Mechanical Seal SHVI and Plan 66A for Unmanned Pump Station of an Oil Pipeline
A well-known Canadian operator of an oil pipeline commissioned EagleBurgmann to develop a sealing solution for crude oil pumps. The requirement: It needed to be a single seal that was just as safe as a double seal with buffer pressure system. In addition, the sealing solution was not to be designed for only one pump type but should be installed in various pumps of one station.
The operating parameters were quite extensive: The seal needed to be suitable for a pressure range from 2.5 bar (36 PSI) to 99 bar (1,436 PSI) as well as for shaft diameters from 115 mm to 155 mm (4.53’’ to 6.10’’). Since the pump stations are operated unmanned, the seal must operate without an additional supply system. To protect the environment and personnel, however, the seal housing must not leak if the seal fails unexpectedly.
The solution: Mechanical seal SHVI from EagleBurgmann
These requirements were best met by the SHV series which has proven itself thousands of times over in crude oil pumps and MOL pumps (MOL: Main Oil Line) of all types worldwide for many years. For the Canadian customer, EagleBurgmann developed the SHVI sealing variant with loosely inserted seal face specifically for the high-pressure range. The seal face is single, but is twice as safe under high pressure and is designed such that it always builds a parallel sealing gap with the stationary seat. The deformation behavior of the seal face was optimized for use in crude oil pumps so that the seal operates reliably even under very high pressures, sliding velocities and temperatures as well as pressure and temperature fluctuations.
EagleBurgmann selected a special quality of the silicon carbide material to be used in the pumps of the pipeline operator. This provides the seal face with particularly good emergency running properties and tolerance for partial dry running. In addition, the sliding faces have extremely precisely ground grooves which allow the seal face to be lifted quickly even in the low pressure range and contribute to stable operation in a wide pressure range.
Safety: Optimized API Plan 66A
Plan 66A, which has been available since introduction of API 682 4th Edition, was the obvious choice for the safety concept. Accordingly, the seal housing contains two throttles, and the seal chamber is connected to a pressure transmitter.
EagleBurgmann optimized the plan and uses a special inner, floating throttle. This can withstand a product pressure of 99 bar (1,440 PSI) in an emergency. The pressure transmitter detects pressure changes in the seal chamber and signals an alarm if certain values are exceeded. At the same time, the seal leakage accumulated under low pressure is discharged to a central collection system in the pump station.
Test and Acceptance
The SHVI seal and the optimized Plan 66A were subjected to dynamic and static tests individually and together on EagleBurgmann test benches. The constant and reliable sealing performance in all operating states and the safe function of Plan 66A in the event of a fault provided impressive results. The required system safety was provided at all times.
The new concept of the SHVI single seal with optimized Plan 66A is economical, modular, reliable in operation, and offers the safety of a double seal.
There are plans to convert further pumps of the pipeline operator. The new concept of the SHVI single seal with optimized Plan 66A is economical, modular, reliable in operation and offers the safety of a double seal. For other customers as well, this type of seal has since proven itself in MOL pumps for several thousand operating hours.