Tank bottom water may contain more than dissolved salts. It can carry rust, sediment, sludge, wax or other solids that change how the liquid flows and how a mechanical device should be reviewed.
The key is to describe the material rather than treating solids as a yes or no checkbox. Belfield asks applicants to disclose suspended solids and refers demanding duties for factory review. This guide explains what to record.
How suspended solids affect a tank dewatering review
Identify what the solids are
Record the known source and composition: rust scale, sand, process fines, sludge, biological material, wax or an unknown mixture. If the material has been analysed, include the report and sample method. If it has not, label the identification as an observation or assumption.
Different materials behave differently. Particle size, shape, density, stickiness and tendency to settle can matter as much as a bulk concentration. Sticky residue or fibrous material may behave differently from free-settling grit.
Describe whether solids appear continuously, after a transfer, during cleaning or only at the beginning or end of a drain. A time pattern can help distinguish settled material from a steady process load.
Record whether a sample came from the tank bottom, drain line, settling pot or downstream receiver, and whether flushing, transfer or chemical treatment occurred beforehand. This context helps the reviewer interpret the reported particle size and loading.
State the quantity and how it was measured
Provide concentration or mass where available, together with units, sampling point and measurement method. A visual description such as cloudy or dirty is useful context but does not quantify the solids loading.
Report normal and worst observed conditions, including whether solids accumulate at the tank bottom between drains. If the quantity varies by tank, product batch or operating season, show the range rather than one selected sample.
Where no reliable measurement exists, say so. Ask the site laboratory or process engineer what sample is representative and how to measure it without changing the operating condition or exposing personnel to a hazard.
Explain how solids interact with flow and settling
A decantation valve is intended to respond to a change between liquid phases. Solids can settle, remain suspended, collect at a low point or contribute to an intermediate layer. Each pattern affects what reaches the inlet during a drain cycle.
Low flow can allow some material to settle in the pipe route, while a higher flow can carry material into the mechanism. The actual effect depends on particle and liquid properties, geometry and operating conditions. Do not assume that either low or high flow is automatically safe.
If the material forms an emulsion, rag layer or sticky deposit, explain that separately from the suspended solid loading. A single concentration number cannot describe the phase behaviour.
Disclose viscosity, temperature and operating range too
Solids do not replace the other liquid data. Provide density or specific gravity and viscosity at operating temperature, plus the minimum and maximum temperatures expected. A cold viscous phase with sludge can create a different duty than warm water with light sediment.
The Belfield performance guidance specifically asks for details of suspended solids when applications over its stated high-viscosity range are referred to the factory. The current selection guide also asks applicants to declare solids, wax and other process risks.
Include the available head, target flow, tank level, inlet size, valve model if known and downstream route. These inputs let the manufacturer assess whether the solids concern is compatible with the complete design.
Avoid unreviewed fixes that introduce restrictions
A screen, filter, strainer, reduced opening or frequent flushing may appear to solve a solids issue, but each changes the hydraulic or maintenance arrangement. A restriction can change flow, and a cleaning procedure can create its own safety and waste handling needs.
Do not add a device, alter valve internals or change the drain sequence based on a generic article. The responsible engineer should assess the location, pressure drop, isolation, inspection access and consequences of blockage.
If a solids control step is proposed, document its purpose, expected loading, inspection method and disposal route. Then review the modified process with the valve supplier and site engineering authority before implementation.
- Solids identity or best available description
- Concentration, particle size and sampling method
- Where and when the material appears
- Settling, adhesion, wax and emulsion behaviour
- Temperature, viscosity, head and required flow
- Current P&ID and any proposed screen or filter
Use the information to reach a documented decision
A review may conclude that the duty can proceed within an approved envelope, that more representative sampling is needed, or that another process should remove the solids before decantation. The conclusion depends on the actual material and model.
Record which values were measured, which assumptions remain, and what operating conditions require another review. Keep the laboratory result and approved drawing with the equipment file so future service staff can compare current conditions with the original basis.
If solids concentration or type changes in service, update the process record and contact the application team. Do not claim that a valve is self cleaning for every material or solids loading unless the manufacturer confirms the statement for the specific duty.
A sample taken only after a flush may not represent the material present during a normal drain. Record whether the line was flushed, how long it had been idle and the stage of the cycle when the sample was collected. That context prevents a clean sample from being mistaken for a clean duty. Where several tanks feed one route, identify which tank produced each sample and whether shared pipework could have changed it.
Frequently asked questions
Can a Belfield Valve handle suspended solids?
The manufacturer asks applicants to disclose the nature and concentration so it can review the duty. Suitability depends on the actual material, liquid pair and flow conditions.
Is a cloudy sample enough information?
It is a useful observation but not a solids measurement. Provide the sample point, timing, method and a measured concentration if available.
Should I install a strainer upstream?
Do not add a restriction without a design review. A strainer can change head loss, blockage risk and maintenance requirements.
What if the solids are only present after cleaning?
Record when they occur and whether cleaning changes the liquid pair or flow. Include the cleaning procedure and waste route in the application review.
Sources and further reading
See the Belfield performance guidance and tank dewatering selection guide for published review requirements.
The automatic separation overview explains why the complete liquid duty matters.
Next steps
Send the solids description, sample data and process sketch through the Belfield application contact page. For more about PMA, visit the PMA website.
