Why is a minimum flow line required for the hydrocracking feed pump?
Thread Content
Why is a minimum flow line required for the hydrocracking feed pump?
The feed pumps in hydrocracking units are generally high-flow, multi-stage pumps with high outlet pressures; the motors associated with them are also large in size. Additionally, hydrocracking units require a stable outlet flow rate. To prevent pressure buildup at the pump outlet, which could lead to accidents such as shaft misalignment, it is generally required to establish a minimum return flow line, which also facilitates the adjustment of the outlet flow rate.
The small-flow line has 2 functions； 1. Testing of pumps, such as those that have been newly installed or those that have undergone maintenance. 2. For high-pressure centrifugal pumps, the outlet flow rate must be at least 20% higher than the designed flow rate; this is done to prevent mechanical energy from being converted into heat during pump operation, which could raise the temperature of the fluid inside the pump, leading to vaporization and pump cavitation, as well as significant vibration
There is another scenario: when starting the pump, it is also possible to slightly open the pump outlet valve instead of using the minimum flow line. This is because the minimum flow line experiences severe vibration. However, if the check valve at the pump outlet is damaged, high-pressure hydrogen gas can flow back into the pump and the feed tank. If the motor used is of increased safety type, electric sparks may be generated, leading to an explosion.
A high-head pump is necessary; otherwise, the pump’s temperature will rise significantly and it will experience heavy vibration. This should be tested during the installation and commissioning process, and attention must be paid to the opening degree of the minimum flow line
Where did you get this data? I’d like to learn about it. The flow rates have all exceeded the designed values – will the pump still work? ?
It takes effect when the inlet flow is low; in addition, it prevents backpressure at the pump outlet
There are two types of design flow rates: a minimum and a maximum, with the maximum value serving to prevent the motor from being overloaded. What others are referring to is the minimum flow rate required for design purposes; such high-pressure pumps cannot withstand pressure buildup, as this will damage the pump. I have seen high-pressure pumps experience pressure buildup, with the outlet pipeline vibrating violently and the seal line tearing apart completely.