![]() It may not be evident from the raw test data how the pump will perform in a specific application, but this information can then be corrected to user conditions, including the user’s fluid viscosity, and operating speeds and pressures. This allows the manufacturer to record detailed performance data at different operating conditions to develop a data set at this known viscosity.įrom standard testing, manufacturers can determine whether or not the output of the pump meets minimum requirements for performance. With fluid sampling and calibration, along with temperature measurements, the viscosity of this test fluid is known. The process involves the following: A test fluid suitable for the pump is selected. This step can instill confidence in a pump’s performance before it ever reaches the end user’s site. This is where standard testing and data correction becomes critical. With many variations in system fluids, pressures and driver speeds, a single manufacturer cannot be expected to be able to test to all possible operating conditions. No two pumps are identical due to differences in the manufacturing process, so how can a manufacturer guarantee that a pump will perform in a user’s specific application? Now that the manufacturer has the correct information to select or design a pump, more questions may arise from the user relative to a guarantee that this pump will perform once it is installed in their system. Another two-screw multiphase pumping system The Role of Testing & Data Correction This can lead to cavitation and excess vibration. In extreme cases, the pump may not function properly due to inadequate suction pressure to fill the suction end pumping elements. In a lubricating oil system, excess flow that is dumped back to a holding tank can aerate the oil and increase its operating temperature. The higher flow produced by the disparity in viscosity will draw more power from an electric motor and could potentially trip the motor’s protection circuit. On the other hand, a pump that is selected for a fluid where viscosity is higher than predicted could also have negative impacts on a system. In a lubricating system, the consequences of lower flow than predicted may lead to oil starvation of bearings. Low flow may lead to reduced output in a crude oil pipeline, which translates into lower throughput per day, and ultimately a financial loss. A positive displacement pump designed or selected for a fluid where the viscosity is lower than predicted will produce less flow than expected. This can have a major impact on the pump, the system or both. Sometimes data is provided to a manufacturer during the quotation phase, but it is incorrect or incomplete. Two-screw multiphase pumping system The Consequences of Inaccurate Data For these and other reasons, it is acceptable to provide a range of viscosities that represent the fluid at varying conditions so the manufacturer can establish operating limitations where required. In this process, off-design conditions such as startup should also be considered, as well as seasonal changes for applications that are affected by outdoor temperatures. Using this chart, the viscosity of a fluid at any temperature in the associated range can be determined. With the kinematic viscosity known at two temperatures, ASTM D341: Standard Practice for Viscosity-Temperature Charts for Liquid Petroleum Products can be used to develop a plot of kinematic viscosity over a range. After recording twice at two different temperatures, the kinematic viscosity of the fluid can be calculated. The time it takes for a volume of fluid to flow through a calibrated viscometer under a known pressure and temperature is measured. One of the widely accepted methods used in determining a fluid’s viscosity is ASTM D445: Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids. If a user is unsure of their fluid’s viscosity range, it is recommended to send a fluid sample to a qualified lab for evaluation. The more viscous a fluid, the higher the flow rate will be for a positive displacement pump at a constant pressure and input speed-an advantage when handling heavy liquid hydrocarbons.įor a user to ensure that they will receive a pump that will perform as desired in their application, specific detail on viscosity is critical. ![]() The viscosity of a fluid is a key element in sizing and developing any pump, and the effects of viscosity on a positive displacement pump are much different than those on a centrifugal pump. (Images courtesy of CIRCOR) Viscosity Calculation Is Vital Conducting fluid viscosity testing in Western Canada, a harsh setting.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |