VEGA VEGADIF 85 Differential Pressure Transmitter

Overview of the VEGA VEGADIF 85

The VEGA VEGADIF 85 is a differential pressure transmitter with a metallic measuring diaphragm, designed for universal measurement of liquids, gases and vapours. VEGA lists level measurement in pressurised vessels and flow measurement in combination with primary elements as its main tasks, along with filter monitoring, density and interface measurement. Nominal ranges from 10 mbar to 40 bar, static pressure ratings up to 400 bar and a deviation below ±0.065 % make it a versatile field instrument for the process industries.

Seven Star LLC supplies the VEGA VEGADIF 85 to oil and gas, power, water and chemical customers throughout the Sultanate of Oman and the GCC. As a supplier with engineering support in Muscat, we help engineers choose the measuring range, flange and diaphragm materials, chemical seal assembly and housing, and we provide the VEGA specification sheet and operating instructions with each offer.

Measuring Principle

A metallic measuring cell forms the sensor element of the VEGA VEGADIF 85. The process pressures on the high and low side act on separating diaphragms and are transmitted through an oil filling to a piezoresistive sensor element, a resistance measuring bridge made with semiconductor technology. The difference between the two pressures changes the bridge voltage; this change is measured, processed and converted into the output signal. An integrated overload system protects the cell when one side is pressurised unexpectedly, which VEGA highlights as a key reason for the instrument’s reliability.

In addition to differential pressure, the cell measures its own temperature and the static pressure on the low-pressure side. These values are processed in parallel and are available as additional outputs, so the VEGA VEGADIF 85 acts as a multivariable sensor. For flow measurement the output can follow a square-root characteristic, and the device supports a turn down that is unlimited in principle, with up to 20:1 recommended by VEGA. Damping can be adjusted from 0 to 999 seconds.

Engineering Design of the VEGA VEGADIF 85

The basic version uses lateral process flanges with ¼-18 NPT connections according to IEC 61518, made of 316L, Alloy C276 or Superduplex, while separating diaphragms are offered in 316L, Alloy C276 and gold-coated 316L. Where the process requires isolation, chemical seals can be mounted on one or both sides with flanges or hygienic fittings from DN 32 or 2 inch, in materials ranging from 316L to Tantalum, Titanium and PFA. Silicone oil is the standard filling, and halocarbon oil is available for oxygen service.

Housings are available as single or double chamber versions in plastic, aluminium or stainless steel, with protection up to IP68 (25 bar) using external electronics, and IP69 for washdown areas. Electronics options include 4–20 mA, 4–20 mA/HART and fully digital Profibus PA, Foundation Fieldbus and Modbus versions, operating from 11 to 35 V DC for the two-wire HART version. A double chamber housing can hold supplementary electronics such as a second current output, a radio module or a power pack.

Key Features

The VEGA VEGADIF 85 combines the following features, as described in the VEGA documentation:

• Nominal ranges of 10 mbar, 30 mbar, 100 mbar, 500 mbar, 3 bar, 16 bar and 40 bar, with a smallest adjustable span of 1 mbar.
• Deviation below ±0.065 % and long-term stability below 0.065 % × TD per year and 0.15 % × TD over ten years.
• Static pressure ratings of 160 bar or 400 bar, with a process pressure range of −1 to +400 bar.
• Integrated overload system for high reliability under one-sided pressure surges.
• Additional measurement of static pressure and measuring cell temperature for multivariable use.
• Process temperature of −40 to +105 °C for the basic version and up to +400 °C with chemical seals.
• Adjustment via the PLICSCOM display module, PACTware with DTM, HART communicator or a Bluetooth app on smartphones and tablets.
• Approvals including ATEX, IECEx, FM and CSA for intrinsic safety and flameproof enclosure, ship approvals and SIL 2 qualification.

Industrial Applications

VEGA’s own application examples for the instrument include flow measurement in steam pipelines, differential pressure across reverse osmosis filters and level measurement in propane bullets. Each of these is common in Oman: steam and condensate flow at power and desalination plants, cartridge and RO membrane monitoring at seawater desalination plants along the Batinah coast and in Sur, and LPG bullet level at gas plants, terminals and filling stations. In upstream oil and gas, the VEGA VEGADIF 85 measures separator and scrubber level with remote seals, and pairs with orifice plates and venturi tubes for gas and water injection flow.

Seven Star LLC supplies the VEGA VEGADIF 85 from Muscat to projects in Sohar, Duqm and Salalah together with manifolds, chemical seal assemblies and complementary instruments. Engineers comparing options can also review the VEGA VEGABAR 82 process pressure transmitter, the Yokogawa EJX910A multivariable transmitter for compensated flow, or the Yokogawa EJA110E differential pressure transmitter.

Technical Specifications of the VEGA VEGADIF 85

Data for the VEGA VEGADIF 85 below are taken from the VEGA specification sheet 53579-EN and the technical data chapter of the operating instructions; values for Ex-approved instruments may differ.

How to Order

To request a quotation for the VEGA VEGADIF 85, send Seven Star LLC an RFQ with the medium, differential and static pressure, process temperature, required span, connection type, chemical seal requirements, output signal and hazardous-area approval. Our instrumentation division in Muscat will confirm the configuration and the current lead time. The VEGA specification sheet can be downloaded from this page, and our engineers support customers across Oman and the GCC from selection to commissioning.