Every centrifugal pump has a point on its curve where the flow is zero, and the pressure it makes there has a name: shutoff head. It is the head the pump develops when its discharge is fully closed, the leftmost point of the head-capacity curve, and it is both the highest head the pump normally produces and a genuine hazard if the pump is left running against a closed valve. This page explains what shutoff head is, why it sets the maximum discharge pressure a system and its instruments must be rated and alarmed for, and how running a pump dead-headed overheats and damages it. It also covers the trip logic used to protect against a blocked or closed downstream valve.
Pump Shutoff Head in one line: Pump shutoff head is the head, and therefore the discharge pressure, that a centrifugal pump develops at zero flow when its discharge valve is closed, and it is the highest point on the head-capacity curve. It sets the maximum discharge pressure the piping, seals, and instruments must be rated for and that a SCADA system should alarm on. Running a pump at or near shutoff, called dead-heading, is dangerous because with no flow to carry heat away the recirculating liquid rapidly overheats and can damage seals, bearings, and the pump itself.
A centrifugal pump's performance is described by its head-capacity curve, which plots the head it produces against the flow it delivers. As flow drops, head rises, and at the far left of the curve, where flow reaches zero because the discharge is closed, the head reaches its maximum value: the shutoff head. This is the pressure the pump makes when it is churning liquid inside its casing but pushing none of it out, and for most centrifugal pumps it is the highest head the machine will ever develop in normal service.
Because shutoff head is the peak of the curve, it defines the worst-case discharge pressure the rest of the system can see. Any valve, gauge, transmitter, gasket, or length of pipe on the discharge side may be exposed to that pressure if the pump ends up dead-headed, so the discharge piping and instrumentation are commonly rated with shutoff head in mind rather than the normal operating pressure. A relief valve or the pressure rating of the weakest downstream component has to account for the fact that a closed discharge does not stop the pump, it simply drives the pressure up to shutoff.
The shape of the curve near shutoff matters too. Some pumps have a steadily rising head all the way to shutoff, while others have a curve that flattens or even dips near zero flow, and that shape affects how the pump behaves when throttled and how a high-pressure alarm should be interpreted. Knowing the published shutoff head for a specific pump and impeller is the starting point for setting protective pressure limits, because it is the ceiling the pressure will climb to if flow is ever cut off entirely.
The danger of running at shutoff is heat. A centrifugal pump is not perfectly efficient, so some of the power the motor delivers turns into heat in the liquid inside the casing. In normal operation the flow of liquid through the pump carries that heat away almost as fast as it is generated, keeping the liquid and the pump at a safe temperature. When the discharge is closed and there is no flow, that escape route disappears: the same small volume of trapped liquid is churned around and around, absorbing heat with nowhere to go, and its temperature climbs quickly.
As the trapped liquid heats, the consequences cascade. The liquid can flash to vapor inside the casing, the mechanical seal loses the cool liquid film it relies on and can be destroyed, bearings and the shaft heat and can seize or warp, and in severe cases the pump can be damaged badly enough to fail catastrophically. What makes dead-heading especially insidious is how fast it can happen on a small pump with a low volume of trapped liquid and how quiet it is: the pump is running, the motor sounds normal, and nothing moves, so an operator not watching pressure and flow may not realize the pump is cooking itself until damage is done.
Dead-heading is usually not intentional. It happens when a downstream valve is closed, mistakenly or automatically, while the pump keeps running, when a discharge line plugs or freezes, or when a check valve or actuated valve fails shut. Because the cause is often a valve rather than the pump, the pump itself can be perfectly healthy right up until the moment it is asked to run against a closed path, which is why protection focuses on detecting the no-flow, high-pressure condition and stopping the pump before the heat does its work.
Protecting a pump against dead-heading comes down to recognizing the signature of a closed discharge, which is high discharge pressure together with low or zero flow, and acting on it. A high-discharge-pressure alarm and trip is set with knowledge of the shutoff head, so that a pressure climbing toward that value warns that the pump may be running against a closed valve. Because shutoff head is the ceiling, the alarm is placed below it with enough margin to catch the condition early, and a trip stops the pump before the pressure and temperature reach damaging levels.
Pressure alone can be ambiguous, so the stronger logic pairs it with flow or a minimum-flow indication. A low-flow condition while the pump is running is the clearest sign that liquid is not leaving, and combining low flow with high or rising discharge pressure gives a confident dead-head detection that is unlikely to nuisance trip. Where a flow meter is not available, some protection infers no-flow from other signals, such as a discharge temperature rise or the pump running with a downstream valve proven closed, and treats that combination as a reason to stop. The intent throughout is to distinguish a genuinely blocked path from normal throttled operation near, but not at, shutoff.
In a cloud SCADA context this protection becomes both an alarm and a piece of interlock logic that an operator can see and trust from a distance. A platform such as Merobix carrying discharge pressure, flow, and downstream valve status lets an operator watch a pump approach its shutoff pressure and confirm whether a closed valve is the cause, while the trip logic acts automatically to stop the pump if the dead-head condition persists. Historizing these signals also turns a near-miss into a learning event, showing after the fact how quickly pressure rose when a valve closed and whether the trip acted in time, which helps tune the alarm and trip setpoints so they protect the pump without stopping it during ordinary throttling.
Shutoff head is the head, and the corresponding discharge pressure, that a centrifugal pump develops at zero flow when its discharge valve is fully closed. It is the leftmost point of the head-capacity curve and, for most centrifugal pumps, the highest head the machine produces. Because it is the peak pressure a dead-headed pump will reach, it is used to rate discharge piping and instruments and to set high-pressure protection.
With the discharge closed there is no flow to carry away the heat that the pump's inefficiency generates, so the small volume of trapped liquid churns and heats rapidly. That heat can flash the liquid to vapor, destroy the mechanical seal, and overheat bearings and the shaft until they seize or the pump fails. On a small pump the temperature can climb dangerously fast, and because the pump still runs quietly, the damage can occur before anyone notices without pressure and flow monitoring.
The strongest protection detects the dead-head signature, which is high or rising discharge pressure together with low or zero flow, and trips the pump before it overheats. A high-discharge-pressure alarm is set below the pump's shutoff head with margin, and pairing it with a low-flow indication avoids nuisance trips and confirms that liquid is not leaving. Where no flow meter exists, a discharge temperature rise or a proven-closed downstream valve can stand in for the no-flow signal.
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