Setting a methanol pump's rate tells you what it is supposed to inject, but it does not tell you what it actually injected, and at a remote wellsite those two can diverge quietly. Stroke counting closes that gap. Each stroke of a positive-displacement injection pump delivers a known small volume of methanol, so a sensor that counts the strokes, multiplied by the volume per stroke, produces a direct measure of the real injected volume. Compare that measured volume against the target rate and it tells you whether the pump is keeping up; reconcile it against the fall in the tank level and it tells you whether the methanol you paid for is actually reaching the well. This is a measurement and verification discipline, not just a rate setting.
Methanol Pump Stroke Counting in one line: Methanol pump stroke counting uses a proximity or reed switch to detect and count each stroke of a positive-displacement injection pump, and multiplying the count by the pump's volume-per-stroke gives the actual injected volume over any period. That measured volume is checked two ways: against the target injection rate to confirm the pump is delivering enough, and against the drawdown of the methanol tank to confirm the strokes are really moving liquid. It turns a commanded rate into a verified volume at a site nobody visits daily.
A positive-displacement injection pump delivers methanol in discrete strokes, and each stroke displaces a fixed volume set by the pump's plunger diameter and stroke length. That volume-per-stroke is the conversion factor that turns a count of strokes into a volume of methanol: total injected volume equals the number of strokes multiplied by the volume each stroke delivers. This is the fundamental idea behind stroke counting. Rather than trusting that a pump set to a certain rate is achieving it, you count the actual strokes it made and compute the actual volume it moved, which is a measurement of what happened rather than an assumption about what should have happened.
Counting the strokes requires a sensor that fires once per stroke, and the common choice is a proximity switch or a reed switch positioned to detect the pump's reciprocating motion. A proximity switch senses a metal part of the plunger or crank passing by; a reed switch closes when a magnet on the moving element passes it. Either way the sensor produces one electrical pulse per stroke, a clean digital signal that a simple counter or an RTU input can total up. Because the sensor only has to detect a passing part, it can be added to many existing pumps without disturbing the process fluid, which makes stroke counting a practical retrofit on pumps that were installed with no instrumentation.
The volume-per-stroke has to be an accurate, verified figure for the count to mean anything, and it is not always exactly the nominal value stamped on the pump. Wear in the plunger and seals, a stroke-length adjustment set somewhere other than nominal, entrained gas, or high discharge pressure that lets a little methanol slip back can all make the real volume per stroke differ from the datasheet. The rigorous approach is to establish the actual volume per stroke by a bench or field calibration, catching a known number of strokes into a graduated container, so the stroke count converts to a trustworthy volume. Once that factor is confirmed, the pulse count becomes a genuine flow measurement of the methanol.
The first thing the injected-volume measurement is checked against is the target injection rate, the amount of methanol the site is supposed to be delivering to keep hydrates at bay. Converting the stroke-derived volume to a rate over time and comparing it to the target tells you directly whether the pump is keeping up, falling behind, or overdelivering. A pump stroking too slowly, because its rate drifted, its drive is weak, or it is partially stalled, shows up as a measured volume below target, which is an early warning of an underdosed well before a hydrate plug forms. A pump running well over target flags wasted chemical and a rate that needs trimming. Either way the comparison converts a vague commanded rate into a concrete pass-or-fail against the actual need.
The second and more powerful check is reconciliation against tank drawdown. The stroke count says how much methanol the pump believes it injected; the fall in the methanol tank level, read by a level sensor, says how much methanol actually left the tank. In a healthy system these two agree: the volume implied by the strokes matches the drawdown of the tank over the same period. When they disagree, the discrepancy is diagnostic. Strokes counted with no corresponding tank drawdown means the pump is stroking but not moving liquid, a lost prime, a stuck check valve, or an empty suction line. Tank drawdown with fewer strokes than it should take, or none, points to a leak somewhere in the tank or lines that is losing methanol without it going through the pump.
Reconciling the two measurements is what turns stroke counting from a single-point reading into a closed-loop verification of the whole injection chain. The stroke count verifies the pump is cycling; the volume-per-stroke converts that to an expected volume; the tank drawdown confirms that volume of liquid genuinely departed the tank. Only when all three line up can you be confident the target amount of methanol actually reached the well. This layered check is exactly what a remote critical-injection duty needs, because any one signal can be fooled, a pump can stroke on air, a level can fall through a leak, but the two agreeing is strong evidence that the injection is real and correct.
Stroke counting is naturally suited to remote monitoring because it produces exactly the kind of signals a SCADA system consumes: a pulse count that becomes a rate and a total, and a tank level that becomes a drawdown. Feeding the stroke pulses and the tank level into a cloud SCADA system such as Merobix lets the calculation of injected volume, comparison to target, and reconciliation to drawdown happen continuously and automatically, rather than during an occasional site visit. The operator no longer has to be present to catch a pump that has slowed or stalled; the trended stroke rate shows it, and an alarm can fire when the injected volume drops below the target the site needs.
Trending these signals over time reveals problems that a single reading would miss. A stroke rate that is slowly declining points to a wearing pump, a fouling suction, or a drifting drive that will eventually underdose the well, and catching that trend allows a service call before the failure. A growing gap between the stroke-implied volume and the actual tank drawdown points to a developing leak or a slipping check valve, flagged by the divergence of the two trends long before the tank runs dry inexplicably. And the total injected volume over a month, summed from the strokes, gives an accurate chemical usage figure for reconciliation against deliveries and cost, replacing an estimate with a measurement.
The broader value is that stroke counting and drawdown reconciliation turn methanol injection into a verified, auditable process at sites that are otherwise blind. Hydrate prevention is a duty where an unnoticed failure can plug a line and shut in a well, so knowing not just that a pump was told to run but that it actually delivered the methanol is worth a great deal. By capturing the strokes, the volume-per-stroke, and the tank level, and reconciling them continuously in a monitoring platform, an operator gains confidence that the injection is really happening at the target rate, catches the failures early through their signatures in the trends, and can prove the chemical was delivered rather than merely assumed, all from a control room far from the well.
Each stroke of a positive-displacement injection pump delivers a fixed volume of methanol set by the plunger size and stroke length, so counting the strokes and multiplying by that volume-per-stroke gives the actual injected volume over any period. A proximity or reed switch produces one pulse per stroke for the counter to total. The result is a direct measurement of what the pump actually moved, rather than an assumption based on the rate it was set to.
Because each measurement alone can be fooled and the two together catch the failures. The stroke count says how much the pump believes it injected, while the fall in the methanol tank level says how much liquid actually left the tank. If strokes are counted but the tank does not draw down, the pump is stroking without moving liquid, such as a lost prime or stuck check valve. If the tank drops without matching strokes, methanol is leaking somewhere outside the pump. Agreement between them confirms real, correct injection.
Not always. Wear in the plunger and seals, a stroke-length set off nominal, entrained gas, or high discharge pressure causing slip can make the real volume per stroke differ from the datasheet figure. The rigorous approach is to calibrate the actual volume per stroke in the field by catching a known number of strokes into a graduated container, so the stroke count converts to a trustworthy volume. Once that factor is confirmed, the pulse count becomes a genuine measurement of the methanol delivered.
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