High Pressure Equipment

for LDPE Plants

03

02

Market Leader

High pressure is spelled Uhde. Worldwide. Uhde High Pressure Technologies:

Our name is our programme. Since it

was founded in 1930, Uhde has been

exploiting the world of high pressures

for the widest possible variety of

applications. Whatever can to be solved

promisingly with high or ultrahigh

pressures arouses the curiosity and

ambition of our engineers.

Creative engineering for the LDPE worldSince the development of high pressure

processes for the industrial fabrication

of low-density polyethylene, Uhde has

played a decisive role in making these

ideas economically usable.

Uhde designs and supplies all the

essential high pressure components

of any plant from any renowned

process-licensors.

Quality creates certaintyWherever such stringent demands and

ex treme pressures are dealt with, the

obvious thing to do is to place great

emphasis on quality management as

well. A strict QM system reliably ensures

compliance with specified sequences

and quality standards. Various certificates

according to EN DIN 9001 or ASME give

our customers additional certainty.

Good workmanship relies on team effortThe people and their attitudes in tackling

tasks and requirements are decisive for

success.

Here, Uhde can rely on more than 230

motivated and competent employees

who, together with the great

effectiveness of modern machinery,

produce top perform ances.

Key responsibilities and businesspolicy We see ourselves as a partner to the users

of LDPE plants as well as to engineering

contractors and LDPE licensors. We

support them all with innovative, safe and

cost-efficient solutions for high pressure

equipment. Our customer service starts at

feasibility studies and development work

and extends through the construction and

assembly of new plants. For operat ing

plants, we guarantee lifetime after-sales

service, including spare parts and

customer advice.

Manufacturing

From Hagen to the world

Test assembly and functional tests in our

workshops

Engineering

A good place for good discussions, good

ideas, hard work and outstanding results

05

04

Our ProgrammeHigh Technology, High Quality and Excellent Service

New LDPE plants: Partnership withlicensors and engineering contractorsWe provide our experience for the

devel opment of licence packages and

equipment specifications. In many

cases, our equipment technology sets

the standards in the licensors' data

sheets. We support the engineering

contractor with excellent project

management services which make sure

that he gets the specified equipment

on time. Our broad database on

procedures, specifications and

documentation in accordance with

the different licensor/ contractor

requirements helps our partners to

save valuable engineering hours.

Existing LDPE plants: Partnership withthe userThe LDPE user can count on us for the

service life of his plant. We still fabricate

spare parts for pumps and valves which

we delivered in the forties. Our high

pressure experts are always available for

advice on equipment use while on

deploy ment to the site for assistance.

We provide state-of-the-art high pressure

equipment independently of the original

supply for the plant. We can provide

much of that equipment from stock,

such as high pressure tubes, flanges

and fittings. This saves inventory costs

for our customers. We also assist our

customers in inspecting the equipment

and advise on preventive maintenance.

Machining of high pressure components on

a boring mill with CNC in six axes

Constant quality testing of the fabricated com-

ponents and measuring tools

Welds manufactured according to all

recognised welding processes

Low-density polyethyleneThe development of the LDPE process

began in 1936 when the possibility of

polymerising ethylene at high pressure

was discovered. First of all, autoclaves

(ICI and Du Pont) were used as reactors

for the technical synthesis and, a little

later, tubular reactors (BASF and UCC)

as well.

Today, the proportion of the total

product ion of thermoplastic construction

materials accounted for by LDPE is very

high at around 20 %. Over 30 million t

of LDPE is produced every year all over

the world according to the different

processes.

Since 1955, Uhde has been designing

and fabricating for all the major

process-licensors.

Advantages of cooperation with us:The advantage of working with Uhde on

a new LDPE project or on maintenance

projects on existing plants is the

advantage of working with the market

leader. We are the supplier which has

the widest scope of equipment supply

anywhere in the world, ranging from

reactors and vessels to pumps, valves

and much more. Also, more than any

other supplier, we can count on broad

experience from coop eration with all

licensors and contractors in this

business.

Project meeting

07

06

Ultrahigh Pressure TubesStrength and Safety

High pressure tubes made by UhdeLDPE plants using the tubular or autoclave

process are built, to a large extent, from

high pressure tubes. It is the single most

important item to focus on when you

invest in new equipment. For many years,

Uhde has manufactured high pressure

tubes by drilling forged bars. But only

recently did this technology become so

successful that 9 out of 10 tubes are now

manufactured in this way. We at Uhde

are fully utilising the benefits of this new

technology in order to provide equipment

suited for the highest demands of the

new plants with a world-scale capacity.

Steel productionWe melt the crude steel in a modern

electric-arc furnace, followed by vacuum

degassing. The steel purity achieved by

this modern equipment is already very

high but can be further improved by

electro slag remelting or, for the highest

demands, by vacuum-arc remelting.

The ingots pro duced in this way then

go through the largest radial forging

machines in the world where the raw

bars are produced. The capabilities of

the steel plant cover all the requirements

in terms of metallurgical capabilities

which are necessary for the production

of materials for the LDPE process

licensors. A team of experienced

specialists is ready to always further

im prove the steel quality and to adapt

the alloys and the production technology

to the market needs. This is how our

stand ard alloy, A-723 Grade 3 mod.

(DIN 1.6959 mod.), came into being:

An alloy design focused on the required

function in LDPE high pressure duty.

MachiningPrecise machining is used in order to

obtain very narrow tolerances on the

bore diameter and the outer diameter.

This helps the process designers to

precisely determine the flow rate and

pressure drop in the tube and in the

jacket pipe. The final surface quality on

the bore which we achieve is Ra = 0.1 µm.

This quality as sures the longest service

life of the tubes. The tubes are then

finish-machined in cluding a sealing face, a

thread and a shrink-ring seat for jacketing.

AutofrettageAll high pressure tubes are subjected to

an autofrettage treatment. This operation

helps to extend the service life of the

tubes. It is carried out by exposing the

tubes to extremely high pressures close to

their burst pressure. The tube is deformed

in such a way that we achieve a high level

of compressive stress at the tube bore.

This protects the tube against cracks

developing from the inside.

Steel gradesDesignation Specification Description

A-723 Grade 3 mod. UHDE-HPM-01 standard low-alloy steel for high pressure

(DIN 1.6959 mod.) tubes PN-4000, combines high strength

with high toughness for any tube sizes

20Cr - 10Ni (HP-160) UHDE-HPT-02 High-strength austenitic stainless steel for

bore sizes from 3 to 25 mm and PN-4000

X12Cr13 UHDE-HPM-03 Ferritic stainless steel for high pressure

(DIN 1.4006 mod.) up to PN-2500

A-723 Grade 1 mod. UHDE-HPM-04 Standard low-alloy steel for high pressure

(DIN 1.6580 mod. K10X) tubes PN-4000

X4CrNiMo16-5 UHDE-HPM-05 High-strength soft martensitic stainless steel

(DIN 1.4418 mod. RM3)

Apart from Uhde works standards, tube

materials can be produced according to

any customer specification.

Sizes

Bore size Max. length possible

3 - 25 mm 7,000 mm

25 - 38 mm 10,000 mm

38 - 100 mm 17,000 mm

Quality assuranceThe complete tube manufacturing line

has been developed in order to guarantee

100 % defect-free production. Every

pro cess step is carefully monitored so

that the specifications are met. Therefore,

the tube orders can be made to the precise

number without any need to worry about

an allowance for overproduction.

Radial forging machine

09

ReactorsA New Molecule is Born

08

Tubular reactorsUhde high pressure tubular reactors can

be found everywhere in the world. Since

1955, we have delivered more reactors

to the petrochemical industry than any

other company. The first reactor had an

inner diameter of 24 mm and was

designed for a pressure of 1,600 bar.

Nowadays, Uhde builds reactors with

inner diameters of 70 - 90 mm, suitable

for pressures of up to 3,600 bar.

Likewise, the production capacities

have increased tremendously from

10,000 t/a to over 400,000 t/a.

Our advantagesDuring nearly 50 years of experience

in the construction of LDPE reactors,

we have learned to build them in

accordance with all process licences,

e.g. Lyondell Basell, Versalis, Sabtec

and Exxon Mobil. More than this, our

know-how and engineering help our

process-licensing partners to further

de velop their technology and

specification package. In the same

manner, all major engineering

companies which are active in this

industry have worked with us

successfully in building new LDPE

plants.

Autoclave reactorsWhereas tubular reactors are used for

large single line production of commodity

polymers, autoclave reactors are the

first choice for special products like

co-polymers and extrusion grades. Uhde

fabricates autoclave reaction systems

as turn-key equipment including all

accessories for reaction volumes from

250 to over 2,000 litres.

High pressure componentsOur scope of supplies includes jacketed

tubes and bends. The bends can be

produced by cold forming for large radii

or by hot forging for compact short

radius bends. All the necessary flange

connections, blocks and fittings are

supplied by us. We also manufacture

the sealings, thermocouples, injection

spargers and other high pressure

accessories. All the high pressure

equipment is subjected to the autofrettage

treatment and to rigorous quality control.

Steel structureUhde also designs and builds the steel

structures necessary to support the

reactor and the intercooler. The design

department uses advanced tools in order

to verify all the static and dynamic loads

on the steel structure. For fast and

efficient installation on site, Uhde

designs equipment in integrated

modules, combining the steel struc ture

and the process equipment.

Tubular reactor PN-3,500, DN-62

Autoclave reactor PN-2,500

11

10

ValvesExtremely Fast and Precise

Scope of valve technologyUhde valves and fittings have proven their

particular reliability and operational safety

in many fields of the chemical industry.

In LDPE plants, Uhde valves with the

pressure ratings of 325 - 4,000 bar are

used as shut-off, control, safety, check

or three-way valves. The diversity of the

drive types and the robust design of the

valves allow them to be used in all the

pressure ranges occurring in polyethylene

production. The connections can be

adapted to any internationally common

standards.

Control valvesThe control valve at the outlet of the

reactor is an essential constituent for the

process control of modern large reactors.

During the development of this control

valve, special emphasis was placed on

the demands for speed, accuracy and

a long service life.

The high stroke speed is achieved by

an electronic valve positioner and an

electronic-hydraulic transducer, designed

for rapid signal conditioning, as well as

by the special type of bearings in the

actuat ing piston.

The positions of the valve and drive

spind les are measured using a high-

resolution electronic travel transducer in

order to obtain great reproduction

accuracy. Many years of experience in

the design-related arrangement of the

seat and the cone and in the selection

of the appropriate materials led to the

achievement of long service lives. The

simple structure of the valve, in

conjunction with careful harmonisation

of the valve and control parts, results in

the highest degree of functional safety.

Hydraulic power unitIn the LDPE plant, the hydraulic valves

are supplied by an Uhde hydraulic power

unit. This station works at a maximum

operating pressure of 160 bar. The

neces sary oil reservoir is dependent on

the hydraulic valves located in the plant

and is optimised correspondingly by

Uhde. The station components such as

the hy draulic pump and the motors are

equipped with stand-by units and are

supplied by an oil/water cooling/filtering

unit in a skid-mounted design.

Valve test stationPrior to delivery, all the valves are

subject ed to pressure and functional

tests on Uhde's own valve test station.

In order to be able to perform these

tests in the plant as well (e.g. after

repairs), Uhde has a skid-mounted

valve test station in its supply

programme.

The following tests can be carried out on

the test station:

• Gas leakage test up to 4,000 bar

• Full functional testing of the valve

actuator

• Measurement of speed and accuracy

Control valve, DN 60 mm,

3,450 bar, 350°C

Emergency blow-off valve

60/60/60, 3,500 bar, 350°C

Hydraulic power unit

Valve test station

13

12

PumpsThe Heart of the Plant

components and the components

wetted by the high pressure process.

The discharge rate of the pump is

infinitely variable from zero to maximum

during standstill and also while the

pump is in operation by simply changing

the stroke frequency. Additionally, the

discharge rate may be varied during

standstill by changing the stroke length.

The patented control system (DBP

2011570) develops extremely short

plunger reversal times, thus

guaranteeing a superior pressure

amplitude and exact feed-rate control,

and leads (e.g. in the case of catalyst

injection) to a very good reactor

temperature stability of up to

± 0.1°C.

4-plunger pumps consist of two

separate HP units operated individually

by one single hydraulic drive. One unit

is in operation and the other in a

stand-by mode.If the stand-by unit is to

be put into operation, it can be brought

up to the operating pressure by a

prepressurising system. Thus, the

second unit can be started im mediately

without influencing the reactor

temperature.

The so-called Uhde HP-4-Plunger

"twin pump" consist of two independent

HP-2-Plunger pumps, each with an

oil-hydrau lic drive mounted on a

common frame. With this system, it is

possible to pump two different fluids

at different pressures and capacities.

This model is chosen, for example, if

the set-up space is limited.

Constant research and development and

the exchange of experience with our

cus t omers leads to excellent service

lives of the main components in catalyst

injection pumps.

Uhde's unique combination of duplex

pump-body design with a tungsten-

carbide liner, a solid tungsten-carbide

plunger, a floating plunger coupling and

the dynamic packing itself maximises the

packing life to as much as 16,000 hours.

The pump body (HP cylinder) even

reaches a service life of 7 to 10 years

and ultralight double-ball check valves

1 to 2 years. All pressure-containing

parts are autofrettag ed at optimum

pressures.

Catalyst injection pump HP 2203

60 l/h, 2,900 bar

Catalyst injection pump HP 2201

30 l/h, 3,200 bar

Dosing pump HP 5002

450 l/h, 2,500 bar

High pressure pumpsUhde is one of the leading high pressure

pump suppliers for low-density

polyethylene plants. Since 1935, more

than 1,000 HP pumps have been

installed worldwide.

Typical applications for Uhde HP pumps

in the pressure range of 125 - 14,000

bar and with discharge capacities of

10 - 20,000 l/h are:

• Injection

• Proportioning

• Testing

• Pressurising

• Product feed

Reciprocating pumps, or so-called

double-acting oscillating pumps, for the

high pressure LDPE market have been

develop ed and manufactured since 1954.

Approx. 600 HP pumps have been

de livered for catalyst injection in autoclave

and tubular reactors and for all known

licensors.

Typical pump services in a low-density

polyethylene plant are:

Catalyst injectionDischarge

pressures: 1,500 to 4,000 bar

Capacities: 10 to 140 l/hr

Modifier & comonomer injectionDischarge

pressures: 250 to 365 bar

Capacities: 600 to 3,000 l/hr

Pressure testing & autofrettagingDischarge

pressures: 4,000 to 14,000 bar

Capacities: 20 to 100 l/hr

These units can be foundation-mounted

or supplied in a trailer-mounted design

which means that they can be used

any where in the plant.

The pumps are hydraulic pressure

intensifiers with an oil-hydraulic drive,

built up from standard component

parts/modules. They are available in a

2-plunger or 4-plunger design.

Pressure-relief valves in the hydraulic

system protect both the hydraulic

15

14

Proportional Injection UnitPulsation-Free and Exact Quantities

The problemIf conventional pumps can no longer

be used, e.g. injection of very small

quantities (less than 1 l/h) or when

pressure pulsation is unacceptable,

Uhde's proportional injection units or

so-called phase-flow intensifiers are the

first choice.

Discharge

pressure range: 200 to 10 000 bar

Capacities: 0.1 l/h to 5,000 l/h

Capacity range: 0 ... 100 %

The solutionUhde solved the problem by developing

long-stroke hydraulically driven pressure

intensifiers, using the experience

accumulated in years of manufacturing

high pressure equipment. Whilst

certainly meet ing the high demands of

polyethylene producers, these pumps are

also suitable for many other applications

at low to ultra high pressure, e.g.

• Catalyst injection (0.1 to 2 l/h) into an

LDPE tubular or autoclave reactor in

pilot plants

• Pressure-controlled lube-oil and seal-oil

injection into a stirrer-shaft bearing of

an LDPE autoclave reactor

• Comonomer and/or modifier injection

• Special applications

Description/operating modeA proportional injection unit (pump) has

a side-by-side design, consisting of two

HP intensifiers, each with a pump head

includ ing the necessary check valves,

hydraulic cylinder, 4/2-way proportional

control valve with integrated electronics,

motion controller and pressure transducer.

Electrically, both HP intensifiers are in an

out-of-phase mode so that, during the

discharge stroke of one pump head, the

other goes through the suction and

preload period.

Electrical control and regulation are

effect ed with the aid of motion controllers

(position transducers) in combination with

pressure transducers.

Irrespective of the process data (pressure

and medium compressibility), a smooth

transition between the pump heads is

thus obtained without the pressure drops

normally as sociated with shifting the

supply from one HP intensifier to the

other. The unique design of the injection

units allows the continuous pulsation-free

injection of medium.

The piston velocity is controlled by

regulating the hydraulic flow over the

proportional valve via an external

(remote) or internal (local) 4 - 20 mA

control signal. Hence, the delivery rate

of the injection unit is infinitely variable

from zero to max i mum.

As an alternative, the units can be

designed with pressure control.

Advantages• Robust design and rugged structural-

steel frame

• Low hydraulic maintenance

• Slower stroking than most double-acting

intensifers

• Simple interface to the customer’s DCS

hardware

• Fastest response to DCS signal

• Precise reproducible setting of the

injection rate (< ± 0.5 %)

• Absolutely pulsation-free operation -

superior pressure signal

• Best reliability and durability

• 30 years’ experience with this kind of

phase-flow intensifier

ConclusionThe described pumps are ideally suited

for high pressure injection systems which

must have absolutely pulsation-free

operation and a perfectly reproducible

and precise setting of the injection rate

of the process pressure. In borderline

cases or in special applications, do not

hesitate to consult the Uhde specialists.

Autofrettage pump HP 10/15

20 l/h, 10,500 bar

Catalyst injection pump

4-Plunger “Twin pump“ HP 2201

30 l/h, 3,100 bar

Lube-oil and seal-oil injection pump SP 25/240

14 l/h, 2,500 bar

17

16

Heat Exchangers and SeparatorsHigh-Safety Vessels

VesselsAn LDPE plant using the tubular or

auto clave process requires a number

of high pressure vessels.

These are mostly used as separators

for the separation of the liquid and gas

phases at pressures between 300 bar

and 700 bar. These separators may have

a volume up to 30 m3 and a total weight

of over 100 t. Others may have a volume

of just of a few hundred litres. Advanced

designs and special high-strength weld

able steel grades make our vessels your

first choice. They are designed to the

requirements of any LDPE licensor and

can be integrated seamlessly into the

connecting piping and valves.

Heat exchangersHeat exchangers are either of the

double-pipe type like the tubular reactor

or are multi-tube exchangers and are

very appropriate for the 300 - 500 bar

range. Multi-tube heat exchangers in that

pressure range are used as recycle-gas,

product or compressor interstage

coolers. They can be protected against

corrosion by seakaphen or copper

cladding. The tube-to-sheet welding is

carried out with great care in two passes

in order to allow for the highest safety

and fatigue resistance of that joint.

We provide both the mechan ical and

thermal design of these exchangers.

HP separator 12 m

3

, PN-325

HP separator 18 m

3

, PN-500

Multi-tube heat exchanger

Intercooler PN-1,600, DN-24

19

18

ServicesReliable for the Whole Service Life

Our equipment documentation makes it

easy for you to order the right spare

parts. We make sure that you always

get high-quality parts which fit and

comply with the latest technical industrial

stand ards. For many parts, we will

maintain an inventory for you, e.g. high

pressure tubes, packings and other

critical components.

Engineering servicesThe engineering for the initial installation

of an LDPE reactor system is frequently

carried out by an engineering contractor.

But what if, later on, you need to

investigate modifications to high

pressure equip ment or failure causes?

Our design depart ment will be glad to

help out with piping-flexibility analysis,

finite-element analysis, vibration analysis

or, for example, with steel-structure

design and analysis.

Long-term partnershipHigh-technology equipment needs

high-quality services in order to be

successful. Our dealings with our

customers do not end once we have

sold a component or system. Instead,

it is the start of a long-term partnership.

It begins with the installation or the

install ation-supervision service. Only

equipment which is installed properly

and tested will ensure you a smooth

start-up of your new production unit.

Then, think of training and education.

It is common knowledge today how

important that part is for the successful

operation of critical equipment.

Over the years that you use our

equipment, you will probably come

to appreciate our maintenance and

inspection service.

Spare partsThe single most critical factor for you to

operate our equipment for many years

to come is the availability of spare parts.

And we guarantee this. We still deliver

parts for machines which are over 60

years’ old and we will still be in the

marketplace when many others will

already have disappeared.

Autofrettaging service

Engineering services Spare parts

LDPE Plant Improvement Conference

Uhde High Pressure Technologies GmbH

Buschmuehlenstr. 20 · 58093 Hagen

Telefon 02331 967-0 · Fax 02331 967-370

www.uhde-hpt.com · info@uhde-hpt.com

gzd-empeer 06/2012, technical modifications reserved