About CRP

CRP (Corrosion Resistant Products) is an independently owned company which has been supplying PTFE lined products to the chemical, pharmaceutical and associated process industries since 1983.

We manufacture PFA lined pipe fittings using carbon steel castings and an automated transfer moulding process at our company headquarters located in a major manufacturing region of the UK, Greater Manchester. At this site we also make paste extruded PTFE liners using one of the most advanced thick wall PTFE liner extrusion processes in Europe. These liners are used to produce lined pipe spools up to 300mm (12inch) nominal bore at our plant and by our authorised manufacturing distributor, ConSys Enterprise in Singapore, both locations operating manufacturing processes to fully accredited ISO9001:2000 quality systems.

Since the first days of our company we have always set out to supply products of the highest quality as we know they are used for handling both high value and potentially hazardous fluids. We supply the Atomac range of lined ball valves, renowned world wide for its superior performance in demanding applications. Over the ensuing years we have progressively added our own range of products produced at our integrated manufacturing centre. We keep all polymer lining processes completely in house and provide 100% traceability on every component manufactured by us.

Many of our customers have long term supply agreements with us and we provide a wide range of project support services as added value to ensure the most cost effective procurement and materials management is achieved. We have innovative new designs of sampling systems available, many of which are the result of working closely together with our customers to help solve their sampling problems. Our extremely high precision transfer moulding capability and our ability to manage component supply through kan ban controls has led to us developing a thriving sub contract lining and moulding business providing very high quality lined components which are incorporated in our customers products and supplied world wide.

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CRP is an ISO 9001:2008 approved company. Originally accredited to BS5750 Part 1 in 1992, CRP has maintained this accreditation since then, through a process of continuous third party surveillance with, six monthly, annual and triennial audit taking place. All of the company’s manufacture and test procedures fall within this regime.

CE Marking On the 30th of May 2002, it became mandatory that all pressure equipment covered by the Pressure Equipment Directive (brought into UK law as the Pressure Equipment Regulations), be compliant with its requirements when placed on the market. Under the requirements of the regulations, all of CRP’s products fall into the “piping” (as opposed to “vessels”) category. Some products are “pressure accessories” but in these cases their nominal bore is more important than their volume, and so are treated in the same way as piping.

CRP’s products are designed to handle group 1 fluids (toxic, flammable, oxidising etc), and are designed to cope with liquids and gases (as opposed to liquids only). Therefore, we have assessed our products against Table 6 in the regulations. This means that all of our products above 1”NB have to be CE marked. All products of 1” and below must not be CE marked – they fall into the “Sound Engineering Practice” category of the regulations. For products of greater than 1” NB, they fall into category I, II or III depending upon their nominal bore and pressure rating (There is a category IV, but it is only relevant for vessels).

To make getting and maintaining certification simple, CRP has opted to be assessed against the requirements of Module H (full quality assurance module for design, manufacture and testing, based upon our ISO 9000 quality management system) which covers category III products, but which can also be used for category I and II products. In addition, although we cannot put our category I and II products into category III, they are manufactured as though they were in category III.

As proof that products are CE marked, CRP has opted to put a CE mark on every item it manufactures (excluding 1” and below NB). This marking takes the form of either an indelibly printed adhesive label, or high temperature plastic tag. Nb. For type 1 spacers and solid PTFE spectacle blinds, since it is impossible to mark the products, the label is attached to the bag in which the product is placed.

Each order of product is sent out with a set of “User Instructions” (a booklet of instructions covering all of CRP’s products), and which contains a copy of our “Declaration of Conformity”. We also have a certificate from our Notified Body (HSBIQ) to say that we have been successfully assessed against the requirements of Module H. The one exception to our CE marking policy is field flare spools.

After discussions with the DTI and the HSE, we have agreed that we cannot CE mark them, because they are not a finished manufactured item. Rather, we have produced a “Technical Note” to provide purchasers with the information they require, thus allowing them to CE mark field flare spools once they have finished manufacturing them. All Flowserve products (Atomac and Durco) are CE marked. As with CRP products, each individual valve has a CE mark on it, and each order for Flowserve products is sent with a set of Operating Instructions.

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Processes

The key manufacturing processes are the paste extrusion of PTFE pipe liners and their subsequent fitting into pipes, fittings or dip pipes, and the moulding of fittings using PFA.

Paste Extrusion

For paste extrusion CRP has a climate controlled blending plant for the cold conditioning of PTFE and its subsequent mixing with a hydrocarbon liquid which acts as a processing agent. After a period of at least 48 hours of warm conditioning the material is ready for extrusion.

The first stage of paste extrusion is the manufacture of a billet weighing anything between 5 and 85kg. (11 and 187lb.) on a PLC controlled preform station. This soft waxy material is then transferred to the extruder proper and loaded into the barrel. Using polished aluminium tooling the PTFE is worked and extruded under great pressure into and over stainless steel support tubes. A number of lengths are extruded to complete a batch. These are then loaded into an oven for sintering. The sintering process takes 13 hours, after which the oven can be unloaded and the liners are ready for use – following materials testing.

CRP has two paste extrusion plants and associated ovens capable of producing liners from ½” to 12” (DN10 to DN300) in both virgin and static-dissipating PTFE resins.

PFA Moulding

PFA is a melt processable fluoropolymer resin that provides all of the desirable properties of PTFE and more, whilst being capable of processing by conventional thermoplastic techniques. This includes transfer moulding – the process used by CRP.

Since high temperature chemical service is very demanding of any polymer, special high viscosity grades have been developed to maximise the performance of a lined component in both extreme harsh chemical and high/low temperature environments.

Because of the flow characteristics of these resins, high viscosity and very low critical shear rate, transfer moulding techniques conform best with such processing requirements.

Transfer moulding differs from injection moulding in that the mould temperature is above the melting point of the resin, also that the resin can be melted statically (in a melt pot) or dynamically in a plastification unit.

CRP has a number of transfer moulding machines, with both static and dynamic plastification units. The static plastification units are used for large sized components and one off specials, whilst the dynamic plastification units produce the higher volume and high precision components. The dynamic plastification units referred to colloquially as “screw-melt machines” are equipped with PLC controls enabling automated control of the complete moulding cycle, including mould filling, injection speed and pressure and all aspects of mould cooling.

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Fluoropolymers

Fluoropolymers are ideal for pharmaceutical and biopharmaceutical processing equipment because they have excellent chemical and thermal resistance. Their molecules have continuous non-reactive surfaces and are compatible with virtually all chemicals and solvents. They are far more resistant to chemical attack than conventional chlorinated and hydrocarbon polymers, and have far higher service temperatures.

There are a number of materials in the Fluoropolymer family. PTFE (Polytetrafluoroethylene) is the original Fluoropolymer, discovered by DuPont in 1938. From this original development there have been a number of other materials developed – trying to improve on the difficult processing characteristics of PTFE. These have been more or les successful, having to trade properties of PTFE in order to attain other characteristics. The principal materials used in the industries that we serve are:

• PTFE
• PFA
• FEP
• PVDF
• Chemraz

PTFE

PTFE is not melt-processable and therefore usually needs to be formed into the required shape prior to sintering.

PTFE comprises both carbon and fluorine atoms, as a straight chain molecule, the carbon backbone being protected by a helix of the fluorine atoms wrapped around it. This carbon fluorine bond is one of the strongest chemical bonds and gives the material its properties of corrosion resistance and non-stick.

Key properties of PTFE

Chemically Inert

PTFE resists the most aggressive organic and inorganic chemicals and solvents over a broad temperature range. This includes:

• Strong mineral acids
• Inorganic bases
• Inorganic oxidising agents
• Salt solutions
• Aldehydes
• Chlorocarbons
• Organic Acids
• Anhydrides
• Aromatics
• Alcohols
• Ketones
• Esters
• Fluorocarbons

Electrical Properties

The ability to resist an electrical charge is measured by surface and volume resistivity. In the case of PTFE these figures are colossal. Depending upon how the test work is performed, values in excess of 1017Ω cm are considered minimum. In the case of equipment lined for the chemical and pharmaceutical industry this property can be a nuisance as PTFE lined equipment may build up electrostatic charges and be unable to dissipate them. This is considered elsewhere in relation to static-dissipating materials.

Low Friction

PTFE has a very low coefficient of friction and for all calculation purposes it can be considered hydraulically smooth.

Thermal Stability

PTFE retains useful properties (i.e. not more than 15% loss of chemical resistance) at up to 200oC and sometimes beyond depending upon the application. In fact it has the highest retention of its chemical properties of any known plastic like material (Please be wary of materials performance data stating that PTFE has an upper service limit of 260 oC. This is true in a laboratory situation, but in service most material properties such as mechanical strength will have been lost preventing it from performing a useful duty.)

PTFE Paste Extrusion

CRP uses the most expensive grades of PTFE. These are coagulated dispersions, often referred to as fine powders. These have a very close process control of grain size range and are uniquely capable of being sheared by lubricated paste extrusion into a coherent fibrous matrix with useful structural integrity. Pipe liners for the chemical and pharmaceutical industry are almost universally manufactured from PTFE. The paste extrusion process provides the highest level of surface finish, the highest resistance to permeation and the closest dimensional control of all of the methods of lining in PTFE. This serves to differentiate what we manufacture from processing technologies using lower quality and priced materials – being ram extrusion, mandrel wrapping and isostatic moulding.

Paste extrusion however is only suitable for making straight lengths of PTFE tubing colloquially known as pipe liners in our industry. It can be subsequently manipulated into bends and other simple forms, but is not capable of lining complex shapes without joints.

PFA

PFA (Perfluoroalkoxy) was developed in order to achieve a true melt-processable fluoropolymer. Its characteristics are such that in service it can be considered as interchangeable with PTFE in terms of its chemical service and temperature and pressure duty. It has the highest permeation performance of the fluoropolymers, exceeding that even of paste extruded PTFE. It also provides the smoothest and least wettable finish of all of the Fluoropolymers. Unfortunately the trade-off is cost, the material being more expensive than PTFE. CRP uses PFA in the production of most of its lined fittings and the Flowserve range of Atomac and Durco valves are available lined in PFA.

FEP

FEP (Fluorinated Ethylene Propylene) is another melt-processable Fluoropolymer. It does not have the almost universal chemical resistance of PTFE and PFA and its maximum operating temperature in service is 150oC. CRP uses the material occasionally for the manufacture of “sheet lined products”. This is essentially a lining made up of sheet and tube elements of FEP welded together in situ. Sheet lining allows one to line complex articles without the use of expensive moulding tools, to cope with the inevitable tolerance errors of welded fabricated steelwork and with the use of bonded linings to provide a degree of vacuum performance. Where the chemical performance and temperature duty are not an issue, the material provides a less expensive alternative to PFA. Flowserve manufacture the Atomac range of valves lined in FEP.

PVDF

PVDF (Polyvinylidene difluoride) is an engineering fluoropolymer and has a more limited range of chemicals performance and an upper temperature limit of 120 oC. Although replaced in many applications by the improved performance of PTFE resins, it remains the material of choice for low temperature halogen applications – Bromine and Chlorine.

Chemraz

Chemraz® is a perfluoroelastomer and is a proprietary compound manufactured by Greene Tweed. It is used specifically in the manufacture of seals, combining the resilience and sealing force of an elastomer with chemical resistance approaching that of PTFE. CRP uses Chemraz 505 seals in the manufacture of sampling systems.

Glass / Alloys

Borosilicate Glass

Borosilicate glass has a very high resistance to attack from water, acids, salt solutions, halogens and organic solvents. It also has a moderate resistance to alkaline solutions. The chemical resistance of DURAN® exceeds that of most metals and other materials even where long exposure times and temperatures in excess of 100°C are involved. Exposure to water and acids only results in the leaching out of very small amounts of mainly univalent ions from the glass. The resultant very thin layer of silica with few pores in it that is formed on the surface inhibits further attack. DURAN® has very high resistance to attack by water, neutral and acid salt solutions, strong acids and mixtures thereof, and also chlorine, bromine, iodine and organic substances.

Hastelloy C276

Hastelloy C276 alloy has excellent corrosion and erosion resistance to an extremely wide range of chemical process environments, including strong oxidizers such as ferric and cupric chlorides, hot contaminated media (organic and inorganic), chlorine, formic and acetic acids, acetic anhydride, and seawater and brine solutions. C276 alloy has excellent resistance to pitting and to stress-corrosion cracking. Hastelloy C276 alloy is a nickel-molybdenum-chromium wrought alloy that is a very versatile corrosion resistant alloy because of this versatility it is ideally used in multi-purpose plants.

Materials Suppliers

It is worth stating that CRP only use fluoropolymers from well respected global producers. This provides confidence in the raw materials in terms of their standards, both quality and consistency of materials and product traceability.

Housings

Pipe Spools and Fabricated Fittings

Pipe spools are manufactured using carbon steel rated for pressure containing purposes. These are either provided with integral stub ends behind which we mount a flange – referred to as Van Stone or Conrac spools, or a welded flange or stub end combined with a loose or rotating flange. Fabricated fittings are made from a combination of carbon steel pipe, forgings, flanges and stub ends. All welding activities are undertaken using “coded” welders.

Cast Fittings

Where CRP differs significantly from the competition is that the majority of pipe fittings are manufactured as investment cast carbon steel components. This has significant advantages over the use of fabrications or iron castings. The dimensional control of the component is extremely accurate. This in turn allows for accurate assembly on site and from a manufacturing perspective ensures a more consistent lining thickness improving product integrity. The lack of welding is an advantage – eliminating a potential source of weakness and the casting is an extremely strong construction in its own right. Not only are those essential elements of the casting machined, but attention to detail improves the product – the rear face of flanges is machined improving bolting and all holes and edges are chamfered for ease of product handling. An additional advantage of castings are that the manufacturers details, product identification and foundry markings are clearly shown.

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CRP has been manufacturing lined equipment for twenty years, but this still makes us the youngest true manufacturer. This has provided us with a number of advantages.

With hindsight we have been able to incorporate all of the best aspects of modern design and set out to manufacture a single standard of product, rather than be stuck with practices from the early development of lined piping systems. In particular we have been able to adopt modern polymers, modern lined equipment wall thickness’s and the best practices for housing manufacture. The company has been independent throughout its life and has not been forced to follow any technology licensing practices.

The principal focus for our design is for corrosion performance at temperature. Other materials properties such as non-stick, purity and low-friction although beneficial are secondary considerations.

The core product range has been designed to withstand full vacuum as opposed to having a number of product standards. It has been designed to use investment cast steel fittings as housings, as they provide great accuracy, high strength, are weld free repeatable and a more aesthetically pleasing component.

CRP have selected the best technologies for the lining processes. PTFE paste extrusion as it produces the best pipe liners for chemical performance, permeation resistance and surface finish. PFA, because of its melt characteristics allowing us to form complex shapes, its translucency, surface finish, geometric accuracy and vacuum performance.

Moreover, CRP continues to invest production time in collaboration with major polymer producers to develop extrusion grades of PTFE and thermally stabilised grades of PFA.

Design Choice

The Lined Equipment Specification

The original CRP specification was a requirement to meet the ASTM standard F423. This has now been superseded by F1545. This is the basic design standard for PTFE lined pipe and fittings and apart from a restricted DIN standard and some national standards such as in Japan (JIS), it is the only worldwide standard for lined pipe and fittings.

CRP also decided to meet the design standard for the then largest user in the UK – the ICI company. They had a piping standard considered to be more stringent than F423. This ICI standard formed the basis for a great number of specifications around the UK.

These design standards fixed the physical standards for the materials. They determined how the housings should be made, their accuracy, the quality and performance of the liners and most importantly how the parts should be type tested and tested in manufacture. Type testing comprises subjecting representative production samples to extended periods of heating and cooling, steam cycling and vacuum resistance testing. All of this is inspected by an independent third party.

Pipework and Fittings

CRP elected to use the accepted design standards for pipework and fittings using ASME Class 150 flanges. Concerning the dimensional standard CRP uses ASME B16.5 Class 150 where there is a definition and elsewhere looks to other industry norms where there is no international standard.

Materials

CRP decided to go for materials with a proven track record and suitable for use in food and drugs contact. FDA (US Food and Drug Administration) are the internationally accepted body for determining the suitability of materials for these uses and CRP only use FDA compliant materials as wetted parts. The only exception to this is in the use of static dissipating (anti-static) materials where only certain grades of PTFE and no grades of PFA are FDA compliant.

CRP elects to use a small number of suppliers with well controlled materials. All paste extrusion PTFE’s and melt processable PFA’s have gone through evaluation and approval by CRP. These materials must exceed the minimum requirements set out in F1545 – these being D4895 for paste polymers and D3307 for PFA.

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ISO 9001:2008

CRP is an ISO 9001:2008 approved company. Originally accredited to BS5750 Part 1 in 1992, CRP maintains this accreditation through a process of continuous third party surveillance with, six monthly, annual and triennial audit taking place.

All of the company’s manufacture and test procedures fall within this regime.

Download a PDF copy of our ISO9001:2008 2008 certificate here.

Pressure Equipment Directive

CRP comply with the Pressure Equipment Directive that became mandatory in May 2002

Under the requirements of the regulations, CRP has undertaken all necessary calculations and tests to conform to the PED. These have been approved by our third party notified body.

You can download copies using the links below:

EC Declaration of Conformity
EC Declaration of Conformity – Sampling

Third Party Testing

CRP has undertaken third party testing to confirm the static-dissipating properties of our lined piping.

Static_Dissipating_Fluoropolymer

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