What is the basic difference between a tanker and a silo trailer?

A tanker has a horizontal tank with a round or elliptical cross-section, designed for transporting liquid materials (fuels, liquid chemicals, water, milk, juices, oils) — discharged by gravity or pump. A silo trailer has a vertical or slightly tilted cylindrical tank for dry bulk materials (granules, minerals, urea) — discharged pneumatically through aeration pads. These are two different designs for different media.

Can bulk materials be carried in a tanker?

Only to a limited extent — some tankers have a pneumatic-gravity system and can carry certain bulk materials (road salt, sand), but these are exceptions. Specialist tankers for dry bulk are called 'bulk tankers' — functionally close to silo trailers, but less common. As a rule: tanker = liquids, silo trailer = dry bulk.

What is the capacity of a tanker vs a silo trailer?

Fuel tanker: 25-36 m³ (typically 30 m³). Chemical tanker: 20-32 m³. Silo trailer for dry bulk: 30-65 m³ (typically 60 m³). The larger capacity of the silo trailer comes from two factors: (1) the vertical cylindrical tank uses the space within the vehicle envelope better, (2) bulk materials have a lower density than liquids — more m³ at the same GVW. Net payload: tanker 22-26 t, silo trailer 25-27 t.

Does PHS Magnum operate tankers and silo trailers?

In our own transport we use silo trailers exclusively (Schmidt Polska, Spitzer, Feldbinder) — a fleet of 31 for bulk materials. We do NOT provide liquid transport by tanker. But in our workshop we SERVICE tankers: TDT inspections, tank repairs, paint renovation, welding. Clients with road tankers come to us for periodic inspections and larger repairs.

When do I need a tanker, and when a silo trailer?

Tanker: fuels, oils, chemical solutions (acids, bases, solvents), dairy products, beverages. Silo trailer: polymer granules (PE, PP, PA), regranulates, minerals (lime, chalk, talc), urea, carbon black, coal dust. Rule of thumb: if the material flows under its own weight at room temperature (pumpable) — tanker. If it is dry and free-flowing (pourable) — silo trailer.

How does the discharge differ?

Liquid tanker: gravity discharge through a bottom valve or by pump (1-3 bar, on-board or stationary). Discharge time for 30 m³ of fuel: 20-40 min. Silo trailer: pneumatic — an on-board compressor (PTO) or a stationary one pushes air at 2-3.5 bar through aeration pads at the bottom of the tank, fluidising the material and forcing it through a hose (4" Storz/PERROT M108) into the consignee's silo. Discharge time for 25 t of granules: 60-90 min.

Do tankers and silo trailers require the same TDT supervision?

Both are pressure vessels and are subject to TDT supervision under the Polish Technical Supervision Act (2000) — they require periodic inspections every 2-5 years, an inspection book and a supervisory decision. But the inspection procedures differ: a chemical tanker — strict inspection of the internal lining (compatibility with the medium), usually a lower pressure test. A silo trailer — inspection of circumferential welds and all aeration pads, pressure test at 1.25× MOP (typically around 2.75 bar for a ~60 m³ silo trailer).

17.01.2025

Tanker vs Silo Trailer – Differences and Applications

Name: PHS Magnum
Address: ul. Kościelna 9, Chorula, Opolskie, 47-316, PL
Telephone: +48 602 716 551
Price range: $$

Transloading granulate from big-bags to a silo trailer

Key takeaways

The tanker and the silo trailer are two different types of specialist semi-trailer for transporting materials in bulk. The choice depends on the state of matter: tanker = liquids and semi-liquids, silo trailer = dry bulk. We repair both types in Chorula — see silo trailer service.

Parameter	Tanker	Silo trailer
State of the medium	Liquid, semi-liquid	Dry bulk
Tank design	Horizontal, round/elliptical	Cylindrical, vertical/tilted
Typical capacity	25-36 m³	30-65 m³
Net payload	22-26 t	25-27 t
Discharge	Gravity or pump	Pneumatic (aeration pads)
Operating pressure	0.5-3 bar	2.2-3.5 bar
Typical materials	Fuels, acids, milk	PE/PP, lime, urea

Design: the fundamental differences

Tanker

Tank: usually horizontal, elliptical or round. Material: 304L/316L stainless steel for chemicals, aluminium for fuels, painted steel for water/milk. Capacity 25-36 m³. Some tankers have multiple compartments (3-4 separate chambers) for different fuel fractions.

Discharge system:

Gravity — bottom valve, natural outflow. Requires the tank to be above the receiving level. Typical for fuel tankers.
Pump — an on-board or stationary pump moves the medium from the bottom outlet. Chemical or dairy tankers — centrifugal or positive-displacement pump.

Internal lining: depends on the medium. Stainless steel for chemicals (acids, bases), epoxy coating for water/food, glass lining for highly corrosive acids.

Silo trailer

Tank: vertical cylinder tilted at ~30° (to assist the gravitational flow of material towards the outlet). Materials: painted steel (Schmidt Polska), EN AW-5083 aluminium (Spitzer SF and SK series), 304L stainless steel (Feldbinder). Capacity 30-65 m³.

Discharge system — pneumatic:

Compressor — PTO-driven from the tractor engine or stationary at the client’s site. Generates 2.2-3.5 bar.
Aeration pads (fluidising pads) — fabric or porous elements at the bottom of the tank. They let air through, fluidising the granulate — the material behaves like a liquid and flows towards the outlet.
Discharge hose — 4" diameter, typically Storz or PERROT M108. Connects the silo trailer outlet with the client’s silo.

Silo trailer specifics: all pressure components require regular TDT inspection — the safety valves (typically 2.2 bar), the aeration pads (replaced every 3-5 years depending on the material), and the manhole seals.

Materials — when to use which

Tanker only

Fuels: petrol, diesel, aviation fuel, biofuels
Oils: machine, edible, lubricating
Liquid chemicals: acids (sulphuric, phosphoric), bases (NaOH, KOH), organic solvents, formalin
Food products: raw milk, fruit juices (insulated tanker), syrups, molasses
LPG and LNG (special pressure tankers)
UAN urea solutions (liquid nitrogen fertiliser)

Silo trailer only

Polymer granules: PE, PP, PVC, PET, PA, PS, ABS, PC
Regranulates: rPET, rHDPE, rPP, rPE
Bulk minerals: hydrated lime, ground chalk, talc, bentonite, Tonsil 571 FF
Solid urea (granulated)
Technical carbon black, coal dust

Borderline cases

Road salt, sand for smooth surfaces — some multi-purpose tankers with an additional pneumatic system can handle them; specialist bulk tankers exist.
Cement — historically carried in cement tankers (a special tanker with an aeration system); today in the EU usually dedicated silo trailers. PHS Magnum does not transport cement.
Liquid lime (lime milk) — chemical tanker, never a silo trailer.

Technical supervision — TDT for both types

Both tankers and silo trailers are subject to the Polish Transport Technical Supervision (TDT):

Periodic inspections: every 2-5 years depending on tank type and medium
Pressure test: ~1.25× MOP (for a ~60 m³ silo trailer with a MOP of 2.2 bar = about 2.75 bar)
Weld inspection: PT (penetrant) or UT (ultrasonic) depending on the inspector’s decision
Inspection book: every silo trailer/tanker must have a current entry

Without a valid TDT decision the vehicle may not be operated — a road inspection spots this immediately. Details: TDT inspections of silo trailers and TDT inspections of tankers.

Tanker and silo trailer service at PHS Magnum

PHS Magnum services both types of pressure vessels:

Tankers (mainly chemical and fuel)

Periodic TDT inspections — preparation + attendance of the inspector
Tank repairs — stainless steel welding (TIG), straightening after an accident
Internal lining renovation — when changing the medium (e.g. fuel tanker → chemical tanker)
External paint renovation

Details: tanker service and TDT inspections of tankers.

Silo trailers (our core specialisation)

Aeration pad replacement (the most common repair)
Repair of safety valves and manhole seals
Welding of aluminium tanks (Spitzer SF and SK series) and stainless steel tanks (Feldbinder)
Paint renovation for Schmidt Polska and other painted-steel tanks
TDT inspections with documentation

Details: silo trailer service and Spitzer/Feldbinder spare parts.

Can PHS Magnum transport by tanker?

No — the PHS Magnum fleet consists exclusively of silo trailers for bulk materials (Schmidt Polska, Spitzer, Feldbinder). We do NOT provide transport of liquids or liquid chemicals by tanker. For clients needing liquid chemical transport we cooperate with industry partners (specialist carriers).

In the workshop, however, we service both categories — including tankers registered to other companies. We complete the TDT documentation, run the inspections and carry out the repairs.

Typical client questions about the choice

Q. “I need to move a lime solution — tanker or silo trailer?”
A. Tanker — lime milk is liquid (a suspension) and requires pump discharge, not pneumatic.

Q. “Urea in solution and in granules — different vehicle?”
A. Yes. Granulated urea (a typical fertiliser) — silo trailer. UAN (32.5% urea solution) — chemical tanker.

Q. “Can I use a tanker for suspension PVC?”
A. No — PVC-S is a dry powder (50-200 µm) and requires a silo trailer. A tanker has no aeration system enabling discharge.

Q. “Cement in a cement tanker or a silo trailer?”
A. In Poland, ‘cement tanker’ historically meant a special cement tank with a pneumatic system. Today it is a synonym for a cement silo trailer. PHS Magnum does NOT transport cement — it is a heavily contaminating material.

Contact

Bulk material transport (silo trailers): +48 602 189 394
Tanker service (TDT, repairs): +48 504 788 385 (Roland Sobota — TDT)
Silo trailer service + spare parts: +48 602 716 551

E-mail: biuro@magnumchorula.pl

Related: Silo transport — a guide · What we carry by silo trailer · Tanker service · Silo trailer service · TDT inspections of silo trailers · TDT inspections of tankers

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