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Recommendations for safe unloading

of metal alkyls

Flexible hoses

PRODUCT

N2

AkzoNobel supplies a wide range of metal alkyls to the olefin polymerization and other industries. The

metal alkyls are transported in carbon steel portable tanks in a variety of sizes. Safe transfer of product

from these portable tanks to the storage or blending tank requires the use of a specially designed

unloading station. The connection of the portable tank to the piping system of the storage tank can be

realized using either flexible hoses or steel loading arms with rotary joints. In a series of technicalbulletins, AkzoNobel describes essential aspects of such an unloading station in detail [1]. This bulletin

provides information on the selection of the proper type of flexible hoses, and on their use in metal alkyl

service. Loading arms with rotary joints are described in a separate bulletin [1].

OMS 96.168.06/August 2008 of 5



OMS 96.168.06/August 2008 of 5

Introduction

Metal alkyls are highly reactive compounds. Many commercially available metal alkyls react explosively

with water and are pyrophoric, i.e. they ignite spontaneously on contact with air. Despite these inherent

hazards, metal alkyls can be handled safely when appropriate procedures are followed [2].

The safe transfer of metal alkyls from a portable tank to a storage or blending tank is highly dependent on

a proper design of the unloading station. When transferring the metal alkyl, a connection between the

portable tank and the facility needs to be made. In practice the position of the portable tank will vary

slightly each time a new tank is placed in the unloading station. A flexible connection from the fixed

pipelines of the unloading station is required, because tension on flanges, valves and piping must be

avoided. For making the connection the use of corrugated stainless steel flexible hoses or specially

designed loading arms with rotary joints is recommended. Flexible hoses are described in this bulletin.

Flexible hoses in metal alkyl service

AkzoNobel has over 35 years of experience in production of metal alkyls. Our production plants are using

flexible hoses extensively in daily operations. They provide a safe, convenient and cost effective way of

making flexible connections for metal alkyl transfers. Several important aspects for a proper choice of the

flexible hose and auxiliary equipment are given below.

Construction materials of the hose

Corrugated stainless steel is the generally recommended hose material for metal alkyl applications. Type

AISI 304 and 321 have proven to give good performance. For halide containing metal alkyls (e.g. DEAC,

EASC or EADC) AISI 316 L is preferred. Stainless steel overbraiding around the hose increases the

pressure rating and protects against external damage.

PTFE (Teflon) innercores/liners can also be used, and they offer advantages particularly for smaller

diameters (1/2 - 3/4 in. or 15 - 20 mm). The bend radius is smaller than that of corrugated steel hoses

and this will offer greater flexibility. Teflon hoses must also have steel overbraiding, and teflon must be

impregnated with graphite to avoid pinhole failure due to static discharge through the liner.

Since failure of Teflon-lined hoses is possible if a fire occurs, automatic or remote emergency shut-off

control should be provided [1].

Pressure rating

The pressure rating should be chosen in accordance with the design pressure of the adjacent equipment

(typical design pressure 30 bar or higher).



Fittings

Flexible hose suppliers can offer numerous types of fittings upon request.

Two different fittings at each hose end are also possible, such that the flexible can be used as an adapter

from the portable tank to the unloading system as required.

Use of swivel fittings or floating flanges prevents torsion of the hose, and thus simplifies easy use.

Figure 1. Hose fitting with floating flange

floating flange

corrugated stainless steel hose

single stainless steel b raiding

Length of the hose

The length of the hose should be carefully chosen, to avoid U-loops (too long hose) or strain (too short).

U-loops will trap the metal alkyl, and are difficult to purge, which is dangerous upon disconnection.

Hose manufacturers can supply hoses of any required length.

Valving

It is recommended that the end of the flexible hose used for product discharge is equipped with a valve.

Thus upon disconnection accidental release of metal alkyl is prevented and slow entrance of air which

will cause oxidation is avoided. The use of blind flanges on both product and vent hose is recommended.

Balancing

Stainless steel hoses equipped with (automatic) valves can be rather heavy. An adequate balancing

system, for example with counter weights, can ease the manipulation of the hose significantly and

contributes to a safe operation.

OMS 96.168.06/August 2008 of 5



OMS 96.168.06/August 2008 of 5

Unloading procedure

A detailed unloading procedure is given in the dedicated AkzoNobel technical bulletins ‘Unloading

procedure for metal alkyls in C-type portable tanks’ and ‘Unloading procedure for metal alkyls in ISO

portable tanks’ [1].

As mentioned in these bulletins, a good purge with dry nitrogen after each product transfer is important

for safety reasons. This will however also increase the lifetime of the flexible hose. It is recommended to

replace blind flanges on the hoses to avoid entrance of air.

Test procedure

To guarantee maximum safe use of the flexible hoses AkzoNobel recommends checking the condition of

the flexible hose on a regular basis but at least once per year. The test will indicate each small defect of

the hose.

A short description of the test procedure used by AkzoNobel is given below:

Before removing the flexible hose from the installation the hose should be purged and rinsed properly

with nitrogen and a hydrocarbon solvent. Good personal protective clothing [1] is a must during this

operation.

Pressurize the hose with nitrogen at 10 barg. Maintain this pressure for 15 minutes and verify the

pressure; a pressure drop is not allowed.

Check the tightness of the fittings by testing with soap solution.

If no leakage is observed depressurize the hose and continue with a hydraulic test.

Pressure up with a hydrocarbon using a hydraulic pump to 25 barg.

(Test pressure can vary depending on hose specification)

Observe for any loss of pressure for at least 15 minutes.

If the hose meets the requirements, mark the hose with a test-date tag and put it in use again.



All information concerning this product and/or suggestions for handling and use contained herein are offered in good faith and are believed to be reliable. AkzoNobel Polymer Chemicals, however, makes no warranty as to accuracy and/or sufficiency of such information and/or suggestions, as to the product's merchantability or fitness for anyparticular purpose, or that any suggested use will not infringe any patent. Nothing contained herein shall be construed as granting or extending any license under any patent.Buyer must determine for himself, by preliminary tests or otherwise, the suitability of this product for his purposes. The information contained herein supersedes all previouslyissued bulletins on the subject matter covered. The user may forward, distribute, and/or photocopy this document only if unaltered and complete, including all of its headers andfooters, and should refrain from any unauthorized use. You may not copy this document to a website.

Akzo Nobel Polymer Chemicals B.V. Akzo Nobel Polymer Chemicals LLC Akzo Nobel (Asia) Co., Ltd. Amersfoort, The Netherlands Chicago, U.S.A. Shanghai, PR ChinaTel. +31 33 467 6767 Tel. +1 312 544 7000 Tel. +86 21 6279 3399Fax +31 33 467 6151 1 800 828 7929 (Toll free US only) Fax +86 21 6247 1129

Fax + 1 312 544 [email protected] [email protected] [email protected]

www.akzonobel.com/polymer OMS 96.168.06/August 2008

2006-2008 AkzoNobel Polymer Chemicals of 5

Conclusion

Flexible hoses are a convenient means of making temporary connections involving transfers of metal

alkyls, for example during unloading.

AkzoNobel advises to follow the recommendations given in this bulletin regarding the choice and use of

flexible hoses.

For more information on this subject or a dedicated advice, please contact your AkzoNobel

representative.

References

1. AkzoNobel technical bulletins available on safe unloading of metal alkyls:

Design of a metal alkyl unloading station

Fail-safe shutdown system

Flexible hoses

Sealant tank

Unloading arms

Operator protection during handling of metal alkyls

Unloading procedure for metal alkyls in C-type portable tanks

Unloading procedure for metal alkyls in ISO portable tanks.

2. Brochure ‘Metal Alkyls from AkzoNobel’ available on www.akzonobel.com/polymer.

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