Poor Wash Down Practices Blocking Your Drainage System ?
How To Prevent Blocked Drains Caused By Poor Wash Down Procedures.
Many industrial processes have a need to wash down plant and equipment. This may be done “in line” or at a remote dedicated location such as a wash room. Typically the design of the area will have a grated floor drain and the residue then runs from this floor drain through an underground drainage system to a pit or treatment plant.
Water and similar liquids which are are relatively clean will happily flow through drainage pipes and there are millions of kilometers of drainage pipes installed throughout the world. However, as every plumber will tell you, it is not always free flowing liquids which finds its way into drainage systems and clearing blocked pipelines is a regular occurrence.
When considering industrial wash down applications there is the potential for many and varied liquids or slurries to find their way into drainage systems. Whilst in theory running a network of underground pipes to a central treatment system or pit can look attractive. It looks far less attractive to the maintenance manager who has to deal with the constant blockages.
In theory the grated drain cover acts as a course filter to prevent large pieces of sediment getting into the drainage system and the operators clean up the sediment which can then be disposed of via a solid waste system. Typically, for an “in line” process, there will be a Standard Operating Procedure to clean up any “operational” spillage during production, in order to prevent it from getting into the drainage system.
Nature of the problem
So much for the theory. In practice, the operators will wash anything and everything into the grated drain and if it won't fit through the gaps, and they can't force it through the gaps then they will lift the grate. Eventually this causes blockages in the drainage system and it becomes a major exercise to clear the pipes. This often becomes a safety issue if grates are removed and not replaced.
Some drainage systems are designed with regular access pits so as to provide ready access to the drainage system for cleaning.
And regardless of Standard Operating Procedures or “education”, the problem will continue to occur.
Options for solutions
Every plant and system is different so that there is not a “one size fits all” standard “fix”. Each needs to be looked at individually but there are some steps which can be taken (other than shooting the operators who you suspect are dumping solids into the system)
a – Grated covers with very small openings are readily available. These can be effective in some cases, but can also restrict water flow and block easily, causing localised flooding and they may restrict larger solids which the system can handle
b – Redesign for a series of small, localised systems. In many cases there can be a labyrinth of underground drainage pipes leading to a central point. Redesign the system to have several small systems with very short lengths of underground piping feeding into pits. The pits can then be fitted with a level sensor and pumped out
Depending on the process, operation or desired outcome there are a number of options
Typically operators washing down using a pressure hose with floor drains will use excessive amounts of water. Its human nature.
To cut down on wastage and to measure the wash down water being used, the pit water can be pumped into 200 litre (44 gallon) drums sitting on a pallet or a 1000 litre tank or similar, adjacent to the pit. The operators are then responsible for disposing of the waste water and it can be easily measured. From previous experience I would expect a significant saving in wash down water.
By using (say) an air diaphragm pump to pump out the pit, large solids can be accommodated and the waste can be taken directly to a processing facility or sent off site.
Another effective solution is to use a macerating pump to pump out the pit, this has the advantage of grinding sediment to a small particle size and the resultant slurry could go to mobile storage or pumped to a central process /storage area.
I don't think that operators will ever resist the temptation to dump sediment into the floor drainage system so the best solution is to “manage” the process.
Unfortunately there is no easy solution. Each plant and wash down area needs to be reviewed separately.
In an ideal world the process would be different, but we don't live in an ideal world and we need to manage what we have.
If re occurring blocked underground drainage pipes are an issue. Maybe the solution is to redesign the systems into a number of discrete units which can be managed individually. This will also often result in direct process improvements, as noted above.
Monday 1 March, 2010 08:58 AM