The invention relates to a method of producing acid-proof valve blocks with internal cavities and channels by powder moulding, as indicated in the preamble of the accompanying claim 1.

Christmas trees and drilling and well- intervention equipment are provided with hydraulically or electrically activated high-pressure barriers which are to safeguard against

uncontrolled blowouts from oil or gas wells in connection with production, drilling, well completion or other well operations. The well-safety elements are valves or shearing devices which are fitted into machined valve blocks, with actuating devices mounted externally on the block. It is common for several valve blocks to be assembled into larger units which are provided with connecting elements for other equipment and necessary structural elements and control equipment .

Offshore oil and gas activities are developing towards increasing water depths. The weight of the equipment is a limiting factor in relation to the maximum water depth. The deep-water regions typically have high reservoir pressure and, in many cases, the well fluid is corrosive. The weight of the drilling equipment increases with the pressure class of the equipment. Stronger materials will provide

possibilities of reducing the dimensions of the equipment and thereby the weight as well. The use of high-tensile materials such as duplex and super duplex acid-proof steels will be a contribution to solving the challenges of corrosion and weight .

The prior art for producing valve blocks that are included in well equipment for the oil and gas industry is forging the blank from a steel alloy which is first coarsely machined, heat-treated and subsequently machined to its final shape. Sealing surfaces and other surfaces prone to corrosion are hardfaced with a corrosion-resistant material with subsequent machining .

Problems with / drawbacks of the prior art are:

• Restrictions when designing the equipment, connected to geometry and positioning of components.

• Uneven material quality.

• Extensive machining to remove material from the blank.

• Need for hardfacing for the corrosion protection of

exposed surfaces.

• Long delivery time.

The invention has for its object to remedy or reduce at least one of the drawbacks of the prior art or at least provide a useful alternative to the prior art.

The object is achieved through features which are specified in the description below and in the claims that follow.

The present application relates to a method of producing valve blocks with internal cavities and channels

characterized by the characteristics set forth in the claims.

A first object of the invention is to provide a useful alternative to the prior art for the production of valve blocks with

• dimensions of the blank close to the finished, machined parts ,

• reduced use of materials,

• great freedom when designing the geometry of the

equipment and positioning components,

• the use of duplex and super duplex acid-proof steels,

• corrosion-resistance without hardfacing of surfaces,

• a reduced need to weld parts for the component.

Another object of the invention is to produce a competitive product with

• reduced production cost,

• internal cavities and channels having good flow

conditions ,

• high material strength and corrosion resistance,

• volume and weight reduction through optimum design of the blank.

In what follows, an example of a preferred method of

production visualized in the accompanying drawing, figure 1, is described.

The technique of Hot Isostatic Pressing (HIP) is a known production method for producing components of different powder materials, such as metal and ceramic powders. The blank for the valve block is produced by a sheet mould 1A, IB being made as shown in figure 1. An external valve block mould 1A is welded to an internal mould IB forming internal cavities in the valve block. The mould 1A, IB is provided with filling sprues 2A-2H for the interior space of the mould to be filled with metal powder. When the mould has been filled up with metal powder, it is heated and vacuumized to remove oxygen and moisture from the powder before the container is sealed and placed in a processing container for the HIP process with a supply of high-pressure inert gas such as argon at high temperature, such as 1100 °C, wherein the contents of the mould is processed into a compact, homogenous material with better qualities than forged steel.

Finally, the blank is worked externally and internally to its final design by surfaces being machined.

It is possible to use the same material for the sheet mould as the HIP-processed material; alternatively, it is common for moulds to be made of a material that is eroded away in an acid bath or is machined away. The choice of method is decided on the basis of production-technical and economic considerations .