Magnetic Coupling Solutions at Saudi Aramco (Advantages of Magnetic Couplings in Oil & Gas Applications III)
In 2010, a small 25 hp “Bad actor,” pump at Tanajib and two 60 hp pumps were retrofitted with magnetic couplings. In 2017, deployment of six 120 hp pumps with magnetic couplings occurred at the Yanbu Refinery. These upgrades were considered after the organization began examining alternatives to the standard couplings previously installed in the equipment.
The designation of a “Bad actor” pump is a piece of machinery not bad enough to replace, but bad enough to drive-up maintenance costs. In order to avoid costly repairs and tie-up the company’s maintenance personnel, Saudi Aramco turned to magnetic coupling solutions for some of their pump applications.
Non-Hydrocarbon vs. Hydrocarbon pumping applications
According to Abdulrahman Alkhowaiter, a machinery consultant at Saudi Aramco, said that air-cooled magnetic couplings are suitable for any Non-Hydrocarbon centrifugal pumping applications of 1,200 hp and below with speeds of 3,600 rpm and below.
For Hydrocarbon liquids, they also consider magnetic couplings a possible choice, but the coupling guard must be equipped with an infrared heat sensor that can shut down the driver motor in case the pump seizes and the coupling overheats. Alkhowaiter said no other precautions were needed.
Pumps with Hydrocarbon Flammable Liquids – A Magnetic Coupling Application
In most cases, standard dry flexible couplings are the recommended choice in pumps with hydrocarbon flammable liquids. However, for variable speed applications, or “Bad actor” machinery with long-term vibration, it is recommended to utilize air-cooled magnetic couplings up to 1,000 hp.
These hydrocarbon pumps were provided with thermal heat sensors in the coupling guard with automatic shutdown as previously noted. Dry flexible shim pack couplings can also pose a safety hazard to pumps when the coupling hub to spacer bolts fatigue or shear, allowing the spacer to swing out and cause severe unbalance. This has caused the pump or motor to be uprooted from its foundation.
Meeting Saudi Aramco Standards
For many of the pump, fan, and blower applications at Saudi Aramco, magnetic couplings offer advantages compared to standard dry flexible shim pack couplings. These include less fatigue, no precision alignment is required, reduces bearing housing vibration levels, and eliminates high torque shock to mechanical seals.
For high speed-power couplings applications, the magnetic couplings are not suitable or compliant to API-671 (an energy standard for special-purpose couplings for the petroleum, chemical, and gas industries). For the low speed 1,800 and 3,600 rpm motor drive in the case of a gearbox, a magnetic coupling should be suitable up to 1,000 hp in ambient air conditions. For special purpose couplings of 1,800 rpm and below the 3,000 hp limit (motor to pump or motor-gearbox-compressor) the fixed speed couplings can also be used.
In our next entry, we’ll examine the advantages of magnetic couplings vs. hydraulic or rubber-type couplings and take an in-depth look at how to replace existing couplings with magnetic coupling technology in the oil & gas industry.