Picture this: you’ve got a water transfer pump moving produced water from a common header connected to several tanks and pushing it into a pipeline. Sounds straightforward, right?
But if the fundamentals aren’t spot on, this simple operation can quickly spiral into a costly mess—downtime, impeller damage, pitted pump casings, or, worse, a cracked pump housing that leads to a full-blown safety incident.
Over the past year, we've seen a significant spike in requests for pump training programs—especially from operators in the Delaware Basin. With incidents on the rise, it's clear that there's a growing need for better training and understanding of pump operations.
But if the fundamentals aren’t spot on, this simple operation can quickly spiral into a costly mess—downtime, impeller damage, pitted pump casings, or, worse, a cracked pump housing that leads to a full-blown safety incident.
Over the past year, we've seen a significant spike in requests for pump training programs—especially from operators in the Delaware Basin. With incidents on the rise, it's clear that there's a growing need for better training and understanding of pump operations.
So, we’re here to give you the quick guide to some essentials every operator should know.
Explore our 3D models in under each section to learn more about the concepts described! Click the mouse icon on the model screen for navigation instructions.
Understanding NPSHa and NPSHr
Let’s start with two key concepts that are crucial for efficient pump operation: Net Positive Suction Head Available (NPSHa) and Net Positive Suction Head Required (NPSHr).
What is NPSHa? In simple terms, NPSHa is the pressure available at the pump’s suction side to move the produced water from the tanks into the pipeline. This is typically discussed in height of fluid in the tanks feeding the pump, but always be sure to consider all the restrictions, fittings, bends - basically any pressure drop - in the piping between the tanks and pump. All these restrictions lower the pressure available (NPSHa) at the pump.
And NPSHr? This is the minimum pressure the pump needs to operate without forming vapor bubbles—what we call cavitation. Cavitation is like your pump gasping for air; it can cause damage to the pump’s internal components and reduce efficiency.
To keep operations smooth, NPSHa must always be greater than NPSHr. If the pressure available (NPSHa) drops below the required level (NPSHr), your pump starts making noise, and that’s when problems arise.
Common operating problems
Here are a three common reasons why pumps don’t do what operators expect and are typically fairly simple to resolve:
1. Low Suction Pressure: One of the most common problems -- when the suction pressure drops below the fluid’s vapor pressure, it will start to vaporize moving through the pump, causing cavitation.
1. Low Suction Pressure: One of the most common problems -- when the suction pressure drops below the fluid’s vapor pressure, it will start to vaporize moving through the pump, causing cavitation.
Typical causes:
- Low tank levels: If your tanks are running low, there isn't enough pressure to push water into the pump.
- Clogged filters/strainers on suction piping: Blockages can restrict flow and reduce pressure.
- Excessive restrictions, valves, or fittings on suction piping: Too many obstacles in the path can choke the flow.
2. High Pump Speed: Running the pump too fast can create low-pressure zones, especially at the eye of the impeller.
Typical causes:
- Operating a pump at speeds higher than recommended in order to maximize flow rate through the pump. Running it beyond manufacturer recommendations can lead to cavitation.
3. Low Discharge Pressure: When discharge pressure is set too low, the pump may run at a higher flow rate than intended, and require more NPSHr than NPSHa, leading to cavitation.
Typical causes:
- Discharge valve opened too wide, reducing resistance in the system and causing the pump to operate beyond its optimal range.
- Inadequate discharge pressure settings during startup or normal operation, allowing the pump to move more fluid than the system can handle, which can lead to cavitation and damage to the impeller.
Making adjustments to keep things running smoothly
Here are three key variables operators can adjust to maintain efficient pump performance:
1. Fluid Head (Level): Keep the tank’s water level high enough to maintain adequate pressure at the pump’s suction. Low levels can lead to low NPSHa, increasing the risk of cavitation.
1. Fluid Head (Level): Keep the tank’s water level high enough to maintain adequate pressure at the pump’s suction. Low levels can lead to low NPSHa, increasing the risk of cavitation.
2. Back Pressure: Dropping the back pressure setting on your pump can increase rate, but if you do too much this will cause cavitation.
3. Pump Speed: Use variable frequency drives (VFDs) to control pump speed based on operational needs, ensuring the pump stays close to its Best Efficiency Point (BEP). Ask your engineers why the tank levels and pump VFD setpoints are set the way they are.
