Mass flow should actually be expressed in units of weight such as g/h, mg/s, etc. Most users, however, think and work in units of volume. No problem, provided conditions are agreed upon, under which the mass is converted to volume.

Our STP or standard temperature and pressure conditions used are stated here:

Normal conditions (l_n/min): a temperature of 0 °C (or 32°F) and a pressure of 1.013 bar (or 14.69 psi) are selected, and these reference conditions are indicated by the underlying letter "n" in the unit of volume used. The direct thermal mass flow measurement method is always based on these reference conditions unless otherwise requested.

Standard conditions (l_s/min): here the reference conditions are based on 20 °C (68°F) instead of 0 °C (32°F). Please be aware of this difference, because mixing up these reference conditions causes an error of 7%!

Our average delivery time is 48 working hours.
This means when the order is placed and paid, the order will be shipped within 48 working hours. The status of your order can be tracked in your account.

Mass Flow ONLINE offers several payment methods.

For customers who are able to purchase and pay at the same time we offer the following real time payment methods:

• Verified by VISA
• Mastercard® SecureCode™
• American Express
• PayPal
• iDEAL (only in The Netherlands)

For customers who have seperate purchase and payment processes, we offer an alternative:

• Wire transfer
• Bank transfer
• T/T transfer
• Money transfer

First you start the purchase process, select wire payment (bank transfer), and finalize the purchase process. The status of your order is Waiting for payment. You will receive an order acknowledgement within a minute. In this order acknowledgement, all our bank details are specified (bank account number, bank name and address, Swift Code, BIC).

This order confirmation contains a link to a detailed invoice, enabling your finance payment department to arrange pre-payment. When payment is received, the status of your order is updated to Paid. You will be notified by e-mail.

If you ordered the wrong article, please read the exchange procedure on our website and act as soon as possible.

It is common to identify pipes by inches using NPS or "Nominal Pipe Size". NPS is often incorrectly called National Pipe Size, due to confusion with national pipe thread (NPT). The metric equivalent is called DN or "diametre nominel". The metric designations conform to International Standards Organization (ISO) usage and apply to all plumbing, natural gas, heating oil, and miscellaneous piping used in buildings. The use of NPS does not conform to American Standard pipe designations where the term NPS means "National Pipe Thread Straight". Based on the NPS and schedule of a pipe, the pipe outside diameter (OD) and wall thickness can be obtained from reference tables such as those below, which are based on ASME standards B36.10M and B36.19M.

This video shows the order process at Mass Flow ONLINE. (video length 4 minutes)