SECTION 1.4 MATERIALS OF CONSTRUCTION

The information summarised below provides guidance on the selection of materials of construction. The user should consult a reputable materials supplier and the bromine supplier to satisfy himself that it will give the required performance under the actual conditions of use including temperature, pressure and presence of moisture.

 

CONDITION OF BROMINE

 

 

Wet (1)

Dry (Below 30 mg/kg)

 

 

Gas

Liquid

Gas

Liquid

Metals

Lead (2) (3) (4)

 

at 25°C

G

up to 50°C

 

Tantalum (3)

G

up to 200°C

G

up to 200°C

 

Mild Steel, Cast Iron

U

U

U

U

 

Aluminium/Adluminium Alloys

U

U

U

U

 

Stainless Steels (Austenitic)

U

U

S(5)

S(5)

 

Nickel, Monel

U

U

G

G

 

Inconel

U

U

 

 

 

Hastelloy "C"

U

U

G

G

 

Copper, Brass

U

U

U

U

 

Bronze

U

U

 

 

 

Silver

U

U

 

 

 

Titanium

[S(5)]

U

U

U

 

Niobium and Niobium/Tantalum Alloy

 

 

 

 

 

 

 

 

 

 

Ceramics

Stoneware, Porcelain, Glass (6)

G

G

G

G

 

 

 

 

 

 

Plastics

PTFE, PCTFE, PVDF, FEP (7)

G

G

G

G

 

Ebonite

U

U

U

U

 

CPVC, PVC

U

U

U

U

 

Polyethylene, Polypropylene

U

U

U

U

G = Good
S = Satisfactory under carefully controlled conditions
U = Unsatisfactory

Notes

  1. The resistance to wet bromine depends upon the water content and temperature. Bromine in contact with air of 80% relative humidity can pick up 300 mg of water per litre.
  2. Chemical Lead, BS 334: 1983 (type A).
  3. Data refer to gas or liquid.
  4. Tin-free flux should be used for lead burning.
  5. Only if found satisfactory after specific trials. Evidence on titanium is conflicting and it should be contemplated for use only with wet bromine gas and then with caution.
  6. Upper temperature limit is determined by factors other than corrosion. Avoid mechanical or thermal shock.
  7. Notes on the Selection and Use of Fluorocarbon Polymers

Considerable experience has been gained with the use of fluorocarbon polymers, especially polyvinylidene fluoride (PVDF). PVDF lined mild steel pipework and solid PVDF (ie pipework made entirely of PVDF, that is, not a lining) are both commonly available commercially. Both have excellent resistance to wet and dry bromine.

All fluorocarbon polymers are permeable, the degree of permeability progressively increasing from PVDF to PCTFE and to PTFE. Experience has shown that PVDF linings are chemically resistant to wet and dry bromine up to temperatures of 120°C. Considerable stress and distortion occur at higher temperatures and the maximum temperature recommended is 95°C.

Where solid PVDF pipework is used it should be of fusion weld construction and jointed with steel backed stub or full face flanges. Socket weld joints are used in sizes up to about 3" ns and butt welds in sizes of 3" ns and above. Severe embrittlement has been reported in both butt and socket welds on certain PVDF polymers. Before using solid PVDF pipework with fusion weld joints the conditions of use should be fully considered and advice sought. In all cases particular attention should be given to specifying and controlling the fabrication methods to be used.

Except over very short distances all pipework should be continuously supported and free from imposed stresses (eg heavy values). Initially most solid PVDF pipework has the advantage of being translucent, but this will be limited in time by permeation of bromine into it. Where BS or Industry Standards have not yet been established the design and construction of plastic pipelines should be strictly in accord with the manufacturer's recommendations and installed by competent personnel using suitable equipment approved by the manufacturer. Pipework should be suitably examined and tested before use with bromine.

Realisation: TiDi Graphics