Basic instructions when using a PLC to control the Pro-Ratatm Line Sampler

Properly operated, the Pro-Ratatm Line Sampler is the most accurate method of sampling milk transports no matter how stratified they might be. Details are in the Installation CD that comes with the sampler, but here are some tips for achieving this.

Air Valve:
Air should be pulsed to the Pro-Rata Line Sampler using a 3-way air valve (normally closed, air in, air out and vent). The Parker Cyclone Direct Acting Solinoid Valve (Catalogue Val-Cyc –E) from Parker Pneumatics (Parker.com) is such a valve. Get a ¼ “ outlet device that will handle 125 to 150 psi.

Do not use over 6 ft of ¼ inch diameter hard wall plastic tubing between the air valve and the sampler. Longer lengths will prevent the impulse air from venting quickly enough through the air valve.

In most situations, maintain 100 psi of air to the air valve for pulsing the sampler. Product line pressures greater than 80 psi may require air pressure up to 125 psi.

Be careful that your air pressure does not drop over the course of unloading a transport. You might need a small reserve air tank to maintain pressure if other equipment is drawing the air pressure down.

Starting and Stopping the sampler:
To get accurate samples of stratified product, sampling must only occur when product is flowing in the line. One way to do this is to monitor the pump’s amperage so that sampling starts as soon as the pump is under load and quits as soon as the load falls off at the end of an unloading.

Sampler Pulse Timing:
The Pro-Ratatm Line Sampler needs a minimum air pulse of ½ second to discharge. This will allow the sampler to take up to 60 samples per minute. Depending on the size range of the transports you receive, the 2 liter bottle that we send with the sampler will typically let you collect the proper minimum number of samples without having to change the sampler speed between transports. A good minimum for all transports is around 400 samples from every received transport. Mathematically, the more discrete and accurate samples that you take from a given volume, the more valid and reliable a description you will have of the total transport.

Mounting the Sampler:
Put the 2” outlet tri-clamp mounting T about 3 to 5 feet from the pump. Make sure that it is easy to change the sample bottle. Do not put the sampler too close to the pump outlet as the pump surge can overfill the bottle. Samplers placed too far downstream from the pump will have to sample excess high test product between loads.

Adjusting the sampler spring pressure:
The spring adjustment cap keeps the sampler’s long valve closed against pump pressure. Set it tight enough to prevent the product line pressure from simply letting milk blow by it, but not so tight that it keeps the air from the air valve from pulsing the sampler. Initially, you may need to frequently adjust this to get the ideal setting.

Cleaning in place:
Set your controls so that air is pulsed to the sampler whenever the product line is cleaned. The solution discharged by the sampler can be recycled or sent to the drain. Be careful as it may be hot.

Finally -Do not lose your valves. Change the diaphragm regularly. And always shake your composite samples well before splitting.