SKF CMSS 793-EE ATEX Intrinsically Safe Accelerometer

Overview

The SKF CMSS 793-EE is an ATEX-approved, intrinsically safe general-purpose industrial accelerometer with a top-exit two-pin MIL-C-5015 style connector. SKF describes it as an industry-standard acceleration sensor carrying agency approvals, and the catalogue lists intrinsic safety for ATEX Zone 0 with the marking II 1 G, Ex ia IIC T4 Ga over a temperature range of –50 to +120 °C. For operators who must monitor rotating equipment inside classified process areas, the SKF CMSS 793-EE provides a standard 100 mV/g measurement point without compromising the area classification.

Seven Star LLC supplies the SKF CMSS 793-EE to oil and gas, petrochemical and gas processing customers in Oman and across the GCC. From Muscat our engineers help clients match the sensor to the required barrier or isolator, the cable type and the installation drawing that SKF references, so that procurement and hazardous-area documentation stay aligned from the start of the project.

Measurement Principle

The SKF catalogue identifies the sensing element as PZT ceramic in a compression design. As general engineering background, a compression accelerometer clamps the piezoelectric ceramic between the base and a seismic mass; vibration of the machine surface changes the force on the ceramic, which produces a charge proportional to acceleration. An internal amplifier converts this charge into a voltage signal on a DC bias, which allows a simple two-wire connection that carries both power and signal. SKF specifies a supply of 18 to 30 V DC with a constant current diode of 2 to 10 mA, a 12 V DC bias output and an output impedance of 100 Ω or less.

The published frequency response is 1.5 to 5 000 Hz within ±5%, 1.0 to 7 000 Hz within ±10% and 0.5 to 15 000 Hz within ±3 dB, with a resonance frequency of 25 kHz. That wide band lets the SKF CMSS 793-EE capture low-speed unbalance and misalignment as well as the high-frequency signatures of bearing defects and gear mesh. Low electrical noise, given by SKF as 600 µg broadband from 2.5 Hz to 25 kHz and 5 µg/√Hz spectral at 100 Hz and 1 000 Hz, supports reliable analysis on slower or lightly loaded machines.

Engineering Design of the SKF CMSS 793-EE

The sensor body is 316L stainless steel with hermetic sealing, which suits high-humidity and corrosive locations such as coastal plants and offshore modules. The catalogue drawing shows an overall height of 61 mm, a 15/16 in. hex, a body diameter of 25.4 mm and a 1/4-28 tapped mounting hole; the weight is 112 g. The top-exit connector uses pin A for power and signal and pin B for common, with the shell tied to ground, and the mating connector is specified as an R6 type. SKF lists ground isolation, ESD protection and reverse wiring protection among the design features.

For installation, SKF notes that the SKF CMSS 793-EE must be installed per drawing 11535, revision F, which defines the intrinsically safe wiring arrangement. The catalogue also recommends the CMAC 5209 cable for ATEX Zone 2 use with SKF Microlog data collectors and the CMSS 908-MD magnetic base where a temporary mount is used. Engineers should always check the certificate and drawing against the specific barrier, cable length and gas group of the installation before commissioning.

Key Features

The SKF CMSS 793-EE combines hazardous-area certification with the measurement performance expected from a general-purpose sensor.

• Intrinsic safety certification for ATEX Zone 0, marked II 1 G and Ex ia IIC T4 Ga, allows use in the most demanding gas hazard zones.
• A sensitivity of 100 mV/g within ±5% at 25 °C keeps the output compatible with standard monitoring inputs.
• The 80 g peak measurement range and 1% amplitude non-linearity cover normal machinery vibration levels.
• A wide frequency response up to 15 000 Hz (±3 dB) supports bearing and gear diagnostics.
• Ground isolation and internal shielding reduce noise from ground loops in large plants.
• The corrosion resistant, hermetically sealed 316L case is suited to humid and coastal installations.
• ESD protection and reverse wiring protection help prevent damage during installation.
• Vibration and shock limits of 500 g and 5 000 g peak provide robustness against impacts.

Industrial Applications

Typical duties for the SKF CMSS 793-EE in the region include centrifugal pumps in crude oil gathering stations, compressor and fan bearings on gas processing trains, cooling water pumps inside refinery process units and electric motors located in Zone 1 or Zone 0 areas. Facilities in the Sohar industrial port area, the Duqm refinery and petrochemical zone, and upstream fields operated across the interior of Oman all need vibration points that satisfy hazardous-area rules while still delivering diagnostic-quality data.

Seven Star LLC supplies the SKF CMSS 793-EE as part of complete condition monitoring packages, working alongside the equipment that many GCC plants already use. Where portable route-based monitoring is the plan, the sensor can be read with tools such as the SKF Microlog Analyzer AX data collector; for protection systems, it is often installed next to permanently wired transducers like the Bently Nevada 190501 Velomitor CT velocity transducer. Our team in Muscat also supports precision maintenance follow-up with alignment tools such as the SKF TKSA 41.

Technical Specifications

The SKF CMSS 793-EE values below are taken from the SKF Microlog Accessories catalogue.

How to Order

For a quotation on the SKF CMSS 793-EE, send Seven Star LLC an RFQ listing quantities, cable lengths and the barrier or monitoring system the sensors will connect to. Our instrumentation division in Muscat will review the hazardous-area requirements, confirm availability from provide the SKF catalogue datasheet linked on this page. Seven Star LLC supplies SKF vibration sensors to oil, gas and utility operators throughout Oman and the GCC.