1-805-484-2992
Quotes - Engineering - SalesFour properties, four effects
Four properties of the product drive most of the selection: fat, total solids, viscosity and particulates. Fat changes the gasket compound and, past about 30%, the channel. Total solids change density, specific heat and fouling. Viscosity, read at the coldest point, sets the film coefficient and the pressure drop. Particulates decide whether a plate is possible at all. A product sheet with these four lines is worth more than any other data we receive.
What each property changes
Fluid milk sits at the easy end. Skim runs near 0.1% fat and about 9% total solids; whole milk near 3.25–3.5% fat and about 12.5% solids. Both behave close to water at pasteurizing temperature and only modestly thicker cold.
Heavy cream at 36–40% fat, ice cream mix at 36–40% total solids, and cultured product after the break are where these numbers start doing real work.
Effect on the pick
- Fat above about 30%: wide-gap plate or tubular, NBR or HNBR gaskets
- High total solids: more fouling margin at the hot end
- Cold viscosity: lower film coefficient, higher drop, fewer passes
- Fines in whey: clarify upstream or open the channel
- Pulp and fruit pieces: single-tube bore sized to the largest piece
- Shear-sensitive curd: low-velocity corrugated tube-in-tube
Fat level where cream changes channelAbove about 30% fat, cream thickens so sharply as it cools that a standard plate channel spreads it poorly and fouls at the contact points.
Fat and the gasket
Fat does more than thicken product; it attacks elastomers. EPDM handles hot water, steam-side duty and CIP chemistry well, but milk fat swells it, and a swollen gasket extrudes and leaks. The compound follows the fat content:
- Skim, whole milk and whey: EPDM is the usual product-side choice
- Cream, butter cream and high-fat mix: NBR (nitrile)
- Mixed fat duty with hot CIP: HNBR, at a higher price
- Every product-contact compound FDA 21 CFR 177.2600 compliant
- Utility-side compound matched to water, condensate or glycol
Call and talk it through with an engineer: 1-805-484-2992
Viscosity is read at the cold end
A viscosity figure is only useful with a temperature next to it. Whole milk runs around 2 cP at room temperature and roughly 3–4 cP near 40°F. Heavy cream at the same cold temperature can be an order of magnitude thicker, and ice cream mix thicker again once its stabilizers have hydrated.
That cold-end number drives three things. It lowers the film coefficient, so the unit needs more surface. It raises the pressure drop, so the pack needs fewer passes or a wider channel. And it worsens flow distribution across a plate, so the outer edge of a channel runs slow and fouls first. A wide-gap channel fixes the third problem; it does not fix the first.
Total solids matter most on the hot side. Proteins, sugars and stabilizers in a high-solids product deposit faster at heating temperatures, and a mix heater that holds temperature for the first hour may loose it by the fourth. We add heater surface for the run length the plant states rather than a fixed percentage on every job.
Particulates are the one property that can rule a construction out entirely. Cheese fines can pass through a plate once a clarifier has taken most of them out; fruit pulp needs open channels; whole pieces need a single-tube bore larger than the biggest piece, which for most fruit preparations means up to about 1 in.
What to send: the lab's fat and solids figures, viscosity at two temperatures if it has been measured, and a description of the largest piece. If viscosity has never been measured, the product name and the recipe range are enough for a first sizing, and we tighten it once samples or lab data arrive.
A viscosity figure without a temperature next to it sizes nothing.
Send fat, total solids and the coldest temperature in the exchanger for every product the line will run.
Request a QuoteFat and solids questions
Rarely the construction, often the details. Added sweetener and cocoa raise total solids, and products with added sweeteners pasteurize at 166°F for 15 seconds rather than 161°F, so the heater runs hotter and fouls faster. Cocoa also settles where flow is slow, so we watch distribution and velocity in the plate channels rather than simply adding plates.
At 10.5–18% fat it usually stays in standard plates, with a higher pressure drop than milk and a cold-end viscosity worth stating. Its fat content is high enough that most plants move the product-side gaskets to NBR once half-and-half shares the line, and it takes the 166°F pasteurizing temperature, which raises the heater duty.
How much and how big. Whey straight off the vat carries cheese fines that can lodge at plate contact points; after a clarifier or fines saver it is close to water and runs well in plates. Tell us whether the whey is clarified before the exchanger, and if not, roughly how much solid it carries per thousand pounds.
The construction stays the same, but the product behaves differently when hot. Hydrolyzed lactose turns into glucose and galactose, which brown more readily on a hot wall, so heater fouling and color change come sooner. We keep the hot-water approach close and give the heater section a little more margin when the line runs lactose-free product for long stretches.
Yes, mostly through viscosity and fouling. Stabilizers and emulsifiers thicken the mix as they hydrate, so cooling sections meet their highest viscosity at the very end. They also deposit with protein on hot surfaces. We give mix heaters more fouling margin than milk heaters and keep the cooling channel wide enough for the cold end.
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