How to choose a suitable high pressure air/gas source

Aspects you should consider

Every METRUS safety valve test bench model is equipped with a pressure inlet for connecting and external high pressure source – a Nitrogen bottle or a compressor. Furthermore, a high pressure hose with a standard Nitrogen bottle fitting is part of the scope of supply. In addition to that, METRUS offers optional, internal high pressure generation consisting of boosters and pressure vessels. This document highlights the aspects to be considered when choosing the best alternative for your safety valve test bench.

1) Nitrogen bottles

Pros

a.  Mobile – ready to use anywhere without further need of infrastructure.
b.  No investment into equipment – usually you only pay the gas, not the bottle.
c.  Max. pressure of 300 bar when fully filled.
d.  Maintenance free.

Cons

e.  Limited capacity – Bottle needs to be replaced or filled frequently.
f.  Decreasing max. pressure – with each and every test, the pressure inside the bottle decreases. The higher the set point to be test the faster the remaining pressure level inside the bottle will decrease.
g.  Possible, useless remaining pressure – once the remaining pressure level is below your set pressure to be tested, the bottle and its remaining pressure capacity becomes useless to you.

Recommended use:

h.  Mobile on site testing – Using an SVM series test bench you bring to your customers site within a shut down.
i.  Occasional testing – You only require gas testing from time to time. Even choosing between two bottles to make best use of remaining bottle pressures is no issue at all.
j.  Testing of low set pressures only – You only need to test low set pressure – e.g. below 20 bar – with the capacity of the Nitrogen bottle lasting for many tests and the useless remaining pressure level inside the bottle being negligible.

nitrogen bottles

2) Compressors

Pros

a.  Constant, inexhaustible source of high pressure up to 300 bar. The compressors’ capacity is capable to even deal with repeated high pressure test, refilling recharging the 80l pressure vessel in shortest time.
b.  Centralized high pressure source – due to its capacity, a compressor can be used to feed several safety valve test benches (test stations) at the same time.

Application requirements (cons)

c.  A compressor requires three phase power, 400 V
d.  Despite silencers a compressor is often installed outside the main building or inside a dedicated compressor room for employees not to suffer from the noise emissions.
e.  Required space – in any case a compressor will demand a dedicated space of similar size like the test bench itself.
f.  Maintenance – The compressor itself is a technical unit that demands frequent maintenance.

Recommended use:

g.  High test load – Safety valve manufacturers with daily, high work load at the test bench.
h.  Many high pressure tests at a time – you need to test many safety valves with high set pressures (100 to 300 bar) in short time e.g. during an outage of a larger process plant.

compressor

3) Internal pressure generation

Pros

a.  Easy to level pressure vessel with max. pressure up to 600 bar.
b.  Independent, rechargeable source of high pressure.
c.  Converts 6 bar workshop air into 600 bar high pressure.
d.  Compact, built in system.
e.  Does not require power supply.
f.  May be combined with Nitrogen bottles or compressor system to create up to 600 bar pressure.

Cons

g.  Extended time for initial maximum pressure charging resp. recharging after significant pressure drop. Charging an empty 5 liter pressure vessel to 220 bar pressure requires appr. half an hour.

Recommenced use:

Frequent, medium test load in combination with temporarily higher test load of medium pressure (e.g. up to 100 bar) and individual high pressure test (up to 600 bar). Typical scenarios:
h.  Safety valve manufacturers with built to custom order production and special, high pressure models.
i.  Valve workshops of refineries, large power stations and nuclear power stations.

internal compressor

Please do not hesitate to contact us at any time for further consultancy when choosing the right high pressure source for your METRUS safety valve test bench.


Relevant for:

Safety Valve test benches:
– SVM 4/100
– SVM 4/250
– SVM 20/200
– SVM 20/400
– SV 20/200 PA
– SV 20/200
– SV 20/400
– SV 50/200 & 400

as well as for other testing applications