In a solvent batch transfer, quantity and purity are protected by the same design decisions. Quantity is set by a meter at a defined delivery point and a batch controller that stops flow when the target is reached. Purity is protected either by dedicating the whole path, meaning tank, pump, meter, hoses and receiving vessel, to a single product, or by verifying the state of that path before and after every transfer. The two goals are linked: every line drain or flush performed for purity changes the relationship between what the meter registers and what actually reaches the receiver.
Target cutoff and overrun compensation are covered on the chemical batch metering page, and meter selection on the solvent metering skids page. This page looks at how solvent behavior changes the batch transfer itself.
Where solvent batches go
· Tank to reactor or mixer: Charging the recipe quantity of solvent into a process vessel in paint, coatings, adhesive or pharmaceutical production.
· Tank-to-tank transfers: Moving a set quantity from bulk storage to a day tank or blend tank.
· Truck or container filling: Filling a tank truck compartment, IBC or drum to an order quantity.
Should the target be mass or volume?
Solvent density changes noticeably with temperature, so the mass contained in a given volume can differ between summer and winter. If the recipe is written in mass, a Coriolis meter, which measures mass flow, density and temperature together, reaches the target directly without any volume conversion. If the recipe or the sale is based on volume, the reference temperature and the product-specific correction coefficients have to be agreed at the outset.
Many solvents have very low electrical conductivity and fall outside the operating range of standard magnetic flow meters. Alcohols and ketones count as high-conductivity liquids in electrostatic terms, but that does not mean a magnetic meter will work: the minimum conductivity is a manufacturer value that depends on meter model and size, and it has to be checked for each product.
How purity is lost, and how to prevent it
Contamination route | How it happens | Design response |
Carryover from the previous product | Product left in a shared line, pump or meter mixes into the next batch | Dedicated line, or a defined drain and flush sequence |
Moisture and air ingress | With water-absorbing solvents, tank vents and open connections admit moisture | Dry gas or nitrogen blanketing, closed connections, fewer lines left open |
Material interaction | An unsuitable seal or hose swells in the solvent, leaches components or sheds particles | Wetted parts selected against the incompatible-materials data in the safety data sheet |
Wrong product or wrong vessel | Transfer from the wrong tank or through the wrong valve | Position feedback on source and destination valves, labeled connection points, permissive interlock |
Flush or purge medium residue | Flush solvent or purge gas is carried into the batch | A check step after flushing or draining; if needed, the first portion is diverted |
Dedicated lines or a shared header?
For high-purity solvents, or products that must never mix, the most reliable route is to dedicate the whole path from tank to receiver to one product. That means more pumps, meters and piping, but it removes product changeovers, flushing and the records those steps require. As the number of products grows, a shared distribution header with product selection valves becomes more economical, and purity then depends on operating procedure and valve interlocks.
On shared lines, product sequencing matters: products that tolerate slight mutual contamination can follow one another, while critical products are preceded by a line drain or a flush. Permitted product pairs are defined in a compatibility matrix that the control system can enforce.
Full line or empty line: the hidden variable in quantity
The piping and hose between the meter and the receiving vessel hold a certain volume. If that line is full at the start and left full at the end, the metered quantity equals the quantity delivered. If the line is drained toward the receiver after the transfer, its contents are added to the batch and must be counted in the target; if it is drained back toward the tank, the receiver gets less than was metered. Keeping the start and end state of the line fixed and defined for every transfer is the basis for protecting purity and quantity together.
If the line is cleared by pushing it out with a gas such as nitrogen, the meter may see gas and register an error. The push is therefore either introduced downstream of the meter, or metering is closed before the push and the line contents are added to the batch as a calculated fixed quantity.
Static and vapor in the receiving vessel
Batch transfers often feed a process vessel from the top, and that vessel may contain an ignitable atmosphere. With low-conductivity solvents, fine filters are among the strongest charge generators; leaving a relaxation volume between the filter and the vessel and delivering the liquid through a dip pipe near the bottom, without splashing, are the recommended measures. All conductive parts, hose connections and portable containers are grounded; details are on the grounding and overfill prevention page.
Recipes, permissives and the purity record
The recipe usually comes from the DCS or PLC, and the batch controller starts only when the permissives are satisfied. Typical permissives for solvent batches are position feedback on source and destination valves, enough free volume in the receiving vessel, verified grounding and, where used, adequate blanketing nitrogen pressure. The record kept at the end is chosen so that purity, not only quantity, is traceable: the product that last used the line, the flush or drain step applied, batch temperature and density, any sample taken and the identity of the receiving vessel.
Design criteria
Parameter | Why it matters in design | Effect on selection |
Product list and purity grade | Determines which products can share a path | Dedicated or shared line, flushing requirement |
Batch size range | The smallest batch must still run within the meter's accurate flow range | Meter size, staged cutoff, possibly two metering runs |
Target unit | Mass and volume targets need different measurement and conversion | Coriolis or volumetric meter, temperature and density measurement |
Electrical conductivity | Governs magnetic meter suitability and how strict static measures must be | Meter technology, filter location, relaxation volume |
Line volume and geometry | Line contents are added to or subtracted from the batch | Line clearing method, meter location relative to the receiver |
Moisture sensitivity | Water ingress can take the product off specification | Blanketing, closed connections, vent dryers |
How TLY Enerji contributes
Depending on project scope, TLY Enerji provides engineering support for solvent batch transfers: selecting a meter and control valve suited to the product and target unit, supplying flow meters, valves and pumps, integrating the batch controller and permissive signals into the plant PLC or DCS, and site installation, testing and commissioning. Which equipment falls within the scope of supply, and how existing lines are reused, is agreed on the basis of project data.
What to prepare for an engineering review
· List of solvents with safety data sheets and purity or specification requirements
· Layout of source tanks and receiving vessels, with line length and diameter between them
· Smallest and largest batch quantity and expected batch frequency
· Whether the target is mass or volume, and the acceptable deviation
· Which products will share a line and current flushing practice
Related pages
· Batch metering systems for chemicals: Target cutoff, overrun compensation and staged closure in detail.
· Solvent metering skids: Meter selection for low-conductivity, low-viscosity solvents.
· Grounding and overfill prevention systems: Ground verification tied into the transfer permissive chain.
· Solvent loading and transfer facilities: Overview of static, vapor and purity risks at solvent sites.
Questions about solvent batch transfer
Can one pump and meter handle several solvents?
Yes, but responsibility for purity shifts from equipment to operating procedure. Product sequencing has to follow a compatibility matrix, the line has to be drained or flushed before critical products, and those steps must be recorded. For high-purity products, or where even slight mixing is unacceptable, a dedicated line is usually the more reliable solution.
Does clearing the line with nitrogen affect the metered quantity?
It can. If the purge gas passes through the meter, the meter cannot measure the gas and liquid mixture correctly. Either the purge point is placed downstream of the meter, or metering is closed before the purge and the line contents are added to the batch as a calculated quantity. In both cases, the line state at the start and end of the transfer should stay the same.
Should a solvent recipe be defined by mass or by volume?
The recipe follows what the process needs, and the metering system is designed around it. Because solvent density changes with temperature, a volume-based recipe needs conversion to a reference temperature with product-specific coefficients. With a mass-based recipe, a meter that measures mass directly removes that conversion and reduces the effect of seasonal temperature swings on the recipe.
What needs attention when transferring a water-absorbing solvent?
The most likely water entry points are tank vents, connections left open and lines that fill with air between transfers. Blanketing the tank with dry gas or nitrogen, keeping connections closed and leaving the line full of product between transfers all limit water ingress. Where the specification sets an acceptable water content, sampling critical batches and adding the result to the batch record is advisable.