Vacuum and Jet Maintenance Standard

Purpose

The two things a customer actually feels are how wet the carpet is when you leave and whether the traffic lane came clean, and both of them live at the wand rather than at the machine. A jet that has scaled 20 percent closed still sprays, so nobody notices; it just under-wets the lane and the tech compensates with more passes, which puts more water in and takes the same water back out. A vacuum path with a loaded screen and a tired lid gasket does the same thing from the other end.

Both degrade slowly enough that no single day looks wrong, which is why this is a scheduled procedure with numbers rather than a thing you do when something breaks. The flow test in step 6 is the core: it converts "seems okay" into a measured gallons per minute you can compare against what the jets are supposed to deliver.

Scope

Covers the wand and hand tool spray jets, the solution path from the reel out, the recovery path from the wand back to the waste tank, and hose and cuff integrity, on a weekly or 40 operating hour cadence, whichever comes first.

Does not cover: engine, blower, pump and heat exchanger service, which the truck mount preventive maintenance SOP owns; the daily startup readings, which the startup SOP owns; and how hose length trades against airflow, which the truck mount CFM reference owns.

Roles and responsibilities

Procedure

1. Take the pressure and the heat out of the solution path before anything is opened. Kill heat, run water until the wand cools, then stop the pump and bleed the line at the wand into the waste tank. Accept: gauge reading 0 psi and the wand stream below 120 degrees F before a wrench touches a fitting. Wrong: trusting that a stopped pump means an empty line. Stop rule: a gauge that will not fall to 0 means a stuck unloader, and the wand does not get opened until it does. Hazard: solution at working pressure injects through skin from a pinhole, and that wound looks like a pinprick while being a surgical emergency, so pressure is proven at 0 rather than assumed.

2. Pull both jets and read them against each other. Compare part numbers, look into each orifice with light behind it. Accept: both jets carrying the same size marking, orifices round and unscored, no white or green scale at the inlet screen. Wrong: two different sizes on one wand, which is how a lane gets a wet half and a dry half. Stop rule: a scored or reamed orifice is replaced, never cleaned back into service, because the score sets the pattern from then on. Hazard: never clear a jet with a wire or a pin, and never blow one out toward a hand; use a soft brush and a descaling soak.

3. Replace jets as a matched set, with new seals. Two identical new tips, new o-rings, snugged to the wand manufacturer's figure. Accept: both tips the same designation, both seals new, no thread sealant on a tapered seat. Wrong: replacing one worn jet and keeping its partner, so the pair now delivers unequal flow at the same pressure. Stop rule: if the shop only has one tip in that size, the wand goes back on the shelf until a pair is available. Hazard: overtightening a plastic tip body cracks it and it lets go later at pressure, so snug to the manual rather than to feel.

4. Bring pressure back with heat off and the wand triggered into the waste tank. This is the step that puts stored energy back into a path you just opened. Accept: working pressure held for 30 seconds with no weep at either jet body and no drip at the wand valve. Wrong: a weep at a jet body dismissed as seating-in. Stop rule: any weep drops pressure to 0 before the fitting is touched again. Hazard: the tech's face and hands are near freshly assembled joints, so heat stays off for this, the wand points into the tank, and nobody stands over the jet bodies while the gauge climbs.

5. Read the pattern on a dry dark surface before it touches carpet. Trigger onto cardboard at a fixed standoff and look at the two wetted bands. Accept: two even fans, no streams, fingers or dry gaps, and the two bands symmetric about the wand centerline within about half an inch, which is the shop's gate rather than a manufacturer figure. Wrong: a finger or a stream out of one tip, which means debris or a damaged orifice, not a pressure problem. Stop rule: an uneven pattern sends you back to step 2 rather than forward to the flow test. Hazard: heat is still off and the board is at arm's length, because a fan pattern at working pressure will still break skin at close range.

6. Measure the flow into a graduated container for 60 seconds at the shop's working pressure, heat still off. Compare the measurement against what the jets should deliver. Accept: measured flow within 10 percent of the computed figure for that jet pair at that pressure. Wrong: a measurement well under the computed figure, which is scale or a partial blockage rather than a weak pump if the gauge is holding. Stop rule: more than 10 percent low sends the wand back to step 2 and the unit to the PM SOP if new jets do not fix it. Hazard: the container sits on the ground and the wand is held at arm's length above it, with heat off, because a bucket held in a hot stream is a scald with both hands occupied.

7. Restore heat and confirm the working temperature came back. Read the stream at the wand tip with a thermometer, per the startup SOP. Accept: the wand back inside the shop's working band for the fiber you clean most, reached within 5 minutes of heat coming on. Wrong: assuming heat is fine because it was fine this morning, when you have just changed the flow through the exchanger. Stop rule: a temperature that will not return to band after a jet change goes to the startup SOP's fallback rule and the unit gets descaled. Hazard: the tip is now hot enough to scald, so the thermometer goes into the stream over the waste tank, gloved.

8. Service the recovery path from the tank back. Pull and clean the waste tank lint screen, check the float shutoff for free travel, inspect the lid gasket and the vacuum relief valve. Accept: screen clear, float moving freely through its full travel by hand, gasket unbroken and seating, relief valve free and set where the manual says. Wrong: a float held partly up by fiber, which lets the tank overfill into the blower. Stop rule: a float that sticks anywhere in its travel is repaired before the next job, because water in a blower is a rebuild. Hazard: the screen and tank interior carry biologically loaded residue, so gloves and eye protection go on, the screen comes out low and slow rather than being shaken, and hands are washed before you eat or touch a phone.

9. Leak-check the hose and cuffs, then the wand head. With the blower running, cap the wand end and compare vacuum at the machine with vacuum at the far coupler. Accept: the capped reading holding steady and within the band the shop set for that hose length, with no hiss at any cuff. Wrong: a slow drop with everything capped, which is a hose pinhole or a cuff gasket rather than a tired blower. Stop rule: a section that will not hold comes off the reel and goes on the van floor for replacement. Hazard: the open inlet takes a glove or a cuff into it, so caps go on with the blower unloaded and hands stay clear of any open port while it is engaged.

10. Log the numbers and set the next due. Accept: jet designation, measured flow, computed flow, percentage difference, pattern result, screen and float condition, capped vacuum reading, and the next due date or hour meter reading, all written before the wand goes back on the van. Wrong: logging pass or fail without the measured number, which makes the trend unreadable. Stop rule: a wand that failed any step goes back with a red tag rather than into a route. Hazard: none at this step; it is paperwork at a bench.

The record this produces

Every service writes: date and hour meter, jet designation installed, measured gallons per minute, computed gallons per minute, the percentage difference, pattern pass or fail, screen and float condition, lid gasket condition, capped vacuum reading with the hose length it was taken at, parts used, and the next due.

The measured and computed pair is the field that makes the log worth keeping. A single reading tells you whether the wand is fit to work today; the column over three months tells you whether your water is scaling jets, which is a water treatment decision rather than a jet decision, and it is invisible from any one service. The capped vacuum reading does the same job for the recovery path, and it only means anything if the hose length is recorded next to it, because the two are not comparable across different lengths.

Worked pass, with a step that failed

Weekly service, one wand with a two jet bar, shop working pressure 400 psi.

Step 2 found both jets marked 8002. That designation means an 80 degree fan rated at 0.2 gallons per minute at 40 psi on water, which is the condition the rating is published at; flow through a fixed orifice rises with the square root of pressure, so at 400 psi each jet should pass 0.2 times the square root of 400 divided by 40, which is 0.2 times 3.162, or 0.632 gallons per minute. Two jets give 2 times 0.632, or 1.26 gallons per minute, and that is the computed figure step 6 tests against. Both orifices looked round, but the left tip had white scale at its inlet screen.

Step 5 read a slightly narrow fan on the left and no fingers, which passed on the letter of the gate, since both bands were within half an inch of symmetric.

Step 6 failed. Heat off, bucket on the ground, 60 seconds at 400 psi gave 1.05 gallons. Against the computed 1.26, that is 1.26 minus 1.05, or 0.21 gallons per minute low, and 0.21 divided by 1.26 is 0.167, so 16.7 percent low against a 10 percent gate. The gauge held 400 psi throughout, which is what separates a scaled jet from a weak pump.

The stop rule sent it back to step 2. Both tips were replaced as a matched pair with new o-rings under step 3, not just the scaled one. The re-test measured 1.22 gallons in 60 seconds: 1.26 minus 1.22 is 0.04, and 0.04 divided by 1.26 is 0.032, so 3.2 percent low, inside the gate. Step 7 restored heat and the wand came back into band in about 3 minutes.

The log line reads: jets 8002 pair replaced, measured 1.05 against computed 1.26 at 400 psi, 16.7 percent low, failed; after replacement 1.22, 3.2 percent low, passed. That is the third scaling failure on this unit in two months, which is the entry that sends the shop manager to look at fill water rather than at jets.

References

• See related: Prochem Everest 650 Truck-Mount Preventive Maintenance SOP - owns engine, blower, pump and exchanger service, including the descale this SOP escalates to.
• See related: Truck Mount Startup and Shutdown Standard SOP - owns the wand temperature band step 7 verifies against and the capped vacuum band step 9 uses.
• See related: Truck Mount CFM and Vacuum Math reference - owns why a capped reading is only comparable at a stated hose length.
• Wand and spray tip manufacturer documentation for tip designation, seat torque and the published flow rating with its reference pressure.