Endress+Hauser NMS80 Proservo Servo Tank Gauge

Endress+Hauser NMS80 Proservo servo tank gauge: what it is and how it is built

The Endress+Hauser NMS80 is a Proservo servo tank gauge for high-accuracy liquid level measurement in storage and process tanks. It belongs to the NMS8x family and is the aluminium-housing version, which makes it the standard choice for hydrocarbon, petrochemical and chemical tanks where custody transfer, inventory control and loss control matter. Seven Star LLC supplies NMS80 gauges in Oman and the GCC as an independent supplier in Muscat, and configures the quotation from the tank data you send.

The NMS80 is not a single fixed code. The family datasheet describes the gauge as a platform in which wire length, displacer, flange, seal material, power supply, I/O modules and accuracy class are chosen from ordering features. For the NMS80 the housing and wetted-part option is feature 070 option AB (coated aluminium transmitter and process section), which separates it from the stainless NMS83.

Reading the model name

• NMS8x: the Proservo servo tank gauge series; NMS80 is the aluminium-housing member, NMS83 the stainless steel member.
• Order features: wire (feature 110), process connection (140), accuracy and weights-and-measures option (150) and housing material (070) complete the configuration in the Endress+Hauser product configurator.

NMS80 technical specifications

How the NMS80 measures level, interface and density

A small displacer hangs on a thin measuring wire that is wound on a finely grooved drum. A stepping motor positions the displacer in the liquid, and the drum is driven through coupling magnets, so the drum housing completely separates the wetted section from the electronics. When the displacer touches liquid its apparent weight falls because of buoyancy. A temperature-compensated magnetic transducer, read by six hall sensors, detects the change in torque, and the motor repositions the displacer to hold the weight signal constant. A magnetic rotary encoder counts drum turns and the CPU turns that into a level value.

Because the displacer can be lowered through the liquid at defined points, the same NMS80 can also report up to two interface levels, density of up to three liquid phases, tank bottom, water dip and spot or profile density. The density profile can use up to 50 configurable points across the tank or only the upper layer. That multi-task behaviour is the main reason servo gauges remain common on custody transfer tanks even where radar is installed on neighbouring tanks.

Where the NMS80 fits in a tank gauging system

The NMS80 integrates other tank sensors. Water-level, temperature, pressure and overfill-prevention sensors can be connected, and the gauge forwards all measured and calculated values to a tank inventory system by Modbus, V1 or HART, or displays them locally. Direct connection of spot or average temperature sensors reduces the number of separate devices on the nozzle.

Within the family, the NMS80 pairs naturally with the NMS83 (stainless steel version for alcohol, food and beverage hygiene needs), and, at system level, with the Tankside Monitor NRF81, the Tankvision Tank Scanner NXA820 and the Tankvision inventory software mentioned in the datasheet. If your tank already carries a Proservo with the same flange, the NMS80 can usually be considered a like-for-like candidate, but confirm wire length, displacer and I/O module before you order.

Selection and ordering checklist for NMS80

• Tank height and the lowest level you need to reach, to select the 16, 22, 28 or 36 m wire.
• Product density and viscosity, which decide the displacer diameter and material (316L, Alloy C276 or PTFE).
• Tank nozzle: NPS 3 in or 6 in Class 150 RF, DN80 PN10/16, JIS 10K or JPI flange as offered for the aluminium version.
• Process seal material: HNBR, FKM, chloroprene, PTFE or silicone, selected for the gas temperature inside the housing and not the liquid temperature.
• Power supply (high-voltage AC, low-voltage AC or DC) and the I/O modules, including Ex d or Ex i HART modules and RTD inputs.
• Accuracy class and calibration certificate: standard 3- or 5-point, or 10-point maximum performance with OIML R85 related options where custody transfer applies.
• Hazardous-area approval required by the site, and whether SIL 2 or SIL 3 architecture is needed.
• Tagging, bus address and any cleaning-from-oil-and-grease requirement.

Installation, commissioning and maintenance of the NMS80

The gauge mounts on a 3 in tank top flange. Mount it on a nozzle that lets the displacer travel freely, and follow the tank-type table of the datasheet: a stilling well is required on floating roof tanks, while guide wires are offered for agitated or turbulent tanks but are not allowed on pressurized tanks. Where the gas temperature at the housing would exceed the seal rating, the datasheet recommends a pipe or chamber between nozzle and gauge, or insulation of the tank, because the sealing temperature is the gas temperature inside the housing.

Commissioning is done from the local display, via digital inputs, through fieldbus commands or with FieldCare over the service interface. The last command received from any source is the one executed. The wire, drum and displacer are the wearing parts, so plan periodic inspection and keep a spare displacer and seal kit for tanks that serve as custody transfer references. Verification against a reference tape on calibration days is good practice.

Typical NMS80 applications in Oman and the GCC

NMS80 gauges suit crude, refined-product and chemical storage at terminals, refineries and petrochemical plants along the Omani and wider Gulf coast, where tank inventory accuracy translates directly into money. High ambient heat, dust and salt-laden humidity are accounted for by the IP66/68 enclosure and the –40 to +60 °C ambient rating. The ability to measure interface and density is also useful for slop tanks, water-in-product detection and blending tanks.

Related Proservo variants

Information to send with an NMS80 RFQ

• Tank type, height, nozzle size and flange standard.
• Product, density range, viscosity and operating temperature.
• Required accuracy class, calibration certificate and any custody transfer rule.
• Power supply, fieldbus protocol and required I/O modules.
• Hazardous-area zone and SIL requirement.
• Existing gauge model if this is a replacement.

Documents and quotation

The official Technical Information for the Proservo NMS80 (TI01248G) is attached on this page as a datasheet. It carries the full ordering features, dimensions and approvals.

Send the NMS80 code you need, or the tank data above, and Seven Star LLC will prepare the quotation and confirm lead time for Oman and the GCC.