Why must a silo trailer be washed between different materials?

Residues of the previous load in the chamber, aeration pads and discharge hoses can contaminate the new batch. For premium granules (bottle-grade PE, medical PA) even 50 g of cement or lime residue means a falsified batch and refusal of acceptance by the end customer. Producers such as Borealis, Synthos and LG Chem contractually require a chamber cleanliness certificate before every loading of their material.

What is the difference between dry and wet washing?

Dry washing: blowing compressed air (4-6 bar) through the chamber, visual inspection with a torch, possibly vacuuming dust with an industrial vacuum cleaner. Used between compatible materials (PE → PP, clean polymer-to-polymer). Time: 30-60 min. Wet washing: water at 100-200 bar pressure, a specialist detergent (alkaline for minerals, neutral food-grade for premium polymers), rinsing, drying with heated compressed air. Used for material changes carrying contamination risk (mineral → polymer, anything → food-grade).

What is an ECTA cleaning code?

ECTA (European Chemical Transport Association) introduced a classification of silo trailer cleanliness levels: code A (highest cleanliness — food-grade, medical, pharma), B (premium chemicals, virgin polymers), C (standard chemicals, regranulates), D (minerals, untreated bulk), E (after cement, gypsum or heavily contaminating materials). Each level requires a specific washing procedure. The producer specifies the required code in the transport order — the carrier must confirm it.

How long does washing a silo trailer take?

Dry: 30-60 minutes (small blow-down bay). Standard wet: 2-3 hours (washing + rinsing + drying). Food-grade washing with detergent and complete drying: 4-6 hours. At peak times, washing is scheduled in advance so the silo trailer is ready for the next loading. In Chorula we have 2 washing bays — wet and dry.

Should I use an external silo trailer wash?

External truck washes offer a standard service for trucks. Specialist tanker and silo trailer washes are few (a few dozen in Poland), located mainly along motorways. PHS Magnum has its OWN silo trailer wash on site — for its own silo trailers plus external clients. This saves time (no detour to an external wash) and gives full control over washing quality.

Which documents do you issue after washing?

The chamber cleanliness certificate contains: the silo trailer's registration number, the date and time of washing, the cleanliness level code (A-E per ECTA), the operator, the detergent used (if wet), the visual inspection result, and interior photographs (for wet washing). The document follows the CEFIC Cleaning Document format — accepted by all CEFIC members in the EU. We archive records for 5 years.

Does washing affect the transport price?

Yes — food-grade or standard wet washing means additional hours of work plus materials. Clients with regular food-grade transports have a contract rate that includes washing. One-off clients receive a quote reflecting the required washing procedure. PHS Magnum does NOT perform food-grade transports after previous mineral loads without full wet washing — no exceptions. Ask us for a quote.

26.12.2023

Silo Trailer Cleaning – Codes, Certificate, Procedure

Transloading granulate from big-bags to a silo trailer

Key takeaways

Internal washing of a silo trailer or tanker between different loads is a contractual standard in bulk material and chemical transport for the larger producers (Borealis, Synthos, INEOS, LG Chem, SABIC). No documented washing = refusal of loading.

ECTA code	Cleanliness standard	Procedure	Time
A	Food / medical / pharma	Wet washing + food-grade detergent + drying	4-6 h
B	Premium chemicals, virgin polymers	Standard wet washing + drying	2-3 h
C	Standard chemicals, regranulates	Dry or basic wet washing	1-2 h
D	Minerals, untreated bulk	Dry washing + visual inspection	30-60 min
E	After cement, gypsum	Intensive wet washing (PHS Magnum does NOT perform)	n/a

Why washing matters

Every gram of residual material from the previous load in a silo trailer creates a risk of cross-batch contamination at the end consignee. Real-world consequences:

PE-LD granulate for food film production + lime residue from the previous load = alkaline inclusions in the film = the consignee rejects the batch, a claim worth tens of thousands of euros in material.
Medical-grade PA66 + residues of a regranulate of unverified history = unacceptable for the medical industry, batch withdrawn.
Bottle-grade PVC + technical carbon black residue = dark spots in the bottles, acceptance refused.

For a premium granulate producer, the cost of one silo trailer wash (a few hours of operator work plus utilities) is many times lower than the cost of a complaint from one end customer. Hence the contractual requirement.

ECTA cleaning codes A-E — the details

ECTA (European Chemical Transport Association) introduced a classification that has become the de facto standard in the EU.

Code A — Food / Medical / Pharma

Receiving materials: bottle-grade PET, medical PA, polymers for food-contact packaging, pharmaceutical sublimates, food additives.

Procedure:

Preliminary blow-down with compressed air (removing loose material)
Wet washing with water at 100-200 bar
Food-grade detergent (e.g. Diversey Suma, Ecolab Topax)
Rinsing with demineralised water (eliminating detergent traces)
Drying with compressed air heated to 60-80°C until RH<10% inside the chamber
Microbiological check (optional, for pharma)
Certificate with a record of the drying temperature and time

Time: 4-6 hours. Cycle: cannot be repeated any faster.

Code B — Premium chemicals / virgin polymers

Receiving materials: virgin-grade PE/PP/PA, PC, PMMA, premium additives, high-standard chemicals.

Procedure:

Blow-down with compressed air
Wet washing with water + standard detergent
Rinsing with mains water
Drying with compressed air until RH<20%
Visual inspection with a torch
CEFIC Cleaning Document certificate

Time: 2-3 hours.

Code C — Standard chemicals / regranulates

Receiving materials: PE/PP/PET regranulates, second-category chemicals, materials without a food-grade requirement.

Procedure:

Blow-down with compressed air (or basic wet washing if the previous load was contaminating)
Visual inspection
Standard certificate

Time: 1-2 hours.

Code D — Minerals / untreated bulk

Receiving materials: lime, chalk, urea, salt, technical carbon black.

Procedure:

Blow-down with compressed air
Visual inspection
Standard certificate

Time: 30-60 minutes.

Code E — After cement / gypsum

Contaminating materials: cement, gypsum, hydraulic materials, highly abrasive silica.

PHS Magnum does not transport cement — which eliminates this problem. A silo trailer that has ever carried cement requires months of intensive washing to return to standard B. Most polymer producers will not accept a silo trailer with a cement history.

The washing procedure at PHS Magnum

Bays in Chorula

We have 2 dedicated bays:

Bay 1 — dry washing: pneumatic blow-down bay, 6 bar compressor, 50 kPa industrial vacuum cleaner
Bay 2 — wet washing: 200 bar high-pressure pump, water heater up to 80°C, water recovery system with separators, hot-air drying system

Standard workflow

Pre-wash: the silo trailer driver enters into the log book: vehicle number, previous load, planned next load, required ECTA code
Procedure decision: the washing operator verifies the required cleanliness level and prepares the appropriate bay
Washing: according to the ECTA procedure (dry or wet)
Drying: especially after wet washing, until RH<20% (food-grade <10%)
Visual inspection: operator + optionally the driver, torch and mirror in the chamber
Certificate: printed with the registration number, ECTA code, date, time, operator
Documentation: a copy on file, the original + 2 copies to the driver (CMR + CEFIC copy)

Internal quality control

Every quarter:

Audit of 10 randomly selected washing operations (documentation completeness)
Checks on pressures, temperatures, detergent dosing
Contamination tests — samples from washed chambers before the next loading

External audit: ISO 9001:2015 annually.

The most common washing mistakes

Aeration pads skipped

Material settles not only in the main chamber but also in the aeration pads (porous elements at the bottom). Washing the chamber alone without exposing the pads = frequent contamination. PHS Magnum always inspects the pads visually + blows them through with compressed air from the underside.

Insufficient drying after wet washing

Residual moisture in the chamber (RH>30%) + a next load of hygroscopic granulate (PA, PET) = the material clumps during transport, a complaint at the consignee. Drying must be thorough — especially for PA.

The discharge hose

The operator washes the chamber but forgets the 4" hose. Material residue in the hose contaminates the first 5-10 m³ of the next load. Procedure: disconnect the hose, wash it separately, dry it.

No tilting of the silo trailer during drying

Static drying leaves droplets in certain spots of the chamber. Standard: the silo trailer slightly tilted during drying (a 5° tilt makes residual water flow down to the outlet).

The cleanliness certificate — what it contains

The full CEFIC Cleaning Document, adapted to Polish practice, covers:

Silo trailer identification: registration number, TDT registry number, model, chamber capacity
Washing operation: date, start/stop time, ECTA code (A-E)
Previous load: type of material, last unloading date
Procedure: dry / wet / combined washing
Detergent: trade name, manufacturer, concentration (for wet washing)
Drying temperature: maximum and final
Post-drying humidity: RH inside the chamber
Visual inspection: positive / negative (with a description of non-conformities)
Operator: name, surname, signature
Certificate number: unique, sequential ID

The document in 3 copies: driver, end customer (with the load), PHS Magnum archive.

Washing external clients’ silo trailers

PHS Magnum also provides the washing service for:

Transport companies whose silo trailers pass along the A4
PHS Magnum clients during a service visit (TDT, repair)
Bulk material importers whose terminals have no wash of their own

Pricing: depending on the ECTA code, chamber diameter and required documents — ask for a quote.

Waiting time: typically 24-48 hours’ notice, up to 72 hours in the peak season (May-October).

Investment vs the cost of skipping it

A polymer granulate producer has a typical “cost of quality”:

The cost of washing a silo trailer before its load (code B): a few hours of work plus a short delay
The cost of a 24 t batch rejected by the end customer: tens of thousands of euros plus reputational damage
The cost of the producer’s annual CEFIC audit: a significant recurring expense

That is why the contractual requirement of washing before every load is the cheapest quality insurance a producer can buy. PHS Magnum builds its position on this principle.