GB2503915A

GB2503915A - Crevice Corrosion Sensor

Info

Publication number: GB2503915A
Application number: GB201212388A
Authority: GB
Inventors: Stephen Munn; Gareth Jones Pugh
Original assignee: MIDLAND CORROSION SERVICES Ltd
Current assignee: MIDLAND CORROSION SERVICES Ltd
Priority date: 2012-07-12
Filing date: 2012-07-12
Publication date: 2014-01-15
Also published as: GB2504214A; GB2504214B; GB201212388D0; GB201312445D0

Abstract

A sensor for monitoring the amount of crevice corrosion which may be taking place in water systems, for example HVAC systems, or be used in refineries or chemical processing facilities, comprises one or more metal wires 2 wrapped around threads or grooves 1 in a non-conducting body 3. The grooves form natural crevices which replicate crevices within real systems. The sensor is inserted into a water system pipe for example and the electrical resistance of the wire is monitored over time to indicate corrosion. The sensor output may provide an easily read user interface or may be captured by a data logger for remote monitoring.

Description

Crevice Corrosion Sensor

Introduction

The claim detailed in this submission is for a crevice corrosion sensor which can be installed in any water system where corrosion needs to be monitored. It may for instance be installed in heating or cooling (HVAC) systems, or be used in refineries or chemical processing facilities. Two variations are envisaged: (i) where the sensor output provides an easily read user interface (such as leds) and (ii) where an analogue or digital electrical signal can be captured by a data logger for remote monitoring.

Sensors already exist which give a measurement of corrosion rates within water systems, e.g. Corrator (LPR probe) and electrical resistance probes. Although these are useful for monitoring corrosion they tend to focus on general corrosion which may occur on exposed metal surfaces. In reality, however, wall perforation and failure of components often occurs due to localised corrosion which occurs in crevices or under debris, due to a differential aeration effect. Radiators or fittings in LTHW (central heating) systems can often suffer from this because the welded seams form such a crevice.

Sensors can be classified into 2 different types. One type provides some sort of output (e.g. visual, audible or meter reading) which is read locally by the person monitoring the system. The other type produces an output in the form of an electrical signal (digital or analogue) which can be collected by a data logger for remote monitoring. This submission is relevant to both types.

Description

A crevice corrosion sensor has been developed which gives an accurate indication of the crevice corrosion likely to be incurring in parts of aqueous based systems. The inside design of the device contains a rod made from non-conducting material (e.g. plastic) with screw threads or grooves around which is wrapped metal wires thus creating natural crevices between the wire and the rod.

These wires form the sensing element of the device. The sensor wires can be made of mild steel, stainless steel or any other metal which may be susceptible to crevice corrosion in the system under consideration.

In its simplest form there may only be one thread and one wire, but a more complex design may contain multiple threads of different pitch and wires of different diameters. These wire(s) sit within the thread or groove in such a way that they can be considered to experience similar conditions to that found in crevices of real systems. If therefore, the system water conditions are such that crevice corrosion is occurring within the system, the wire sensing elements within the device will corrode resulting in a gradual increase in resistance. An external electrical circuit is provided which measures this resistance and provides some sort of indication (visual, audible or electrical) which can either be easily read or heard by a person or can be captured and transmitted by a data logger for remote monitoring purposes. Failure of any wire would result in a sudden increase in resistance,

Detailed Description of Drawings

The device shown in figure 1 contains a plastic rod having 3 different diameters. Each of these 3 sections has a thread cut into it which contains a wire sensing element wound inside the thread such that its outer edge is contained within the thread (see enlargement, figure 2). The end of each wire is fed through the body of the plastic in such a way that electrical connection can be made.

The plastic rod containing the wire sensing element may be enclosed in an outer water tight casing (such as plumb fittings) to enable the system water to flow over the internal body of the device and the sensing element(s) -see figure 3.