Dosing Pump SOP: How to Write an Operating Procedure Shift Teams Will Use

A good dosing pump SOP passes one test: a new operator can follow it alone, start and stop the pump correctly, complete an inspection round, and know what to do first when something goes wrong. Many sites either copy the manufacturer's manual, which nobody reads, or write one line saying "operate per manual", which helps nobody. What works better is a short document split into six parts, each listing only the actions this site actually needs. This article gives supervisors a framework they can adapt.

The structure of a dosing pump SOP

A workable dosing pump SOP usually covers:

1. Scope: which pumps, which chemicals, which dosing points.
2. Start and stop: daily start, daily stop and long shutdown.
3. Inspection: what to look at, listen for and record each shift.
4. Handover: settings, pressure, tank level, anything unusual.
5. Fault response: the first step for common faults and when to escalate.
6. Safety: chemical hazards, PPE, spill response.

Write short numbered steps, one action per line. Use the same valve and instrument tag numbers that are on site, so an operator can walk the plant with the procedure in hand.

Start and stop: fix the order

This part does not need theory, only sequence:

• Start: check tank level, open suction and discharge valves, confirm the injection point is open, start the pump, check pressure returns to normal.
• Stop: stop the pump, close the discharge valve, then the suction valve.
• Long shutdown: flush the head and lines with water; always flush crystallising chemicals.

Put one line in bold in every dosing pump SOP: never start a dosing pump against a closed discharge valve. A positive displacement pump builds pressure fast, and this is the most common cause of avoidable damage.

The inspection round: look, listen, feel, record

Most of the value in a dosing pump SOP sits in the routine round. At least once per shift:

Look

• Tank level enough for the next shift.
• Discharge pressure in normal range, without large swings.
• Leaks or crystal build-up on the head, fittings and lines.
• Gearbox oil level and colour on mechanical pumps.
• Visible bubbles in the suction line.

Listen and feel

• Even running sound, no knocking or clunking.
• Motor housing not unusually hot.

Record

• Stroke and frequency settings.
• Discharge pressure and tank level.
• Anything unusual and what was done.

Easy things to miss

Relief valve return lines and back pressure valves are often mounted high on a pipe rack, and nobody looks up. If the return line is running, the relief valve is lifting or passing and the delivered dose is falling. Injection quills that scale up raise discharge pressure slowly. Add both to the route. Repeated bubbles in the suction often mean a leaking fitting or a gassing chemical; see how to deal with air in a dosing pump.

Handover and records in the dosing pump SOP

Keep the handover sheet simple but fixed in format, and fill it in every shift. Trends over several days say more than a single reading. Output falling slowly at the same setting usually points to wearing valves or diaphragm, so maintenance can be planned before a failure.

Include replacement intervals in the maintenance section of the dosing pump SOP; how often to replace a metering pump diaphragm and our metering pump spare parts list are useful references.

Fault response: the first step only

An SOP is not a repair manual. List only what the operator should do first and when to call maintenance:

• No output: check tank level and suction valve, bleed the head; if still no output, stop and report.
• High pressure: stop immediately and check the discharge valve and injection point for blockage.
• Leak: stop, relieve pressure, follow the chemical safety sheet, report.
• Abnormal noise or hot motor: stop and report; do not keep running.

That way operators do not strip pumps themselves, and maintenance staff are not called out for minor issues.

Training and sign-off

Writing the dosing pump SOP is half the job. Walk each operator through it at the pumps, have them carry out a start, a stop and an inspection round while a supervisor watches, and record the sign-off. When the procedure changes, repeat the briefing for the changed steps. A short laminated card at each pump, taken from the full procedure, helps on night shifts when nobody wants to open a binder.

Safety section

Make the safety part specific to each chemical. Sodium hypochlorite, sulfuric acid, hydrochloric acid and caustic soda carry different hazards. Common rules: gloves and eye protection when handling chemical, stop and relieve pressure before opening fittings, an eyewash station in the dosing room, and isolate a spill before cleaning it up.

Review the dosing pump SOP every year and after any equipment change. Add sections when a new pump or chemical arrives. For replacement pumps, see our metering pump range.

Conclusion

A dosing pump SOP is only useful if people can follow it. Keep six parts, write short numbered steps that match site tag numbers, and include only what this site needs. On each round, check pressure, level and leaks, listen and feel, and record settings and anything unusual, because trends reveal wear early. Send us your pump models and chemicals, and contact our engineers for help drafting operating and maintenance points.

FAQ

Should a dosing pump SOP follow the manual word for word?

No. Base it on the manual, but keep only the steps this site uses, written as actions an operator can follow.

How often should a dosing pump SOP require inspection?

At least once per shift. Increase it on critical duties or after maintenance.

The pressure gauge is swinging a lot. What should the operator do?

Check the pulsation dampener and back pressure valve, then look for air in the suction. Record a sudden change and report it.

Should operators be allowed to change stroke settings?

The SOP should say who can change settings and require every change to be recorded. Unrecorded changes make dose problems hard to trace.

What makes dosing pumps last longer?

Correct start and stop order, never starting against a closed outlet, no long dry running, scheduled oil, diaphragm and valve changes, and flushing crystallising chemicals before shutdowns.