martes, 13 de mayo de 2008

Peristaltic or Diaphragm Metering Pump ??







Reliability can be defined as the probability an item – in this case, a pump – will perform a required function, without failure, under stated conditions for a stated period of time.



System Parameters
There can be as many definable parameters in a specific system as there are required functions. Although it would be impossible to identify all of them, the basic metering pump system parameters are: fluid, pressure, control capability and required maintenance. We can analyze each of these parameters with respect to a diaphragm and peristaltic metering pump system and compare their effect on the reliability of the overall system.



Diaphragm pumps typically employ a large number of “wetted” components:
Suction strainer with check valve – typically includes a filter screen, valve body, check valve/ball, rubber seal/seat and a metal spring.
Suction tubing or piping.
Pump head with inlet/outlet valves – includes a pump head, valve bodies, check valve/balls, rubber seal/seats and (depending on the manufacturer) metal springs.
Discharge tubing or piping.
Injection fitting with check valve – typically includes a valve body, check valve/ball, rubber seal/seat and a metal spring.
Peristaltic pumps employ much fewer “wetted” components:
Suction tubing or piping.
Peristaltic pumping tube – typically includes inlet and outlet fittings.
Discharge tubing or piping.
Injection fitting with check valve – typically includes a valve body, check valve/ball, rubber seal/seat and a metal spring.

Conclusion
Both diaphragm and peristaltic metering pumps have proven themselves in a multitude of commercial, industrial and municipal chemical metering applications. Still, each pump type has its strengths and weaknesses. A quick review of the system parameter requirements can guide the user in selecting the best pump type for the specific application.
About the Author: Bill McDowell is a sales engineer with Blue-White Industries, of Huntington Beach, CA. With nearly 25 years at Blue-White Industries, he also has held positions as project engineer and engineering director. Contact: 714-893-8529, sales@blue-white.com or http://www.blue-white.com/

To see the complete report on this publication go to: http://ww.pennnet.com/display_article/327631/64/ARTCL/none/none/1/Peristaltic-or-Diaphragm-Metering-Pump-–-/, on the Industrial WaterWorld edition of March 2008.


Publicado por EMILIO MALAGUTI en 9:21

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GREEN CHEMICALS

The Green Seal certification is granted by the organization with that name and has a great number of members contributing with the requirements to pass a raw material or a chemical product as "green". Generally for a material to be green, has to comply with a series of characteristics like: near neutral pH, low volatility, non combustible, non toxic to aquatic life, be biodegradable as measured by oxygen demand in accordance with the OECD definition.
Also the materials have to meet with toxicity and health requirements regarding inhalation, dermal and eye contact. There is also a specific list of materials that are prohibited or restricted from formulations, like ozone-depleting compounds and alkylphenol ethoxylates amongst others. Please go to http://www.greenseal.com/ for complete information on their requirements.
For information on current issues regarding green chemicals, see the blog from the Journalist Doris De Guzman, in the ICIS at: http://www.icis.com/blogs/green-chemicals/.
Certification is an important — and confusing — aspect of green cleaning. Third-party certification is available for products that meet standards set by Green Seal, EcoLogo, Energy Star, the Carpet & Rug Institute and others.
Manufacturers can also hire independent labs to determine whether a product is environmentally preferable and then place the manufacturer’s own eco-logo on the product; this is called self-certification. Finally, some manufacturers label a product with words like “sustainable,” “green,” or “earth friendly” without any third-party verification.
“The fact that there is not a single authoritative standard to go by adds to the confusion,” says Steven L. Mack M.Ed., director of buildings and grounds service for Ohio University, Athens, Ohio.
In www.happi.com of June 2008 edition, there is a report of Natural formulating markets that also emphasises the fact that registration of "green formulas" is very confused at present, due to lack of direction and unification of criteria and that some governmental instittion (in my opinion the EPA) should take part in this very important issue.