Valve technology

Uhde valves and fittings have proven their particular reliability and operational safety in many fields of the chemical industry. In LDPE plants, Uhde valves with pressure ratings of 325 – 4,000 bar are used as shut-off valves, control valves, safety valves 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.

Nominal diameters

Inch
1/4 | 1/2 | 3/8 | 3/4 | 5/8 | 1 | 1 1/4 | 1 1/2 | 2 | 2 1/2 | 3 | 4 | 6 | 8 | 10
mm
6 | 10 | 16 | 24 | 25 | 30 | 39 | 40 | 45 | 50 | 55 | 60 | 65 | 70 | 76 | 90 | 120 | 156 | 200

Fabrication

Materials

Name Description Note
SA350LF2 Carbon Steel
ASME SECTION II 		 
TSTE 355 1.0566, P.355NL1 EN10028-3
1.4021 RM2, X20Cr13 EN10088-1-3
1.7258 K3, 24CrMo5 EN10269
1.7218 K2, 25CrMo4 EN10083-1
1.7779 N9, 20CrMoV13-5 EN10216-2
C22.8 S2, 1.0460, P250GH EN10222-2
Materials for EHP applications    
1.6580 K10/K10X
30CrNiMo8 		EN10083-1
SA723G1C1/1 Carbon Steel
ASME SECTION II 		 
1.2767 Tool Steel
X40NiCrMo4 		DIN17350
1.2344 Tool Steel
X40CrMoV5-1 		DIN17350
Materials (stainless steel)    
1.4418 RM3
X4CrNiMo16-5-1 		EN10088-1
1.4034 X46Cr13 EN10088-1-3
SS316L 1.4435 EN10088-3
1.4571 RA4
X6CrNiMoTi17-12-2 		EN10088-1-3

All materials meet the specific requirements of all licensors such as:

  • Exxon Mobil
  • BASELL
  • SABTEC
  • Dupont
  • Dow
  • Enichem
  • ICI

On / Off Valves

Various types with various drives:

  • Manual type
  • Gear type
  • Electric type
  • Pneumatic type
  • Hydraulic type
  • Check valve

Optional with heating bores or heating jacket.

Safety valves are designed by Uhde as spring-loaded safety valves or as hydraulically actuated quick-opening blow-off valves (< 200 mm sec).

Control valves

The control valve at the outlet of the reactor is an essential constituent for the process control of reactors. This valve is characterized by high speed, high positioning 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 actuating piston. The positions of the valve and drive spindles 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 and robust structure of the valve and the control parts results in the highest degree of functional safety.

Control unit for control valves

The digital positioner guarantees:

  • high dynamics
  • high positioning accuracy
  • high reproducibility

Please ask for our technical data sheet.

Hydraulic power unit

In the LDPE plant, the hydraulic valves are supplied by an Uhde hydraulic power unit. This station works at a maximum operating pressure of 180 bar. The necessary oil reservoir is dependent on the hydraulic valves located in the plant and is optimised correspondingly by Uhde.

The most important station components such as the hydraulic 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. This guarantees a maximum of operational reliability.

Valve test station

Prior to delivery, all the valves are subjected to pressure tests 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 tests for packing and seat up to 5,500 bar
  • Full functional test
  • Measurement of speed and accuracy

These tests guarantee 100% operational reliability before the components are installed in the production plant.

Tests

  • Flow measurement
    Sizing of process-critical control valves for LDPE plants
    (Cv measurement)

In the LDPE process control valves are used to control process flows. Satisfactory control operation of these valves depends on the fluidic design, particularly the design of the contour of the control cones.

This aim is frequently reached iteratively by fluidic measurements of the valves using empirically given cone contours.

However, this procedure can cause considerable costs due to both repeated measurements of the valves and the replacement of the control cones.

An exact forecasting calculation of the cone contour is therefore of great importance with regard to cost-optimized fabrication, especially for high-pressure LDPE valves with large nominal diameters.

Uhde High Pressure Technologies in Hagen has decades of experience in the design of high-pressure valves.

With regard to the fluidic design of high-pressure valves with large nominal diameters, the accuracy of forecast for Cv values and for the characteristic curve of the valve, especially for valves with relatively high Cv values for world-scale LDPE plants, will be tested in a section of measurements and documented.

Uhde High Pressure Technologies offers this valve testing service for angle valves and straight-way valves from DN 1" (seat 24 mm) up to 14“ (seat 280 mm).

Flow measurements according to DIN EN 60534-2-3
Valve DN-6“
Seat diameter: 84 mm

KV100-Ist = 148 m3/h (actual value)
KV100-Soll = 160 m3/h (set point)

Characteristic curve complies with equal-percentage characteristic curve according to DIN IEC 534-2-4
Stroke Cv-
Set point 		CV
Actual value 		Deviation
[%] [%] [%] [%]
100 100 93 10,0
90 68 70 10,8
80 46 48 11,6
70 31 34 12,5
60 21 21 13,4
50 14 14 14,4
40 9,6 10 15,5
30 6,5 7,3 16,7
20 4,4 4,4 18,1
10 3,0 2,3 19,4
5 2,4 1,5 20,2

 

 

 

Uhde High Pressure Technologies guarantees rapid spare parts supply for many years as well as stockkeeping of the standard spare parts.