet is a helix made of an alloy with high magnetic permeability. As the spring deflects, the magnetic field turns the helix, and the red-tipped pointer mounted on the helix shaft sweeps across the scale. There are no mechanical links or gears between the diaphragm and the pointer.

The helix rides in shock-resistant jewelled bearings and its motion is damped with high-viscosity silicone fluid, which is why the reading is steady and the response to pressure changes is quick. The small amplitude of spring motion supports long-term consistency, and the live length of the spring is adjusted for calibration. In practical terms the frictionless movement of the Dwyer Magnehelic 2000 gives a clear, repeatable reading for very low pressures that would be difficult to resolve on a Bourdon tube or liquid manometer.

Engineering Design of the Dwyer Magnehelic 2000

The Dwyer Magnehelic 2000 uses a die-cast aluminium case and bezel with an acrylic cover. The case is iridite-dipped and finished in baked dark grey hammerloid, and Dwyer specifies it to withstand a 168-hour salt spray corrosion test. An O-ring seals the cover, the zero adjustment screw is accessible through the cover without opening the gauge, and moulded rubber pointer stops prevent over-travel damage. The dial face is 4 inches (101.6 mm) and the standard gauge weighs about 510 g.

Process connections are 1/8 inch female NPT, duplicated as one high and low pair on the side and one pair on the back, with plugs supplied for the unused pair. Every Dwyer Magnehelic 2000 is calibrated for the diaphragm in a vertical position. It can be flush mounted through a 4-9/16 inch panel hole or surface mounted using three spacer pads, which keep a gap behind the case so the rear blowout plug can vent if the gauge is overpressurised at roughly 25 psig.

Key Features

The main features of the Dwyer Magnehelic 2000 that matter to specifiers and maintenance teams are:

• The frictionless magnetic helix movement gives a fast response to pressure changes with no gears or linkages to wear.
• A wide choice of 81 models covers inches of water, mm, cm, Pa, kPa, psi, zero-centre and dual air velocity scales.
• Standard Dwyer Magnehelic 2000 accuracy is plus or minus 2% of full scale, and the -HA option tightens this to plus or minus 1% with a mirrored scale and six-point certificate.
• The IP67 weatherproof die-cast aluminium housing resists shock, vibration and corrosion in outdoor installations.
• A rear rubber blowout plug vents the case at about 25 psig on standard gauges to protect the instrument.
• Medium pressure (-MP, 35 psig) and high pressure (-HP, 80 psig) options suit higher static line pressures.
• The -SP option adds a red LED set point indicator powered from 12-24 VDC, and -ASF adds an adjustable signal flag.
• Integrated mounting plate options -AHU1 and -AHU2 simplify mounting on air handling units, with -AHU2 adding an installer kit.

Industrial Applications

Dwyer lists filter monitoring, fan pressure indication, blower vacuum monitoring, duct, room and building pressure, clean room positive pressure and air velocity measurement with a pitot tube as core applications. In Oman these translate directly to air handling units in Muscat hospitals and malls, district cooling and HVAC plant rooms, pressurisation of electrical substations and control rooms in oil and gas facilities, and filter houses on gas turbine air intakes, where a Dwyer Magnehelic 2000 across the filter stage tells operators when elements need replacing.

Pharmaceutical and food plants in the Sohar and Salalah free zones use the Dwyer Magnehelic 2000 to display room-to-room pressure cascades, while laboratories and isolation rooms use the low-range and zero-centre models to confirm airflow direction. Seven Star LLC supplies the Dwyer Magnehelic 2000 with matching accessories such as A-605 air filter kits, A-610 pipe mounting kits and A-310A vent valves, so a complete monitoring point can be ordered in one package for projects across the GCC.

Technical Specifications

The table below summarises the Dwyer Magnehelic 2000 specifications published in the Dwyer catalogue datasheet.

For an electronic output from the same kind of duty, compare the Dwyer Series MSX Magnesense differential pressure transmitter, the Setra 264 low differential pressure transducer or the WIKA DPGT43 differential pressure gauge with output signal.

How to Order

To order the Dwyer Magnehelic 2000, send Seven Star LLC a formal RFQ with the model number and suffixes, or simply the pressure range, units and mounting style you need, and our instrumentation team will confirm the configuration. We supply on request and provide engineering support from Muscat for customers across Oman and the GCC. Download the Dwyer Magnehelic 2000 datasheet from this page, and contact our instrumentation division for accessories, calibration certificates and delivery times.