Pig Detectors and Pig Detection Systems

A pig detector (or pig detection system) is a device that determines the presence of an HPS pig when in it’s in close proximity. An essential component of pigging systems, pig detectors are usually located close to launch and receive stations, enabling highly efficient, safe and reliable operation – whether automated, semi-automated or manual.

Benefits of HPS Pig Detectors:

• Reliably detects HPS pigs travelling at high speed or stationary
• Easily and conveniently mounts to new or existing pipework
• Specially designed for hygienic and sanitary applications
• Ultra-reliable stretched detect signal for PLC and pigging automation software
• Uses multiple data detection points for total dependability
• Detect Signal output fully compatible with the Input of industrial PLC’s
• Works with any pipeline diameter that’s suitable for an HPS pig
• LEDs provide useful visual indications of pig presence
• Simple clamp fixings – no cutting, drilling, welding etc.
• Accurate, safe and robust
• Fully electronic operation: no troublesome reed switches or mechanical parts
• Electrical power connections have reverse polarity protection
• Non-intrusive, minimal risk of contamination

How the Pig Detection System Works

The animation below shows an HPS pig detection system.

As the pig approaches the pig detector, it detects the first magnetic pole of the pig and an indicator LED lights. As the pig travels under the detector there is a short period of non-detection due to the null point in the centre of the pig. As the pig passes the detector, it detects the second magnetic pole. Note: As the HPS pig detector has a one-second stretched output signal, in actual operation you will only observe one signal.

Pig detectors are usually fitted close to the pig launchers and pig receivers, and the control system will use the signal to initiate the next phase of the operation (for example, starting a CIP sequence, venting the line, using the receiver to return the pig, returning to normal processing and so on).

Visual Indication with Output Signal for PLC

HPS pigs have special magnetized silicon cores. The pig detectors sense the pigs magnetic field, which provides a momentary signal as the pig passes. When the instrument detects the presence of a pig, it also lights an LED. This provides a visual indication to the system operator of the pig’s presence.

One of the key benefits of HPS systems is that, as well as a visual indication, the signal can also be used to determine events programmed into a PLC or pigging automation software. This enables semi or full automation of the product recovery and pigging process.

Stretched Signal Length Provides Highly Reliable Detection

By validating three detection data points and using a stretched signal length variable up to 1.5 seconds, the HPS pig detector is extremely reliable. This is important because it overcomes problems associated with standard proximity switches. Standard proximity switches send out a small signal length of only 1/10 of a second. Shorter signals are unreliable because they can be missed by PLC’s, resulting in false detects and potentially shutting down the entire production process.

Detects Moving Pigs

A major technological advantage of the HPS pig detector over other pig detection systems is that it detects the pig when it is moving. This enables extremely accurate and precise control of the pig. Other systems need to have the pig at a stationary position (i.e. stopped) to sense it, which causes excessive wear on the equipment and low-efficiency operation.

Externally Mounted, Easy to Install

HPS pig detectors mount externally on the pipeline. This makes them easy to install on both existing and new equipment. They conveniently yet firmly clamp on to the outside of the pipe. There’s disruptive or intrusive drilling, cutting the pipe, welding or so on. They are also extremely safe and robust and can be installed in hazardous areas.

Non-Intrusive Pig Detectors

Because HPS pig detectors are non-intrusive, no part of the pig detector comes in to contact with the product, so there’s no risk of contamination. In addition, because they are clamped externally, there’s also no danger of contamination from poor welds, poorly fitting screws, fittings and so on. As well as being easy to install, they are also easy to move if required. Because they have no moving parts, they have a long life expectancy and are extremely reliable.

To find out more about pig detectors and pig detection systems for your organisation, please contact HPS.