Refinery pump - maximum leak tightness

Metal bellows seal MFLWTI and Plan 66A for a process pump

KeyVisual_CaseStudy_MFLWTI_refinery_pump

Situation

  • The proportions of steam, water and sand in crude oil change just as constantly as the temperature of the medium

Challenge

  • Space conditions required a single seal with the reliability of a double seal

Solution

  • Metal bellows seal MFLWTI from EagleBurgmann with DiamondFace coating and Plan 66A

CaseStudy_MFLWTI_refinery_pump

High demands are placed on seals in a process pump for refineries. When crude oil or crude oil products are transported, the seal is exposed to very high temperatures. Solids in the crude oil rub against the sealing surfaces and wear them out. Robust solutions with reliable security features are in demand.

Changed process conditions in a refinery meant that the double seal of a process pump resulted in an MTBF value (MTBF: Mean Time Between Failure) of only four weeks and resulting in considerable leakage. The cause was the repeated change in the medium: sometimes the crude oil was hotter, sometimes it contained steam, water or a higher proportion of sand. The shrink-fit seal faces and stationary seats deformed and carbonated oil was deposited on the atmosphere side of the seal. The sealing gap became unstable and the spring in the seal could no longer compensate for axial displacements.

The end user decided to install seals from a different manufacturer and commissioned EagleBurgmann to develop a reliable and durable solution.

The specification sheet contained many challenges: The consequence of the problematic nature of the media and the demanding operating conditions would have been a double seal with a buffer fluid system in accordance with API Plan 53 or API Plan 52. However, there was no room for such a solution where the pump was installed. Only a single seal with the safety properties of a double seal could be considered. The high safety requirements also stipulated that there should be no leakage to the atmosphere - even if the seal failed.

EagleBurgmann chose the mechanical seal MFLWTI with metal bellows and API Plan 66A to meet all the requirements. The key design element of this seal is the loosely inserted seal face. The seal face demonstrates its positive deformation behavior during operation. It is so flexible that the sealing gap is always parallel. Compared to shrink-fitted seal faces, the number of suitable materials is also significantly higher. Silicon carbide was the material of choice for use in the process pump. EagleBurgmann additionally processed the seal faces with DiamondFace technology. This provides the sliding faces with a microcrystalline diamond coating that protects them from wear caused by solids-laden media and from the consequences of a momentary dry running.

DiamondFace has already proven itself in numerous applications, for example in the oil and gas industry, in refinery technology and power plant technology. Minimal friction, low wear and high chemical resistance - seals with a DiamondFace coating achieve particularly long service life even in demanding applications. Users can rely on long MTBF and MTBR (MTBR: Mean Time Between Repair) intervals.

CaseStudy_MFLWTI_refinery-pump_EN

The operation of the seal and the monitoring of the leakage on the atmosphere side according to API Plans 65 and 66A offer maximum operational reliability.

In accordance with the principle of Plan 66A, EagleBurgmann integrated two throttles in the seal housing on the atmosphere side. Should the seal fail unexpectedly, the floating internal throttle will withstand the entire product pressure. The leakage of the mechanical seal is directed specifically to a leakage monitoring unit according to Plan 65. A differential pressure transmitter detects the level of the collecting tank and triggers a signal when the tank becomes too full and needs to be replaced or when the seal fails.

A steam quench on the product side supplies the seal according to Plan 62. This prevents the above-mentioned deposits of carbonized oil. Leakages are also discharged into the collection system according to Plan 65.

The benefits at a glance:

  • Single instead of double seal
  • Safety through Plan 66A
  • Significantly higher reliability
  • Optimized emergency running properties
  • Sealing of various media

The refinery pump was equipped with the EagleBurgmann solution and put into operation in October 2015. The seal has been operating reliably in all operating conditions with constant performance without any complaints or interruptions ever since. The plant availability was significantly increased to the satisfaction of the end user and Plan 66A proved to be an enormous increase in safety for the personnel and the environment.

Operating conditions:

  • Suction pressure: 3 bar (44 PSI)
  • Outlet pressure: 8.2 bar (119 PSI)
  • Temperature: 281 °C (538 °F)
  • Speed of rotation: 1,470 min-1
  • Medium: Hydrocarbons with hard solids content

Solution: MFWLTI refinery pump

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