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Quotes - Engineering - SalesLine circuit
Heating the CIP circuit for a pipeline
A pipeline is the simplest CIP circuit to describe and the easiest to get wrong. There is no spray device and no tank to fill; the pipe is the vessel, and it is cleaned by running wash solution through it fast enough to scour and hot enough to lift the soil. Flow is fixed by diameter: at the 5 ft/s a line circuit needs, a 2-inch line carries about 30 gpm, 3-inch 70 gpm, 4-inch 120 gpm and 6-inch 200 gpm. Heat loss is fixed by length and insulation, and on a long bare run it is not small. A 4-inch stainless line through a cool plant drops a few degrees per hundred feet at 160°F, and a 1,000-foot route from receiving bay to process floor can hand back 15°F before the solution reaches the far end.
So a pipeline heater is sized on two figures the plant already knows: the gpm the diameter sets and the temperature the far end must reach after the loss. The rest follows. If the line is cleaned once-through, the heater lifts the full flow from makeup to set point plus margin in one pass. If it is cleaned from a CIP tank, the heater brings the tank up and then covers the loss the line pulls out of each pass. Either way the thermometer that matters is at the return. A supply reading proves the heater; a return reading proves the pipeline.
The far end of the line is the one you are cleaning
A 6-inch line at 200 gpm lifted 40°F per pass of a tank loop is about 4 MBtu/h, roughly 4,100 lb/h of 15 psig steam. A 1,000-foot bare run can give back 15°F of that, so the supply is set above 160°F to land the return on it.
What a line circuit runs at
Caustic at 1–1.5% and 160°F for 20 minutes handles product film in a transfer line; the acid step is 0.5–1% at 130°F, nitric in dairies for milkstone and phosphoric where gaskets are the concern. The pre-rinse is warm plant water and the final rinse 120–140°F. None of that is special. What is special about a pipeline is hold-up: a 3-inch line holds about a third of a gallon per foot, so 600 feet of it is 200 gallons, and every step begins by displacing the previous fluid with the next one at circuit flow.
That displacement is why long lines are often run once-through on the rinse steps and recirculated only on the caustic. It is also why the first minutes of the caustic step arrive at the far end cold: the solution has warmed the pipe wall on the way. On a tank loop the return climbs for several passes before it levels, and the step clock should not start until it reads set point. On a once-through pass there is no second chance, and the heater outlet carries the whole margin.
The heater by line size
A U-tube shell-and-tube with steam in the tubes and solution in a 316L shell covers every pipeline size on the list. On a tank loop a 6-inch line at 200 gpm lifted 40°F per pass is about 4 MBtu/h, roughly 4,100 lb/h of 15 psig steam; the 2-inch line at 30 gpm from 60°F makeup once-through to a 165°F supply is a 105°F rise and about 1.6 MBtu/h. Both are ordinary duties. The design choice between them is the steam valve, which has to meter a third of the full flow when the plant switches from the 6-inch header to a 3-inch branch.
Pipeline solution is as fouling as the product the line carried, so the bundle pulls and the shell carries a fouling allowance of 0.001–0.002. Connections match the line: tri-clamp to 4 inches and flanged at 6 inches, 316L on everything the solution touches, EPDM head gasket with FKM when nitric runs hot. The shell-side pressure drop is kept low so the CIP supply pump keeps the line at 5 ft/s with the heater in the path. Shell rated 150 psig at 250°F.
To size a pipeline CIP heater
Two numbers do most of the work; the rest confirms them.
- Line diameter and the length of the longest circuit
- Insulated or bare, and the room temperature it runs through
- Once-through or returned to a CIP tank
- Caustic and acid set points, measured at the return
- Makeup water temperature at its coldest
- Steam pressure at the heater inlet
- Connection size and style where the heater ties in
Call and talk it through with an engineer: 1-805-484-2992
Pipeline circuit questions
Measure both ends at the same moment. If the supply is at set point and the return is 15°F low, the pipeline is losing it and the answer is insulation, or a supply set point raised to cover the loss, with the heater surface confirmed at that higher outlet. If the supply itself is low, the heater is short, usually because it was sized at a steam pressure the header does not deliver at the heater inlet.
Yes, if the steam valve is chosen for the range. The surface for 200 gpm is far more than a 30 gpm branch needs, which does no harm. The valve has to throttle to about a seventh of its full flow without hunting, so we specify a high-turndown valve or a split-range pair with the heater. A second small heater for the branches is worth it only when they sit far from the header.
Only where the line it serves is held to one. A CIP heater on a dairy raw-milk transfer line is usually utility equipment with a mill-finish shell and tri-clamp ends; a pharmaceutical transfer line often carries its 32 Ra and drainability requirement onto everything on the circuit, heater included. Tell us which case yours is, and whether the inspector wants a 3-A symbol on the loop.
Less than the pipe. A shell-and-tube sized for a 4-inch line holds a few tens of gallons on the shell side, against the 600 gallons or so in 1,000 feet of 4-inch tube. It drains to a low-point connection like the rest of the line, and because the solution is in the shell rather than the tubes, there is no bank of tube ends for the pre-rinse to flush one at a time.
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