Pall Ring Packing · Technical Reference & Specifications

Product Overview

A Pall ring is a random tower packing formed as a short cylinder whose diameter is equal to its height. Two rows of staggered windows are punched through the cylinder wall, and the material displaced from those windows is bent inward to form tongues. The ring is produced as a single piece — moulded in plastic, or fabricated from strip in stainless steel — and it is supplied in a range of diameters for dumped beds.

The form is an evolution of the plain Raschig ring. A Raschig ring is a closed cylinder with open ends, so gas passes through a relatively small free area and the liquid tends to run down the wall in fixed paths. Punching the wall of the same nominal cylinder opens the structure up, and turning the displaced material inward converts it into contact surface instead of discarding it. That is the design intent published for this packing class, and it is the reason the Pall ring replaced the plain ring in most absorption, scrubbing and stripping duty where a dumped packing is used.

This page describes the packing class and the product form we supply. Measured performance depends on the column diameter, the packing height, the liquid distributor, the gas and liquid loadings and the medium itself, so we do not publish pressure-drop, efficiency or removal figures for this product. The parameters that depend on size, material or batch are stated as on request and are confirmed in the quotation.

Geometry & Structure

The ring is a cylinder with a height equal to its diameter, so a dumped bed sits without a preferred orientation and no stacking pattern has to be maintained. Two rows of windows are punched around the wall at staggered positions, which means that a window in the upper row does not sit directly above a window in the lower row. The displaced material from each window is turned inward as a tongue that projects into the bore of the ring.

That geometry produces the behaviour the packing is chosen for:

• More free area for the gas — the punched wall leaves a largely open frame instead of a closed tube, so the path available to the rising gas is larger than in a plain ring of the same nominal diameter.
• Renewal of the liquid film — the inward tongues intercept the descending liquid and re-spread it across the wall and the inner surface, so the film is refreshed rather than channelling down one path.
• Contact surface on both sides of the wall — the outer wall, the inner wall and the tongues all carry liquid, so the wetted area is used on the inside of the ring as well as on the outside.
• Resistance to nesting and plugging — the staggered windows, and the absence of fine openings or large continuous flat plates, make it difficult for rings to nest into one another or for particulate to lodge in the bed.
• Straightforward loading and unloading — the bed is filled by dumping the rings in bulk and can be unloaded, washed and re-loaded, which is what makes the packing practical for repacking work.

The wall form in the rings we supply follows this standard geometry: cylindrical body, two rows of staggered windows, inward-formed tongues. Photographs of the actual rings made for your order are available before dispatch.

Specifications

Type	Size d × H × δ / mm	Bulk density / kg/m³	Surface area / m²/m³	Void space / %	Dry packing factor / m⁻¹	Packing count / pcs per m³
Metal Pall ring — 1Cr18Ni9Ti · 0Cr18Ni9 · 304 · aluminium alloy
16 × 16 × 0.8	216	240	94	300	143,000
25 × 25 × 0.8	427	219	94	250	56,900
38 × 38 × 0.8	365	130	94	150	13,000
50 × 50 × 1.0	390	112	95	130	6,500
76 × 76 × 1.2	313	70	95	80	1,860
Plastic Pall ring — PP · R-PP · CPVC · PVDF · PFA
16 × 16 × 0.8	141	287	91	250	112,000
25 × 25 × 0.8	100	194	89	294	63,500
38 × 38 × 0.8	98	155	89	220	15,700
50 × 50 × 1.0	87	112	89	146	7,000
76 × 76 × 1.2	71	73	90	90	1,930
Ceramic Pall ring
25 × 25 × 3	680	260	78	—	50,000
50 × 50 × 5	430	135	74	—	6,500
80 × 80 × 8	610	110	70	—	1,900

Why these values are stated as on request

Surface area, void space, packing count and bulk density all move with the nominal diameter, the wall thickness and the material, and published figures for the same nominal size differ between suppliers. Rather than publish a table that describes the class in general and may not describe the rings that reach your site, we state the value we can guarantee for your order and confirm it in the quotation. Price is always on request.

Materials & Service Conditions

Polypropylene is the standard material for this packing and is supplied in pigmented white and in semi-transparent natural form, both of which are shown in the gallery on the product page. Stainless steel is used where a plastic packing would not hold up — higher temperatures, aggressive media or a requirement for a metallic packing in the column. Tell us the composition, the concentration and the temperature of the stream and we will confirm the grade.

Type	Size d × H × δ / mm	Bulk density / kg/m³	Surface area / m²/m³	Void space / %	Dry packing factor / m⁻¹	Packing count / pcs per m³
Metal Pall ring — 1Cr18Ni9Ti · 0Cr18Ni9 · 304 · aluminium alloy
16 × 16 × 0.8	216	240	94	300	143,000
25 × 25 × 0.8	427	219	94	250	56,900
38 × 38 × 0.8	365	130	94	150	13,000
50 × 50 × 1.0	390	112	95	130	6,500
76 × 76 × 1.2	313	70	95	80	1,860
Plastic Pall ring — PP · R-PP · CPVC · PVDF · PFA
16 × 16 × 0.8	141	287	91	250	112,000
25 × 25 × 0.8	100	194	89	294	63,500
38 × 38 × 0.8	98	155	89	220	15,700
50 × 50 × 1.0	87	112	89	146	7,000
76 × 76 × 1.2	71	73	90	90	1,930
Ceramic Pall ring
25 × 25 × 3	680	260	78	—	50,000
50 × 50 × 5	430	135	74	—	6,500
80 × 80 × 8	610	110	70	—	1,900

The two PP values are the resin properties published for polypropylene tower packings of this class. They describe the material itself and are not a guarantee for a specific aggressive medium; service temperature and service life for a given duty are confirmed with the order. We do not publish a nominal service life for this product.

Operating Characteristics

The characteristics published for this packing class, in the vendors' own terms, are:

• A large free area through the punched wall, which holds the resistance to gas flow down and allows a high throughput for a given column diameter.
• A low pressure drop, which reduces the duty on the fan or blower serving the column.
• Renewed liquid distribution from the inward tongues, so the wetted surface is used more fully and the gas–liquid contact is more uniform across the bed.
• Good resistance to plugging and to nesting of the rings, which keeps the bed open over time and makes the packing suitable for streams carrying solids or polymerisable material.
• A low unit weight compared with ceramic or metal ring packings of the same size, which keeps the load on the packing support and on the vessel structure down.

These are design-intent statements published by vendors of the packing class, not measured results for a particular column. Actual pressure drop, flooding behaviour and separation efficiency depend on the column diameter, the packing height, the liquid distributor, the gas and liquid loadings and the medium. We do not publish efficiency or removal figures for this product — the correct approach is a design check against your duty, which we carry out on request.

Applications

Random tower packing of this class is used mainly for gas–liquid contact in packed columns, and for stripping, degassing and deaeration duty in water and wastewater treatment:

• Absorption, washing and scrubbing towers; acid-mist and waste-gas treatment.
• Flue-gas desulphurisation and other absorption columns.
• Stripping, degassing and deaeration of water and process streams; CO₂ removal in decarbonation towers.
• Odour control units and bio-trickling filters where a durable dumped packing is needed.
• Distillation, rectification and liquid–liquid extraction; solvent recovery.
• Cooling towers and direct-contact heat transfer columns.
• Repacking of existing columns where a low-pressure-drop, non-plugging packing is required.

Ordering Information

To quote accurately we need the following, and price is always confirmed on request rather than published:

• Column or tower internal diameter and the packing height required.
• Gas and liquid flow rates, and the liquid distributor type.
• Medium composition and concentration; operating temperature and pressure.
• Target: scrubbing efficiency, pressure-drop limit or flooding margin.
• Material preference — polypropylene, semi-transparent PP, or stainless steel of a stated grade — and the nominal size.
• Quantity in m³, plus the destination port and the preferred packaging.

Send these details through the contact page and we will reply with the confirmed size, material, the packing parameters we can guarantee for the batch, and the commercial terms.

Type	Size d × H × δ / mm	Bulk density / kg/m³	Surface area / m²/m³	Void space / %	Dry packing factor / m⁻¹	Packing count / pcs per m³
Metal Pall ring — 1Cr18Ni9Ti · 0Cr18Ni9 · 304 · aluminium alloy
16 × 16 × 0.8	216	240	94	300	143,000
25 × 25 × 0.8	427	219	94	250	56,900
38 × 38 × 0.8	365	130	94	150	13,000
50 × 50 × 1.0	390	112	95	130	6,500
76 × 76 × 1.2	313	70	95	80	1,860
Plastic Pall ring — PP · R-PP · CPVC · PVDF · PFA
16 × 16 × 0.8	141	287	91	250	112,000
25 × 25 × 0.8	100	194	89	294	63,500
38 × 38 × 0.8	98	155	89	220	15,700
50 × 50 × 1.0	87	112	89	146	7,000
76 × 76 × 1.2	71	73	90	90	1,930
Ceramic Pall ring
25 × 25 × 3	680	260	78	—	50,000
50 × 50 × 5	430	135	74	—	6,500
80 × 80 × 8	610	110	70	—	1,900

Compiled from the published product description and structural definition of the Pall ring packing class, together with the material we supply and our order conditions. Every parameter that depends on size, material or batch is stated as on request and is confirmed per order.